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Mike Richards
Thu 24 August 2006, 10:53
This is Version 4 of my 3:1 belt-driven gearbox. It takes me forever to design something that I like enough to keep.

http://www.mechmate.com/Forum/messages/12/1152.jpg
This version is cut from 1/2-inch thick polycarbonate. The spacers are 1-inch aluminum. (The extra-long shaft and rusty gear are left-overs from other projects.)

Starting at the shaft, there is a 1/2-inch clamp collar, #9 rubber O-ring, 1/2-inch shielded ball bearing, motor plate, 60-tooth XL gear, main plate, 1/2-inch shielded ball bearing, #9 rubber O-ring, 1/2-inch clamp collar, 20-tooth, 20-pitch, 20-degree spur gear. The aluminum spacers are 1-1/2-inch high, threaded for 1/4-20 machine screws. There is a 20-tooth XL gear bored out to 14mm to fit the Alpha stepper motor. The belt is a 150XL037. The original 3/8-inch mounting bolt was replaced with a longer 3/8-inch bolt, due to the extra thickness of the polycarbonate. The motor mounting bolts are 1/4-20 X 1-inch socket head bolts (so that the belt can easily be adjusted from the rear of the motor).

This version took about 1.5 hours to cut (Y-axis, 2 X-axis, no Z-axis) using a 1/4-inch O-flute cutter at 1.25-ips. Machining the spacers took forever. (Whatever made me think that using a metal mini-lathe would be fun? Can you say one full day machining and threading spacers?)

The 3:1 gear reduction on the X and Y axes reduced the normal Alpha 'chatter' problem enough that I can accept the occasional 'chatter' mark. Torque is 3X greater. Ted, at Shopbot, suggested that I try setting the Alpha drivers to 500 steps per revolution, rather than the default 1,000 steps per revolution so that the factory software/controller could supply pulses fast enough for a 3:1 reduction. The resolution on either 500 or 1,000 steps per revolution were nearly identical. In fact, the 500 steps per revolution setting seemed to produce smoother edges in the majority of cuts. It seems that the reverse should be true, but the proof is in the cut. I'm beginning to think that the increased torque is the main factor in getting better cuts. It might just be possible that the 3X increase in torque holds the 'inactive' axes in position so that they're not shoved around by the active axis.

I would have used higher reduction, but that would require a multi-stage unit - which would have been fairly bulky. The 20-tooth XL gear is the smallest that can be bored to fit the 14mm shaft on the Alpha stepper motor (according to W. W. Grainger's catalog). The 60-tooth XL gear fits better than the maximum size 72-tooth XL gear.

In any case, the 3:1 unit really helps with cut quality.

Evan Curtis
Thu 24 August 2006, 14:34
Mike,

Nicely done! How is the unit tensioned up to the rack? The same as the Stepper was, with spring and turnbuckle?

Thanks

Sheldon Dingwall
Thu 24 August 2006, 17:59
Very nice Mike. I wonder if the belt has any smoothing effect on the step marks?

Mike Richards
Thu 24 August 2006, 22:34
Evan,
The motor can be adjusted vertically about 1/2-inch, which is more than enough to adjust the tension on the belt. The spring and turnbuckle are still used, except that I used 4-turns rather than the 3-1/2-turns recommended by Shopbot.

Sheldon,
The belt is pretty tight. Actually, it is tighter than I would normally run a belt - only about 1/8-inch deflection when tightened. However, it could be that the natural 'softening' of the belt helps cut down the 'chatter'.

Gerald_D
Thu 24 August 2006, 22:49
Nice job Mike!

Any comment on how it stands up to sawdust?

Mike Richards
Thu 24 August 2006, 23:01
Gerald,
In my shop, I've mounted a sign stating, "Only 'anti-cling' sawdust is allowed". Because of that sign, I don't have to worry about sawdust collecting on the belt and gears.

Seriously, sawdust hasn't been a problem. After every sheet, I customarily sweep the table and blow off the gears, rails, and motors. So far, there hasn't been any problem of any kind with sawdust.

Gerald_D
Thu 24 August 2006, 23:43
"I'm beginning to think that the increased torque is the main factor in getting better cuts. It might just be possible that the 3X increase in torque holds the 'inactive' axes in position so that they're not shoved around by the active axis." I totally support this theory. I believe that a stepper motor cannot "hold" a micro-step. It will hold a full step, and even so, with some "spongy-ness". I plan to clamp a stepper in a vice, put a 2foot long lever arm on the shaft, and then feel by hand how a stepper actually steps, micro-steps and holds.

Good news on the dust. An open casing is probably better than a closed box.

Mike John
Thu 24 August 2006, 23:55
Mike
Can you send me the file to make that sign for my workshop,please?

..............Mike, the other one!(or is he the other one?)

Gerald_D
Fri 25 August 2006, 00:16
Your sawdust doesn't understand English

Mike John
Fri 25 August 2006, 02:36
Drat! foiled again!
Hang on! Does anyone from Utah speak real English? http://www.mechmate.com/Forum/clipart/happy.gif

............Mike

Gerald_D
Fri 25 August 2006, 04:28
Yes, the sawdust does.

Mike John
Fri 25 August 2006, 05:34
Now that is true, as the trees were probably planted back in colonial days!

Mike Richards
Fri 25 August 2006, 06:53
Mike J,
English? Never heard of it! Here in Utah, we speak American - when we're speaking to outsiders. Among ourselves, we speak the pure Adamic language.

Gerald,
One of my concerns a few months ago was reduced current holding torque on stepper motors. It seemed to me then that as soon as an inactive motor went into standby mode (automatic reduced current mode to reduce motor heating), that axis basically lost almost all of its holding power, meaning that that axis could be pushed around by the active axis. My thought back then was to have Ted modify the Shopbot code so that whenever any axis became active, the other axes would move one step CW and then one step CCW continuously to keep all axes active (full holding torque).

I think that holding torque while motionless is the biggest argument in favor of servo motors. If I understand the concept of servo vs stepper, the servo motor/driver consumes almost no power when stopped, but instantly goes to as much power as necessary to resist movement - meaning that a servo motor can't be shoved around like a stepper motor. Of course there are significant factors favoring steppers over servos, but, if we have to use gear boxes to make a stepper work properly, why not go the full distance, install servos w/gearboxes and encoders (at 1/3 the cost of the Oriental Alpha stepper/driver)?

Gerald_D
Fri 25 August 2006, 06:57
And Adam spake to Eve: "...with what router shall we smite the apple tree?"

David Rosenbleeth
Fri 25 August 2006, 17:09
"You're in luck if you gotta a McCullogh chain saw"

Moral of the story: If you wish to smite the tree-use a saw; to carve it use a spindle and Geckos.

Been cutting parts with the Agek rig for a while now and my guys still have nothin but smiles.

Dave

Joe Crumley
Fri 25 August 2006, 19:15
David,

Could we see some of these parts? I allways enjoy seeing products made with a router.

Mike Richards
Thu 07 September 2006, 15:08
Here's the 3:1 ratio belt-driven-transmission cut out of aluminum on my Alpha.

http://www.mechmate.com/Forum/messages/12/1195.jpg http://www.mechmate.com/Forum/messages/12/1196.jpg http://www.mechmate.com/Forum/messages/12/1197.jpg

Cutting speeds in the 1/2-inch thick 6061 aluminum were 0.60-ips XY-axes, 0.05-ips Z-axis, 12,000 RPM, 0.075-inch step down per pass, using a HSS 3/8-inch cutter designed especially for cutting aluminum. Those speeds required flooding the cutter with tapping fluid made especially for aluminum. If you look carefully, you'll see some edge marking in various places. That was caused by letting the cutter get too dry (thus getting too hot).

After using the 3:1 ratio for several weeks, it seems to work perfectly for the kind of work that I do. There hasn't been any problem with 'chatter'. The open frame has not been a problem - no dust on the belt or gears. In short, with the 3:1 transmission, my Alpha is cutting like a real CNC router.

Dirk Hazeleger
Sat 21 October 2006, 09:23
Hey Gerald ran across this belt reducer produced in your neck of the woods. Ever heard of them?
http://www.microdyne.co.za/motorgear.htm look at the bottom of the page
Dirk

Gerald_D
Sat 21 October 2006, 09:44
Microdyne have always been out of my price range but I'll call them on Monday to see if they have respectable prices for these belt drives.

http://www.mechmate.com/Forum/messages/12/1515.gif

Gerald_D
Tue 24 October 2006, 04:32
$600 a piece. Ouch!

Michael Cunningham
Mon 19 March 2007, 21:37
Does anyone have a set of cad drawings to build a belt/gear reduction box.. maybe a list of parts? I need to build two belt reduction units for my nema 34 steppers.. say 3 or 4 to 1 reduction. I however an a complete noob at this with no lathe or mill. Something very similar to the ones shown here. Suggestions? Ideas? Plans? Does the metal kit have provisions for making belt gearboxes?
Does anyone make these on the side for people?

Thanks,
DeviousMW

Greg
Tue 20 March 2007, 05:20
Michael

These are a couple of pics just to give you more ideas.

I don't have any drawings. And this is obviously not a mechmate.

Same principals apply though. Keep the relationship between the pivot and the pinion shaft no more than 45 degrees from horizontal. I would make it less if I was starting again.

I see the weak point of other designs to be the pivot mechanism. Any slop here goes straight to backlash.

Whenever I drill a hole and put a bolt or shaft through it, it usually ends up with about 3 to 5 thou slop. Then the rapid back and forth of the axis will increase this with wear.

That's why I put bearings on the pivot and made them a firm fit in their housing and on the shaft.

Also be careful in your belt selection. Mine are T5 and the "cog" on the belt is smaller than the "groove" on the pulley.

So far this has not showed up in accuracy but this is not a good place to start. http://www.mechmate.com/Forum/clipart/happy.gif

http://www.mechmate.com/Forum/messages/12/3686.jpg

http://www.mechmate.com/Forum/messages/12/3687.jpg

Michael Cunningham
Tue 20 March 2007, 14:46
Greg,

Thanks for the info.. couple more questions..

On you pivot point I see you have a press fit bearing on each side of the shaft. What keeps
the shaft in place? Is there some sort of clips I dont see? Same question on the other shaft as well. Where did you get your gears from? How do you keep the large gear in line with the smaller one. Again another clip? Interested in making another set of these for some extra cash?

Thanks,
Mike

Alan_c
Mon 04 June 2007, 15:51
This post originally made in the motors thread - now moved to here...

A request for all the great minds out there...

something we have not discussed much in detail is a design of a self built reduction drive using say a toothed belt and pulleys, although it has been mentioned on occasion and references are made to them at cnczone.

If one is limited to using only an ungeared motor (eg PK299-01AA or PK299-F4.5A) what are the best options / methods for achieving a reduction drive in the mechmate spirit - i.e. buildable with the resources one would have available for building a mechmate.

How do you decide on the belt and pulleys, how do you tension the belt, what sort of bearings should one use for precision etc?

If you are going to use a reduction drive, are these motors mentioned best suited or should you be looking at alternatives?

I suppose another interisting question would be, is it really necessary if so many guys are using direct drive, or am I just chasing the elusive resolution genie:rolleyes:

edit - sorry its late, found the answer to some of the above in the drive mechanism thread

Gerald D
Tue 05 June 2007, 01:29
Alan, all very valid and important questions.

Let's start with the belts. Most people are using XL (eXtra-Light) belts, but if I look at motor torques and speeds in the book, the XL seems to be too light. The proof of the pudding is whether the folk with XL belts have needed to replace them?

Then you can look for the range of pulleys available for the selected belt. The theory says that the small pulley must not have too few teeth for a precision/smooth/high-speed application. It seems that folk are getting away with "coarse" (few teeth) small pulleys?

On the big pulleys, I have found that the off-the shelf stuff doesn't go all that big, and then I worry about them behaving as flywheels. Idealy we want big alu pulleys and they are a bit scarce around here.

Converting the direct-drive motors with reduction doesn't seem to be an issue. You could actually go to smaller, lower-torque motors, but there is no apparent harm in recycling the big direct-drive motors.

Bearings, adjust and hinge points don't worry me - it is that darn book on the belts that is my problem.

(Years ago a lecturer asked our class to design a gearbox and gave us the torques/speeds/etc. The smallest box any of us could come up with was about the size of a chair. Then he showed us what specs he gave us - Ford escort! Where the reliable box is about the size of a shoebox. This is what happens if you stick to the book.)

Richards
Tue 05 June 2007, 06:52
So far there has not been a problem with the XL belts. (Remember that the specs on some stepper motors specify < 8 lbs. of radial force on the shaft. The belt design keeps radial force to a minimum.) My plan is to replace the belts every year when I replace the pinion gears. That way I'll probably never now how long a belt will actually last. I'm coming up on about 8-months of use with absolutely no adjustment of any kind.

If you look carefully at the JPG in the post at the top of this thread, you'll see that there is about 3/8-inch of up/down adjustment for the motor. That is more than enough for belt tensioning.

The toothed pulleys that I use are 20-teeth an 60-teeth. The belt is the 150-XL size. Center to center distance on the pulleys is 3" minimum and 3.375" maximum.

I've made several versions, all very similar to the polycarbonate version shown in the first JPG. My latest version uses Delrin instead of polycarbonate. The Delrin works perfectly, but I'm willing to guess that 1/2-inch thick Baltic Birch plywood would work just as well.

Gerald D
Tue 05 June 2007, 10:00
Oriental Motor allow 75lbs radial load on the shaft of the PK29_ series motors, 0.4" in from the tip of the shaft (57lbs right at the tip), so that is not an issue for belt loading (nor spring-loaded direct pinions for that matter).

McMaster-Carr offer the following pulley teeth numbers for XL series belts:
10|11|12|14|15|16|18|20|21|22|24|26|28|30|32|36|40 |42|44|48|60|72

If a 10 tooth were used with a 72, the ratio would be nice, but only about 3 teeth of the small pulley would be engaged with the belt. To get more "wrap" on the small pulley, the center distance would have to be increased drastically, making a big drive system. Mike's 20/60 choice is a good conservative selection, giving a compact package.

Richards
Tue 05 June 2007, 21:57
Gerald,
I couldn't find the specs for the radial load on Oriental Motors, so I'm happy that you found that information. In fact, I may have been remembering data from a tech seminar that Oriental held years and years ago. (With my short term memory beginning to be just a memory, I find it hard to remember anything that happened less than 15 years ago; however things that happened in my ancient past are still sharp and clear.)

The reason that I selected the 20 tooth pulley and the 60 tooth pulley for my units is that the 20 tooth pulley is the smallest pulley that I could use with the 14mm shaft of the Alpha stepper motors. Pulleys smaller than that had a recommended maximum bore less than 14mm. The 60 tooth pulley was mostly selected because I had six of them on hand and only two 72 tooth pulleys. Also, the 60 tooth allows a more compact unit than the 72 tooth pulley. The difference in ratios 1:3 vs 1:3.6 does not seem to be an issue.

