Z Axis Wobble / Delrin Nut Run-out

I’ve looked through some other posts but they didn’t seem to be the same issue. This is a new build with only a few test runs.

I was noticing binding in the Z axis after assembly. With some tweaking of the motor current, V-wheel adjustments, and a little lube on the ACME screw, I was able to free the axis to some degree. I did my first test run yesterday and after a few minutes the Z axis bound up again. After troubleshooting the carriage, V-wheel tension, I wasn’t able to find it. I removed the carriage and focused on the ACME screw and Delrin nut. Holding the Delrin firmly and spinning the ACME screw, there is a TON of wobble in one 360 rotation.

I verified the ACME screw isn’t bent and is further verified by the wobble being in 1 rotation, and not over the length of the screw. It appears to either be the flange bearing itself, or the ACME screw being pulled slightly off center when tightening the Nyloc. Looking at the ACME rod threads that contact the flange bearing, this area is not flat and looks like it would allow it to be pulled in an off center direction. I’ve been in contact with a CS. I don’t think he quite understands my issue.

Is the ACME rod suppose to have a flat area where it contacts the bearing? Some quick tests of the flange bearing using a large bolt shows it seems to be straight.

Added a picture:

Thank you for the response. Inventables sent a replacement rod. Following your instructions and using the new rod I set it up and tested the run-out. Everything looks good. I can’t detect any movement.

That said…
My Z axis has never seemed right. Once I fixed the rod and tested the motor it was noisy, weak and changed direction intermittently. I fought with this for an hour and delved into the wiring. With nothing found I swapped the Z axis for the Y and retested. It worked perfect leading me to believe it was the shield. After a short time I found an open between the connector pin 4 and pin 18 of the Z axis driver. I fixed the connection and can finally say, I’m ready to start some test cuts.

You can see right side of Z driver toward the bottom were I added and reflowed the solder at pin 18