Build a functional MechMate at lowest cost - what can be done cheaper?

[Gerald D]

How can one build a functional MM that could start earning funds for "upgrading" it later? What is the minimum needed to get it producing sawdust?

1. Stay with the laser cut parts. You could bandsaw/jigsaw & drill those parts if really desperate, but you would spend a lot of time getting everything lined up. It would be a false economy to try plasma cutting instead of laser.

2. Make the rails as per the "grind angle iron down" method. Go gentle on your grinder unless you have a decent brand with a powerful motor.

3. The V-wheels at under $15 a piece from Superior Bearing is good if you live in the US. Make your own mild steel wheels if shipping costs from Superior Bearing are too much.

4. Talking of shipping/transport costs, see if you can consolidate stuff into fewer shipments. Share with a friend.

5. Use direct drive motors with the pinion gears direct on the motor shafts. Motionking ships worldwide. You can get a motor and geckodrive for $209 as a package from www.homeshopcnc.com (http://www.homeshopcnc.com).

6. The "sexy" Gecko 203V's are not essential. G201's work as well.

7. Don't fit any pushbuttons or limit switches. Apart from the saving on switches, housings and cable, you won't have the concerns of interference entering the electronics on that circuit.

8. Use cheap unscreened cable for everything except signal cables. Separate power and signal cables by more than 100mm [4"].

9. Don't use cable chains. Hang the cables from the ceiling.

10. Use a cheap router.

11. Don't bother with a control box. But do put in ground fault protection if you are going to have open wiring.

12. Stay with domestic voltages

13. Use recycled steel wherever possible.

14. Consider a wooden table with the steel rails screwed on top.

Any other ideas?

[Fronzel]

What about swapping the Break Out Board and the Gecko 203's for the Gecko 540?

[isladelobos]

ideas = 1999 but no thanks. We make a mechmate.

[Gerald D]

Fronzel, that can help too. Your motor selection must be more careful to match the G540.

[Lex]

What about the 'over' existing work bench design as mentioned somewhere before by Gerald.
If one uses the y-gantry and z- axis as is - make up two short rails support structures from the wall cantilever out. The y-gantry will become the x-gantry.
Starting the business of with sign cutting!

[Gerald D]

Yes Johan, that huge solid table is not essential to get going. Wooden longtudinals on an existing table, with the x-rails on top of that, will get you going. (The first ShopBots were on DIY wood tables)

[J.R. Hatcher]

Before I found the MechMate site, I was considering using a product for the main beams and the cross supports called "microlams". It looks like it's made by gluing up a lot of 1/2" X 96" construction grade plywood and staggering the joints lengthwise. They are very stable and strong.
http://www.howelumber.com/microlam.htm

[Gerald D]

I would not suggest going out to buy new wood beams for a temporary wooden table. If buying, you might as well get re-cycled steel channels. Here (http://www.flickr.com/photos/campshopbot/159924487/in/set-72157594154965065/) is a ShopBot on wood.

[J.R. Hatcher]

Or you might go to your local lumber yard and see if they have an accumulation of shorts (10' and less), they need to get rid of...... cheap. These things come 40' long and they cut them to the customers needs.;)

[DocTanner]

You could do away with the fancy break out board.

DonRoss

Much better to build like the prints show ;)

[domino11]

Here (http://www.flickr.com/photos/campshopbot/159924487/in/set-72157594154965065/) is a ShopBot on wood.

Wow, that looks interesting. Mike Richards has some nice cabinet doors in that post as well.

[William McGuire]

Gerald...
What about using a flex hose like on your original, rather than the chain?

[William McGuire]

Another thought...
Didn't you, at one time, mention getting by using 1" X 2 1/2" angle iron without the V grinding?

[Talons]

Hi Ya'll I'm new to these forums and to the cnc. I've noticed one main factor in all threads I've read to date! skimping out! I'm like any married man my shop 24' x 32' is my shop but my wifes storage bay! So i spend a lot of time keeping my space usable and unrestricted! the prupose of a steel base is steady strong support and welded is to reduce the walking of the precision square it forms. There are several ways to make the base portable and not lose stability or intrude on it's intrigity!welded x-braces and bolted in place for one! I'm just startingn to build the MM and i've looked at 100's of homebuilt uints and the MM is the premium unit on the market today!