You're correct about the danger of using a 10 tooth pulley that has only 3 teeth engaged with the belt. I used a 10 tooth and a 60 tooth pulley extensively with a PK268 motor in a Kodak S-printer electronics package. Testing showed that I needed to use a much longer belt to get more teeth engaged. That particular design required almost no torque and minimal speed, which is much different from the requirements in a CNC router.

Gerald D
Wed 06 June 2007, 00:21
Mike, the radial loads spec is from the sheet that comes in the box with the motors. I hadn't seen that same sheet online before, but a new search this morning revealed this excellent document (http://www.orientalmotor.com/products/pdfs/SteppingMotors/SectionBIntro_B2-B42.pdf). See page B-37

I have a few L-series pulleys lying around, but they are a lot bigger and downright ugly. The book on belt drives has to assume continuous operation at full speed & torque. On the stepper driven CNC router we don't get to full speed at full torque simultaneously, nevermind doing it consistently 24/7. If the XL belt is working in this application for everyone, then the book can be revised.

Gerald D
Wed 06 June 2007, 03:23
Being an ex-automotive person, I have a fondness for using car parts.....

A waterpump bearing (http://www.zxz-bearings.com/pumpbrg.htm) could be useful to the belt drive designers. That is if the motor is swung around compared to the above layouts......

Marc Shlaes
Wed 06 June 2007, 05:31
My build is still in the planning stages. But that is how I work. I think a lot about what I am going to do before I start. Now here is the question. For a new builder, should I even be reading this stuff on belt drives or should I just plan on buying geared motors? Is this information primarily for retrofits or are there pros and cons to belt drives vs. geared motors? Is the price difference the driving factor? Oh, one other question, where are the US builders buying there Oriental motors?
:confused:

Thanks.

Marc

Gerald D
Wed 06 June 2007, 06:30
Last question first: I'm sure that the US builders buy their OM's direct from OM. (The link is in the motors thread). Even I bought them direct and had them delivered to a friend in the US who on-shipped them to me. Buying from OM with a credit card was the easiest purchase, with the fastest delivery, that I ever had.

The issue on which motor/belt/box combo is best, is largely driven by price vs. resolution vs. effort (nobody has mentioned space yet - the gears/belts make the gantry a bit longer and hits you in the stomach a bit more.)

Lowest price, effort & resolution is a direct drive non-OM motor at around $100 each in the US and $50 in China. Most of us are reading this thread because we are tempted to start cheap & easy and then see if we need to add some (belt) reduction to the motor at a later stage.

Top price, with lowest effort and highest resolution are the geared Oriental Motors at $257 each in the US and quite a bit higher in the rest of the world because of agents or transport.

Experimenting with retrofitting belts could even be the most expensive option if you have to find outsiders to do all the machining for you.

I would venture to say that most people who have direct motors on their CNC routers have been happy to accept them as they are, and that they might only have a passing interest in spending some effort and money to get a better resolution.

Richards
Wed 06 June 2007, 07:23
My goal for attaching the belt transmission was to reduce 'chatter'. The factory 'resolution' on my Shopbot PRT-Alpha was about 0.00314" per step. (20 tooth gears with a 1" pitch diameter. 1,000 steps per shaft revolution. Using the same pinion gear with a Gecko driven stepper would have given about 0.00157" per step due to the 2,000 steps per revolution of the Gecko.) When I added the belt drive transmission, I had to change the steps-per-revolution to 500, which gave me about 0.0021" per step with the 1:3 ration belt-drive. However, the belt-drive virtually eliminated the 'chatter'. My theory is that the 3X increase in torque helps hold the off-axis motors in position. Whatever is happening, the belt-drives cured the problem. As Gerald pointed out, the belt-drive is bulky and costly. Parts cost about $200 to $750 for three drives depending on whether you do your own milling or have a local shop mill the bearing pockets.

The Oriental Motors PK296 motor with either the 1:3.6 gearbox or the 1:7.2 gearbox would be ready to go right out of the box. (I have four of the PK296B2A-SG3.6 motors that will be installed in my next project.)

Gerald D
Wed 06 June 2007, 10:17
Just to avoid any misunderstanding, Mike was getting 'chatter' even along straight orthogonal cuts, when only one axis was running. In other words, the the holding axis wasn't doing a good job of a fixed position. That issue seems peculiar to the "Alpha" motors which had a local closed-loop control, and which may have been "hunting". His gear ratio change cured those chatters. As he says, probably because of the extra torque - his resolution ended up with 500 steps/motorrev being 1500 steps/pinionrev.

But, with standard old steppers, they do a good job of holding the stopped axis in a fixed position. Where we do see some "chatter" is when one axis is stepping at a certain speed ratio to the other axis. On curves and circles there are short distances where "chatter" (resonance) can be seen and heard when cutting fairly fast. On direct drive we will have 2000 steps/pinionrev - actually a finer resolution than Mike's 1500 steps/pinionrev.

Marc Shlaes
Wed 06 June 2007, 10:37
These last posts helped me understand a lot but... Gerald, your last post made me think that new non-geared steppers are just fine. The problem I see is that if I buy non-geared steppers and then am not satisfied with cut quality, I either buy new geared motors or fabricate belt-drives. Shouldn't I just avoid the whole problem and buy geared motors? I understand that they are significantly more expensive but I want to end up with a machine that does what I want. In the overall scheme of life and overall cost of the machine, the price difference seams reasonable. If geared motors are complete overkill on the MechMate (as opposed to the Alpha), then spending the money is dumb. Thanks for further advice.

Marc

Gerald D
Wed 06 June 2007, 11:43
Have a look at the first post in the motors thread here (http://www.mechmate.com/forums/showthread.php?t=254). If I lived in the US, I would use the geared motors for my next MechMate. Not because they are necessarily so good, but because I am so curious! :) By all accounts the extra $50 dollars per axis is extremely good value for money, and nobody is suggesting that it might be an overkill - nowhere near it.

However, on the other side, a direct-driven MechMate is also a very useful (profit-making) machine - one learns to live with the occasional little chatters on some cuts when pushing it hard. I've always known that I could add belt boxes to our 2 MechMates, and that I am well-equipped to do it easily and cheaply, but then I think there are more important things to look at first. (like a vacuum table). I initially went direct-drive because our ShopBot was like that. I say again, if I had to start all over, I would probably be getting those 7.2:1 ratio geared motors.

Richards
Wed 06 June 2007, 11:52
Marc,
There are some minor problems with the Oriental Motor's PK296A1A-SG3.6 and SG7.2 geared motors. The main problem is that the gearbox limits torque to about 320 oz*in for the 1:3.6 gearbox and about 2X that for the 1:7.2 gearbox. (I assume that you could push the gearbox harder but with greater wear and possible damage to the gears.) The other problem is that the SG gearboxes have some backlash. Backlash may or may not be a problem depending on what kind of work you do.

Why not ask someone to make some sample cuts for you in the kind of material that you will be cutting? If someone with geared motors cuts the part(s) and someone with non-geared motors cuts the part(s), you'll have side-by-side comparison. The cost to do that should be minimal and then you would have peace of mind. (That's exactly what I should have done before buying the PRT-Alpha. As much as I like the machine now, it took the better part of two years to adjust/modify the machine before I was satisfied.)

zetacnc
Tue 04 December 2007, 08:47
Hello all,

These are photos taken this weekend - the machine is ready to rock with all the belt reduction installed and tested.

It's soon to say but the best thing I discovered was the VFD inside panel did not interfered in any moment with the drivers...

The spindle motor became quite hot after 30 minutes running at 12000 rpm when was doing ligth cuts to experiment, and this week will talk to the manufacturer about this, but it proved to be very powerfull...

The maximum velocity reached 21 meters/minute (830 in/minute), but i limited to near 15 meters/minute (590 in/minute)

I hope you enjoy...

larry1larry
Sun 30 December 2007, 15:12
I will probably get a lot of backlash on this idea,but only from the members.:D
You guys will probably"give me the gears"besides the "lashing"OK I am ready,got my helmet on.
For gear reduction why not use spur gears,rather than belts and pulleys?May be much more compact.8Teeth and 40Teeth will give 5 to 1.Rather than elaborate and confirm my lack of knowledge,I ask for the expert advice of the forum.
Larry

J.R. Hatcher
Sun 30 December 2007, 16:16
I was thinking if you could spring load the gears together like we do the rack and pinion how could it have backlash.

Bill McGuire
Sun 30 December 2007, 21:44
:)Apparently, the oriental motor guys thought gears was a good way to go...since they are selling them, and I for one will be purchasing four of them...

One concern I do seem to recall in a post several months ago is that the angle of the motor (or gears or belts, I suppose) needs to be somewhat perpendicular in relation to the racks... but I could be wrong... not the first time this year either... and there's still one more day left for many more mistakes...
Bill

Doug_Ford
Mon 31 December 2007, 06:25
Larry,

Maybe I'm misunderstanding your question. Why would you build a gear reduction using gears when you can buy a stepper motor with a gear box made specifically for it from Oriental Motors? I guess you might save a little bit of money if you were lucky but I don't believe your creation would be nearly as reliable or as accurate as the factory product.

Charlie
Mon 31 December 2007, 14:34
The 7.2 and 3.6 from oriental are getting reports of looseing steps due to the gear box binding from workload. I just bought four 7.2's and I want torque, so we shall see. Mike is saying dont ask to much of them because the gearbox strains/binds under load. Plus they are the smaller motor. Mike is useing 600oz*in motor with a 3to1 belt that transfers full torque. 600X3=1800oz*in
If the OM 7.2 gearbox can only handle 640oz*in of torque you dont get your full 300X7.2=2160oz*in transfered to the pinion. In fact you only beat Mike's direct larger stepper by 40oz*in. That also means that you can only use 89oz*in of the motors 300 rating. It just doesnt sound right. Like I said I own four of them(7.2's), building the 4'X8' Mamba and want torque so we shall see whats up with em. Plus I am fortunate enough to live in the same town as Mike. So with his trusted word and my sacrificial motors and full Mamba setup I trust we will get to the bottom of it.

Does all that sound about right Mike? Or at least close :)

Edit: As Bill said maybe its the angle of the mount that is giving some people problems. Or maybe other parts of the gantry are binding due the new found torque with3.6's or 7.2's on old shopbots? At this point I am still only guessing.

larry1larry
Mon 31 December 2007, 16:00
Bill & Doug,
My first post here was in Selecting motors thread and noticed the gear motors had less torque than the un geared motors.Orential motors are very expensive compared to others.When a geared version is only $57 more I ask what kind of gear box are you getting.Other gear heads are $600+from other sources.
From reading Mike's post and Charlie's post,I thought the general consensus or at least in my mind it is preferable to direct drive with a larger motor and or gearbox.
This means for some real performance I am back to belt drive.How does one get 7 or 10 to one without a bulky package or two stages?3to1 is max for two pulleys.I thought actually using the pinion gears as gears it may be possible to get higher ratios in a smaller package.
Happy New Year
Larry

Richards
Tue 01 January 2008, 08:51
I hope that I haven't started a panic about motors and gearboxes. Let's go over the things that we can gleen from the data sheets.

- The PK296A2A-SG3.6 motor has about 320 oz*in permissible torque.

- The PK296A2A-SG7.2 motor has about 720 oz*in permissible torque.

- The PK299-01A motor (no gearbox) has about 800 oz*in holding torque when wired bipolar series and about 550 oz*in holding torque when wired half-coil.

Those are the basic numbers that Oriental Motor publishes. You'll note that the PK299 motor without a gearbox and the PK296A2A-SG7.2 both put out similar torque, depending on how the PK299 motor is wired. So, the speeds that Gerald is getting with his PK299 equipped MechMate would be very similar to the speeds that you should expect with the PK296A2A-SG7.2 equipped MechMate. The main difference is that the 7.2:1 gearbox would give you 7.2X better resolution, but would also require a pulse train 7.2X faster than the non-gearbox motor.

All of the e-mails that I've received where people are having problems with the PK296 sized motors are NON-MechMate machines. As we all know, Gerald has done an excellent job of designing the MechMate, including the use of larger V-rollers for smoother operation and the use of welds and bracing to reduce or eliminate machine flexing. So, the problems that I've been reading about MAY never be seen with the MechMate.

IF you're building a machine that MUST run as fast as possible, you'll PROBABLY want to look at large motors with a belt-drive transmission. A single-stage belt-drive transmission will have a maximum of 3.6:1 reduction. That is the result of the fact that the smallest pulley that can be bored out to accept a 1/2-inch motor shaft is the 20-tooth XL pulley. The largest pulley readily available is a 72-tooth pulley. The math shows that 72 / 20 = 3.6. I can't imagine a 3.6:1 belt-drive transmission being a problem. With a 30-tooth spur gear, the resolution would be 30 / 20 X 3.14159 / 3.6 / 2000 = 0.000654 inches per step. That is 5X finer than the thickness of a piece of copy paper. Believe me when I tell you that you will never get resolution anywhere near 0.0006 inches on any CNC router when you're cutting wood. Wood changes size from minute to minute in my unheated shop - especially as the humidity shifts from the deseret-like dryness to near tropical monsoon-like wetness in August. With a 3.6:1 belt-drive transmission and a PK299-F4.5 motor wired parallel, you'll get more than 2,500 oz*in of torque. The XL belt will probably be the limiting factor with that motor (although I haven't had any problems with XL belts on my 3:1 belt-drive setup).

If you already have 7.2:1 motors, use them. Cut thousands and thousands and thousands of parts with them. By the time that you've worn them out, you'll have both the experience and the money to buy whatever type of motor and gearbox that best suits your needs.

BernardR
Wed 02 January 2008, 02:28
I recently joined this forum as I am contemplating building a router / Plasma cutter. My previous experience was converting a Bridgeport size import to 4 axis control using servos, driven by Geckos and Mach2.

Being a Brit and growing in an environment where hobby activities were possible only by doing as much DIY work as possible, I soon found that in 2001 there was comparatively little advice available on motor sizes and gearing ratios and that larger size pulleys were often very difficult to obtain and fairly pricey. I investigated and measuring a variety of pulleys found a couple of constants that enabled any size pulley to be fabricated.

(I just noticed in reviewing the word version of the AutoCad drawing that I just gave the diameter. It is calculated as PD - 0.839= 94.653, Published data = 94.65.)

Currently having drilled the center hole I mount the blank on an arbor and then drill the peripheral holes using a rotary table. However it is also possible to mount the blank and use a standard G-code program to drill the holes, this ability will be dependent on the accuracy of your system.

I have found that there is no real standard for either the pulleys or the belts for T5, some pulleys are obviously machined with a hob as per normal gears but there are others that appear to been drilled and after cutting to the Outer Diameter both sides of the cut holes are edge releaved. It is a similar story with the belts, some have chamfered teeth and slight gearing depth while others are very deep with virtually parallel teeth blending to a radius. Both combinations appear to work equally well together and in the intervening years have not had a broken or damaged belt.

