The Dreaded X axis stepper error using UC400ETH and UCCNC !!!

[m_c]

The entire point of the VFD cable screen is to absorb the EMI from the VFD cables, and drain it to earth. Due the VFD cables carrying a fast switching AC signal, an AC signal will be generated in the screen.
The fact that there is a voltage present, tells me that's it not correctly grounded. And also that connecting it to the machine frame makes things worse, tells me the machine frame isn't grounded correctly. If the screen was correctly grounded, then there should be negligible voltage in it, as it should be getting drained to earth without causing any problems.

Which brings me back to my earlier question, are you sure your power supply earth is correctly earthed?

[Clive S]

Which brings me back to my earlier question, are you sure your power supply earth is correctly earthed?

This is what I mentioned several posts back but you make a good point re the anodised stuff so as M_C has said ground each part ie Z plate to gantry to machine frame to Star point

[dachopper]

Ok - I thought I would put some closure in here..... The random X and Z axis ' jams' were 100% due to electrical interference from the spindle control wires.

I had unshielded control cable, with shieleded stepper cable

Then I tried shielded control cable but mistakingly placed the machine earth inside the Spindle power cord, and in doing so charged the entire machine up with a generated AC signal.

Then I earthed the frame + spindle + spindle shielding + stepper motor shielding seperately to house earth, and finally, no issues !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!