[Talons]

BTW thanks for great discussion! I too have very tight budget and space! and the open ideas sure help in more then just one aspect. i hope to move mine around the shop with the aid of my car rotating stand i built 20 years ago.

[Gerald D]

Bill, we would still use the looped hose for the x-axis cable control. Cost isn't the only factor in that decision - it is less obtrusive and less likely to get bumped or stood on.

Leaving out the grinding of the angle iron is not a real money saver.

Welcome Talons. I am trying to make one easily readable thread here for the guys who want to work their way up to a "full spec". For some people reading this forum, they get the message "you have to have proximity switches, you must have cable chains on all the axes, you must sandblast and paint, you must use stainless steel fastners", etc. etc. and I think that is an intimidating message. All of that stuff is not essential (stainless steel is actually even undesireable).

The main message I want to give is "Build a machine that pays for itself"
That could mean that the machine must start earning before it is completely finished, which is a good thing.

Back to money saving ideas:

- Scrounge old PC, keyboard, mouse, monitor, table, chair.

- Check your timber supplier for "end" boards, the top/bottom boards of the stacks they purchase. Those boards are slightly damaged by the forklifts and strapping, but they make good spoilboards for the table top. They could be less than half the price.

- don't be tempted to buy old stepper motors unless you are very sure of their specs and how badly they have been treated.

[javeria]

For the PC I would suggest that folks us the Intel Atom Processor and motherboard combo, which comes for under 100USD, you need to just add powersupply (even a 100W will work) RAM, HDD, Monitor, keyboard and mouse.

For the capacitors I use the ones which are taken out of older UPS - they are usually rated at 10000uF 100V which are sufficient for our purpose.

Even the 220V cooling fans come from these old UPS (they still have a lot of life left and I have more than one)

All the steel(80% by cost) I have used is recycled.

for the router i am presently planning to experiment with blender motors - this is towards making a low cost low noise spindle for wood cutting.

I hope I was on topic on the above rant :)

RGDS
Irfan

[Gerald D]

Perfectly on topic :)

[Richards]

I'm a little concerned about the electronics. No one "needs" an expensive enclosure or expensive push-button switches or terminal blocks. But I hope that everyone understands that a CNC router is an electrically noisy piece of equipment. The logic signals that send the step and direction pulses to the stepper driver may be less than 3VDC while the AC voltage to the spindle can be about 340 Volts peak to peak (SQRT(2) X 240VAC). What that means is that the large signals tend to telegraph their signals onto the low voltage signals. That can cause lots of difficult to diagnose problems.

Be sure to separate the signal lines from the power lines. Be sure to use grounding wires that connects all parts and pieces of the machine to one common ground.

My Shopbot shipped without shielded cables. I replaced some of them and left others unshielded.

Although many of us are on tight budgets, remember that trouble-shooting "glitches" can take hours or even days, so use good common sense when you wire your machine. Follow the guidelines that Gerald has suggested. Remember that doing things on the "cheap" requires that you pay even more attention to wiring details.

Those of us who have built a lot of process control computers wouldn't hesitate to build a bare-bones controller, because we have the experience and the monitoring tools to check things out. For the inexperienced, first-time builder, just take your time and know WHY you're doing each step in the wiring process. If you know WHY a step is important, you'll be more prepared to fix any problems that may result.

(Believe me when I say that I've built a lot of bare-bones controllers for a lot of different customers since 1977. Every controller eventually worked. Most worked with a minimum of "fix-ups", but a few took substantial time before I got everything working properly.)

[Gerald D]

I remember the first ShopBots had an E-stop button as an optional extra (at a fee). . . .

This is one button that shouldn't be left out if you are going cheap. But it does not have to be in the signal circuit where its wires can pick up interference. It can just be a mains breaker/switch (or 2 or 3 in series) that goes between the wall outlet and the rudimentary MM control system, with the router also on that circuit. Mount these switches on the stationary table.

[Gerald D]

The screening of spindle and stepper motor cables is not only for the purpose of preventing glitches when your CNC machine moves. The chopper frequency in a VFD, or a stepper motor at high speed, involves high enough frequencies to cause interference on other electronic equipment nearby. See: http://en.wikipedia.org/wiki/Low_frequency . . . . you don't want an aircraft to home in on your MM do you? :)

[isladelobos]

FDA-ISO-CE-UNE-OHSAS-EN
minimum standards required in engineering.
can overcome our beast arround the world?
I think yes.

