Z Axis Why 2 motors vs 1 motor?

So far all the designs i have seen use 2 motors for the Z Axis, I did read a comment somewhere, that an earlier design used 1 motor for the Z Axis. One motor makes more sense to me, as it is nearly impossible to keep two motors synched for any length of time, while one motor using belt tensioners would be able to synch the Z axis, and if it unsynched it would be easy to fix, remove tension, and adjust.

I am interested in building a 3d printer, and have found the RepRap to be one of the options. Heavily modified to fix some down sides i see with the Prusa, Mendel, Wallace, and Huxley designs.

It seems that if you had the excruter head move X and Y, and the Bed move Z, then the whole thing would be more efficient.

You can answer your questions and get a bit of history lesson if you start at the reprap wiki.

Quick answers:
1. An extra motor is actually cheaper than a belt and additional gears. Synchronization is not really an issue with properly matched and installed z motors. When they go out of sync, it's quite easy to adjust.

2. Reprap is not one option. It is MANY options!

3. The movement in the Mendel and derivatives was an a improvement over the earlier design, Darwin. Watch the video in this page: [reprap.org]. There are of course present day designs that use both movements. You can pick whichever you like.

Edited 1 time(s). Last edit at 01/27/2014 10:36PM by brnrd.

While I think I agree that 1 motor would be better than 2, I agree with brnrd. Two motors is still a viable solution as well... both price-wise and functionally.

Thank you brnrd, that video answered my question very well.

I still have some design ideas in mind, some that could change things if they work. But i guess i need to ask what parts besides the bushings/bearings, do i need?

Extruder
Step motors
bed, prolly heated
belts