I prepared an AutoCad drawing of a T5-60 tooth pulley. The reason for this size was because it was the largest that I could obtain Manufacturers data, for those interested it will be seen that the nominal Pitch Diameter is easily caclulated, though it is only used to establish the remaining critical dimensions.

On a different subject, I have noted that several people have discussed jerky movement and less than optimum performance. For those users that are interested I submitted some information that may be of interested in looking at ArtSoft's work in this direction, where they have been delving into these problems, the subject heading is: Quantum, long term software solution?

Hopefully some of the data that I have shown may be of some use to you.

J.R. Hatcher
Wed 02 January 2008, 03:20
When I was considering making a belt reduction I was going to use the parts from a craftsman 3 X 21 belt sander. They were very cheap and only needed slight mods. If anyone is interested I think I could find the model # and post it.

BernardR
Wed 02 January 2008, 23:40
In reading through the various posts I have noted a couple of times that mention has been made of being limited to a minimum of 20 teeth for a 14mm shaft and I would comment as follows:

It is increasingly common that pulleys and pinions are bonded to shafts without any form of mechanical fastening. Loctite 609 is a classified as a general purpose retaining compound and is good to retain from press fit to up to 5 thou clearance. When the parts are properly degreased and Primed with 7649 strengths over 2,200 psi are attained.

I regularly use this product if I need to do turning operations on a previously completed part and then release the parts by applying a small propane torch to raise the local temperature above 170c.

Examining the xl profile the inner diameter of the teeth is 0.125" less than the outer diameter. Subtracting the 14mm shaft = 0.5512" diameter and using a 16 tooth pulley with a published OD of 0.999" and an inner tooth diameter of 0.874 - .5512 = 0.3028", i.e. a wall thickness of 0.15" which is more than adequate.
I used this method when working on the gearing of the knee (Z) axis of my mill.

The link to Loctite 609 data sheet is: https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/3E906D6B842166B0882571870000D855/$File/609-EN.pdf
609-EN.pdf (application/pdf Object).

Depending on distributor a small bottle of 609 is in the region of $US12 and the Primer 7649 around $14.

Hope this info is of some use.

Robert M
Fri 28 March 2008, 12:28
http://www.mechmate.com/forums/attachment.php?attachmentid=1129&stc=1&d=1196783106

Hi Fabio,

May I be audacious and ask you to tell/share more on the how you did & conceive you motor gear belt reduction system ?
I’ve gone through your personal pages, read post 3, got the pics from #1 & #19 but for me, I’m still in the dark as to how you built them ! Never done any but would very much like to give it a try. I’m daring to ask “Better yet, any plans & parts list ? “ :eek:

From what I can understand there are some advantages to make your own “gear system” vs buying one that is part of the motor as many do to keep it simple The KISS approach !!!
I‘ve read many sources say it can be an advantage & flexible if ever needing for some better resolution or speed !!
But, with this in mind, I can’t seem to see how you kept it all in a close confined mater and with what type bearing/bushing on the shafts & how they stay/hold from the alu plate to shaft ?
Thanks for considering !
Robert

zetacnc
Sat 29 March 2008, 07:19
Hello Robert,

Well, the idea to build my own belt reduction was born when i tried to search already made reductions for stepper motors, or even motors with gear reduction like those from Vexta that are used by a lot of people here (in forum)...

As I told before, Brazil is not so good to find these kind of products, and importing taxes are very high...

I used as a starting point the original pieces (M5 10 312 and M5 10 322 motor swing plates) and imagined how to place one big aluminium 72 teeth XL belt gear as driven gear and a small steel 20 teeth XL belt gear as driver gear mounted on motor axis...
I also bougth a XL size belt (sorry don't remember correct length size), calculated the center distance between gears and started scatching some ideas.

The reduction is made basicalliy by two steel 10mm plates (but you can use aluminium) separated by 3 small collumns.

The final design is attached in DFX format - sorry if they are incomplet, but I asure you it's possible do build funtioning unit from them...

Each main axis, as I named the axis that the big 72 T gears is mounted is a 12mm diameter steel axis mounted on two 6001 ball bearigs.

Each bearing is press fit in a recess made in each plate as you can see in drawings, and there are two thin spacers between gear and plates (one each side) to maintain gear centered and not touching plates...

I then milled a flat recess in the shaft and installed a Allen screw to block the gear in the shaft.

The main shaft is protuding to one side to allow the module 1,5 pinion to be fixed with two allen screws (in milled recesses)...

In the plate where the motor is fixed, I milled a kind of recess to allow the motor slide in and out to adjust belt tension...

If you note in drawing, the width of the recess is smaller than the front of a NEMA 34 motor, and because this I milled two paralell flats in the motor front cover plate (without dismantling it! ) - (sorry I don't have photos).

The homemade reduction was them assembled over bench and then easily assembled in machine the same way the original one is mounted...

1122
1123

Robert M
Sat 29 March 2008, 08:23
Fabio…the Fabiolous !!! < :0))

This is very well and superbly explained. It is very motivating & inspirering for me.
I’m no genius when it comes to metal working, I’m a meticulous custom & studio furniture maker.
Love Metal working, but do not practice nor do much, so… I’m not inclined to see those little things that may be obvious to others.
Thank for showing the way on this one to me… I owe you one ;)
Robert

zetacnc
Sat 29 March 2008, 14:41
Robert,

Please, feel free to ask me any other detail that interest you.

I'll be glad to help someone else...

Best regards,

Fabio
O.T:
I don't know if you know this, but i'm very impressed with the detail:
http://br.youtube.com/watch?v=kvHYaRzGEO8&feature=related
http://br.youtube.com/watch?v=GK5_Blpav8c&feature=related

J.R. Hatcher
Mon 05 May 2008, 18:36
Marc and I have designed this 3 to 1 motor reduction. If time permits I will install one on the Z tomorrow and report how it does.

jeep534
Sun 18 May 2008, 00:34
Jr,
Those reduction units look slicker than snot......
patiently waiting for more info. I would like to build one of the MM's to run a Plasma cutter. Keep Up the good work.

Happy Hunting
archie =) =) =)

(newbe to this forum but not cnc)

J.R. Hatcher
Sun 18 May 2008, 05:02
Jeep 534,for more information on the trannys look in my personal thread. Later when Gerald returns, he will possible transfer info here?

Robert M
Sun 27 July 2008, 07:34
Have a problem as far as where to post my question, here or with the power supply section, so Gerald please see to this & feel free the reroute my question ?!

Initially I got soooo intrigued by Mike’s posts on his polycarbonate belt reduction but then I got itch & influence with Fabio’s version that it got me to the drawing board but finally got the kick and seduced by Marc & JR interpretation of their belt reduction trany system that I have no doubt anymore that I too will be making my own version but only after finishing & getting to run with success my version of the MechMate.

Question I would like someone’s help with is with the famous motor selection question.
Unbelievable the amount of time one like me who nose didly on motor / power supply section can spend on reading, sorting info & trying to learn to make the right final decision on those !!. :o

A note about my future set up is I’m designing my MM with an indexer. So, as far as this motor selection goes I’m still confused about the proper transformer/power supply.
should I consider getting all identical 5 motors to balance my future application or 4 identical for the MM and a different 5th for the indexer would not matter?
Would it cause some challenges when time comes to properly select the power supply ?

Example of what I came to select after some reading. No certain if those are ok but I’m aiming for 4 - PK299-F4.5 for the basic MM with 4:1 belt reduction and one PK2913-F4.0 for the indexer. I also intend to have belt reduction to the indexer motor set up in the range of….say +/- 15 to 25:1 via a double gear / belt set up ?

To some, maybe the possible torque obtained by this belt reduction with a PK299-F4.5 will be enough for the usage of the indexer, but on the other hand the extra torque available with the PK2913-F4.0 should be welcome if it as no penalty or negative effect in the electrical control box components selection & set up aside of it’s extra +/- 100$ for it ??

Amicalement, Robert ;)

Gerald D
Sun 27 July 2008, 09:14
Calculate the voltage of the power supply by taking:

32 times square root of milliHenry inductance

So for the PK299-F4.5 you get 50V and for the PK2913-F4.0 you get 65V. That means your power supply, if you use only one, must be 50V. That means your PK2913-F4.0 will produce less torque because it has a reduced voltage. About 23% less.

Robert M
Sun 27 July 2008, 18:03
Thanks Gerald for your input.

Before going further Gerald, I thing this post should go to another thread. Please fell free to edit this one and the one before and redirect them !! ( or Maybe I should think starting my own personal page ?? )Anyway…..

Allow me to question on yours :eek:
But before, I should have been more specific about the how I intend to run the indexer motor at max torque possible since no speed is in need, therefore I’m assuming a Bipolar parallel motor mode is the right choice. If I’m perceiving this wrong, please redirect me, but bipolar parallel voltage needs to be set at 0.707 of the unipolar !
If I understand this math thing correctly, in the case of the PK2913-F4.0, inductance is 4.2mH unipolar or parallel, then the math goes:
S.root of 4.2 x 32 = 65V, but 65V x .707 = 46V
Due to my ignorance in this field, I’m not in a position to assume correctly, but couldn’t I use this motor set up ( Pk299-F4.5 need 50V, & PK2913-F4.0 @ .707 needs 46V ) with a +/- 50 to 56V or even higher ?
Some are using the 56V with the Pk296A2A-SG motors, rated at 1.5mH and reported good results, questionable about their findings but still !!! ( S_root 1.5 x 32 = 39V ??? )
Where I’m getting even more puzzled about this voltage math, is when I read out of the Oriental Motor spec sheet their testing the PK299-F4.5 in parallel at 60V ??? See page C-229 (http://www.orientalmotor.com/products/pdfs/C_VEXTA/StPk29.pdf)

where I’m with another dilemma is all this complexity worth my trouble for some extra torque, especially if I intend to have a +/- 30:1 to 36:1 multi-belt / gear set up ! ( I revised my gearing calculation vs the 15 to 25:1 as previously written :o )

Pk299-F4.5 Bipolar Parallel = 880oz-in x 30:1 = 26 400oz-in = 137.5 ft-lb of inertia capability
PK2913-F4.0 Bipolar Parallel = 1320oz-in x 30 = 39 600oz-in = 206.25 ft-lb
That’s a 50% more inertia torque capability, but still only +/- 69lb !!!
Me to sort out, you to tell me I’m nuts or on track ??!!
Again, sorry to pull some of you guys hair, but haven’t you all gone through or close to this in the past :cool:!!

Thanks you very much, Robert ;)

D. van Randen
Mon 25 August 2008, 02:36
Sometimes its nice to see how the big companies put there product together.

Investing millions in making and maintaining their reputation in the CNC market they pin it on belt drives, a rugged, simple way of gear reduction that looks to have the ability to have backlash adjusted out when ever needed.

I have seen this method used on their smaller budget machines and also on their higher end models with complete tool changing systems.

The gear reduction is 3.75:1 . Sorry I did not count the pitch on the drive pinion or the rack.

D

Gerald D
Mon 25 August 2008, 04:41
Interesting parallelogram they have there - seems like the pinion is already on the small side and the motor is in danger of fouling the housing at the top. Thanks for the pics :)

Gerald D
Mon 25 August 2008, 09:20
2044

The yellow are the horizontal links of the parallelogram - they can swing up and down:

2045

The alu plate is slotted at the red marks - very similar to the stabilising slots in the MM motor plates. Their system is just way more complicated, with no obvious benefit over what we are doing.

D. van Randen
Tue 26 August 2008, 03:30
Hey thanks for that!

I had been scratching my head trying to figure out the two adjusters. At first I thought the slots you drew were at some kind of slight angle that allowed the adjusters to draw the gear up to an exact position , but that didn't explain the spring. Now it makes more sense.

I can only think of two benefits.
1) ergonomics, it makes for a very flat side as the motor is tucked in the cross beam for the Y axis.

2)Possibly the motor cannot drive the gear off the rack , it is constrained by the slots and linkage from moving too low to grind the teeth and stalls instead. But the slots are still big enough to allow the spring to pull the assembly upwards and keep the backlash very low.

Bottom line is that belt drives are a valid method for driving your CNC machine

I love my Alpha Step SB machine but I am not convinced that it was the best way to go. I now think gear reduction through belts with no feedback on the similar size motors would give better cut results for less cost.

D

Alan_c
Thu 12 February 2009, 13:54
Busy making prototypes for a customer on a tight deadline who's normal supplier of this item has dropped them. Not the most technically challenging job but interesting none the less - apparently these are destined for Cape Town newest swishest Hotel in the Waterfront (refer to recent star studded opening of another hotel from the same group in Dubai)

3656

cut from soild Oak, using straight 11.25mm router cutter, 3 passes rough (2mm oversize) 1 pass finish on size. Radiused edges done on the table router.

3657

I am having a vision... I see gearboxes in my future...:rolleyes:

MariusL
Mon 23 February 2009, 22:29
Sorry for the delay but the MM webserver or ISP blocked my IP from connecting to the forum.
Well here goes, we completed the machine last week and have done some cutting. I now find the biggest problem is to obtain the tools we need to do the cutting jobs that we have. I have a 8mm and a 12mm collet with the bosch router but found out that those are not the popular sizes for tools. I also need longer tools to cut the 3d plugs from foam. I guess this will be an ongoing battle.
The dust collection system works very well, almost to well. It leaves nothing behind.
I opted for a 4:1 reduction on all motors. See pics.
Thanks Gerald your effort made it possible for us to have a good working machine in under two months.
Also thanks to Greg from CncDirect for all his help.

Gerald D
Mon 23 February 2009, 23:08
Marius, that's a beauty!

Even your dust hose is a matching colour! :D

Those belt drives are very interesting, it looks like you got standard flanged bearing unit somewhere . . . . . . (some car engine water pumps are similar . . . old merc. . . )

MariusL
Mon 23 February 2009, 23:50
Allan,
I attached the drawings. Take note that the Z axis has a problem. I had to lift the motor plate by 40mm on order for the plate not to snag on the spider plate bolts. I took one of the large spacers and welded a 40x10 flat bar with a hole onto it and therby lifting the motor plate. I also had to extend the rack in order to achieve the correct travel that I wanted.

javeria
Tue 24 February 2009, 05:35
Good Job Marius - especially the belt drives.

where's the video?

MariusL
Tue 24 February 2009, 14:38
I meant to include these two pic to clarify the reduction assymbly. What is not shown on the drawings is that you must counter sink the bearing flange mounting holes and mount with m6 x 12 CSK cap screws from the front.
Take note of the hand of the motor plates. They only mount one way after you counter sink them. The Z axis plate only fits one way as well.

