Z axis zero changes

I have had this happen multiple times. Set Z zero and part way thru the cutting, the Z axis will raise about .1". I’ve rerun the program several times and the same thing happens.

I’ve also had a problem while running a pocketing program where a few areas are missed. On a 6 x 9" plaque, there are areas aabout .75 x .75" cut at a different height - usually .8 higher. Problem related to one above?

Gcode generated by Aspire and using UGS new platform to send. Have upgraded to GRBL 1.x. Have reprogrammed the 3D file to attempt to eliminate this by using smaller and larger tools (started with a .25" endmill). Have changed feed up and down. No Change. Any thoughts?

The Shapeoko is an open CNC system, it sends a signal to Go There, and no signal to confirm it is there (open), a closed system would have a second system to confirm it is there.

The motor on your Z pushes down (or maintains position) with 18 pounds of magnetic force. If you push the machine too hard, the motor will skip (or slip) and will result in a change to the Z position.

So IF the set screw is on the motor flat, and all is tight, it means you are pushing the Z too hard.

The fix? Less feed, sharper cutter, etc…

Does this help?


Thank you. Good possibility the cutter may be bottoming out as it slips down the side of the model. I’ll reset the offset in the toolpath and give it a try.

I believe you hit the nail on the head. I changed the offset from 0.06" to -.001" and it cut without any problems…Thanks for your help!!!

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Just reread my original post…the .8" should have been 0.08"

In some of my work, there is dramatic changes in Z and even after using your concept (that worked!) for a few projects, a new design had the same issue as originally reported.

What I finally did to solve the problem was remove one of the springs for the Z axis. I’ve run over 50 complex pieces (including lithophanes) thru it and haven’t had any problems. I’m going to get 2 lighter pull springs so I have even pull on both sides of the axis plate.


Seems like a recurring problem - see https://www.shapeoko.com/forum/viewtopic.php?f=7&t=7446&hilit=Z+axis+force&start=10. Is there a recommended fix?

If need be remove one spring — contact us at support@carbide3d.com if you continue to have difficulties.