Closed loop stepper motor encoder help

[JohnHaine]

I was recently told that you can include linear scales in the loop using LinuxCNC, but as far as I know it isn't possible with Mach 4.

I don't think it would work just connecting the encoder output to the input of the motor driver because the motor driver probably doesn't understand anything about backlash since there isn't any between the motor and the usual rotary encoder. Also the control dynamics of the motor are quite different to the table, which has much more mass and more friction. You don't want to be making a compound cut when the table can't keep up with what the controller thinks it should be doing.

Don't overthink things. I can't see why for your first DIY CNC router you don't just use ordinary stepper motors, especially if you are using ballscrews already. The screws are likely to be at least as accurate as your build, and will have low enough backlash that you can just use the inbuilt compensation routine. Modern stepper drivers are pretty cheap and work very well.

If you manage to get a stepper motor to break its shaft I'd be VERY surprised!!!