[Gerald D]

Ros, I am sorry, but I don't understand your post :confused:

[isladelobos]

I think the mechmate, and his security systems, it is possible approved anywhere in the world in any professional installation for industrial engineering projects. (legal workshops and small enterprises).
Based on the standars ISO-UNE-EN-ETC.. these standards, studies in each country, the best way to build and create industry.

[Gerald D]

If you want to avoid problems with the laws in your country. . . . . then you must obey the laws of your country. It is as simple as that.

You cannot tell the judge in your court that you had permission from www.mechmate.com (http://www.mechmate.com) to break the laws! :D

[hennie]

Is steel not cheaper now with the economic downturn?

[Gerald D]

Here are two price lists:
SectionsPlate 20081001 CAPE.xls (http://www.macsteel.co.za/files/download/current/TRA/SectionsPlate%2020081001%20CAPE.xls) <----- October '08
SectionsPlate 20081201 CAPE.xls (http://www.macsteel.co.za/files/download/current/TRA/SectionsPlate%2020081201%20CAPE.xls) <----- December '08

Prices have dropped about 20% over those 2 months

[Fronzel]

What about using Linux and Linux CNC software like EMC (http://www.linuxcnc.org/)?

[Gerald D]

Good one Fronzel - it is used with success.

[WTI]

http://www.craigslist.org/about/sites or http://www.freecycle.org/

If you have Craigslist in your town (or near your town) your computer will be free. Everyday in the "free" section of CL there are computers and monitors free for the taking.

Mach3 requires a 1ghz or faster computer. I've seen desktop computers offered for free all the way up to 2.4ghz. It seems that everyone only wants laptops nowadays.

Also watch for tube type (non LCD) monitors. 15-21" tube monitors are always given away, often several from the same person. Remember that WindowsXP will run 4 monitors at the same time, this can give you a really big desktop.

[WTI]

Also, those big, tower computer cases make for a cheap metal box to put all the MM electronics in.

Look for the Dell server cases with the hinged side panels - they usually have Xenon 2 processors that run at 450mhz. It seems that businesses can't GIVE these things away, as I see them come up in groups of 5-10 at a time.

http://www.mironet.cz/fotoadd/92401417.jpg

The blue paint awaits....

[domino11]

James,
Can you run xp on those machines? Never tried running xp or vista on a server board before. :)

[Gerald D]

We run Mach on Win2000 - it is much easier to move from one machine to the next

[domino11]

No I meant on server motherboards with Xenon processors. They are different than standard pc motherboards. :)

[Talons]

w2k and xp will run on any mobo with even a 233mhz cpu but boot time is real slow 350mhz or higher work great only drawback i find with 233mhz upto 1ghz is hhds most older mobos only see 8gig hdds or smaller hope this helps

[Talons]

The questions i have is lasercut Nobody here has it but i have a friend who does waterjet and it's just as precise and cheap for me here. and is there a problem if some of the gantry and router base mount parts are aluminum? i have both steel and aluminum i'm just thinking of overall weight. btw thanks :)

[Gerald D]

Thanks for the mobo info Talons.

Alu will not save costs (the topic of this thread). We are not desperately on a mission to save weight because weight does more good than harm. The best CNC routers are built heavy and use little alu.

[WTI]

You can get a free, heavy duty transformer for your power supply out of any large microwave oven. These are also free on craigslist every day.

Most broken microwaves fail because the door switches wear out, so the MW blows the safety fuse instantly.

If you take the transformer out and cut off the high voltage windings with a hacksaw, you can quickly wind a few wraps of wire until you get the voltage you need. It is usually about 1v per turn of wire. Don't forget that you want a secondary winding for about 9-12V to power your BOB.

Just Google "microwave transformer power supply" for many easy to follow directions.


EDIT: Don't touch the high voltage capacitor if you take a MW apart. It will still have juice in it unless it has a bleeder resistor.

[Gerald D]

James, that hack makes me nervous! If anyone wants to pursue this for a MM, I'll give you a thread where you can field the lawyers all by yourself! :D

James started his own thread and I copied the above posts over there (http://www.mechmate.com/forums/showthread.php?t=1185).

