| Author |
Message |
    
Gerald_D
Registered
Username: Gerald_d
Post Number: 331
Registered: 11-2005
| | Posted on Friday, October 27, 2006 - 11:34 am: | 
|
Our first MechMate has Oriental Motor Vexta-Step type PK299-01AA motors, directly driving the pinion gears to the racks, without any gear reduction. This is a relative low-cost, low risk option - I know it well, it works.
However, because Mach3 can pulse at higher frequencies, you can use a geared motor for better cut quality. In this case, ShopBot suggests the standard PK296A1A-SG3.6 as being a close equivalent of the geared motors specially built for them. (reference). Better cut quality, higher price, and the risk that I don't know what I'm talking about  . But, I have designed the MechMate so that this geared motor *should* screw straight on. Most ShopBots use the similar motor & gearing, but they were handicapped by poor drivers - now that the Gecko-type drivers are freely available, folk are squeezing amazing performance from these motors. See thread 1, thread 2 This could be my first choice today.....? (Edit on 2 Feb 2007: Instead of a 3.6 ratio gearbox, I would now lean towards a 7.2 ratio gearbox instead. It is becoming easier to supply the step frequency required by the 7.2 gearbox, and Doc Tanner says it works well. He is using the PK296A1A-SG7.2 motor)
There are motors within the Oriental Motor range, with the same frame size, than can produce more torque at higher speeds, consuming bigger currents, but I am a bit concerned that the higher torque makes them run "rougher", the higher current makes them hotter and that cut quality will suffer. Art Fenerty made an interesting comment on his forum recently about maximum torque for a stepper motor for a CNC router. (link). I have some PK299-F4.5A motors that I want to test sometime.
Oriental Motor have worldwide representation. Their USA division has on-line shopping with public prices at these pages (page 1, page 2). The ungeared PK299-01AA is $205, and the PK296A1A-SG3.6 is $257 on that list. (Some of the international offices of Oriental Motor have differences in their model ranges and numbers) The MechMate needs a quantity of 4 identical motors.
Having sung the praises of Oriental Motor, it must be recognised that stepper motors (not talking of gearboxes here) are not high-tech devices and many other manufacturers will probably offer comparable quality at a wide range of prices. (if the motor is with a gearbox, then I would probably stick to the OM brand) When looking for alternative motors to those suggested above, the following need to be taken into account:
The shafts need to be at least 12mm [0.5"] in diameter to carry the spring load and not bigger than 13mm so that a small pinion gear can still be fitted. The shafts must be at least 32mm long to reach the rack, but not longer than 40mm otherwise they will collide with the rail supports. The motors must fit on the MechMate's mounting plates. They must be compatible to Gecko G202 drives
Added 22 March '07: The motor bodies should be of the modern square style (heavier, contains more iron, better for micro-stepping)
For the really forward-looking folk, consider motors with shaft extensions to the rear for encoders in the future, or consider that stepper motors may give way to servo motors. . . . . |
Donald W. Ross
Registered
Username: Doctanner
Post Number: 1
Registered: 11-2006
| | Posted on Thursday, November 09, 2006 - 07:17 pm: |
|
I am building a 4X8 router along the same lines a MechMate. With the proper gear Would the PK296A1A-SG7.2 be a viable replacement for the PK296A1A-SG3.6? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 413
Registered: 11-2005
| | Posted on Thursday, November 09, 2006 - 07:35 pm: |
|
Apparently yes, but I am not so sure about its internal backlash. The 3.6:1 has only one pair of mating teeth (as far as I know) and this must have tiny backlash. The 7.2:1 might have 2 pairs of mating teeth with twice as much backlash?
