http://www.orientalmotor.com/in_motion/october_2004.htm

This page shows some zero backlash gearing for stepper motors. Can we use any of this to our advantage?

Thanks for that link vadeem, it cleared up the mystery of the "Taper Hob" gear for me.

Sure, you can use it, but I don't know if there will be a significant advantage compared to the cost. The MechMate style machine doesn't particularly have a backlash problem, so I don't think you need to look for a cure.

CNCZone has a thread dedicated to this topic.

http://www.cnczone.com/forums/showthread.php?t=20527

Greg, that CNCzone discussion is purely on backlash for screw driven axes. Backlash on low-cost screws is a big problem and a reason for a MechMate to use spring-loaded rack & pinion instead. A MechMate with pinions direct on the motor shaft has zero backlash. Period.

The folk using the standard gearboxes from Oriental Motor, also with spring-loaded rack & pinions, are not complaining of backlash either. But I have no personal experience of it. That is something that I still want to try for myself - my gut feel is that it will be fine.

It uses the same prencipal, spring loading on the threads. Your's is a lot more simple if in fact there is zero backlash. With what I have in mind for building, I'll be using both ACME rod and rack and pinion systems, so I need all the input I can get.

I haven't measured it, but there's a lot more play in my gearboxes now than when they were new.

The gearbox offering from Oriental Motor is only available on some of their $$$ motors. The motor/driver/gearbox combination cost more than $2,200 when I last checked. After-market gearboxes with basically the same specs can be found at www.baysidemotion.com. Their gearboxes are in the $700 to $1,000 range.

Ballscrews with double nuts usually can be adjusted to near-zero backlash. Since typical ball-screws aready have a 5:1 ratio, doubling or tripling the ratio can be done with a belt-drive gearbox. By the way, a 5:1 ball screw would require 10,000 steps from a Gecko driver to move one inch. On a non-geared rack/pinion machine using a 1-inch pitch diameter spur gear (20-tooth, 20-pitch), it only takes about 636.94 steps to move one inch, meaning that resolution on a non-geared r/p is 0.00157 inches while resolution on the 5:1 ball screw would be 0.0001 inches - or 15.7 X better than the r/p. (Be aware that there are many other factors that make ball-screws less atractive on a CNC-router. A rack/pinion system is relatively accurate, robust, simple to maintain and inexpensive to build. I haven't found the need to improve the resolution when cutting wood products - that start warping the second after I take them off the Shopbot.)