Salvaging parts

Do you guys think i could find an old printer or scanner (from my garage or craigslist) and take parts? I know there would be a toothed rubber belt, but what other parts should I look for? And what else should I take parts from?

I'm currently using stepper motors and a stepper driver board from an old dot matrix printer in my repstrap. The older the printer the better as the technology will be easier to adapt. Scanners will only have one stepper motor (and may be less powerfull) whereas most printers contain two often identical motors. The motors i'm using are significantly less powerful than the ones in the darwin design, so need gearing / using in a mcwire style design.

i took apart a few printers (and one scanner) recently to gather parts, so here's my observations:
i've dismantled 3 semi modern / modern inkjets - two HP's ( a 712 and a 6??) and a Canon bubblejet 2010 - probably mid 90s ?
both HP's use a DC motor and a optical diode / detector with a striped belt for x position. both contained two steppers - one for advancing the paper and one for the "head cleaning / parking area" - these were pretty small and 24 / 48 steps / rev.
the Canon relied on a stepper for x position, but it's 48 steps / rev (and had another smaller 48 steps / rev stepper - i don't remember for what).
All three had a toothed belt for x drive, but no two use the same pitch / size. You do get nice ground shafts from these, useful for cartesian robots.
The scanner (mustek 600 II ep) has only one motor - a 48 steps / rev stepper, geared down. i'm going to use the overall mechanics as one of my axis - but it really is too low res / too high backlash and rather fragile, so it's just going to serve as a first attempt.
So none of these had anything close to the 200 or 400 steps / rev steppers that you'd really want, and even the ones i got are 20-50 ohm coil resistance, so much lower power than desired. Seems that you need a much older printer for quality parts ;-)
niv

... i extracted some very strong 200-steps-motors from NEC-Needle-printers and HP-Inkjets form the early '90-ths and smaller qubic-shape motors from old floppies and hard-drives (very, very old, out from the MFM/RLL-age )

The oldest 5-volt 200-step-motors i found im IBM-card-readers and -printers.

*** appended ***

I sneaked through my scrapery in the cellar and found some very old XY-writers and Pen-plotters from Gould, Computagraph and Picom, a type-wheel-printer and a laserprinter from Brother and some more recent printers from Canon, HP and Lexmark.

Ye older the printer, ye better/bigger/stronger the motors (the XY-writers have servo-motors instead of steppers).

But the finest motors i found in old harddrives, where the stepper-motors moved directly the R/W-heads.

In the older drives (full HE) the motors are mostly cubic-shaped, in the drives from early '90th on some have very flat cylindrical motors - mostly have 1,8

Edited 1 time(s). Last edit at 09/23/2007 04:17PM by Viktor Dirks.

In my experience, the best stepper motors (and many of the associated components) are found in dot matrix printers. Up 'till the mid-80s, the tractor drive for the fanfold paper (remember that? ) had some fairly powerful motors. I have a stack of steppers I took from, if my memory serves me right, a pile of broken old Apple Imagewriter IIs that I got at the MIT electronics flea market a few years ago. If you are in the Boston area, it is a _great_ place to pick up electronics salvage, and to meet other local geeks. Check out: [web.mit.edu] for more information on the MIT Swapfest.

i remember as a kid my parents getting me a broken photocopier to pull apart.. for what i remember it had some large steppers in it. if you went to a copier repair place they should have some dead machines to get rid of

The machines I took apart were very old Epson machines. Got some quality 200 step motors out of those. They weren't cheap/low-end models however. Frankly, they were built like tanks! I initially thought I had a couple 400 step ones but I was wrong. :-( Such is life.

However, I wonder how much we are saving ourselves as the Darwin design makes use of a shaft coming off the back of a motor? Also, these motors may be drastically under powered. I don't know enough about them.

I know of a couple copier repair places around here. I'll check them out for old steppers.

yeah, that is IMHO one of the biggest design flaws of the darwin design is using a dual shaft stepper motor. it really ties you down into using a specific (and expensive) stepper motor :-/

... best workaround to avoid a dual-shaft-motor would be to set the motor beside the (then longer) rod and drive the rod over a tooth-belt.

Then the motor can be smaller, coarser and weaker - with the right ratio of the gears i can make the wished power-translation ...

Viktor

i can quite understand why twin shafts are needed. looking at the pics only the front shaft is used?

Hi moonspud,

... i think it's needed only for the Z-axis to adjusting the extruder and manually turn the axis, until the extruder-tip is in the right plane ...

With the motor parallel by the rod you can make the same thing with a knob on the end of the rod too (if the motor isn't to strong).

Or you insert a freerun(?) ...

Viktor

Edited 1 time(s). Last edit at 10/16/2007 01:51AM by Viktor Dirks.

From what I've read, there isn't a real need for both shafts. Earlier in the design when they settled on a standard stepper motor, they noticed that the dual shaft model cost the same as the single, so they selected it to give themselves more options down the road. It looks like it was easier to make the motor mount for the Z axis if they used only the rear shaft instead of only using the front shaft.

I think a few people were planning on mounting a regular single-shaft stepper upside-down, just using longer bolts. Never heard if that worked.