Some people recently started using 7.2 gearboxes on ShopBots and they rave about them, but it is early days yet... |
Dirk Hazeleger
Registered
Username: Dirk
Post Number: 45
Registered: 12-2005
| | Posted on Thursday, November 09, 2006 - 08:30 pm: |
|
According to Oriental, the 7.2 has less backlash. It is still a single stage gear reducer. The standard gearbox sold on orientals site is a spur gear reducer, which can produce from 60 to 90 arc minutes backlash, the Tapered Hob is 15 arc minutes. This is all according to Oriental, others claim it is a very tight reducer. It may loosen up after running a while. I noticed John Forney had one of the original spur Gear reducers and I checked it and didn't notice any play.
I would choose the Pk296A2A over the PK296A1A. The torque curve is much better.
The following is the torque curves, notice the B designation is just for a double ended shaft
 |
Gerald_D
Registered
Username: Gerald_d
Post Number: 415
Registered: 11-2005
| | Posted on Thursday, November 09, 2006 - 09:16 pm: |
|
Dirk, I wish I was within telephone distance of an Oriental Motor product specialist. The questions I would like to put to them are:
1. PK296A2A verus the PK296A1A. Are the motors in fact different? Isn't the 1 amp version just a labeled down 2 Amp motor? Who would be buying the 1 Amp? (presumably because of driver limitation - but surely the 2 Amp could be under-driven). Is the 1 Amp "smoother"? I can see the one has thinner wire in the stator coils (more resistance/inductance) what is the overall effect of this? (smoothness, detent, heating, etc.)
2. The "tapered hob" issue: A hob is a tool for cutting a gear, why is Oriental practically the only company in the world that makes an issue of the tool with which the gear is cut? Its like saying my house was built with a 2lb claw hammer - why is that supposed to make a difference? |
Dirk Hazeleger
Registered
Username: Dirk
Post Number: 46
Registered: 12-2005
| | Posted on Thursday, November 09, 2006 - 10:12 pm: |
|
Gerald
Your questions are valid. I think the motors are different. Running the higher amp motors increases cost both on the driver and the power supply (If you mounted the 3 amp motors on your machine you would need a 600 VA transformer and 2 more caps because the max voltage would be around 35 volts).
Some applications don't need the high-speed torque. I would think under driving the higher amp motor would kill the low speed torque. So my opinion is they offer several motors so it will fit the application and not create unnecessary expense. If there’s more to it (or less) I don’t know.
I have no idea as far as the tapered hob issue. They don't publish the spur gear spec, and I think the rep was guessing when I asked him. It would be interesting to break down both reducers and see what the real difference is.
On a side note, I’m still curious as to Mike’s theory that torque has as much to do with smoothness of cut as resolution. I’m mounting my 1300oz motors on my PR direct drive to see how it will cut. May be interesting.
Dirk |
Mike Richards
Registered
Username: Richards
Post Number: 53
Registered: 05-2006
| | Posted on Friday, November 10, 2006 - 05:30 pm: |
|
Be aware that the PK296A2A-SG motors are rated at 1.4V (unipolar) while the PK292-02AA motors are rated at 3V (unipolar). I didn't notice that difference until I touched a geared motor that I was running at about 70V. It was HOT! Reducing the voltage to about 30V works well and is within the 25X limit suggested by Gecko.
I'm still thinking that torque of the motor, while in standby mode, is very important when running a multi-axis machine. Using a 3:1 gearbox on my Alpha greatly improved the cuts. Since the resolution of the machine without a gearbox should have been 3.14/1000 = 0.00314 inch per step, it should have been adequate for cutting wood with minimal chatter. (The offending chatter marks were certainly much larger than 0.00314 inches!) My theory is that 3X the standby torque keeps the non-moving axes from being pushed around by the active axis. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 506
Registered: 11-2005
| | Posted on Friday, November 24, 2006 - 06:48 am: |
|
The "taper hob gear" is actually a "taper gear". From their page:
I suppose the pitch diameter is an average across the width of the gear. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 507
Registered: 11-2005
| | Posted on Friday, November 24, 2006 - 06:51 am: |
|
 |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 1
Registered: 12-2006
| | Posted on Wednesday, December 06, 2006 - 06:06 pm: |
|
Hey guys, I'm new here, and I'm a litte puzzled. Is the Steppers connected directly to the Rack&Pinion drives, or should I use one with a gerabox on it.??? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 598
Registered: 11-2005
| | Posted on Wednesday, December 06, 2006 - 07:00 pm: |
|
Welcome Kim! The first post at the top of this thread is still applicable. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 30
Registered: 12-2006
| | Posted on Tuesday, January 30, 2007 - 06:10 am: |
|
Hi Gerald should this stepper here be just as good as the Oriental stepper...
