Rack and Pinion Mini Kossel or Rostock?

Hey Guys,

I recently saw http://www.thingiverse.com/thing:37787 and http://www.thingiverse.com/thing:6011. I had this concept for a Mini Kossel using these as a drive, with the pinion mounted near the top, and the carriage mounted on the bottom of the rack (the rack being the long strip and the pinion being the gear).
The main reason for having the rack move and not the pinion is to keep the carriages small and light. The motors would likely have to have significantly higher holding torque than most, as well.

This would be significantly easier to implement on a Rostock, because of the fact that the frame uses smooth rod, not alu extrusion. I'm going to do a belt-driven version first, but I hope to eventually get a system like this up and running.

Do you guys think this is doable?
I'm very interested in printing as much as possible of a printer. My local hackerspace charges a small monthly fee and gives unlimited use of the printers. I think that there will always be a need for non-printed printers, because some people don't have access to a printer, but in general I think we should print as much of the printers as we can...


Anyway, thanks for listening to/reading my rambling...what do you ppls think?


--evamvid

I think this gives you a very sturdy and rigid connection, unless you have play between pinnion and rack. You may want to think a little about the pinion diameter (speed vs. resolution).
May be its an idea to put a ball bearing (or two) at the other side of the rack, so the rack is between the pinion (adjustable by long holes for the stepper) and the ball bearing(s).

if parts are printed good why not.

just one detail.

in this system motor is often spring loaded to avoid backlash between rack&pinion, because they will wear out.

so i suggest to do the same thing..




when i searched for image, found another interesting concept

Is that a roller pinion?

sorry for grammar/typos etc, im on a mobile device..

Rack and pinion have an issue of Backdrive when powered off when used in the Z axis. I have not built my printer yet, but was curious if the belt drive versions also backdrive when the power is off? Asside from cost, is there a reason leadscrews are not commonly used in the Delta printers?

Marc

Leadscrews are too slow (unless you use high speed ones, but those are more expensive than regular old threaded rod)

Edited 1 time(s). Last edit at 08/12/2013 05:00PM by evamvid.