Jayson
Thu 12 March 2009, 06:22
I haven't posted in a while so I thought I had better give an update.
I have not made anything spectacular just cut out a few MDF letters for a friends kids. Something for them to paint and put on the wall no pictures but you get the idea.

Now on to something I do have pictures for :)

I have started working on the belt reductions. They are based on the ones that J.R. made, thanks for sharing... I ordered the pulleys and belts from a local supplier who got them in promptly for me. Unfortunately they did not get exactly what I wanted and instead of a 3:1 reduction I ended up with what would have been 2.9333333333333333333333333333333:1. This was not going to be acceptable as far as I was concerned, so they returned the 44 tooth pulleys and got me some 48 tooth. This results in a ratio of 3.2:1. There was not as much room with the original belt as I had hoped but at least it should still work.

3962

Due to the belt and pulleys not being exactly the same as J.R. used I had to change the design slightly.

3963 3964

The plates machined well and I managed to press the bearings in without much hastle. (made on my CNC mill)

3965 3966

My motors have 14mm shafts, but the only bearings I could get quickly and cheaply have 1/2 inch bores. This meant that I needed to make shafts with a small step in them, not a big deal to do just a little more time.

3969

I also make a few spacers for the bolts between the plates

3970

I was a little concerned as to how I was going to bore the small pulleys but I came up with a plan. I bored a piece of aluminium the same size as part of the pulley and then used loctite to "glue" the pulley into this while it was still in the lathe. I then drilled and bored the pulley. This kept it as close to centered as I could get it. I was very happy with the way this worked, and none on them slipped.

3967 3968

That’s about it for now. Hopefully I will get the pulleys drilled and tapped over the next few days so I can test them out.
There will be no working on the machine on Saturday though as I am off to an Air show with a friend but I am sure to be eager to get it finished once I get back.

http://www.airshow.net.au/avalon2009/index.html

Jayson
Wed 18 March 2009, 04:51
Sorry all for not posting on the weekend, I was just too excited about getting the gearboxes finished. They went together perfectly and have made a difference of course. My maximum speed has been reduced from 27 meters per minute down to 15 meters per minute. I am still happy with 15m/min rapids, the table is not all that big so it gets from one end to the other quickly. The added safety of the slower speeds is also a bonus ;)
Some pictures...

4019 4020
One X axis gearbox and the y installed

I got a delivery of some 6mm acrylic sheet during the week that I had hoped to make an edge lit sign with. The sign is 230mm high by 530 long and is to go over a friends BBQ area. I was not sure how it would go so I was conservative with my machining feeds and speeds. The finished depth was 4.5mm and this was done in 4 passes at 1900mm/min using a 12mm 45 degree V cutter. It took around 45 minutes to machine. If I was to do it again it would probably be in 2 passes at the same speed.

4021

The picture does not do the finished product any justice, it does look fairly good even if it’s me that says so :)

4022

Here is a close-up of one of the letters just so you can see how badly the machine does curves...

I still need to mount some LEDs and a way to hang the sign but so far so good.

That’s it for now, off to dream up another small project before I start the next big one.

jeffa
Wed 18 March 2009, 07:15
Jayson,

I assume you're being sarcastic about "how badly the machine does curves". This looks really good. Congratulations!

Jeff

Jayson
Fri 20 March 2009, 21:30
Hi Jeff,

Yep I was being sarcastic. I feel very happy with the cut quality.

Regards,

Jayson.

P.S.
4051
Sign Finished.

Rad Racer
Fri 08 May 2009, 17:39
Here's a couple of pictures of the complete reduction units...all axis's now have a 3:1 reduction drive installed.

There is a noticable difference in the smoothiness of operation and cut. Definently a worthwhile upgrade.

mikefoged
Thu 04 June 2009, 10:33
I decide to try and gear my Mechmate, the arc cutting quality began to be a little irritating. So I went out and bought some parts and the last ones came today.

Looking forward to get it all mounted, hopeful this will work out better for me.

The gearing is 3.2 : 1

domino11
Thu 04 June 2009, 10:45
Mike,
Did you machine the plates for your reduction on the MM? Give us some details on your reduction build! :)

mikefoged
Thu 04 June 2009, 15:39
I had the plates machine in a machine shop just 2 min drive from my home, the also made the shaft and machine the drive wheels. I made the drawings after J.R.'s model with a small modification. Thanks J.R. for sharing with us.
I just finish mounting the gears and I must say that it is running much better with the reduction on, tomorrow I will test cut to see if my ARC is smoother.

My feed rate is now 12000 mm/min and I'm very happy with that.

DeadGuy
Thu 04 June 2009, 21:46
A few more gearbox pictures.

Dennis

MattyZee
Wed 10 June 2009, 19:22
I am planning on having a belt reduction drive. (3.2:1). The geared motors are too expensive for me an i think i remember reading the performance of the belt drive should be superior than the gearbox motors (esp. w.r.t backlash).

Here are some CAD pics

4789
4790
4791

domino11
Wed 10 June 2009, 21:01
Matt,
Those pics look good. Are you planning on cutting them on the MM once it is done with the direct drive llke JR did?

MattyZee
Wed 10 June 2009, 21:12
I am in the process of seeing what they will cost to be made. I would try and cut them with direct drive but my motor brackets have a bore slightly smaller than my motors so they don't fit directly to the plates. So the Aluminium plates has been sized to fit my undersize motor plates and accept my motors. I will post pics when/if/how they are made.

stan stuart
Wed 10 June 2009, 22:57
Hi Matt
Under motor selection it does say the belt drive is better as far as backlash is concerned. If the price is ok woud you be interested in getting 2 sets made at the same time.

Robert M
Thu 11 June 2009, 04:25
Hi Matt,
3.2 :1, interesting combo !!
I too am planning to make my trany,

4792

4793

not only to save a few $$$....but mostly and the obviously, doing it for this sefl fuzzy fun feeling of making your own...:D

I managed in the past to find source & material (drive, driven gear & belt) to get 3.0:1 reduction, but could not find source & material to configure 3.2:1 ?
Could I ask you to tell us more about your source & part# for your gears & belt set up so we all could look it up ?
Thanks in advance, Robert ;)

MattyZee
Thu 11 June 2009, 05:15
Hey Robert,

Nice CAD model. What pitch belt are you using there?

Funny we a re talking about this today because my pulleys and belts arrived today.
4794

I have gone with the T5 (5mm pitch) size. To get the 3.2:1 i have chosen a 15T &48T combo. Used with a 56T (280mm) belt gives a centre distance of ~55mm. This only gives 5 teeth engaged at any one time which is 1 less than the recommended 6 so i went with the wider 16mm to compensate. It allows for quite a compact design.

I sourced them from a local supplier. www.piesau.com.au (http://www.piesau.com.au/) i'm sur they can be sourced easily anywhere.

Robert M
Thu 11 June 2009, 09:11
Matt,
My drawings and part for this drawings are strictly for a temporary conception purpose. I used for this set up a “XT pitch” with a 3/8” wide belt.
I understand it may be “frail” for our MM set up !!
Haven’t gone spending the required in verifying & calculating this YET :o
This tempo set up has an easy 6teeth engaged, so I stop at that and figured when time comes I’ll take the required time to select the proper set-up...TBC !

Out of curiosity, would you know who makes (what brand) are those pulleys ?

Castone
Tue 14 July 2009, 19:23
This post was originally put in a thread of it's own, but it became clear that it was another belt drive....

I made this drawing after looking at JR's drawings. It is made using two flange bearings, the oringinal motor mount design other than changing the holes size for the bearings and one laser cut mount. The flange bearings are recessed into each of the plates. This would be a low cost build for gear reduction.Once I get one put together and it will work properly, everyone is welcome to a copy of the drawings , as long as Gerald does not have a problem with me doing that.

Gerald D
Wed 15 July 2009, 00:15
Leo, the only big area of concern is the backlash between the gears. Maybe some springloading can be arranged?

Keeping them clean doesn't seem to be a big issue - the belt guys don't seem to loose sleep over dirt that might get into their drive. We don't have hassles with our z-axis rack/pinion either.

You are welcome to post drawings.

(As you have drawn it at this stage, your flanged bearing will foul the gantry)

bradm
Wed 15 July 2009, 06:19
Gerald, if I'm not mistaken, that looks like a belt drive, drawn with "belt removed for clarity".

Leo, I think placing the flanged bearing on the other side of plate that attaches to the gantry will solve the fouling, if you have enough room in there.

Gerald D
Wed 15 July 2009, 06:51
Leo picked the title "gear reduction" in a new thread separate to the belt reduction thread, so I assumed the novelty was in having gears instead of belts. But I wasn't quite sure so I changed the title to "gearbox" and kickstarted a gear discussion - it is worthwhile discussion, even if Leo meant something else (that has already been exhaustively covered) :)

Don't know if those flanged bearings exist in true life - they look a lot slimmer than the stuff I can get around here.

javeria
Wed 15 July 2009, 06:54
if gears are the point of discussion - my friend with the chinese machine has them all over the 3 point of motion.

its a simple spur gear arrangement - with a metal gear on the stepper and a nylon gear on the shaft providing the drive to the pinion.

I told him that if this does not last long enough we always have the beltdrives to replace em!

RGDS
IRfan

Castone
Wed 15 July 2009, 19:08
It is a belt drive design. I know it has been talked about in great detail. All I am trying to do is make it a little cheaper and easier . The bearing is from Mcmaster Carr Part # 5913K71. $11.33 each. Turning the bearing over did fix the clearance problem. I will post some pics when I get one together.Thanks , Guys

MattyZee
Wed 15 July 2009, 19:16
I think Leo's contribution is quite novel and a welcome contribution to the belt reduction concept. It makes a belt reduction drive feasible for those with only basic tools available to them (which is what i thought the concecpt of the MechMate was about?)
The bracket would be low cost if added to the initial order. If you mount the plates to a face plate on a lathe then you could bore the bearing holes to suit flanged bearings like these.
5305
The total cost should still be less than geared motors and you would have better performance w.r.t. backlash.

chopper
Thu 16 July 2009, 20:16
Hi, I have designed and built two sets of transmissions with 4:1 drives that are now being tested on two different mech mate machines with great results, they are quite actually very simple in design and I am thinking of offering them for sale as a kit, or a completed transmission, so depending on what your skill level is you will be able to use them, and I was wondering what the response to this would be here, if there would be enough of a demand to make this worth while, and keep the costs down so they are affordable, you could use a cheaper nema 34 motor on these transmissions and out perform the oriental motors with the gear reductions, and have less money in them,
let me know what you think.......
Thanks
//chopper

chopper
Fri 17 July 2009, 22:06
I will try to go a little deeper into these, they are made of steel, and utilize the original motor plates, I machined a bearing cup to fit into the hole in the original motor plates and welded them in, cut the holes into the new motor plate and slotted the holes for the motor to allow for belt tension adjustment, and also made a second bearing cup to fit into the new motor plate and welded them on, then machined a motor adjustment plate to fit between the motor and the new motor plate, this plate fits around the motors round extrusion on the front of the motors to allow the motor to fit flush to the new motor plate and allows for easy belt tension adjustment, the shafts are made from cold rolled steel, and have flats machined into them to accommodate the set screws in the 72 tooth pulley and the gear pinion.
then two plates were cut from band iron to hold the new motor plate to the old one at the proper distance so the pulleys would move freely with out binding or rubbing, and were welded in place, the clearances were checked and adjusted
as needed for proper fit of the pulleys....
these are made of steel so they could be welded to the original motor plates
and so they wouldn't wear out, also if a bearing locks up and galls a bearing cup, the cup can be replaced easily.

chopper
Fri 17 July 2009, 22:16
more pictures..... let me know if there is any interest in these I am thinking of maybe a kit with the bearing cups, new motor plates and the shafts,and band iron plates
or completed transmissions with everything but the motors, these will out perform plastic and aluminum, you will be able to get better,smoother,quieter cuts, than with the oriental motors with the 7.2 gear reductions for less money
it is quite amazing when the the backlash is removed how much easier the machine will cut through your material. it is almost effortless.
//chopper

Gerald D
Sat 18 July 2009, 00:38
Welded steel . . . . . now you have my interest! :D

I like it!

Doug_Ford
Sat 18 July 2009, 12:14
Beautiful craftsmanship Chopper.

chopper
Sat 18 July 2009, 13:42
Gerald,
if it isn't steel it isn't real! just and old expression from my metal fab days....
Doug thank you for the compliment,
I also wanted to ad that the parts came from stock drive here is their link http://sdp-si.com/
the 72 tooth pulley is part number A6A3-72NF03716 @ 31.97 each
the 18 tooth pulley is part number A6A3-18H3716 @ 10.98 each
the belt is a 200xl with Kevlar reinforcement part number A6B3-080037 @ 7.61 each
I bought the bearings locally, I think they were about 6.00 each ( I tried some cheap internet supplier but the bearings were crap)
the steel plates were scraps that I had laying around say 10.00-20.00 worth for all 4 transmissions I also went to my local steel supplier and acquired some cold rolled .5 inch steel round stock to make the shafts the rest is just time...
//chopper

Gerald D
Sat 18 July 2009, 22:55
Chopper, what level of machining (what tools), did you need to do?

MattyZee
Sun 19 July 2009, 06:55
While a belt reduction is not a new idea i thought i'd share pics of my pulley reduction drives. I got a friend of a friend to machine them for me from 1/2" 6061. Its only a 2.4:1 drive.

Pulleys and pinion bored to size and shaft. Still have to put flats on the shafts.
5376

Machined plate. The counterbore for the motor is slotted by 3mm total (+/- 1.5mm) for belt tensioning.
5374

Machined second plate. These were made to fit snuggly in the motor bracket plates.
5375

The mounting screws protrude by a little over 2mm in the pics but i didn't have the spring washers fitted yet.
5369

5370

A with the pinion (not fastened yet, just sitting there)
5371

Yes, the belt does clear the spacers :)
5372

5373

Jayson
Sun 19 July 2009, 07:04
Well done Matt. Great pictures.
These should work well.

Jayson.

jhiggins7
Sun 19 July 2009, 07:58
Great work Matt.:) Very professional. Thanks very much for sharing such detailed pictures.:) We are standing by to see how they work for you.

chopper
Sun 19 July 2009, 09:23
Gerald,
I used a late to turn the bearing cups,
an iron worker to cut the plate and punch the slots
and a welder, on the shafts I used a mill to cut the flats.
//chopper

chopper
Sun 19 July 2009, 09:38
here is a picture of a sign cut on my friends mechmate using the above transmissions, no sanding this is straight out of the machine, I don't know if you can see the detail in the v carved letters and the 3-d carving around the center of the Maltese cross where the ladder, helmet etc. are,.
the absence of cut marks and machine marks is obvious.
//chopper

Gerald D
Sun 19 July 2009, 09:49
Chopper, I have converted all your pics to .jpg's and removed the facility to load .bmp files. They were unreadable to some of our users. Also, a .bmp file takes up a lot of memory space - the pics are now a third of the memory size without any obvious loss in quality.

chopper
Sun 19 July 2009, 10:57
Gerald,
thanks for converting the pics, I don't know much about that stuff
//chopper

javeria
Sun 19 July 2009, 11:19
Lovely matt - that Alu will sure help a lot to dissipate the heat from the motors, tellin from experience!

jhiggins7
Sun 19 July 2009, 16:19
Hey Chopper. Lots of great work! Thanks for sharing.

