I have an Anilam Crusader M 3-Axis Mill with Westamp Servo Drives. The machine started to hunt for position and would not hold zero when at home. It would dither back and forth around zero by up to .001" either way. This machine has Tachs and glass scales.

I got the drive tuning procedure from Anilam and set out to tune the drives. I went through the process several times...

I have now tuned the drives the best I can and it holds position better and does not hunt as much as it did before. However, now when I try to set zero on an axis it will move .001" out of position in the positive direction.

The first time I tuned the drives the z-axis did this and would add .0005" to its position, I couldn't get the X and Y quite right either. After tuning several times the z-axis is rock steady, but the X and Y will add the .001" to their position.

Any idea what is going on and what I can do to fix it? I have balanced the control and the drives to as close to 0mV as I can get.

Procedure in a nutshell is:

1) Disconnect scales from counter board.
2) Adjust the red tabbed board until all axes read 0mV.
3) Adjust the balance pot on the servo drive until it reads 0mV.
4) Reconnect the scales and set the signal.

Thanks,
Steve