[javeria]

OK folks - on cable chains - if the ready made ones are expensive then you can make your own on your Mechmate

http://www.cnczone.com/forums/showthread.php?t=25257&page=10

look at this thread and there will be no heading back for you - I am going to do it this way for sure :)

[normand blais]

Here something I had though doing ,not to save money but be practical,in that case . I was doing some cuts for movie at some studios ,my idea was to build 2 concrete curbs and put some spare rails on it to ride the gantry. Screw the first ply to the concrete floor then glue the sacrificial board on it .
When not in use I could easily take the gantry home or some other place by myself in a small van .

[Doug_Ford]

I would have saved a lot of money if I had read the plans carefully and made a list of all the fasteners (bolts and nuts) that I needed and placed one order from Enco or MSC rather than running down to Lowes or Ace Hardware and paying full retail price.

[gmessler]

I'll back you up on that one Doug!:)

[Greg J]

I think Doug makes one of the best cost savings suggestions so far.

If I was better at project planning, I would have saved numerous hours and cut costs substantially.

Take your time men (only because no women are building so far), and document your plan to the end. Easier said than done. :)

[dragonfinder1]

In the first post of this thread there is a link to homeshopcnc which has a motor RS23-570 which is a 420 in oz holding torque motor ( uni polar). I know this is a nema 23 motor and it is small, but I plan to use a 3:1 belt drive, so the torque will be over 1000 in oz. Might this motor work with the belt drive?

Dave

[MetalHead]

Why would you need the PK296A2A-SG7.2 for the Z Axis?

Why not use a cheaper Motion King for the Z or one of the NEMA34 Motors?

Or have I missed something that says they all need to be the same motor? All the threads I see say the Direct drives are working and for some savings you could use the MK for Z and SG7.2 to drive X and Y.

[Gerald D]

Dave, the smaller motor with a belt reduction could work, but I don't see it making the system much cheaper. Plus there is the risk that it might not work. Can the small motor handle the belt load? How is that motor's torque at working speeds? (Small motor torques at working speeds are generally good compared to bigger motors - overlay some graphs for fun).

MetalHead, if you mix motors, you make fault-finding difficult. Out here, we stock a spare motor. It just makes our life easier if all the motors, drives and power supply voltages are the same. The other thing to consider is that the high detent torque of the gearbox helps to keep the z-slide from dropping when the power is switched off.

[MetalHead]

Makes sense. Did not think about spares.

[dragonfinder1]

Gerald I think the savings would be substantial IF these motors would work.

OM motors $250 each = $1000
BOB $100
Power supply $140
Drives $130 ea $520
Total $1760

MK motors With shipping $550
Drive G-540 $300
Power supply $140
Belt reducers $140
Total $1130

RS23-570 w/shipping $325
Drive G-540 $300
Power supply (less than) $140
Belt reducers $140
Total $905

True the motors might not take the side loading of the belt drive, but I’m working on that. I have a design that would only add about 50mm to the motor length, so there would be no side loading on the motor at all.

So IF these motors would work, there would be quite a savings for me, I have a machine shop available to me to build the belt drive reducers and the coupling device (if needed).

Is it worth the $350 or so gamble? On paper it would seem so. Will I try it? I’m not sure yet, the RS23-570 motors are pretty small. On the other hand, they are the same length as the MK motors, just the cross section is MUCH smaller.

Dave

[gmessler]

Another cost savings would be using silicone to attach the racks to the rails instead of the VHB tape. $3 tube of caulk vs $45+ roll of tape

[Gerald D]

Greg, that could work. Will need a good long curing time because of the 2 metal surfaces.

[shaper]

Been lurking for a while now and considering the G540 as a driver largely because it's a bit more straight forward from the electronics side. Which MK motors are you considering for use with the G540, I haven't found one yet that appears to fit the requirements of the G540, keep ending up back at the OM PK296A2A-SG7.2 which I'd like to get away from as to purchase them here (Australia) your talking almost AUS$3500 or trying to import from US which I can't imagine being a lot cheaper.