Just a tip about pictures...now that you'll be using .jpg, you'll find that you don't have to resize your pictures down so much. .jpg seems to be MUCH more efficient than .bmp, so you can resize to say, 650 X SOMETHING and the picture will still fit within the guidelines. On the Forum the pictures will be a lot bigger and easier for us to see what you're showing us. In IRFANVIEW, when you select SAVE AS, you'll need to select the format .jpg rather than default to .bmp. Just a thought.

domino11
Sun 19 July 2009, 19:10
Chopper,
Those transmissions look top notch. Does your friend have a build log here? If not get him to post some pictures with blue and logo and get himself a serial number! :)

chopper
Sun 19 July 2009, 19:59
Heath,
no, he doesn't have a build here and neither do I on mine, I guess I didn't see the need since my machine is similar to Sean's #5 and that it isn't Blue
but I don't mind sharing the changes I made I think that is where my machine differs slightly from others, just like the transmissions, I had an Idea to do something like JR"s transmissions but I wanted to have a higher ratio than he used and I also decide to use steel, I believe for many reasons that using steel is better, and it allowed me to fit a higher ratio into the same space of JR's aluminum units for one, thanks for the comments, for those of you who PMed me and for those who want to know I will be determining a cost for both the completed units and for the kit, and maybe an assembled unit with out the pulleys and belts,
thanks for the feed back keep it coming...
//chopper

domino11
Mon 20 July 2009, 08:15
Chopper,
There have been other guys on the forum with non blue, and they still got a serial number! :) Yellow, Black, White and Red have all been used for one reason or another. Lets see some pics if you have the time.

smreish
Mon 20 July 2009, 18:16
Chop,
Thanks for the shout-out! :D
Ah, just post a pic or two, that's what keeps us all in this together...pictures.

PEU
Mon 20 July 2009, 20:37
you will be able to get better,smoother,quieter cuts, than with the oriental motors with the 7.2 gear reductions for less money
//chopper

Cheaper I understand since OM are $250 apiece, but why better?

chopper
Mon 20 July 2009, 20:51
Pablo,
the difference between the 7.2's and the belt drive is the backlash in the geared drives on the 7.2's there is about 5 thousands back lash,
I know this is not much and will probably depend on what you are cutting to see the difference, with the belts the back lash is eliminated making the cuts smoother, less power is need to make the cuts, since your router/spindle doesn't have to work as hard to do the same work, it is kinda hard to explain but one you see it in action you will understand, I wouldn't have believed it my self if I didn't see it, I made a set of these for a friend of mine and he said the same thing, that He wouldn't have believed it unless He seen it for Him self,
it is quite really amazing difference, since I installed the belt drives I leave my router set at 8k and never move it it cuts sooooo much better...I hope that helped //chopper

chopper
Mon 20 July 2009, 20:54
here are some more pics of the belt drives, I think these will be better tha the other ones//chopper

chopper
Mon 20 July 2009, 21:04
one more

MattyZee
Mon 20 July 2009, 21:20
They look great! I like the adjuster screw for the motor tensioning. Very handy.

MattyZee
Mon 20 July 2009, 21:24
I'm guessing your shaft is a straight shaft with no steps or shoulders on it? (So you can remove the shaft to install/replace the belt). Do you have any teflon shims/washers either side of the large pulley?

chopper
Mon 20 July 2009, 21:45
Matt,
yes the shafts are straight held in by the set screws on the pulley,
and no there are no washers or spacers between the pulley an the bearing
there is about 10 thousands gap between the pulley and the bearing,
I haven't experienced any rubbing from this, but if you desired you could you could put them in there, but since it is up against the bearing center that spins with the shaft there is no issue//chopper

javeria
Tue 21 July 2009, 01:15
how many teeth of of smaller pulley mesh with the belt??

chopper
Tue 21 July 2009, 10:46
Ifran,
if you look at post 19, you can see that the belt contacts about 1/3 of the pulley, it has 18 teeth, with would put it at about 6-7 teeth
//chopper

Gerald D
Tue 21 July 2009, 11:12
It has 5 teeth in full contact (110 degrees of wrap)

chopper
Tue 21 July 2009, 13:11
sorry didn't mean to mislead I didnt do any calc's to figure it out just by educated guess
//chopper

javeria
Wed 22 July 2009, 02:54
is not 5 teeth is contact less than the recommended value?, it will work no doubt , but..

Gerald D
Wed 22 July 2009, 03:41
5 or 6 teeth in contact seems to be very common for these typical belt-drive transmissions. You could always reduce the big pulley diameter and increase the center distances, but the number of teeth gained is not big.

However, I think we are already breaking the design rules in terms of torque vs belt size and enclosing for wood chips, so another rule or two broken might fit in with our "design philosophy"? :D

javeria
Wed 22 July 2009, 04:41
G- what i was considering was a small idler which will correct this (might require a bit larger belt - but it would then be much closer to the design specs of 6+ tooth engagement.

adding a idler should not be thought to be another complex thing - but a necessity in this sort of small center distance situation.

RGDS
IRfan

chopper
Wed 22 July 2009, 10:55
I do not know what the worry is about with how many teeth contact the pulley,
I do understand the more the better, but if you are worried about jumping a cog or ripping the teeth off the belt it wont happen, the machine will drag me across the table and not skip a beat, I think over engineering is also a problem,
//chopper

javeria
Wed 22 July 2009, 11:25
Per the link below

http://www.sdp-si.com/D265/HTML/D265T056.html

the minimum tooth engagement is required in the case of loaded pulleys and in our case I am assuming it is not, so I think we are still ok

chopper
Tue 28 July 2009, 20:29
for all that are interested I will be placing a post in the marketing section with pricing etc..
thank you //chopper

chopper
Sat 01 August 2009, 18:08
I am not trying to make a sale, I want you all to know that the belt drives are better, and as mentioned in above posts, no they wont slip, or jump cogs, the motors will loose steps before that happens, unless you are using really large motors, anyway here are some pics of the difference between the oriental 7.2 geared reductions and the 4 to 1 belt drives:

5562

The top thinner plate is the belt drives the lower the 7.2's

5563

These were cut with the same router, same type of bit, both bits were new when the cuts were made, no lube.

5564

I am also considering drawing these up in a dxf file so they could be included with the laser cut parts if Gerald will allow this, the bearing cups and the shafts would need to be machined, I am currently working on a way to make it easier build these, but quite frankly I don't think it can get much easier. I could supply the bearing cups and the shafts or you can get them made locally.

//chopper

chopper
Sat 01 August 2009, 18:14
you can see that the top has no chatter marks in them this is because the backlash has been removed, the aluminum looks kinda rough but the pics are really close up so you could see the difference also I checked the run out on the router and it is at 6thousands of an inch, just think of how smooth the cut could be with a spindle with 2-ten thousands run out to 1 thousands run out instead of a router....
//chopper

domino11
Sat 01 August 2009, 19:15
Chopper,
Those cuts look great. Do you have any comparison cuts in 3/4 MDF for example? Im sure Gerald would not mind you posting the DXFs for the reducers.

chopper
Sat 01 August 2009, 19:37
no I do not have a comparison for the mdf, I rarely cut it, I mostly cut aluminum and plastic,
//chopper

chopper
Tue 04 August 2009, 16:44
I have had little time to do much lately but I took some time today to draw up how the transmissions are made, so you can do these yourself, and if you do not have all the equipment need to do the work A local machine shop will easily be able to do this, all my measurements are in the inch system those of you using metric parts will need to convert the sizes to fit your bearings and shafts you are using
most of these measurements are not critical there is room for deviation,
the holes in this plate were punched with an iron worker, you could use a drill press, a drill and a vise etc... the center hole for the motor shaft doesn't need to be exact as long as the shaft clears the mounting plate and moves freely for adjusting the same goes for the holes where the motor bolts to the mounting plate, you may want to elongate them to fit what you are doing or if you need more adjustment, if you use an iron worker you will need to check to make sure that the plates are flat when you are done, the iron worker can curl a plate when punching holes in them.. the material I used was .250 thick
//chopper

chopper
Tue 04 August 2009, 17:04
the next part is the motor adjusting plate, this could be omitted if you desire,
I thought it supported the motor better, you could use washers under the mounting bolts, as an example ( use this information at your own risk ) the line to the left side of the drawing is where it would be broke (bent) at 90 degrees to the base this is where the adjusting screw pushes the motor to adjust.
the holes that the mounting screws go through need to be large enough to allow clearance from the mounting bolts I drilled mine .200.
the center hole is the key to this part, it should fit close to the shoulder on the motor but not bind on it, I cut mine out with a hole saw and then used a boring bar to size them correctly, but with the right size hole saw and a file you could get close enough, or a plasma cutter with a hole jig etc.. it doesn't need to be exact, it just needs to move the motor when you adjust the screw.
I used a .0625 1/16 of an inch plate to make these, when you brake (bend)
the part put the end with the large hole into the brake or vise if that is what you are using otherwise the big hole will distort, I don't know if the hole sizes will differ from motor to motor or if this is a nema 34 standard you will need to check your motors before you make the large hole in the plate to make sure that it is sized correctly
//chopper

chopper
Tue 04 August 2009, 17:10
the next part is the drive shaft
these are quite simple to make I used .5 cold rolled round stock, cut them to length and milled the slots in them at 90 degrees to each other,
you could put the flats in with a grinder, they do not need to be to deep just low enough so the set screw gets a good bite... this also makes it easier to remove the parts since the shaft will not get marred from the set screw making it difficult to slide parts on and off the shaft, but if you desire you could also omit the flats.
//chopper

chopper
Tue 04 August 2009, 17:45
next is the bearing boss,
this one is the hardest to make but not difficult if you have a lathe, or mill (drill press)
I used a piece of pipe to make mine,
what is critical here is the 1.125 bore that goes into the part you need this loose enough to put the bearing in but tight enough so the bearing doesn't spin
you also want to leave a little bit of the bearing sticking out aprox. 10 thousands of an inch ( this does not need to be exact) the reason for this is when you assemble the drives you want the big pulley to rub against the bearing not the bearing boss since the bearing is spinning on the shaft the same as the pulley it will not wear the pulley by rubbing etc. when you look at the drawing you will see two different side views because there are two different bosses ( this is an improvement from mine) the boss that is thicker will be welded to the new motor plates to give more clearance for the large pulley and the bolts that hold the motors on you will understand this when you assemble the parts, the smaller ones will work but since you are making them why not make it better..
once these are machined I checked the bearings fit, in the boss you want them to go in with finger pressure or a light tap with a hammer but you do not want them to tight or it will distort the small bearing making it hard to turn, also if the bearing is to loose all is not lost ( unless it is really loose)
you can clamp a small rod or similar device into your vise slide the boss onto the rod and heat the boss up red hot and quickly grab it with a pliers and put it into a cold bucket of water this will shrink it slightly and tighten up the fit to your bearing you can repeat the process till it fits, but you will only gain a few thousands doing this, ( this is the reason I chose to make these out of steel )
also when you weld these to the plates you need to weld them evenly around the boss to keep it from distorting the boss, also you want small welds not much more than spot welds I welded mine in three spots around the boss.
after you are done welding them check the fit of the bearing if it seams tight from the welding use a die grinder and ease a little off the boss where the welds are till the bearing fits.
when you weld the boss to the motor plates make sure you have them on the correct side of the plate, on mine I put the transmissions together so they would use the weight of the motor to push the pinion gear into the rack, on the z drive the plate goes to the outside of the mechmate plate for clearance issues on the z assembly also when you weld these to the plate make sure that you clamp them down tight so they do not move
while welding, also you want to weld them quickly when welding if you do not do them properly the boss will lift up on the side that isn't welded as the weld cools.
//chopper

chopper
Tue 04 August 2009, 18:03
next part is the stand offs they are made from band iron I use .250 thick
1.125 wide and cut them to length, mine were 2 inches log but if you are using the bigger bosses you will need to be 2.250 long there are two of these on the Y motor and both X motors, on the Z you will need to brake the band iron to go around the big pulley for clearance if you look back at the pics you will see what I mean, I attached it to the 45 degree angle on one side of the motor plate, you need to put these in a location that will allow you to put the big pulley in place and remove it if say a belt breaks, look at the pics for reference
also when assembling these I put a piece of card board between the pulley and one of the bearings for clearance ( milk carton box) or a thin washer will work. I would rather have to much of a gap here than not enough, it is easier to squeeze the plates than push them apart.
also be careful when welding the stand offs in if you get them to hot you could warp them.. and this will require more work to get them straight...
when you Finnish welding and let the part cool check the clearance on the pulley and the bearings
if this gets to tight you may need to push them apart with a porto-power duck bill, to get the clearance back that is needed for the pulley to spin freely
no pics for these reference back to the pics of the drives if you have questions please ask
//chopper

chopper
Tue 04 August 2009, 18:06
if you want to know I am running the kelling
450 ozin motors # KL34H260-60-4A

chopper
Tue 04 August 2009, 18:25
also if someone wants to add these to the laser parts kit it would make it a lot easier to build these things , then I that would be needed would be the shafts,stand offs and the bearing bosses
//chopper

Gerald D
Tue 04 August 2009, 23:24
Thanks for all that info Chopper.

Castone
Thu 27 August 2009, 17:44
I have still have been working on a low cost belt drive and think that I am about there. I have used two press fit bearings with the flanges to the inside,I also added a thrust bushing on each side of the pulley so there would not be any play. The bushings are .500" ID by .630" OD so they will ride on the inner race of the bearings. Pictures do not show the standoffs. These bearings were press fit into the laser cut holes with no machining. I inspected the parts on our CMM to check the roundness of the cut and before and after pressing the bearings in. Bearing flex was about 3 tenths of a thousands.The laser cut plates ran out about one and a half thou true position.But by using a thrust bushing on each side and turning the flanges both to the inside the press fit can be a very light fit. I have counter sunk all the bolts on the working side of the motor mounts so that it is flush. The stand offs on that side could be tack welded after assembly. Thanks goes out to JR and all the others who have help by ofering there input. Total in parts so far around $180.00 for all 4 motors not including laser parts and standoffs. I will be glad to share the plans I have to anyone building a MechMate. I will post some updates after some more testing.

domino11
Thu 27 August 2009, 22:27
Leo,
Looks very interesting. :)

Gerald D
Thu 27 August 2009, 23:40
Wow, you have amazing tolerances on your laser cutting!