www.motionking.com
Motor Type
34HS5804 |
Gerald_D
Registered
Username: Gerald_d
Post Number: 790
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 07:54 am: |
|
Kim, that is a tricky question. It might be as good, but I have no experience of it. You have selected a much bigger size than what I use, and I am a bit concerned that this may give problems such as rougher cuts. (See this thread which was added later) |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 31
Registered: 12-2006
| | Posted on Tuesday, January 30, 2007 - 08:28 am: |
|
Gerald.. Could you direct me to the model that is closest to the Oriental stepper..???
The Steppers you use is also Nema34 right..???
KM |
Gerald_D
Registered
Username: Gerald_d
Post Number: 791
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 08:52 am: |
|
From the first post on this thread, the motor that I am experienced with is the Oriental PK299-01AA. From the link, it is 85mm square, 96mm long, the mounting screw holes are 69.6mm square pattern, housing spigot 73mm diam by 2mm deep. (The spec does not say Nema34 exactly).
Physically, the MotionKing nearest this size is the 34HS980* group. The mechanical interface (Nema34?) is identical. (Nema is an American standard, not everyone uses it)
The holding torque is nearly identical at 430 to 450 N.cm.
Electrically, the nearest MotionKing is the 34HS9803 with 2.7A rated current, but after this point I have no idea how to pick an equivalent motor... |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 33
Registered: 12-2006
| | Posted on Tuesday, January 30, 2007 - 08:56 am: |
|
ok. Maybe motionking can give me an answer if they compare them.. The bigger motor there I could get for only $57 a piece plus postage and packaging... But stille very cheap for that big a motor... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 793
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 09:10 am: |
|
That is an excellent price!
The Chinese stepper motors seem to be okay in general. If they were bad, there would be a lot of people complaining, but I don't see complaints about their stepper motors. If you open a stepper motor (some people say you are crazy to do this) you can see that it is really a stupid/simple device. The magnets need to be a good quality, but China is doing good magnets.... |
Bob Cole
Registered
Username: Bob_cole
Post Number: 23
Registered: 10-2006
| | Posted on Tuesday, January 30, 2007 - 06:01 pm: |
|
Gerald:
regarding these, (or any) motors for the MechMate. Do you recommend 4 wire or 8 wire motors? and why?
Do you think an 8 wire motor affords the user more flexibility in setting up his router?
Regards,
Bob C. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 796
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 07:43 pm: |
|
Bob, 8 wire obviously gives more options than 4 or 6 wire, but I am still at a loss to understand whether we should be using unipolar, bipolar series or bipolar parallel wiring. Here is an exchange on the Gecko forum about 2 months ago....
Me:
Mariss, could you enlighten us why that Nanotec wiring diagram says:
8 lead wire parallel for high freqency > 1kHz, and
8 lead wire series for low freqency < 1kHz?
For CNC machines, the motor will spend most of its life in the low frequency range, no? I have difficulty deciding when to use series or parallel - the rule always seemed to me to use the parallel if the drive could cope, otherwise reduce current with series. Now there is another selection criteria....?
Thanks
Mariss:
You have "two motors in one" when you have an 8-wire motor.
1) "Both" motors have the same low-speed torque.
2) The series connection phase current is 1/2 the parallel connected
phase current and runs out of low-speed torque at 1/2 the speed of the
parallel connected motor for the same supply voltage.
