Z-AXIS Losing height

Over a long project the Z axis appears to incrementally lose height so it cuts deeper and deeper on the project. The project I am trying to cut is 50 Stars. The first row cuts perfect, the second row cuts perfect until about midway then starts cutting deeper, and the machine continues to cut deeper throughout the project so that it is begins cutting each star at .25 but towards the end is cutting to about .50 deep. I attempted to increase the “safety height” as initially on a smaller project the only issue I saw was the bit scraping along the top of the project, but this had no effect on the current project

Project file

Here is the project file I am using.

Watch this video, your Z axis is not parallel to your waste board or the material you’re engraving is not flat.

I appreciate the info Russell, but this is not the issue, I am losing at least 1/4" of height from the start of the project to about 2/3’s into the project. I have checked the distance between the waste-board and the bit and if there is any discrepancy it is negligible.

I think the next thing would be to check and see if you are loosing steps somewhere. Maybe the z axes is slipping and loosing steps.

When the carve is done does the bit end up at the safety height?
Check the set screws in the pulley on the Acme screw.
They have often been reported to come loose.


You saved me Mark. Somehow BOTH set screws came out and disappeared. It seems to be doing well now. Thanks much!!!

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