I don't think that all laser companies have the same tolerances (and kerf width) so any published plans would have to be treated with caution. However, there is nothing wrong with cutting slightly undersize and then licking the holes with a file or pencil grinder.....a dash of LocTite will always be welcome.

On countersinking lasered screw holes:
Here at my factory, I make the lasered hole much bigger so that the countersink cutter has less work to do - it does not weaken the joint at all. Further, the hard crust of the lasered hole tends to wear only one spot on the countersink cutter - in my day job designs I vary the "pilot" hole diameters to spread the wear on the cutters. But I avoided doing that in the MM designs because there would have been too many questions. :)

Castone
Sun 30 August 2009, 08:46
In the drawings I will under size the bearing hole as it is fairly easy to open it up , with hand tools. I did have to play with the kerf to get this cut, but was repeatable. I think I may start offering these in the kits, which would be real low cost way of building a belt drive and could be built by most all MechMate builders. And as I mentioned before since the bearing flanges are inside and there is a bushing on each side of the pulley that rides on the inner race of the bearing. The press fit only needs to be tight enough to keep the bearing housing from spinning and yes a little green loctite would not hurt anything. So far everthing is working very well.

obuhus
Wed 16 September 2009, 03:03
September 2009. Has begun assemblage belt-drive.
Many thanks to Gerald for the help with step-motors. After long searches and reflexions I have decided to go the checked up road, but have a little changed a traditional design of the mechanism of a reducer.
Reducer classical 3:1 (pulleys LS27T5/20-2, LS27T5/60-0, a belt 16T5/355). Has more low loaded drawings in dxf. It is not accurate a little - forgive, I only have started to study AutoCAD.

sailfl
Wed 16 September 2009, 03:09
Dmitiry,

Looks like you have a great start and Welcome to the site.

Though it may seem like you need to have lots of fans to combat the heat, the one fan works find. I agree with Irfan.

Your rails and belt drives look great. Keep taking pictures, we like to see what others are doing.

javeria
Wed 16 September 2009, 04:22
I love your reduction drive - good thought given to it.

javeria
Wed 16 September 2009, 08:41
G' I think seriously we should standardize this design for the reduction mechanism. Its metal laser cut welded and no bends reqd and can order a special shaft and pinion combined. Also we can avoid all nut's by tapping the motor plate by making it 6mm thk, that way we can use screw of upto M6.

ok nuts are reqd to adjust the belt tension a bit :)

Gerald D
Wed 16 September 2009, 09:25
Dmitriy's design seems to have all the bearings (or one wide bearing) on the outboard side of the reduction unit.

javeria
Wed 16 September 2009, 09:40
yes thats what I like too - hmmm is that wrong, ???? I feel it would be ok - I think one more of our forum member has done this already.

obuhus
Wed 16 September 2009, 12:17
Dmitriy's design seems to have all the bearings (or one wide bearing) on the outboard side of the reduction unit.

Gerald, you are confused with length of a shaft from the bearing to a gear wheel? In my case the shaft is made of stainless steel. For a usual steel there is more reliable configuration, but more bulky.

Gerald D
Wed 16 September 2009, 12:55
I am a little bit worried about the flexibility of the shaft. It is quite a long distance from the bearing to the pinion gear. There is no real difference in the flexibility of stainless steel compared to usual steel - the vibration frequency will be the same. It will be interesting to see if you get good cutting results.

bradm
Wed 16 September 2009, 13:26
Would something like a simple sintered bronze sleeve in the opening by the pinion gear help or hurt?

obuhus
Wed 16 September 2009, 13:41
I am a little bit worried about the flexibility of the shaft. It is quite a long distance from the bearing to the pinion gear. There is no real difference in the flexibility of stainless steel compared to usual steel - the vibration frequency will be the same. It will be interesting to see if you get good cutting results.


Gerald, I thought of it. For myself I have chosen a variant with stainless steel - there was at hand suitable preparation. And design more graceful. But the second variant obviously is stronger. And quality of processing we will see when will earn :)

Gerald D
Wed 16 September 2009, 22:41
Would something like a simple sintered bronze sleeve in the opening by the pinion gear help or hurt?

It would remove the concern about flexing. But then that bronze sleeve becomes the most heavily loaded bearing in the system and needs to be upgraded for long life. Which puts you back to having a standard bearing there in the first place.

Gerald D
Wed 16 September 2009, 22:43
I think this picture (http://www.ez-router.com/index.asp?PageAction=VIEWPROD&ProdID=158) at E-Z router is new. Might give some ideas; the shaft is static.

obuhus
Thu 17 September 2009, 00:44
It seems to me, I have thought up an absolute variant of a reducer. It has a possibility to protect a belt and pulleys from a dust. In drawing I have designated a cover a blue line.

javeria
Thu 17 September 2009, 01:10
that is a good design - but for motors with different height it might be problem. so need to decide what depth it will be.
may be that can be left as a motor dependent variable.

also since the plate is laser cut on the pinion side a flange and bolt arrangement might not be necessary on the shaft case, we can just have the casing of the shaft match with the hole in the plate and make it go thru.

RGDS
Irfan

sailfl
Thu 17 September 2009, 02:23
I like the way they did the stops.

But back to the belt drive plate, it would seem to my thinking that having the shaft that drives the pinon is less likely to have problems if it has two plates with bearings on each side of the larger toothed pulley.

Gerald D
Thu 17 September 2009, 02:50
I forgot the picture of the drive gear (http://www.ez-router.com/index.asp?PageAction=VIEWPROD&ProdID=117).

sailfl
Thu 17 September 2009, 03:00
I was too quick with my comment about the link not work. Sorry!

Greeny
Thu 17 September 2009, 15:18
I like the idea of a fixed shaft with only one motor plate.

The small pinion limits the shaft size though, i wonder if something like this would work?

smreish
Thu 17 September 2009, 18:31
...or you could weld the small pinion to the larger and just use the smaller diameter shaft.
That would make all your parts off the shelf and a simple "bolt" on like shaft for the assembly.

Just thinking outside the box.

Gerald D
Thu 17 September 2009, 20:26
We have a space constraint caused by our gantry and y-car end plates, which at present nearly touch the grub-screws in the pinions. (Due to the heap of guests in our house, I cannot access the cross-section drawing right now)

Greeny
Fri 18 September 2009, 03:39
The interference issue seems to rule out fixing the pinion in the pulley.
how about this?
(pulley wheel is now narrower, for a 10mm belt)

Greeny
Fri 18 September 2009, 05:13
Or maybe,

Gerald D
Fri 18 September 2009, 05:24
I think the overhang beyond the bearing is too much, and I don't really see the advantage in having a single plate.

Greeny
Fri 18 September 2009, 07:47
I was mainly thinking of weight, but i suppose a single plate would have to be thicker, negating most of the difference.
The distance from the bearing was always a worry. initially it was much closer, but interference..well interfered :).

woodfish510
Thu 24 September 2009, 08:06
Hi:
What size and pitch is the rack gear?

Gerald,
if it isn't steel it isn't real! just and old expression from my metal fab days....
Doug thank you for the compliment,
I also wanted to ad that the parts came from stock drive here is their link http://sdp-si.com/
the 72 tooth pulley is part number A6A3-72NF03716 @ 31.97 each
the 18 tooth pulley is part number A6A3-18H3716 @ 10.98 each
the belt is a 200xl with Kevlar reinforcement part number A6B3-080037 @ 7.61 each
I bought the bearings locally, I think they were about 6.00 each ( I tried some cheap internet supplier but the bearings were crap)
the steel plates were scraps that I had laying around say 10.00-20.00 worth for all 4 transmissions I also went to my local steel supplier and acquired some cold rolled .5 inch steel round stock to make the shafts the rest is just time...
//chopper

chopper
Thu 24 September 2009, 23:24
the parts listed here are for the belt drives which has nothing to do with the rack and pinion, the rack is 20dp @ 20 teeth per inch same goes for the pinion,
and the pinions I run are 20 tooth..
//chopper

eesanopi
Sat 26 September 2009, 08:06
Take a look at cncrouterparts.com, they are selling a 3:1 belt drive, this belt drive is similar to the ez-router's belt drive. They show how the sytem works with two cool videos.

http://cncrouterparts.com/product_info.php?cPath=21&products_id=50

Richards
Sat 26 September 2009, 08:20
Edgar,

It looks like the 3:1 belt drive that you referenced is for use with 23-frame sized motors. I would not recommend that size motor. They're just too small for the job.

eesanopi
Sat 26 September 2009, 08:53
Edgar,

It looks like the 3:1 belt drive that you referenced is for use with 23-frame sized motors. I would not recommend that size motor. They're just too small for the job.

You´re right, the intention with my post is only to show the system because might give additional ideas.

Austint
Mon 05 October 2009, 11:12
Hello,

I have been a forum member for a while and just recently became extremely interested CNC routers. I have a degree in mechanical engineering and electronics and I am particularly interested in reduction transmissions for CNC machines. Over the last few months I have designed a belt reduction transmission that I would like to soon release! There are some great minds on this forum and it would be beneficial to receive some feedback before I finalize the design. I would primarily like to know the desired final gear ratio? The transmission will utilize either a nema 23 or a 34 motors. What would be a desirable final ratio for the design? The transmission can be between 3-1 and 9-1 with the current design. Any feedback would be appreciated.
Thank you,

Daniel Thompson

Gerald D
Mon 05 October 2009, 11:53
It is all a compromise . . .

3-1 is practical minimum for simplicity, low mass, low space needed, low cost, high reliability, high tolerance of flying dust, and still a significant improvement over a direct-drive.

9-1 sounds as if it will give the biggest improvement over a direct-drive, but how does it affect the other factors mentioned above?

Austint
Mon 05 October 2009, 13:30
The 3-1 is the most simple but the design is modular in that a second stage can be added at any time.
1. Mass
The transmission will be cast aluminum and will use aluminum pulleys for the reductions. The only parts on the transmission that are steel will be the shafts, bearings and some misc fasteners.
2. space needed
needed space depends on the final ratio so I don't have definite dimensions at this time. I certainly don't want to build a transmission that will not fit the mechmate requirements. Any information on size requirements would be appreciated!
3. Cost
Final cost will again depend on the ratio. Two stages will cost more than a single stage but will be worth the reduction. I can say that after I add the second stage cost difference between 3-1 to 9-1 is not significant. I will know more on cost after we do a prototype run with the casting shop.

4. Reliability
Reliability will not be affected by the final ratio. Pulleys and belts are selected to maintain a sufficient number of teeth in contact. I am working with Gates to select a belt size that will meet the tension requirements and still be an off the shelf item. Other factors such as shaft sizes and bearing placements are being considered and evaluated for deflections. There is a big difference in a part that works and one that works well:)

4. Dust

Currently the design is an open design , the belts and pulleys are exposed. We could integrate a cover into the design if needed? Those with open designed reductions how are the reductions tolerating the dust?

Thank you

ger21
Sat 10 October 2009, 20:57
The best ratio depends on the specific motor used. As you increase the reduction, you get diminishing returns, as the steppers torque drops as rpm's increase. Different motors have different torque curves, so you'd need to tailor the reduction to a specific motor/drive/power supply combo for maximum performance.

chopper
Sat 10 October 2009, 22:29
this maybe true but in the process of reducing the output it also multiplies the torque, so if you had a 450 oz-in motor and were using a 4 to 1 drive you would end up with 1800 oz-in of torque ( I am sure that a small amount will be lost in the transmission assembly) but for the sake of simplicity we will say it is zero loss so if you are running fast enough to loose half of your torque you would still be at 900 oz-in of torque which is well above what you would be getting from the oriental's with the 7.2's and I doubt that you would have that much loss or even close....
//chopper

Gerald D
Sat 10 October 2009, 23:27
Chopper, the oriental 7.2 behaves like a belt-drive at 7.2 ratio. For a discussion on the best ratio, there is no need to bring in a discussion of gear vs. belt.

Gerald D
Sun 11 October 2009, 02:10
The best ratio depends on the specific motor used. . . . .

. . . . and the type of cutting that you want to do, and the jog speed you want to achieve while not cutting.

On the cutting, working in soft woods is different to working in hardwoods.

The question of "which ratio is best" would be the same as asking the owner of a stickshift car "you can only have one gear - which one do you want?" (Of course, if you have a very powerful engine, the exact choice of gear is not so critical)

chopper
Sun 11 October 2009, 08:59
Chopper, the oriental 7.2 behaves like a belt-drive at 7.2 ratio. For a discussion on the best ratio, there is no need to bring in a discussion of gear vs. belt.
Gerald,
there was no intension of discussing belt drives vs. the 7.2's
the only reason was for the loss that is generated through the gear drive which limits the 7.2's to around 700 to 750 ozin and all I am saying is if the 7.2's will drive the gantry with 700-750 ozin then the other reduction will be fine with a 50% loss of power since it will still have more than the 7.2's
and the reason I compared to the 7.2's is it seems to be the standard that is used here
//chopper

Gerald D
Sun 11 October 2009, 11:50
There is a serious misunderstanding of the amount of torque available from a "OM 7.2" motor/gearbox package. It gives a lot more than 700-750 ozin, but the spec says that you must not design your system to use that extra torque. Same goes for the belt-drive - the thin belts that most use for these reductions should also not be used at the torques levels that are needed on our routers.

For the OM 7.2, there is NO "loss that is generated through the gear drive which limits the 7.2's to around 700 to 750 ozin" That limitation is put on by the design engineer who needs to guarantee you long life running 24/7 under full torque.

chopper
Sun 11 October 2009, 17:02
Gerald,
if the engineers limit the torque it is for a reason, that being it will cause gear wear or failure, in other words the gear box cannot handle the load, so what good is a higher rating of torque if you cannot use it?
so the limitation of the 7.2's is going to be at the rated torque which is in the 700-750 oz-in range which quite frankly I could care less about.
but as far as the belt drives go the xl belts with .375 inch width have a breaking point of 390 lbs, which is equal to 74,880 oz-in
so if the operating range is say half of the breaking strength that would put us at 195 lbs or 37,440 oz-in which is way more than these motors can produce, I also have to believe that the operating strength of these belts would be closer to 75% of the breaking point which would be 292.5 lbs.
or 56,160 oz-in which is also way more than the motors will produce.
so I guess I will have to disagree with you that these smaller belts will not handle the load, the specs show that they will, and can handle the load what you have stated is incorrect.
//chopper

Gerald D
Sun 11 October 2009, 23:03
Chopper, for belt drives, the engineers publish charts like this:

6645

The bottom left corner of the chart starts at 0.1kw (100 Watts) and 100rpm., which would be quite a common situation for us with our routers. The engineers there deem it too much for a XL belt.

This is just a general example of what the supplier's (belt or gear) engineers put out in public. But we have seen that our router application happily runs beyond the supplier's spec . . . . . for both belts and gears.

