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-   -   Build a functional MechMate at lowest cost - what can be done cheaper? (http://www.mechmate.com/forums/showthread.php?t=1174)

jhiggins7 Wed 22 April 2009 20:18

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 Thu 07 May 2009 13:35

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.

Code:
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 Thu 07 May 2009 13:58

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

lumberjack_jeff Thu 07 May 2009 15:30

Quote:
Originally Posted by domino11 View Post
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 Thu 07 May 2009 15:53

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 Thu 07 May 2009 15:57

Quote:
Originally Posted by domino11 View Post
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 Thu 07 May 2009 21:17

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

lumberjack_jeff Fri 08 May 2009 00:10

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 Fri 08 May 2009 03:20

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 Sat 11 July 2009 23:54

Reducing cost???
 
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 Sun 12 July 2009 02:32

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 Mon 13 July 2009 11:33

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 Mon 13 July 2009 11:42

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 Tue 14 July 2009 06:56

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 Tue 14 July 2009 10:14

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 Wed 15 July 2009 07:35

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 Wed 15 July 2009 08:25

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 Sat 18 July 2009 07:32

Quote:
Originally Posted by KenC View Post
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 Mon 20 July 2009 07:59

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 Thu 25 February 2010 14:00

Local Surplus Outlets
 
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. 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/s...a/DSC_4437.jpg
http://i585.photobucket.com/albums/s...a/DSC_4440.jpg
http://i585.photobucket.com/albums/s...a/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 Thu 25 February 2010 14:23

My kind of place !!!

Travish Thu 25 February 2010 15:16

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 Thu 04 March 2010 11:44

Surplus in Washington
 
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 Thu 04 March 2010 12:03

Joe,

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

Travis

Besser Thu 04 March 2010 13:47

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 Thu 04 March 2010 18:05

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 Thu 04 March 2010 18:10

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

Travish Sat 06 March 2010 19:21

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.


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