Jed

[dragonfinder1]

Been lurking for a while now and considering the G540 as a driver largely because it's a bit more straight forward from the electronics side. Which MK motors are you considering for use with the G540, I haven't found one yet that appears to fit the requirements of the G540, keep ending up back at the OM PK296A2A-SG7.2 which I'd like to get away from as to purchase them here (Australia) your talking almost AUS$3500 or trying to import from US which I can't imagine being a lot cheaper.

Jed

The MK motor that I would use if I were going to go with the Motion King motors would be the 34HS9801.

When I contacted Gecko Drives, they told me to add a 3.5K resistor for the current set resistor. They calculated that that would give about 87% of rated torque.

If you decided to use this motor, or any nema 34 motor, you should contact them directly to verify the figures, before you buy a drive. Also you have to remember that with the G-540 drive, you don't get the option of an indexer.

Which ever motor I use, I will use a 3:1 belt drive. We're working on a design that will allow me to change a broken belt in about 5 minutes. Even at 87% torque, I would have more than enough power to suit my needs.

Dave

[shaper]

Dave

thanks, will contact Gecko for more info, just on the face of it the 34HS9801 didn't appear to match the info in the 540 manual:(, but if they say it works I'll take their word for it:D.

I don't need an indexer anyway I'm looking at building a heavily modified mechmate for cutting surfboards and occasionally some ply or mdf sheet. Was figuring that the G540 was a good place to start and relatively cheap if I wanted to get more complicated down the track then I can build new control box with G20x drivers.

Not sure about the quality of the MK gearboxes but they tell me I can get 5:1 or 10:1 for $120 with the motor still asking questions about that.

Thanks again
Jed

[dragonfinder1]

Jed

Here is a link to a very good thread on motors and power supplys ( I hope )

http://www.mechmate.com/forums/showthread.php?t=932

Also the math that I used for the 3HS9801.

Dave

[Mike94531]

sorry for bumping such an old thread....had a crazy idea while sitting in traffic today....

if you don't mind leaning over near the floor and have nice concrete slab, use concrete machine screw anchors, up to 5K lb pull out rating, more if using a better contrete

http://www.confast.com/products/tech...ew-anchor.aspx (http://www.confast.com/products/technical-info/machinescrew-anchor.aspx)

reason I was looking into these was that I've been thinking about my lack of space, so if made a basic frame that I can bolt and unbolt to the floor, I can move the frame for the few times a month I see myself using it...when not in use, I can park my car in the garage where it belongs

[Gerald D]

Hey, in this forum we don't have old threads, unless they are locked in the Archive, and it is much preferred to post in topical threads rather than start all over again. If a thread is not locked, that's an invitation to post - absolutely no need for apologising. :)

[inventall]

some things I did to save $$

My control box was from Digi-key 377-1580-ND only 15.75X15.75X7.87" it is a little small but cost $86 and was ordering from them anyway.

Found a great steel place in Reno NV (Proto- Fab) that would sell me any length at good prices. The 1.5" square by 9 inch long solid bar that I used for the ribs cut on 45's on both sides cost me $4 a piece. That allowed me to use a lot less steel under the table.

I ordered most of the bolts from McMaster carr and Bolt depot.

I used the G540 With the pk296a2a-sg7.2 motors. I will worrier about the indexer later, if ever. The G540 got me up and cutting fast and cheap.

I used Cable chains with cheep foil shielded wire, 250ft for $80 off ebay. My thought is that it really did not need the braiding because it is not really rubbing on any thing. Anyway I have plenty extra. and we will see how long it lasts.

I used Cold-rolled steel for the Z-slide plate instead of tool steel. 1/4"x4"x36" was $24 instead of $150.

I used household light switches for E-stop buttons. and a $6 numerical pad for my bump remote, Works Great.

I did not use a machine shop at all. Only tools i have there are a Hobart mini mig, A drill press, 14" abrasive cut off saw, 4" grinder, and a 3/8 Dewalt drill.

I bought the router re-manufactured as well.

And no paint. Yet.

[[email protected]]

What does it cost to be up and cutting in the US? Any rough ideas on budget?

[domino11]

Robb,
It depends on what you have already, what you buy new and what you get deals on, as well as the options you choose. I know several have built in the $4500 to $8000 range.

here is one guy

...I built my 5x10 machine with 3HP router for 5819.00 - give or take a few hundred in receipts I probably lost along the way.

