Hi
My issue is this-  when my VFD is on and spindle is turning, and Mach 3 is engaged (that is, I can move all axis via keyboard controls)-  in this condition when I click 'RESET' the axis lurch several inches.   I know that both x and y lurch, but I have not confirmed that z axis also moves, although I suspect this is true as well. 

Also, when Mach3 is disengaged and I cannot move the axis via keyboard, and then I click 'RESET' to engage I do not get any lurching. 

I suspected a grounding issue, so I checked continuity with a meter.   All these points are grounded to a common point, and showed continuity to that point: 

Spindle
X, Y, and Z axis
Computer and power backup
Ascension controller (Gecko 202 drivers)
VFD

Is there a setting in the VFD or in Mach that can cause this?  What issues should I be looking for here?   

Thank you!
Wayne from White Salmon

UPDATE:  I was tracing the spindle cable, and found I had zip-tied it to the Z Axis limit switch cable.  I removed the ziptie, and as I moved the cable away from the limit switch, it moved close to the Z Axsi motor cable.  Without pressing reset, the exact same lurching happened. 

Looks like I'm facing some EMI interference from the spindle cable.   The cable is shielded, but the shield may not be connected properly.   I'm going to take the time to fix several related cable and connector issues, including upgrading the spindle cable, upgrading the stepper motor connectors and chassis connectors to shielded ones, and in general clean up wire paths.   

I think I will also add an EMI Filter on the power line, and some ferrite rings on the cables to reduce the chance of errors from this issue.

Any other key points I need to consider when I go after EMI from my VFD/Spindle?

Thanks