Gerald D
Mon 12 October 2009, 09:35
A chart which says to limit XL to 180 oz.in torque:
http://www.torquetrans.com/pulleys/timing-pulleys/images/xl-l-timing-belt-pulleys.pdf

http://www.misumiusa.com/CategoryImages/Metric_2009_pdf/p2823.pdf

http://www.roymech.co.uk/Useful_Tables/Drive/Timing_belts.html

http://mechatronica.eu/en/design-manuals/synchronous-belts/Belt%20drive%20selection%20procedure%20(21-26).pdf

chopper
Mon 12 October 2009, 19:31
Gerald,
I have never found charts like that before,
but I also didn't see the charts list what belts they were testing,
and what I mean by that is what type of material the belt was made from and what type of material was used to reinforce the belt, unless I missed it....( the belts I am running are reinforced with Kevlar and are much stronger than the regular XL belt)
there is a lot of reading there and I am not going to go through everything,
what it comes down to is you may want to run a heavier belt so built a transmission with a heavier belt, not a big deal, I have had zero problems with the XL's I am planning on changing them out every so often which I feel would be good maintenance. I don't know if this is necessary I will monitor them, to see what happens, also the pinion will walk out of the rack before you could put enough force on the belts to damage them.
but the issue still remains with the back lash in the gear heads of the OM 7.2's
and this you cannot get away from with out switching out the transmissions,
I am only stating what I have done you can choose to use the information or not, it really doesn't matter to me my machine works and works well, with great cut quality that quite frankly I thought I would never get from this type of machine, I also know that it is not a fluke since I have had the same result on two different machines, the second machine had a bad chatter issue just as bad a Nils, if not worse, in fact it was so bad that when he cut a file and the machine would come back to zero it would not be in the same spot, which was caused by backlash, once the belt drives were installed the problem was gone, you can run a file over and over with 100% repeatability
and accuracy, on both our machines,( just the other day I ran a repeated file over and over the first few cut parts were not deep enough so I adjusted the depth and cut the rest of the pieces and set the first part back in the jig and it dropped right into the drilled holes with out even touching the sides of the existing hole) I know you cannot do this with the 7.2's,(I had them on my machine ) now maybe you don't want to or need to have that kind of accuracy,and again I really do not care but I thought why not make the machine as accurate as possible,
that is why I shared what I had done, I am not trying to mislead anyone
all I have to say is the proof is in the cuts,
also I want to ask if any one using there mechmate can get this quality of cut with there machine, I really want to know I mean no disrespect this is a request to see the cut quality comparisons if you need to know it was cut in 6061 .250 thick on the diagonal to the machine, ( with a Milwaukee router) I am quite sure that you will not see the 7.2's be able to accomplish this, again this is from my experiences, with having the 7.2's they seem to be tight at first but as they break in the backlash becomes apparent..I am not going to argue about belt vs 7.2's this will be my last statement on the subject unless asked, you can see that they work by the quality of cut produced,
//chopper

Gerald D
Tue 13 October 2009, 00:08
Relax a bit Chopper. Nobody is saying that you have built a bad drive, and nobody is saying that the backlash in a geared motor can be ignored.

I do not understand how these marks. . . .

6696

. . . . can be caused by backlash in a geared motor. Those marks are about 1/4" apart. (since been confirmed that material is 1/4" thick)

Did you see such widely spaced, very regular marks when you were running geared motors? I cannot recall that your "before" photographs showed anything like this.

Bear in mind that there are many other users out there with geared motors who are not seeing these wide apart, even spaced marks. (I don't call that "chatter")

chopper
Tue 13 October 2009, 09:03
Gerald,
mine were similar but not as deep,
the other machine that my friend has was very similar to this if not worse..
what I think happens is once the first pass happens it sets the chatter for the rest of the passes, the bit will follow the path of least resistance and that is why you end up with the chatter lining up from top to bottom, on different cut paths, I also believe that the equal marks along the cut path are generated by the tool, because it is say a two fluted up spiral bit it will grab or dig into the material at equal measurements, since the marks are about an 1/8 inch apart I would say he used a 1/4 inch bit two flute up spiral, but this is conjecture I cannot prove it.
ok I will back the springs of a little bit(relax)
//chopper

sailfl
Wed 14 October 2009, 03:07
Gerald,

The material I cut was .25" in the picture you have marked.

Gerald D
Wed 14 October 2009, 04:36
Thanks, the post above has been edited.

salewis
Fri 06 November 2009, 18:37
Do you have the transmission plates available?

Stan

chopper
Fri 06 November 2009, 21:00
I can make them for you if you want or you can build them from the plans
//chopper

chopper
Sat 14 November 2009, 13:34
these bits are for the cnc machine world like a haas or equivalent,
also onsrud makes some look up there 83-300 series www.onsrud.com
feeds and speed are listed there, I want to throw out a disclaimer here I have done quite a few things to make sure my machine is tight... and backlash free,
without getting into a pissin' match I just want you to know that these cuts may not be accomplished with out the proper modifications to your machine excessive backlash may cause adverse effects like bit breakage etc. and always wear safety glasses, I also want to state that I have an extensive background in metal fabrication / machining / welding etc. which might give me a slight edge on experience in doing this type of work...... and here are a few pics of mild steel 1/8 inch
//chopper

chopper
Sat 14 November 2009, 13:57
What were your feed and speed settings for this? Also what kind and size of bit (Mill bit?) did you use?

I used a 1/4 inch shank with a 1/4 inch tool dia. the feeds and speeds may very from brand to brand, I used 20 ipm @ .020 cut depth, if you have a machine shop supplier near you or on line with a little looking you will be able to find some that work, just specify that you are doing high speed machining..
the bits I used are from my local supplier and it is there house brand that I used.
//chopper

chopper
Sat 14 November 2009, 13:59
chopper
can you post the bit data?, brand, type, and where to order?

Thanks

Im a fan of your work!

I hope the above answered your questions also if not please ask I will help with what I can.
//chopper

salewis
Sun 15 November 2009, 05:45
Chopper, you mentioned "mods" to the MM, what kind of mods (beyond the 4:1 trannies)?

Stan

chopper
Sun 15 November 2009, 09:17
I modified the Z,
and the rack,
and the spider, but the most important thing is to spend the time to make the machine right, pay attention to the details and tolerances, make sure things are square, and parallel, etc..if you look under my build (http://www.mechmate.com/forums/showthread.php?t=1951) you can see some of the z and spider mods.
//chopper

lumberjack_jeff
Sun 15 November 2009, 11:16
That is very nice work chopper.

chopper
Sun 15 November 2009, 16:11
here are some more pictures. these are MM motor plates, kinda funny a MM making a MM,
these are .250 thick and are really smooth these pics are blown up a bit, you can reference to the quarter, I do not know how you can not believe that the 4 to 1 belt drives do not make a difference after seeing these cuts. I am getting better cuts in steel than most of you can get in wood,
//chopper

it has been brought to my attention that the above statement has upset some of you,...the statement I made was in no way meant to be offensive, but I can see how it could be taken that way even though it was not intended to be...( for that I apologize I am very direct and to the point and some times it is taken the wrong way)
all I want to do is show you all what is possible with your machines to think out side the box, to do what they say cannot be done, did I think my machine would cut steel ? or stainless steel? no way but I tried it to see that is all, and to my surprise it did,

as I stated before I have a background in metal fabrication, welding and machining..that allows me to understand what I am doing, and may also give me an edge.. when I was in metal fab we did a lot of work for demanding customers that required perfection, and I have brought those work ethics over into all the work that I do, the mech mate is no different, so what I am saying is the MM is what you make it, if you want to perfect it you can...(from the above posts you can see what is possible), if you do not that is your choice, some will be able to do this and some will not, that I am afraid is a fact, (but the ones who can shouldn't be held back by the ones who can not) and it shouldn't stop you from trying, and as time goes on your understanding will grow and so will your abilities, if you never try you will never know or achieve the impossible,

I also want to say that my belt drives are not the cure all for all the problems that are faced in the building of the MM ( they will not make up for a poorly constructed machine) if you do not spend the time to understand what you are doing or cheap out on parts, or decide that your rails are good enough, or compromise on the quality of your fabrication, you will be limiting your machine.....you and only you can decide what you do, so you can choose to limit yourself or not. but you cannot blame Gerald, myself or anyone else if your machine doesn't preform the way you want after all you built it.. the advise here is given freely you have to decide weather or not you use it and if you do you are responsible for the out come no one else.
with that said all I want to say is good luck on your builds..
//chopper

chopper
Sun 15 November 2009, 16:15
That is very nice work chopper.

thanks
//chopper

Robert M
Mon 16 November 2009, 05:14
Offended or not ( BTW as a woodworker by trade, I one of those exception who was not offended…) I can see by you direct approach why some where !
Among critics, one thing some of us can and should admit, we thank you for your contribution and the time it takes to share some of your result to us.
Yes I agree you should tame or change some of those words as it would get your message across smoother without changing the context, but on the other hand, as with many other here, we also have to understand where one wants to go when a statement is made ! It goes both ways !!!....and sometime ( personally I’d say most often…but that is my opinion) sometimes other tent to jump to fast as if it was a personal offence !
Well, for what my opinion is worth, I thank you for your contribution as other should also pad their back to contribute POSITIVLY to this great community that Gerald started !
Amicalement, Robert ;)

jhiggins7
Mon 16 November 2009, 07:23
Chopper,

I agree with Robert. Please keep your unique and substantial contributions to this Forum coming!

chopper
Mon 16 November 2009, 09:30
Thanks,
I do not intend on going anywhere, unless I get into big trouble,
I just want to clear the air so to speak and I know that some of the stuff I say is taken the wrong way I am the first to admit I am no word smith, so I just wanted you all to know why I say what I say, but I will try to use a better choice of words in the future..
//chopper

MetalHead
Thu 19 November 2009, 12:05
OK folks - I drew these in Visio and exported them to DXF format. Can someone check me on the mesument and placement of the holes.

The motor plate holes seem to be to far to the right of the bracket, but I think I did all by the measurements.

I centered the motor drive shaft hole and the slave pully hole. I figured that was correct, but it was not on the drawing that I could see.

MetalHead
Thu 19 November 2009, 12:09
Chopper - you may have addresed this, how does the assembly come apart to replace the belt?

NM - I found it .

I attached it to the 45 degree angle on one side of the motor plate, you need to put these in a location that will allow you to put the big pulley in place and remove it if say a belt breaks, look at the pics for reference

MetalHead
Thu 19 November 2009, 12:24
OK reading that led me to this mod to save welding , but it would add some bends.

riesvantwisk
Thu 19 November 2009, 13:11
Chopper,

If I may Ask... what is the purpose of the bearing cups?

I am highly surprised that you could do the steal with it, amazing!
Good job, good pictures.. thanks

Ries

chopper
Thu 19 November 2009, 16:24
Ries,
the bearing cups or bosses hold the bearing that the shaft turns on,
the shaft that has the large pulley and pinion..
chopper

chopper
Thu 19 November 2009, 17:00
OK reading that led me to this mod to save welding , but it would add some bends.

Mike, I see you have added "wings" to the design, I think this is a good idea..
however I do not know if it will work since the plate that goes onto the pivot point arm goes somewhat behind the plate, you would need to try this to make sue it will fit correctly.
I actually redesigned the plates to make them easier to build they remove the funky angle bended plates and replace them with straight ones, you could add "wings to these much easier, take a look and let me know what you think,
they also guard the pulley ( to keep fingers out and add a dust shield if desired) I also wanted to add that the hole in the bottom of the new Z plate is not to size I left it small so it could be drilled out to what ever size is desired ( I am using these on a plasma machine) so we will be drilling them to an inch size
//chopper

riesvantwisk
Thu 19 November 2009, 17:14
Ries,
the bearing cups or bosses hold the bearing that the shaft turns on,
the shaft that has the large pulley and pinion..
chopper

Chopper,

in that case, is this because the metal is potentially to thin to hold the complete ball bearing?

I may sound like a dummy, but never did any metal working, just trying to understand :)

Ries

chopper
Thu 19 November 2009, 18:01
Ries,
never apologize for asking questions,
you are correct in the respect that the bearings are wider than the metal plates the plates are 1/4 inch thick and the bearings are a little more than 3/8 inch thick if I remember correctly, and it is also because the MM motor plates already have a hole cut in them way bigger than the bearing, also the bearing boss requires machining to fit the bearing correctly and it is easier to machine a small part in the lathe than a large plate, I suppose you could use a flange bearing but most of them are really poor in quality, and with the bearing boss the bearing is supported correctly, do it right the first time and you wont have to do it again, at least that is the way I look at it...
//chopper

riesvantwisk
Thu 19 November 2009, 18:14
Ries,
never apologize for asking questions,
you are correct in the respect that the bearings are wider than the metal plates the plates are 1/4 inch thick and the bearings are a little more than 3/8 inch thick if I remember correctly, and it is also because the MM motor plates already have a hole cut in them way bigger than the bearing, also the bearing boss requires machining to fit the bearing correctly and it is easier to machine a small part in the lathe than a large plate, I suppose you could use a flange bearing but most of them are really poor in quality, and with the bearing boss the bearing is supported correctly, do it right the first time and you wont have to do it again, at least that is the way I look at it...
//chopper

Chopper,

thanks for the explanation, all clear now!
With your permission, I would like to take your plane and build my own next year based on your design.

Ries

chopper
Thu 19 November 2009, 18:28
Ries,
these plans are here for all to use, use them change them what ever you want to do that is why I posted them,
//chopper

MetalHead
Tue 24 November 2009, 05:44
Have you built a tranny with these plates yet? I would like to see pics of it.
Does it use the same bearings,gears and belts?

chopper
Tue 24 November 2009, 09:32
it is just a cosmetic change all the parts are the same,
//chopper

MetalHead
Tue 24 November 2009, 11:02
So just so I am following (I am slow :) ) . The belt drive plate is the same but is rounded off for laser/plasma cutting.

The Z plate is a Moded M510312PB swing plate?

Could I just mod M510312PB plate and the M510322PC motor plate to take the gears and shafts with regular bearings? ie take out the large holes?