You can look at his build log here

http://www.mechmate.com/forums/showthread.php?t=460

[jhiggins7]

Robb,

As I've said elsewhere, I built my 97" X 49" MM for about $4000. My major savings was in acquiring 3 USED Oriental Motors Vexta Stepper Motors for $125 including shipping. I had to buy one new OM Vexta Stepper at $257 plus shipping.

Had I bought all new steppers, my cost would have been about $4700.

As Heath said, your cost will depend on choices you make along the way.
I did not "go cheap," but, I saved money where I could.

[lumberjack_jeff]

I'm intrigued by this thread.

If you total up the numbers for a 48 x 96 machine built about as economically as possible using the ideas here, the total is significantly less than $4000.

item qty cost ea total cost
router 1 $200.00 $200.00
motors and drives 4 $230.00 $920.00
laser cut parts (with shipping) 1 $500.00 $500.00
pmdx-122 1 $100.00 $100.00
bolts, screws, bearings, racks, pinions 1 $800.00 $800.00
power supply 1 $150.00 $150.00
gantry steel 1 $300.00 $300.00
x-rails 2 $25.00 $50.00
x-rail table attachments 2 $25.00 $50.00
wire 1 $120.00 $120.00
panel goods for deck, braces and spoil boards 1 $150.00 $150.00
$3,340.00


Am I missing any major expense items?

The gantry could ride on a wooden table essentially made from four torsion boxes with large timbers supporting the x rails. Getting the rails perfectly parallel might be a challenge, but as Gerald has noted elsewhere, once the table is surfaced, panel goods will sit "flat" to that surface.

[domino11]

Jeff,
Looks like you put some thought into this. :) What about a computer to drive the table? :)

[lumberjack_jeff]

Jeff,
Looks like you put some thought into this. :) What about a computer to drive the table? :)

In my case, computers, like lumber, are not a constrained resource. There are six functional computers with 30 feet of this chair, and another half-dozen nonfunctional ones. I also have a couple of buddies in the computer repair business. They're happy to let me take away the (surprisingly good but) functionally obsolete ones. Last year's gaming platform is perfectly suitable for machine control. :)

This assumes a machine running ubuntu/emc which is pretty performance-tolerant. I have good 2d cadd software, and g-code compiler software isn't prohibitively expensive.

When needs dictate 3d carving, one can upgrade.

Unlike boards (the wood kind as well as the circuit kind); steel, welding talent and money are significantly constrained. :(

[domino11]

Jeff,
Ok sounds like you are all set for the computer then. Take note that some users have had problems with multi core processors for machine control.

[lumberjack_jeff]

Jeff,
Ok sounds like you are all set for the computer then. Take note that some users have had problems with multi core processors for machine control.

Cool! This makes my Flintstone-ish tech collection even more useful. :)

As soon as arcnet cards and 2400 baud modems become collector's items... I'm all set, baby.

(My only multi-core computer is the least reliable machine I've ever had - for EVERY purpose. Especially for Ubuntu 64, but Vista isn't much better)

[Gerald D]

Jeff, a quick scan of your list misses the cable chain and springs (gas+motor)...ie. the McMaster order

[lumberjack_jeff]

Thanks, I should have elaborated, my intent was to try to quantify all the suggestions given including omitting cable chains, and instead "Hang the cables from the ceiling".

But I definitely forgot about springs.

I'm strongly tempted to try this, to push the envelope. Within the constraints of safety and RF noise, how inexpensively can a a MechMate be built? Let's see where the points of possible economy lie, and which savings are penny wise and pound foolish.

There's something about working with local resources and available materials which appeals to me too.

I promise to lay bare all my stupid cheapskate mistakes for all the world to learn from. Momma always said I'd be a good role model... or a bad example. I also promise to not beg for a serial number until after I've upgraded beyond the bailing wire and duct tape and into a proper paint job ;)

[Gerald D]

Jeff, I like your attitude, and you are obviously going into this with your eyes wide open. Will be watching with very keen interest.

Why use duct tape? Masking tape is cheaper! :D

[felix]

Gerald,

you basically said to me that an MM is an overkill for what I want to use it for (non production work or hobby like stuff) and you referred me here to this thread to see what could be done to reduce building cost.