3) The series connected motor runs cooler than a parallel connected
motor for the same supply voltage.
4) Use a series connection and/or a low power supply voltage for
low-speed applications. Use a parallel connection and/or a high power
supply voltage for high-speed applications.
Mariss
Me:
With a CNC router table, which can use the full speed range of the
stepper motor, what are the signs (or effects) that tell you it might
be wiser to use series rather than parallel? Only motor heating?
Roughness of cut? Etc. My impression is that parallel should be the
first choice if the driver can handle it, but then to drop to series
if the motor gets too hot. Is this simplistic logic faulty?
Another way of looking at it is to leave the motor parallel, but
change the resistor to limit the current at a lower value?
Thanks
Those questions are still in my mind... |
DocTanner
Registered
Username: Doctanner
Post Number: 23
Registered: 11-2006
| | Posted on Tuesday, January 30, 2007 - 07:48 pm: |
|
Bob,
The GeckoDrive G202 - Step Motor drive that Gerald specs, doesn't care how many wire come with the motor. http://www.geckodrive.com/photos/Step_motor_basics.pdf
Ton's of good info there. I have had good luck using the http://catalog.orientalmotor.com/item/stepping-motors-/pk-series-stepping-motors /pk296a1a-sg7-2?&plpver=11&origin=keyword&by=prod&filter=0 |
Gerald_D
Registered
Username: Gerald_d
Post Number: 797
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 08:33 pm: |
|
Doc, did you try the two different wiring options (unipolar & bipolar) and would you recommend one version over the other? My experimentation in this area didn't give me a conclusive result. |
DocTanner
Registered
Username: Doctanner
Post Number: 25
Registered: 11-2006
| | Posted on Tuesday, January 30, 2007 - 09:35 pm: |
|
I set mine up as 1 amp at 70volts and was so impressed by the power, speed and cut quality that I didn't even think of changing it!
Drives and motors produce no noticible heat. If the leds weren't lit up, you wouldn't know it was on.
When it gets back from the powdercoater tomorrow and I get it back together, I will give it a try.
I have an ncpod sitting on the desk, was thinking of giving it a try. But I'm not sure how it could be better! |
Gerald_D
Registered
Username: Gerald_d
Post Number: 799
Registered: 11-2005
| | Posted on Tuesday, January 30, 2007 - 09:44 pm: |
|
Very good to have a satisfied customer!
But, in the interest of science, it would be interesting to get a definitive answer on the best way wire the motors. Would appreciate you experimenting a bit. (Remember to change the current limit resistors accordingly). |
Gerald_D
Registered
Username: Gerald_d
Post Number: 807
Registered: 11-2005
| | Posted on Friday, February 02, 2007 - 07:14 am: |
|
The Motionking discussion has been moved here.
Those who are actively pursuing this MotionKing option must consider the following:
1. Those motors have never been tested on a MechMate. They should work, but we don't know for sure.
2. Those motors are without gearboxes. They should work as well as my setup. But, the evidence is that my setup could work a lot better if I had gearboxes. Those geared motors mentioned at the start of this thread appear to be a much better (albeit more expensive) option.
3. If the Motionkings don't work, then please don't say you got bad advice from MechMate. I would love to be able to endorse a cheaper option, but I have to be cautious. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 46
Registered: 12-2006
| | Posted on Friday, February 02, 2007 - 02:00 pm: |
|
Gerald...
