RepStrap Lego failure

Hello everyone,
I've spent a few days playing around with my old lego mindstorms sets, I have 2 X RIS 1.0 and 2.0 sets, and all the expansion sets, I don't have the NXT, as i've kinda grown out of lego now.
In any case, i've found that lego is a bad choice for anyone doing a RepSrap, for three reasons,
1) Cannot span an axis overhead, as the plastic flexes too much
2) Difficulty with interfacing metric parts with it
3) Lego has too many small parts, while its fine to make small things it ain't so good at making anything medium scale.

The last expansion set I bought was "Robotics Discovery Set", which allows you to build a pneumatic X-Y plotter, which I found wasn't too good, and won't be any better with stepper motors.

So now i'm looking at buying cheap printers and tear out the mechanics to build a RepStrap.
I did find some nice printers real cheap, but before I buy them i'd like to get an idea of the stepper motors inside them, they are Canon PIXMA 190, would anyone know anything about them?

Thanks

Edit: Oops, I put this in the wrong section

Edited 1 time(s). Last edit at 05/30/2009 09:16PM by Grogyan.

I pulled apart a pixma printer a while back, I think it had DC motors and an encoder tape, disc inside it.

Do you you know much about the scanner part of it?

Estimating how the one at home works (printer/scanner), it sounds like its running off a stepper.

I finally found some decent torquey steppers, Linear Engineering's are no whre strong enough, off the shelf that is, but Keiling's look ok, and are fairly cheap enough to import. Trying to save money where I can, so if the motor in the scanner part is a stepper, and it can shift the weight easily, that'll save a whole heap of time and money.

Of the 5 or 6 scanners I have asimulated to date.. they all seem to have the same drive mechanism a geared 7.5 degree per step driving a tothed belt all of which with a little enginering skill and heath robison enginnering inventivness could make the x axis stage for a repstrap device.

[www.bbc.co.uk]

[en.wikipedia.org]

For the Y stage you would need two identical scanners and more heath robison enginnering inventivness.

The Z stage would be the bigger chalenge by far I think you would need a much more powerfull stepper or steppers to lift the work area.

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Yep, I could get the X and Y stage ok with Lego, but it flexes too much.

Z axis is impossible with the limited bricks that I have.

Right now the scanners are what i'm working on. I have two different scanners, the first i've already hacked and driven successfully, i'll be hacking the scanner soon.

Do they really have to be matched? Isn't there like a speed offset in the host software to compensate?

You only need identical scanners if you use two scanners for the y axis.

ie 2 drive belts moveing the x axis at both ends of the x axis like the reprap system.

X uses a 1 belt drive system Y uses a 2 belt drive system thus 3 scanners needed for two only 2 Axises 2 of which need to be identical.

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I'm only using one for the x axis, and one for Y axis.
I'm sorry, I don't quite understand where you're coming from for needing two drive trains for the Y axis.

I'm going on the premise that I can offset motor speeds by the host software as getting two identical old scanners is nigh on impossible.

Yes the SW provides the ability to have differnt drive resolutions on the axies

If you look at Darwin one belt is used on X axis and two drive belts are used on Y.

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

well i'll see how it goes with one, as I can't add any more belts or motors into either scanner.

However my tests over this weekend have showed that there is ample torque to carry the extruder and stepper for it. Been driving it all day at full step, which is showing plenty of accuracy (its geared down).

This is a RepStrap after all, a prototype of sorts, just trying to reduce costs as well, so far its just been $5 for the scanners, the other materials will be next weekend, while this week i'll be concentrating on the problematic Z axis.

If it doesn't work out, i'll just buzz Vik to print out a bunch of parts for a Darwin he's just half way across the city from me.