I'm thinking about making a C/A head for my next router (rotates the router about the Z and X axes to give 5 axis movement). It needs a large gear reduction between the servo and the head - something around 64:1. Going with timing belts and pulleys commonly available from SDP/si, it looks like that would require 3 sets of pulleys. I've been reading a bit, and all I can find is that the GT2 belts are the lowest backlash commonly available. However actual backlash is never really specified... Does anyone know or have a feel for how this would work out? Would backlash add up to unacceptable levels with this many reduction stages?
In comparison, I've been looking at the Thompson Micron Ultra True gear drives and they typically spec backlash in the 10 arc second range, I believe (although that's just from memory). When I was doing the calculations, I think that translated to a 0.015" movement (or lack of movement) of the tool tip on a long tool which didn't sound particularly great to me.