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Jul 5, 2022
Hi all,

I would like to post here to inquire about an issue I am currently encountering on my 1997 HAAS VF3.
I recently acquired the machine with no apparent issues, after a few weeks of idle, I powered the machine back up and I started dealing with:
During the "power-up restart" procedure, X, Y home fine, but sometimes the z doesn't and I get the error message above. I have attempted single-axis homing and sometimes it works and lets me continue using the machine.
But recently the issue has been consistent and has been preventing me from using the machine.

symptom observation:
1. While the machine is idle (on) and the z is at any random position, I can hear the servo correcting (attempting to move) though the z value does not change on the HMI
2. While moving the z-axis up and down, unbearable shaking is observed (please see this video) to see what I am dealing with.

I have not yet switched axis on the motor control board to see if it's a board issue. Would switching the axis on the controller board be a good idea? is there a risk to changing say x with z?
I also have not switched servo motors with another axis to see if it's a servo issue.

Would really appreciate any type of assistance/recommendations.




Cast Iron
May 29, 2014
ca, US
This is brushless, yes? Could be one of the legs of the servo board is out. Swap cables with the X or Y to check. It would ratchet all the time if this were the case. Be sure to compare the parameters and copy over the Z to whichever axis you change cables with.
See if you can turn the Z ball screw by hand. It should turn easily and smooth.
Check the encoder attachment to the motor. If loose it could be moving around causing the motor to try to catch up.


Hot Rolled
Dec 11, 2013
Alberta canada
I thought the with brushless the z axis has an internal break that engages when windings are de-energized?
Unless it’s counter or nitrogen balanced.

Just be carful the head does not drop and hurt you. There is a lot of weight there

If it’s brushed check the brushes too, could be worn right down.