Can McWire bootstrap a mendel?
February 19, 2010 08:09AM
Lately I've been reading quite a few posts, stating that the McWire is too slow to be used as a Repstrapper, some say that the extruder cannot be run at the slow speed required by the McWire, others that the print times are very high, 200-300 hours of print time.

It is quite important to me to find out if this is indeed the case, since I'm currently building a McWire like contraption.

My plans go something like this:
1) Complete the McWire and get it to print (may possibly involve using it as a light CNC machine to help create the extruder)
2) Print pulleys to help convert from threaded rod to belt and pulley
3) use the modified McWire to print mendel parts

Or should I completely abandon my McWire efforts, and if so, what direction should I take?
Re: Can McWire bootstrap a mendel?
February 19, 2010 09:24AM
My plans are very similar!

There are a couple of discussion ongoing as to whether anyone has built a Mendel (or Darwin) using a McWire as the RepStrap.

I have seen on YouTube a number of McWire machines using belt and pulley and they are as fast as a Mendel (if not faster).

I am planning on using M8 threaded rod instead of the ~M6 in the design and if that turns out to be too slow to convert to belt and pulley just as you plan on doing.

The extruder I intend to build simply with my own design (McWire Extruder V1) that requires no laser cut or extruded plastic pieces.

Edited 1 time(s). Last edit at 02/19/2010 12:39PM by rhmorrison.


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Can McWire bootstrap a mendel?
February 19, 2010 06:53PM
Interesting video.

I'm sure you will find problems when you get to actually building it. Keep everyone up to date.

What did you draw it with? I wish everybody would make their drawings available. Especially if it's in Google Sketchup. I can zoom in on the details that way. Not to well versed in AOI.

I definitely am in need of an extruder. My repstrap is one of those that is more like a glacier than a cnc. It's fun to watch move but just too slow to use.
Re: Can McWire bootstrap a mendel?
February 19, 2010 10:53PM
Yes It can. By doing the following:

Build the original repstrap with the threaded rods for movement and use that structure to create only the herring bone rack and pinion that Forrest designed.
Then replace the threaded rod assemblies with the rack and pinion assemblies and get the speed increase necessary to build a Mendel.

Forrest how long do you think that it would take to make a rack that is 18" long even in segments and a second rack 9" long. Plus 2 pinion gears using the threaded rod system.

Remember to bootstrap the bootstrap as many time as you need to get something to work.


Bob Teeter


Bob Teeter
"What Box?"
Re: Can McWire bootstrap a mendel?
February 20, 2010 04:03AM
Yes, I used Google Sketchup to design the part (and generate the animation).
As soon as I get the design finalized I will also post the Sketchup file.


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Can McWire bootstrap a mendel?
February 22, 2010 12:41PM
The answer really is "Yes, Theoretically." As near as I've been able to tell, nobody has actually done it. I feel like I'm in a race with a few different people to actually accomplish this feat. smiling smiley

If we do find that Seedling really is incapable of printing a Mendel simply as a matter of time economy, I think it's time to start designing a second generation Seedling. I've been writing down some ideas, before we jump into it though, I've wanted to see my McWire in action. (I'm probably a week or two away still)
Re: Can McWire bootstrap a mendel?
February 22, 2010 01:17PM
Although I haven't built the McWire yet I would say that it is easy to obtain the parts and put it together. The only apparent problem is the threaded rod drive. If we simply change the design to a belt drive (for the x and y axis only) then we should have a cheap RepStrap machine that is as fast as the Mendel and should therefore be capable of creating the needed RP parts to build a Mendel.


Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Can McWire bootstrap a mendel?
February 22, 2010 03:32PM
bobt Wrote:
-------------------------------------------------------
>
> Forrest how long do you think that it would take
> to make a rack that is 18" long even in segments
> and a second rack 9" long. Plus 2 pinion gears
> using the threaded rod system.
>
> Remember to bootstrap the bootstrap as many time
> as you need to get something to work.
>
>
> Bob Teeter

On my Rapman running at 16 mm/sec it takes about 120-180 minutes to print 4 pinion gears. I do them in groups because when you try to print a single one with Skeinforge it either gets wrapped up in a cocoon of ooze threads if you use the orbit cooling scheme. If you don't orbit the time the extruder head spends over the gear makes a melted mess of it. Printing multiples gets you away from orbiting if you make enough of 'em. They are much easier to clean and prepare for use that way. smiling smiley

I'd probably do three, six inch racks at a time since if I run them diagonally you tend to lose a bit of definition and can only print one at a time that way.

I haven't run three at a time of that length, only two, but I'd estimate that it would take about 2 hours for three.

Keep in mind that I'm using a 0.3 mm extruder nozzle, not the usual 0.5 mm, so it takes me longer to do things. I haven't tried to do this with 0.5. You may lose too much definition with 0.5.

You could easily do that all in a couple of 8 hour shift on my machine. McWires are typically very slow by comparison which would magnify that time and create additional problems for you with the hot extruder head spending too much time over the print surfaces and you'd have to orbit, most likely. Could take you several days on a McWire. I wouldn't try it, personally.

Edited 3 time(s). Last edit at 02/22/2010 03:35PM 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
Re: Can McWire bootstrap a mendel?
February 28, 2010 01:49PM
I was starting to suspect that I was actually building an interocitor, now I'm sure of it. Oh well, to late to turn back now I suppose.
Re: Can McWire bootstrap a mendel?
February 28, 2010 10:47PM
thethompsonfive Wrote:
-------------------------------------------------------
> I was starting to suspect that I was actually
> building an interocitor, now I'm sure of it. Oh
> well, to late to turn back now I suppose.

And this isn't paper! It's some kind of Metal...
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