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

[dachopper]

Hi MC,

I measured the voltage that the shielding on the VFD cable produced when the Spindle was turned on, it's was straight to a 40 Volts AC signal, between the shielding, and the CnC frame. When I connected that shielding to the frame, the steppers went ape shi*T. Motors were stuttering and I could " hear" the motors struggling to just run normally. Now, the machine wasn't grounded at this stage, but that was the effect of attaching the noise directly onto the frame of the machine.

I then unattached that end of the shield, and tried to attached what i thought would be a suitable ground ( it was an unused wire from inside the VFD shielded cable ) Big mistake - now this wire WAS on the Earth ground at one end, running through the VFD cable, and attached to the Z axis / stepper motor mount at the other end. I think all I did, was make a big long antenna inside the VFD cable, which even though it was grounded, was helping to turn the machine into another noise generating machine.

Then I got desperate after about 5 jams in 10 minutes, so I undid the " VFD " ground wire from the spindle / Z block and this made a big difference, but now the machine is not grounded any more.

So I am going to run another two grounds, one from the machine frame to house ground ( which is the same as the start point, but from a different socket) , and another shielded cable up the cable tracks and onto the spindle/ z block, which will then go to the other house ground.

I keep reading about these star grounds, but the fact is the VFD cable is creating an AC type noise signal, and If I run that into my electronics enclosure base plate, what is stopping it going straight back up my Stepper controller shielding which is connected to the same base plate? hence I'm connecting these two at a different socket of house earth, in the hope it weakens before reaching the base plate again.

I don't think Im going to connect the VFD cable screen back up to the frame, it just seemed to make the situation far worse.

[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 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!