If I understand correctly, one of the biggest expense comes from the electric and electronic components requirements. If this is actually the case then I wonder if reducing the mass of the moving parts wouldn't be a practical approch. This of course should be done with minimal (if any) sacrifice to the structural integrity of the machine. Say one would build the grantry, Y car and Z axis from mostly aluminum.

Since the Young's (elasticity) modulus of alu is about 3x less then that of steel one could more or less compensate for this by choosing a different cross section in order to increase the moment of inertia and get the same level of deflection. In simpler term, the formulas to compute stress, deflection and what have you, don't change but the properties of material do, so using aluminum would flex more then steel if both have the same cross-section but choosing a different cross-section for alum parts could reduce that to a minimum and still weight less.

This weight reduction alone may not solve vibration problems (in fact it could increase), that's complicated stuff but it could allow one to use smaller motors and less costly electronics (drivers, power supplies, etc) and bring the overall build cost down. Vibration could be minimised by lowering the feed rate which may be a problem in a production environement but it may not be such a big deal in other situations.

Just an idea,
Yves

[Gerald D]

The MM design is based on parts being DIY-weldable, small z, big x&y, 24/7 processing of softish boards/sheets. If you want to use lighter parts (non-weldable) and smaller motors, for processing tall parts in hardwoods then the MM is the wrong design for you.

[Richards]

There would be minimal total difference in cost whether you buy size 23 motors (too small) or size 34 motors. The PK296A2A-SG7.2 motor costs about $260 each. The much smaller PK264A2A-SG7.2 motor costs about $160 each. So, you would save $400 dollars, but you would have a motor that puts out 17.7 lb*in of torque compared to 44 lb*in for the size 34 motor.

The same electronics could drive either motor with only a change necessary to limit the current to 2A for the 264 motor or 3A for the 296 motor.

[Gerald D]

Another misconception is that the mass of the MM requires it to have big motors. . . . . The main reason for biggish motors is to power a 3HP router at full speed making loads of sawdust. Contrary to popular belief, the mass of the gantry has little effect on motor size.

[Fronzel]

My own research showed me that unless you go for something that holds a Dremel, the scale of the mechmate doesn't really affect the price as much as you would think.

[domino11]

I know of several people within an hours drive from my house that have build the MDF type routers. I have seen them cut and they do work remarkably well. One I visited, the guy had build a Joes 2006 and spent around $4000.00 on it. That made my mind up to build a Mechmate for a little more. :)

[KenC]

Would like to expend on Gerald's clarification on the mass.
1)
Remember this?
Force=Mass x Acceleration

As long as the force is sufficient to provide enough or more acceleration, the mass is really no concern at all.

2)
Also, with his beautiful sliding rail design, the static friction is negligible, so it won't add more work for the motor...

3)
Leveling of MM is done with a spirit level, when done correctly, the static force acting on the car is purely vertical gravity...

Heath, IMHO, these people has enough resources for self-indulgent. Perfectly fine to me. I'll do the same if I have the means.

[KenC]

I've been sourcing around and scrounge hard for my 1st MM build. Here is my take

1) BOB + Driver + Motor from US$500 (Frugal direct drive + DIY BOB + direct chinese import of your choice) to US$2000 (PMDX + gecko drive + 7.2:1 Geared OM + all bells and whisle )
*DIY BOB is an option, but DIY driver is not for the light hearted...

2) Frugal Built, MM on concrete floor without table structure and work on your knee.
*Faster and less work too...

3) Free/give away old PCs + CRT monitor + Linux + EMC2.

4) DIY V-tyre with any material in the junk box. since there are good result reported even with plastic.

5) No remote control, Zero Set, start, pause. No proximity switch.

6) Rack is surprisingly expensive... Look hard for better price...

7) size the work size for minimum left over

8) Chinese water cooled spindle + VFD isn't that much more expensive the high power router.



I echo Gereld's concern on safety.

It is admirable if one pursuing a goal till death, but it is plain idiotic to kill himself doing it.

[felix]

Would like to expend on Gerald's clarification on the mass.
1)
Remember this?
Force=Mass x Acceleration

As long as the force is sufficient to provide enough or more acceleration, the mass is really no concern at all.