Of course youo won't be held responsible. This is just a way for me to cut cost a little, and I'm wiolling to give it a try, even though I have been advised not to... One has to learn from ones mistakes right. But then again, I could get lucky and maybe end up with a motor that works fine at one quarter the cost of an Oriental motor... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 808
Registered: 11-2005
| | Posted on Friday, February 02, 2007 - 02:14 pm: |
|
Kim, I would be very happy if you tested those motors and told us all about it. I am just a bit nervous about those folk already talking of bulk buying the experimental stuff. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 47
Registered: 12-2006
| | Posted on Friday, February 02, 2007 - 02:29 pm: |
|
I would never bulk buy something I haven't tested. But I would however buy them for my self only. I'm also not keen on being the fall guy if everyone suddenly didn't get what they wanted from these motors. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 48
Registered: 12-2006
| | Posted on Friday, February 02, 2007 - 02:33 pm: |
|
And on another note, if the motor seems to run a little uneven, the I'm going to build my own gearbox for it with belt pulleys and high tension belts. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 809
Registered: 11-2005
| | Posted on Friday, February 02, 2007 - 06:30 pm: |
|
I have made an edit to the first post in this thread - see the bit in red.
To summarise the choices of motors....
1. Best cut quality (highest step frequency) will be obtained with the most expensive $257/motor option from Oriental Motor. (The backlash factor of these gearboxes is not discussed much - that is a bit of an unknown)
2. A commercially acceptable cut quality (smoothed with a few wipes of sandpaper if necessary) could be obtained with direct drive motors from about $50 to $110 each (Chinese) or $200 (Japanese). (Backlash is not a factor with this option. I have years of experience with this setup and 99% of our customers are happy with the cut quality)
A lots depends on where you live and what the shipping charges will be to your destination. |
vadeem
Registered
Username: Vid1900
Post Number: 30
Registered: 10-2006
| | Posted on Tuesday, February 13, 2007 - 03:38 am: |
|
Hey guys, I believe I'm reading the Motor specs right, and the PK296A1A-SG7.2 motor is 4.4 volts?
So I need to build a larger power supply than the example shown under power supply in order to have the recomended 25x voltage, right? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 875
Registered: 11-2005
| | Posted on Tuesday, February 13, 2007 - 05:17 am: |
|
Not quite right. The 25X is the absolute limit - it can be less. In this case the Gecko is limited at 80V, and this becomes your design voltage. The motor draws 1.5 Amp max. So the 75-80Volt / 300VA power supply illustrated there will do just fine. |
vadeem
Registered
Username: Vid1900
Post Number: 34
Registered: 10-2006
| | Posted on Wednesday, February 14, 2007 - 12:49 am: |
|
Thanks Gearald, I placed my order today.
I might remind everyone that the free UPS shipping ends March 31st 2007 at Orientalmotor, so you may want to pull the trigger now. |
eric thomas
Registered
Username: Arnoldarnold
Post Number: 1
Registered: 03-2007
| | Posted on Sunday, March 04, 2007 - 04:00 am: |
|
http://www.xylotex.com/4AxSysKit-425.htm
can you use this system for the mechmate?
why, why not |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1095
Registered: 11-2005
| | Posted on Sunday, March 04, 2007 - 05:37 am: |
|
Sorry, too small and underpowered. |
Loren Gameros
Registered
Username: Moron_wizard
Post Number: 10
Registered: 02-2007
| | Posted on Monday, March 05, 2007 - 07:31 pm: |
|
Hi Gerald,
In a post on Fri. Feb 2 at 6:30 PM you had said the following:
"A commercially acceptable cut quality (smoothed with a few wipes of sandpaper if necessary) could be obtained with direct drive motors from about $50 to $110 each (Chinese)"
My question is which brand motor can be used for $50 to $110 dollars, and would you recomend them? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1111
Registered: 11-2005
| | Posted on Monday, March 05, 2007 - 08:15 pm: |
|
Have a look at the posts above that one - I don't think I can say much more than that until I have actually tested the motors myself. (If shipping costs out here were not so darn expensive, I would have tested these economical options long ago) On the other hand, it will help if other guys tell us how the cheaper motors work in their MechMates, but nobody has gone this route yet. Want to be the first guineau pig? |
Loren Gameros
Registered
Username: Moron_wizard
Post Number: 11
Registered: 02-2007
| | Posted on Monday, March 05, 2007 - 10:12 pm: |
|
Sure I'll be the g-pig, recomend some $50 range dollar motors and I'll try them out ASAP. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1115
Registered: 11-2005
| | Posted on Tuesday, March 06, 2007 - 07:12 am: |
|
Have a look at the MotionKing page. |
Thomas M. Rybczyk
Registered
Username: Rypper
Post Number: 11
Registered: 07-2006
| | Posted on Tuesday, March 06, 2007 - 02:25 pm: |
|
Loren,
For a very good motor from an excellent supplier between $69-$89 follow this link. http://www.kelinginc.net/
I have been using this model KL34H280-55-4A on my current cnc machine http://accurate-inspections.com/pr%20cnc%20upgrade/ for about six months with excellent results.
