McWire vs. Reprap

Hi everyone, I am considering building either a cartesian bot or a reprap. from what ive seen, the reprap is more accurate as far as plastic extruding goes, however i also wanted to use one as a milling machine. it seems like the mcwire is better suited for milling. my question is, how accurate is 3d printing on a mcwire? is it comparable to a reprap? also, is there a cheaper way to do the electronics for a mcwire. i will probably end up using a reprap mobo, but just curious.

Thanks, - Joey

also another quick question, i found some 24v stepper motors on ebay. [cgi.ebay.com]

are these too high of voltage to work with reprap electronics?

The McWire is slower and more accurate than the RepRap designs. The McWire uses a threaded rod to drive the x and y axis, and so it moves around 1 or 2 mm per revolution. The RepRaps use a belt drive for the x and y axis and so they move around 40 mm per revolution.

Generally speed is more important for additive processes than subtractive processes because the amount of work you have to do is proportional to the total volume. Big things take a long time to make.

I haven't seen anyone put a router on a RepRap. I believe the main problem is that the rods that hold the tool will likely flex under the weight. There may also be a problem with the tool moving when it contacts the work piece (although this may be minimized in the Mendel design).

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Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]

Thanks for your input. I'm definately going with the mcwire then as milling is fairly important. Does anyone know if 24v steppers will work for this project?

jg Wrote:
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> Does anyone know if 24v steppers will work for
> this project?

They should. You get a 24v power supply with them so you should be able to get the full rated torque. Here is a catalog of steppers provided by that Japanese company.

[tamagawa-seiki.com]

Looking through, it appears that your particular model is no longer made under that serial number. Looking through, however, it appears that the modern equivalent to what you have is...

TS3103N255

You've got about 95 oz-in of torque out of it, which is pretty good for the amperage you are putting in.

Edited 1 time(s). Last edit at 12/20/2009 01:21PM by Forrest Higgs.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Thanks Forrest. That info is definitely what i was looking for.

jg, I spent a little while with zero luck trying to find a gallery of McWire milled objects.

You may want to do a bit of research and confirm that the McWire has the precision and power that you need; I've become skeptical of it, but without any actual experience; just absence of evidence.

If you decide the McWire is no good, you may want to go with a small CNC router or CNC mill or mill/drill. e.g.:
[cgi.ebay.com]
[cgi.ebay.com]

Sherlines and Taigs seem to hold their value well, which will hurt when you buy it and help when you sell it.

[www.cnczone.com]

Thanks for the suggestions, but they are out of my price range... When i said i would be doing milling, i meant very light milling, plastics and thin aluminum, also cutting traces on copper clad pcb. its more of a lets see if i can get this to work kind of project. i realize that it wont have the accuracy of the higher end cnc's but thats not the point, its so cheap to make one its worth a shot.

We have built a repstrap based on the McWire, and I've had great luck milling wood (both hardwoods and mdf) with a Dremel tool. Including milling a very nice pinchwheel driveblock (in two pieces) for plastic extrusion. It does NOT work well on aluminum, even with carbide bits though.

When I get around to it, I'll post some pictures, but it has spent about 30 hours total doing milling (bookmarks with engraved names for Christmas), and has held up very well.

One thing that is a pain with the Dremel is the maximum 1/8" size for bits. I got some really nice coated carbide bits from carbidedepot.com, and have been happy with them, but a 1/8" endmill takes a LONG time to face a piece of wood with a machine driven by a leadscrew (it is slow...).

I wouldn't put a full-size router on a McWire-type machine. The way the z stage is constructed, it would likely not hold up to the combination of weight and vibration, especially at the higher feed rates and cut depths you'd be able to do with the full-size router. I've been playing with the idea of putting a mini-router (called a trim router or laminate router ususally) though, which would at least allow me to use 1/4" bits (and make those facing operations a ton faster).

