Here is an advanced idea that is quite feasable and completely possible.

When you get backlash on your system, it has to be compensated, and as I understand it, software can compensate for it, but how well, and to what resolution? I can imagine it being even worse when trying to engrave back and forth on something very small and fine.

Usually the servo motor drive has an encoder on the rear, so your software/electronics knows exactly where the motor position is.

The idea is to have the optical encoder not read directly from the motor shaft, but from the gantry position itself.
A simple construction of this is to have an optical encoder operated by a thin tight high tensile wire attached to the gantry and running across to the encoder shaft, on the side of the machine. (less moving wires too!)

Or the wire fixed at each end and running along the axis, and wrapped a couple of times around the encoder shaft (specially made pulley, like in an old wind up clock mech.) The encoder which is mounted on the gantry.

I am sure there are more methods of actual construction, including an optical laser based position sensor? (prone to dust though) and I ask anyone, if they have any thoughts on this, to reply & include them here.

The reason I mention this is that my servo gearbox (3:1) has some noticable backlash within the gearing, and I'm thinking of ways to eliminate it, as I've not yet had any experience with a complete machine. Still building!

My intro: http://www.cnczone.com/forums/showthread.php?t=27905

My gallery: http://www.cnczone.com/gallery/showg...0/ppuser/36476
Thanks

Tony