These are not geared so you will have to go the gear box route for better resolution, but even at 1-1 I have done some very nice v-carving with these.
Tom |
bugmenot dillbert
Registered
Username: Soulvoid
Post Number: 4
Registered: 02-2007
| | Posted on Thursday, March 08, 2007 - 10:12 pm: |
|
I'm curious of the specs on those motors. They are rated 5.5amps at 2.4v which then require a 55-60V powersupply at 23-25x rated voltage but then with four motors in theory you need 22amps from the powersupply thus a 1200VAC powersupply for optimum performance? (but then you need to multiply this with that and so on and so forth and this is worst case, the motor may not be wired as bipolar(series/paralell?) which the rating is for, I'm totally at loss when it comes to figuring out this stuff, etc.) It also seems to have a little lower holding torque than the recommended vextra, but that may not matter.
What I wonder, if you can use a 300VAC powersupply with the vextras and the kelling motors may require four times as much power with possibly lower holding torque, where does all that energy go? Heat? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1129
Registered: 11-2005
| | Posted on Friday, March 09, 2007 - 08:19 am: |
|
Bugmenot, the guys who were recommending the 23-25x are now saying 20x as the max voltage - you can use less.
But, to get to your main point, where does all this power go....? This is a question for which I would really also like an understandable answer. If I had money/time/space I would be buying all these motors and testing them against each other.
One group of guys have the logic that more power is always better. (Tim). That's fine, but then we must have a reliable way of getting rid of the excess heat. A 300VA supply is easy to cool without blowing it full of dusty air. The big power supplies need breathing air and get choked on dust. |
bugmenot dillbert
Registered
Username: Soulvoid
Post Number: 5
Registered: 02-2007
| | Posted on Saturday, March 10, 2007 - 12:03 am: |
|
I tend to agree that more power is better than being short of power if optimum performance is needed, obviously considering cost.
Doesn't more current mean more heat, thus the vextras should run cooler? I would really like to know if there is a rule of thumb where more current is better for high speed or vise versa or better for low speed torque, but I guess that is a question for the people at geckodrive. |
Mike Richards
Registered
Username: Richards
Post Number: 83
Registered: 05-2006
| | Posted on Saturday, March 10, 2007 - 05:52 am: |
|
Generally, current relates to torque and voltage relates to speed. For a given motor, the more current that it has available (up to the maximum rating for the drive) the more work it can do. And in the same way, the more voltage available to a motor (up to the maximum allowed by either the stepper driver or the maximum recommended by Gecko, i.e. 20X or 25X of the rated voltage), the faster the maximum speed will be.