Also would it be possible to use the stand off "posts" (4 of them) to join the plates instead of welding them? This way all of it could be screwed together.

chopper
Tue 24 November 2009, 16:57
Mike,
the plates are basically the same it is just mostly cosmetic..
you are correct the Z plate is modified, from the stock MM plate the only reason for this is to eliminate the funky bends on the Z spacer plates... go back in this post and look at the Z drive plate pictures, you will see what I mean http://www.mechmate.com/forums/attachment.php?attachmentid=5414&stc=1&d=124814485
the roundness is to guard the pulleys from fingers etc. getting into them, and to make it easier if someone wanted to build covers for the drives to keep out dirt etc.

you could use stand off posts if you like, I did not design for them I feel that the welding makes a much stiffer part than bolting, bolts can move welds do not, also it is harder to fit the 72 tooth pulleys in the space if it is bolted together, so you may not get the 4 to 1 ratio,( I believe that the 4 to 1 ratio with the 20 tooth pinion is the optimal resolution)

you could take out the large holes if you want and re-size them for bearings, this is why I used the bosses since the bearings I used are .375 wide and the plate is .250 wide you wont get the proper support for the bearing, and if the fit is to tight the bearing will bind, to loose it will fall out,

I also built them to be used with the stock MM motor plates since they are included with all the laser kits, why not use what you already have, that way
I thought it would be an easy transition to the belt drives, if some one decided later on to go to them like I did,

Mike feel free to modify change alter redesign, etc..etc.. you just might come across a great design in the process, I am just sharing what I have done, I am sure someone can improve it,...
//chopper

chopper
Tue 24 November 2009, 18:01
Mike,
I also wanted to add that the bearing bosses (cups) were designed to fit into the holes cut into the existing motor plates that is why there is a shoulder on them and they are machined to fit into them..hope this make sense to you
//chopper

MetalHead
Mon 30 November 2009, 11:04
Here is the plate with tabs. How long would they need to be to allow for bends?

chopper
Mon 30 November 2009, 17:05
Mike,
the wings should be 2.250 in length if you use the same pulleys that I did
(width) and you use the longer bearing boss on the motor side..
//chopper

swatkins
Thu 07 January 2010, 10:45
Chopper I noticed you're using the Kreling motors. Do you have the model number for them? Also what size and brand of rack and pinion gear are you using? I would like my machine to work as well as yours!

Thanks!

chopper
Thu 07 January 2010, 13:34
swatkins,
I am running the kelling
450 ozin motors # KL34H260-60-4A (remember that the 450 ozin is mutiplied by 4 with the transmissions so the end torque is 1800 ozin)
the following are the parts for the belt drives stock drive,http://sdp-si.com
the 72 tooth pulley is part number A6A3-72NF03716 @ 31.97 each
the 18 tooth pulley is part number A6A3-18H3716 @ 10.98 each
the belt is a 200xl with Kevlar reinforcement part number A6B3-080037 @ 7.61 each
the rack and pinion are from mc master-carr www.mcmaster.com/ and the pinion is a 20 tooth, the rack and pinion are as per the plans
if I remember correctly it is a diametrical pitch of 20, and 20 degree tooth angle you need to check with the plans to make sure...
the reason I run the 20 tooth pinion is the smaller pinions do not magnify back lash issues, the larger the pinion the more magnification of back lash
also the smaller the pinion the more resolution that is gained, (others may disagree with this this is just my findings)
if you want your machine to cut as well as mine you will need to take your time and be patient as you build, and pay attention to detail
I have also made a few modifications to my machine nothing to significant, but it seems to work, check out my build here http://www.mechmate.com/forums/showthread.php?t=1951 hope this helps...
//chopper

swatkins
Thu 07 January 2010, 15:03
swatkins,

if you want your machine to cut as well as mine you will need to take your time and be patient as you build, and pay attention to detail
I have also made a few modifications to my machine nothing to significant, but it seems to work, check out my build here http://www.mechmate.com/forums/showthread.php?t=1951 hope this helps...
//chopper

Oh it helps tremendously! I do plan on taking my time and being anal as hell about the tolerances :D

I was going to build this machine and then a smaller one for metal cutting but after seeing the results you are having I think a single MechMate will take care of almost all my needs!

You posted a link for the bits you were using for metal. I was having trouble bringing up the series you suggested on their site... Would you happen to have the part numbers for your favorite metal cutting bits handy? Light steel and thicker aluminum will be the metals I use most as I am hoping to use this machine in place of my mill drill in most cases...


Thanks for all your help !
Steve

swatkins
Thu 07 January 2010, 15:47
Oh this is so exciting ( and expensive!) I just ordered the motors and now I am looking for the correct rack and pinion....:)


The McMaster-Carr page you linked to only had 3/8" wide racks.. Looking around I found this page (http://www.mcmaster.com/#5174t21/=59y88w) that had 1/2" wide , 20 degree and 20 pressure angle items... The 20 tooth pinion also was large enough to bore 1/2" where the one on the other page would only allow 3/8" shaft size...

Do these items seem familiar ?

5172T12
Steel 20 Deg Pressure Angle Spur Gear 20 Pitch, 20 Teeth, 1" Pitch Dia, 1/2" Bore
In stock at $16.76 Each

5174T21
Steel 20 Deg Pressure Angle Spur Gear Rack 20 Pitch, 1/2" Face Width, 1/2" Height, 6' Length
In stock at $46.50 Each



Thanks
Steve

lumberjack_jeff
Thu 07 January 2010, 15:49
One of the reasons a MechMate cuts well is because the gantry has a great deal of mass.

It may be counterintuitive, but if you want to cut aluminum, make it big.

lumberjack_jeff
Thu 07 January 2010, 15:50
These guys (http://www.stdsteel.com/gear.htm) are cheaper than McMaster for racks.

swatkins
Thu 07 January 2010, 16:04
One of the reasons a MechMate cuts well is because the gantry has a great deal of mass.

It may be counterintuitive, but if you want to cut aluminum, make it big.

I should have been a little clearer :) I was meaning smaller as in Table size.

Thanks for the link... There are no prices on their website so I am going to send them an email... How much better are their prices?

Steve

chopper
Thu 07 January 2010, 16:34
Steve,
the bits that were listed were onsrud look at their web site and search for high speed metal cutting bits,
the actual bits I used were from a local supplier that has a house brand mill with the proper coatings for stainless steel, if I were you I would look for a local machine shop supplier they should have the bits you need and more than likely cheaper than onsrud,
then you can experiment with different flutes and coatings...and get them locally..also the slower you can get your router/spindle to spin the better off you will be for metal cutting...
//chopper

orotemo
Tue 19 January 2010, 08:24
Chopper (or anyone else who knows)

Is there such a thing as 'zero backlash' timing belt&pulley?
I saw you use 0.2'' pitch, which translates to about 5mm. Is it plain timing belt & pulley? clearly you get no backlash.

I intend to use quite harsh acceleration values - would you say that regular timing pulley, made of aluminum, with 0.375'' (9mm) kevlar reinforced belts will give a backlash free machine for years to come, or would you recommend steel pulleys? maybe .625'' belt?

What say you?

Gerald D
Tue 19 January 2010, 09:26
Chopper got out of hand (link (http://www.mechmate.com/forums/showthread.php?t=2438)) and he is no longer allowed to post here.

orotemo
Tue 19 January 2010, 12:09
You must admit it is funny in some way (the shared IP of Jimbo & Chopper). shows enthusiasm :).

Gerald, as probably the person who was involved in every debate on this forum, and quite a few on others, please do advise. maybe as a nice closure to the loud tones this thread experienced:

I have backlash. no lost steps, always manage to get back to the exact same locations, only that there is a 'play'. I grab the gantry in my right hand (the strong one:)), and I am able to get a 1mm movement when moving by hand back and forth. this is quite a problem. if I always cut the same direction, I'm able to get by with perfect cuts. if I change direction on the same cut in a different cut level, the backlash shows, you see a stair on the material. I also cut decorative panels (when will sales pick up...:mad:), and then it becomes a major problem.

I want to cancel the backlash, and from threads around here I learned that the timing belt and pulley is a solution, and a great one.
I also have now SG7.2 geared oriental motors, want to change to keling 906oz-in with 3.6 ratio belt (20-72 teeth).

1. will the timing solution do? I have very high acceleration values.
2. one of the sales people here told me there is such a thing as 'zero backlash' in timing pulleys & belts, did anyone hear of it?
3. isn't it better to use steel pulleys rather than aluminum? I mean aluminum is prone to develop backlash due to high accel, isn't it? on extreme take a hammer, slam steel, slam aluminum.... you get me.
4. any advice on solving backlash? definitely the gear is the problem. didn't employ the machine too much, yet already I have meaningful backlash. you can hear the gear slam as you rock the machine while idle.

peace!

Gerald D
Tue 19 January 2010, 12:19
You talk of very high accel values in your case, but I don't believe they can be very high because the stepper motor would lose steps (slip). Your torque/force/impact limit is set by the stepper motor's magnet field strength. Everybody increases their accel values until the stepper motors cannot handle it, and then back a bit......therefore I believe there is nothing special about your application and you can use the same belt drives as everyone else.

orotemo
Tue 19 January 2010, 13:17
would you say plain timing belt & pulley setup will do the trick and solve the backlash issues? this is what remains unknown to me, because of all the discussions I already read, I haven't a firm understanding if that is it. Does it do the trick?

bradm
Tue 19 January 2010, 14:09
Orotemo, if, in fact you have a sloppy set of gearboxes with backlash, then the belt drives should help you to eliminate the backlash.

Will eliminating that backlash solve your cutting issue? That is harder to be sure of. There are two things that I would check before spending a lot of money. Both of them should be checked during your test of pulling on the gantry.

The first is to make sure that your pinions are fully engaging the rack, and stay fully engaged. The second is that the pinion gear isn't sliding on the motor shaft.

Based on your description above of hearing the gears slam around, it does sound quite possible that your gearboxes are bad. There seem to be a lot of people for whom the OM gearboxes aren't a problem, so it might be worth checking with OM; maybe they'll replace them. Have you always had the problem, or did it develop over time?

MattyZee
Tue 19 January 2010, 16:21
I had a similar issue early on with my belt drives, I tried to get away with small grub screws and the pinions came loose and i could move the gantry a millimeter or two. After changing to bigger grubs screw i haven't had the issue again. So i agree with the others, a belt drive won't solve your backlash issue if your motors are in good order.
But to answer your earlier questions, if you do go for a belt drive, i wouldn't worry about a steel pulley, aluminium is fine. I went with a 16mm wide pulley just to give me a bit more margin but many people seem to run 10mm (3/8") without any issues.

MattyZee
Tue 19 January 2010, 16:32
I have been playing around with a design based on choppers info here. One thing i noticed is that he claimed he used a 200xl belt with a 18T & 72T pulleys. His drawing shows a centre distance of 3.125". This doesn't work out. I put more trust in his measurement of centre distance than the belt number, so i assume he actually used a 160xl belt. This gives a theoretical centre distance of 76.49mm (~3.01"). But this means he only had 4 teeth on contact, not 5. I know he said he didn't have any issues but i think this is too far outside the recommended engagement and may cause premature belt failure. I'm working on a design that uses a 170xl belt to give 5 teeth in contact. not a big change to the design but gives 25% increase contact area. Will post some concept pics soon.

Gerald D
Tue 19 January 2010, 20:19
We have found that the most common source of "backlash" seen in the x and y direction is caused by a loose z-slide. The z-slide roller eccentrics should be adjusted up to hold a pre-load on the z-slide. The z-slide should not wobble side to side.

lumberjack_jeff
Tue 19 January 2010, 21:20
With the steppers energized, I can get .4mm of movement (entirely gearbox movement - I can feel the pinion rotate) in my y axis. For reasons of which I'm not entirely certain, I have much less in my X axis.

my z-slide is quite rigid.

When doing things like cutting signs, this hasn't proven to be a problem. It only becomes a problem when I try to do inlay-type work.

I'm able to work around this with backlash compensation, but my next machine will have timing belts.

MattyZee
Tue 19 January 2010, 21:33
why wait for your next machine? you can retrofit belt drives...

Gerald D
Wed 20 January 2010, 08:15
I have copied the posts regarding excessive backlash in the OM geared motors to Backlash in the gearhead of the Oriental Motor PK296A2A-SG7.2 (http://www.mechmate.com/forums/showthread.php?t=887)

This thread has been re-titled to focus on building your own belt-drive. I took the 4:1 out of the title because that may not be the "ultimate" ratio . . . . there is no such thing as the ultimate ratio in this case.

Edit: This thread also now merged with the original "Build your own" thread.

Oleks
Thu 21 January 2010, 11:38
There are reasons not to have on pulleys excess ring for grab screw. Many (http://www.poggispa.com/prod-dett-EN.asp?id=12) types of locking devices (http://www.poggispa.com/prod-dett-EN.asp?id=14) available but all are rather expensive. Could somebody suggest design not too complex to make with manual lathe. For shaft 14mm, width of pulley 19mm. What kind of metal (treatment) to use?

Oleks
Thu 21 January 2010, 12:26
OR just make two holes for grab screws through teeth and give it LockTite as well?

Gerald D
Thu 21 January 2010, 22:33
The above posts, and reply, copied to:
"Grub"/set scews for pinion gears, with LocTite ? (http://www.mechmate.com/forums/showthread.php?t=795)

javeria
Fri 29 January 2010, 05:45
II'm working on a design that uses a 170xl belt to give 5 teeth in contact. not a big change to the design but gives 25% increase contact area. Will post some concept pics soon.

matt - any progress on this one - or I missed it out some where else?

MattyZee
Fri 29 January 2010, 16:24
irfan, yeah, i've finalised the design and will be making a prototype over the next few weeks. i was going to post some pics but then i discovered the 4:1 thread had been butchered and incorporated into this thread. Theres not much point posting it here as it will just get lost amongst other designs and discussion of grub screws and collars. PM me your email address if you want some details.
Cheers
Matt

Gerald D
Fri 29 January 2010, 21:30
Matt, there is nothing special or unique about Chopper's 4:1 drive that made it any better than any other drive in this thread. In fact, it has the poorest angle of wrap on the small pulley and some are going to find that problematic.

KenC
Fri 29 January 2010, 22:19
Matt, don't worry about your design getting lost in this thread. Keen MM builder & genuine builder-to-be will go through every word in the thread, eventually...

Combining is doing us a favour, we can have every possible design in a single place & IMHO, these design evolve & improve over time. An excellent example is the grinding skid design.
Post your design & lets have fun with it.

I opt for the belt reduction path, love the highest possible gear ratio but also worry about the grip. I have a vivid idea of using an idler pulley running on bearing to increase the wrap angle.

I wonder if I could just push use a plain 6001-zz bearing onto the belt for the job.

MattyZee
Fri 29 January 2010, 22:43
I disagree with you Gerald. Choppers was the only one i have seen that used laser-cut and welded steel. It only required a couple of accurate (turned) parts so was within the reach of all mechmate builders, unlike the other designs which need a proper milling machine or working mechmate to build.
and as i said in a previous post, i was addressing the wrap angle in my modifications...

Ken, i agree combining was good as it gave a good overall snapshop of peoples implementations, but i think the original threads should have stayed separate so those that want to contribute on a particular design can do so without wading through other unrelated posts. the combined thread could then have a summary of the design and a link to the full thread. But Gerald has every right to run the forum the way he wishes and i accept that.

isladelobos
Fri 29 January 2010, 23:03
I agree with Matt.

Maybe a solution is to centralize all the pulleys in a thread of links to other threads.

KenC
Fri 29 January 2010, 23:12
Something like this with a 180 deg wrap & same foot print.

8348

This is the concept, the holding structure can be any metal.