I know about that dremel problem.... i wish they had a way to put larger collets in. i was looking into one of those laminate routers, as they seem like they have more flexibility as far as bits go. I would really be interested to see some pics of your build. Im getting the parts together, but my stepper motors are 24v. how did you do your electronics? did you do reprap 3rd gen? the standard reprap stuff is 12v, so it will be interesting to see how it comes together. i found this thread for 24v pwm controllers, but it seems a little old, not sure if its the same thing for gen3 electronics. if anyone has any info on this that would be great. i plan to have the assembly section built before the end of january, so i will post pics for all interested, however i think the electronics part will be the hardest.

I'm not too familiar with what the clearances are on the McWire, but Dremel makes a flexible extension. You could mount the motor on a separate stand and only bind the extension to the McWire. I dont know what kind of slop is in the end of the extension though.

I had a question regarding the McWire - what is the thickness of the acrylic sheets? I don't see a reference to it anywhere. Do people have recommendations? Right now I'm at the stage of pricing things out to try to get a real evaluation of the cost, and I'm trying to figure out what the sheets would run. Thanks!

I just built one up using 0.25 inch. I would not do the bearing swing arms in plastic as they are breaking and I am having to replace them. Also the opto end stop pEts ar not needed. Only do the platforms. Also some of the holes need to be corrected for size.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Hi B^2,
Thanks for the reply! I had a few follow up questions if you'd be willing to answer. Did you make your own platforms or have someone laser-cut them? If you had someone laser cut them, who did it? Secondly, what did you make the bearing swing arms out of if not plastic?

Thanks!

Edited 1 time(s). Last edit at 01/03/2010 07:35PM by kevin_e_schmidt.

I had the plastic pieces made with pololu.com's laser cutting sevice. I hear Big Blue Saw is good to but I haven't used them.

I did have the bearing arms laser cut too but unfortunately they are failing. They could be made out of aluminum or 1/8" to 3/16" fiber board. I have been using fiber board to replace the ones that have failed. I have been documenting my journey through the build. Here is my entry for the laser cutting. I need to go back and alter the files to reflect what I have learned.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Hi B^2
Do you mind if I ask how much pololu charged?

$40 for the clear acrlylic.
$83 for the cutting.
$17 for the shipping.

This will be Lot less if you only do the platforms. They will give you a quote before you commit to a puchase.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Hi again,

Is there any reason not to simply get some plexiglass cut to roughly the correct size & use the "stickers" as guides to drill? As far as I can tell, the only features other features are the curved corners and the notches. I can't see any mechanical use for these features.

Kevin

That would work just fine. You'll want curved corners for the acrylic. I didn't use the notches. They are intended to line up with the opto end stops but didn't work out for me.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Yet another question - why are there two copies of the Vertical Base in the laser cuts file (both your version & the "official").

No problem with the questions. They are all good and others will benefit from them.

I think it is for stiffness encase you want to mount a rotary tool. That's the only thing I could think of. I only have one installed and it is fine for the plastruder. I do plan to have the Dremel tool mounted to it one day so I had it made. However, I have a 1/2" plywood interface/adapter between the pipe flange and the Z platform. That is adding stiffness so I probably won't need the second copy.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

bjbsquared, could you put those files up on the wiki? Ideally human-viewable, rather than a zip?

Cheers,
Sebastien

SebastienBailard Wrote:
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>> Ideally human-viewable, rather than a zip?

As to be seen inline by the browser? or PDF?

I can do it how ever you want but I was going to incorporate some things I learned first.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Inline in the browser is better, because then we can wiki fiddle the text around the images. pdf is useful for people printing paper before fabricating parts, but inline takes precedence, generally. Inline is 10x better for people skim-reseaching the wiki - 'So that's what that is, I can make one of those ... Ok, let's go with it!'.

I can do it how ever you want but I was going to incorporate some things I learned first.

Research takes priority over documentation, as always.
I think it helps, though, to simultaneously cross-post into the wiki while blogging. Otherwise, it stays on the todo list and becomes a massive chore, or falls off the todo list.