2)
Also, with his beautiful sliding rail design, the static friction is negligible, so it won't add more work for the motor...

3)
Leveling of MM is done with a spirit level, when done correctly, the static force acting on the car is purely vertical gravity...

Heath, IMHO, these people has enough resources for self-indulgent. Perfectly fine to me. I'll do the same if I have the means.

Ken,

in the case of moving mechanism such as the MM, one should use something like E = 1/2 mass * speed^2. As others have said, moving the gantry doesn't require much force or energy but if you add a working 3hp router and try to move it as fast as possible then you'll see why you need a more powerfull (step) motor then what would be suggested to just move the gantry.

Yves

[KenC]

Yves,
Yes, Kinetic Energy is another analytical approach. But I thought F=ma is more well known.

As Gerald mentioned, the predominant force the stepper motors required to handle is actually the reaction force of the cutting action (dynamic load).

When feeding the cutting tool into the job, it is like running it into a wall, the tool bit relied on the spindle + cutting edge geometry to "clear the way" by chewing away the "wall". So theoretically, if the spindle has enough power and the cutting bit is efficient enough to chew and clear the way, the reaction force will minimised and feed speed can be infinitely fast, like a hot knife cutting through butter ;). BUT, in reality, there is always a point of diminishing return...

Steel is the cheapest metal known to mankind. Buying Aluminum with equal structural properties will only INCREASE the cost (3X more expensive is the general overall ballpark figure).

I'd detailed my cost estimate, for now, $3380 is the best that I could do for 2440x1220...
Frugal build, optimise steel usage, put a 2nd hand price tag on all the components from my junk box & salvage, c/w spindle + VFD, exclude all tools, consumable, workshop setup and my labour hours.

Can't wait to start
;)

[Temuba]

Another source for inexpensive/cheap material and supplies is your local surplus place. If you live near the NJ, PA or DE tri-state area, it will be worth the trip to Fazzio (http://www.josephfazzioinc.com/). This place has everything from all types of metals to surplus, going-out-of-business, bankruptcy items they buy at auctions and sell very inexpensive.

While there the other day I purchased for my build the following:
(1) NEMA 12 Enclosure: 24"x20"x8" new w/scratches for $45.
(2) Emergency Stops w/boxes new for $12 each.
http://i585.photobucket.com/albums/ss292/temuba/DSC_4437.jpg
http://i585.photobucket.com/albums/ss292/temuba/DSC_4440.jpg
http://i585.photobucket.com/albums/ss292/temuba/DSC_4434.jpg

Just be warned!!! This place is like a candy store for guys :D. I usually spend a minimum of two hours just looking around before buying anything.

[MetalHead]

My kind of place !!!

[Travish]

What a steal on the Hoffman case! Cool! I wish I knew of a place here in washington. They might have a few at Boieng surplus though. I'll have to look next time I'm down there.

[jehayes]

Travis: There is a place in Bellingham that has lots of used/surplus building supplies. Can't remember the name but can look it up if you want it.

[Travish]

Joe,

Yes please! Wonderfull to hear. That's just up the road from me. Thank you! Do let us know.

Travis

[Besser]

In my current build I have found the 2B's saves lots of money. Begging and Borrowing

Borrow Tools:
I borrowed the rail cutting saw and grinding setup, took care of them, kept them clean and saved on buying!
Borrow the welder, Horses whatever!

Beg:
So many people have sheds full of jars of Fasteners they will never use. I begged a bucket full of 5/8UNF grade 8's and other stuff.
Computers, just find a kid about 16yo they will be looking to upgrade their computer sooner then later.
Steel, using purlins that were retired to a back yard heap of someone

With the 2B's the worst you get is a "No"

[jehayes]

Travis: It is the ReStore. Here is a link to their web site. Mostly building stuff but some electrical/hardware. I found a tone of cedar molding there once, did all my cabinet tops with it.

Good Luck.

Joe

http://www.re-store.org/index.php

P.S. I just noticed they have a Seattle store too.

[sailfl]

That looks great, they need those across the country....

[Travish]

Nils and Joe,

I went out today to check out this re-store and it was like a big home based materials thrift store. All the stuff was used stuff that was salvaged off of demo'd houses. Like doors, windows, molding and etc.... I didn't find anything that I neede today, but was good to go and check it out.