4th axis

[golash]

Hi all
I have a diy cnc I build some years ago http://www.woodsolutions.com/diy-cnc.htm I`m wondering
if anyone has purchased a 4th axis from ebay. There are a vast number of these items on ebay. The
most common seems to be a pulley reduction and at the other extreme the high end harmonic drives.
Hoping for some ideas.

Barry

[Magicniner]

The ones with pulleys at the back have some backlash, if you try to limit backlash with a bearing to tension the belt the stepper shaft bends and you still have backlash, I added an outboard support bracket and bearing to the end of the stepper pulley to support the shaft when the belt is tensioned.
This allowed the addition of the tensioning roller without shaft flex and I have near zero backlash,
Regards,
Nick