Losing the origin in the middle of the cut. EMI?

I added a 220v 2.2kw water cooled Spindle/VFD to my Onefinity earlier this year. Since then I have experienced what I assume are EMI related problems on a random basis. I’m not sure exactly what EMI does to a CNC so I’m not sure if my problem is common or unique.

The symptom is that in the middle of a cut, usually during a rapid move, the gantry stops suddenly (seems to stall) and I hear a loud grinding noise that sounds like stripping gears. Then the cut continues but the origin has shifted and the cut is in the wrong place. If I do a return to origin, the origin is in the wrong place. The shift seems to be only in the X axis.

I have been working on this problem for several months. I am using properly sized double shielded cable. I also isolated all the high power on the opposite side of my CNC cabinet from the controller. The power cable is routed so that it does not get close to the signal wires.

I have done everything that I can think of to avoid EMI but still getting this problem on some cuts. Most cuts work fine.

Any ideas or suggestions would be appreciated.

It sounds more likely that the motor to ball screw coupling is slipping on that axis rather than an EMI caused pulse miscount. Rapid moves spike torque very high so if the set screws are not perfectly seated the shaft could slip in the coupling.


Hey Tim,

I would check the points in this support document one by one:

Also did you check that your machine is rectangular? If it is not, the gantry can block.

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I ran the process to tighten the coupling on the X axis. It was not loose but I retightened all the set screws and the ball nut. The ball nut appears to be clean. I need to run some tests.

Hi Tim,
Please remove the unsupported spindle and see if the makita router has this same issue.

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I had the same problem. It was caused by too many nodes in the G Code. Edited out a bunch of nodes in VCarve, problem resolved.


Clean your ball screws. You have sawdust build up in them.

I don’t think this is related to the vcarve gcode. It happens when boring a series of simple holes.

I have cleaned the ball screws. I replaced the spindle with the original makita router to rule out electrical issues with the VFD. The problem repeated with the Makita. It appears to be mechanical related.

I have run through all the troubleshooting steps. No obvious culprit. I have noticed that when I jog the X axis back and forth, slowly, the gantry kind of vibrates or jitters as it moves. It does not move smoothly like the Y and Z axis.

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If that’s the case when just jogging, it’s either the wires or motor our coupler.