Recent tests on my test bench have shown that a moderately sized motor (PK296B2A-SG3.6) can be spun faster than a larger motor, so, if gearing is available, the PK296 (300 oz*in) or PK299 (600 oz*in) seem ideal for the job. Even without gearing the PK299 size seems to be a very good match. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1175
Registered: 11-2005
| | Posted on Thursday, March 22, 2007 - 08:23 pm: |
|
First post edited to prefer the modern square body motors. |
Frank D
Registered
Username: Pamarine
Post Number: 3
Registered: 05-2007
| | Posted on Sunday, May 13, 2007 - 04:25 pm: |
|
I have been turning over the stepper vs. servo motor option all week. I was wondering if anybody new of a N. American source for servo motors that will work with the gecko 320/340 drives. Most of the Motors i am finding are designed to use their respective manufacturer controllers (I'm finding some that have bus voltages of 325vdc-560vdc!). Any idea would be great. The conclusion is if i can afford a servo setup, that the way i will go, if not, then geared stepper like the $260 ones from oriental. looking to build the controls by june 30, then start in on the steel. |
Frank D
Registered
Username: Pamarine
Post Number: 4
Registered: 05-2007
| | Posted on Sunday, May 13, 2007 - 06:04 pm: |
|
AHHHHHHHHHHH!!!! whew, i feel better now. All this stepper vs servo stuff is making me go bananas. After i posted the above message, i read the servo vs stepper thread. Ok, I need to know a little more before committing to a motor.
How much hand finishing would be required on a circle cut using a mechmate with properly sized and configured stepper motors?
I am believing that a geared stepper motor can hold the stationary axis stationary. Is this correct?
Ok, originally i was typing the desired accuracies of the machine, then i divided out the fraction and realised that even the most basic control system will be more than accurate enough.
So I guess as long as i'm not gonna hafta spend an hour filing or sanding cut parts, it's steppers and little green lizards for me! |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1353
Registered: 11-2005
| | Posted on Monday, May 14, 2007 - 05:32 pm: |
|
Hi Frank
I was hoping that somebody else would chime in here since you all must be very tired of hearing my biased opinions.......
To answer the easy question first; We have un-geared steppers on two tables and we don't have problems holding the stationary axis stationary. My impression is that the people who have reported problems in this area are using Oriental Motors Alpha controller's with feedback from the motors, and that these motors "hunt" to hold a fixed position (The I in PID?).
The tricky question, "how much sanding on circles". It won't help you if I honestly replied that we never sand any circles, because we simply don't do any post-cutting finishing service. Our clients do that themselves and we don't compete on their turf. The few times that I have made things for myself, and have wanted to remove the chatter marks that occur on parts of circles only, I reckon that it took about 10 strokes with 80grit paper?? Can anyone else give a better answer to this valid question?
Realising that we have direct drive motors, the general client feedback is that they are happy with MDF and softwood cut for them, but that they want better for acrylic plastic (perspex). If we had gearboxes, we could probably also satisfy the plastics guys. |
Loren Gameros
Registered
Username: Moron_wizard
Post Number: 32
Registered: 02-2007
| | Posted on Monday, May 14, 2007 - 06:06 pm: |
|
Hi,
Here is my 2 cents.
I don't really know how much "mill mark" there will be when cutting circles using ungeared motors since I haven't used them yet so in that respect I can't comment.
How about someone posting some pics with wood and plastic?
I do know this, if was to cut circles say with my bandsaw, I would have a considerable amount of sanding with a power sander then alot of hand sanding. If all I have to do is sand 10 strokes with 80 grit sand paper, I will be most pleased. I have purchased the ungeared motors from Oriental (as recomended) and will using them. I will play around with them when I get them moving. I would think that no hand held or hand propelled power tool would be able to hold any kind of smooth transition through a radius. I don't know if this is a better answer but I will take a router cut over my bandsaw any day much less my jig saw. |
Frank D
Registered
Username: Pamarine
Post Number: 7
Registered: 05-2007
| | Posted on Monday, May 14, 2007 - 06:29 pm: |
|
Guys, thanks for the info. I agree with the notion that 10 strokes of sandpaper is nothing, I always dress cuts anyway. And Gerald, your opinions are what got me thinking i could build one of these things. And the guys in this forum reaffirm that. So anyhoo, I guess now I'm on the hunt for some motors. Any thought on the gecko drive? 202 v 203. Can't figure out what the differences are from the blurbs on there site. I'll keep reading and can't wait to start posting pics. |
Motors