Originally Posted by
TTalma
It sounds like you are losing steps in the z- direction there could be a few causes:
Since it's always creeping up, I think you may be trying to drive your tool into the work to fast, causing Z to skip. Are you moving Z down in a ramp motion, or straight down? Are you using a center cutting bit? Is it a large diameter bit? is it dull? Try running the code without any stock (air cutting) and see if your Z axis is correct at the end of the cycle. If it is this is most likely the culprit. If not you need to look for something else:
- Noise on your Z axis wires, But generally this would cause loss in either direction, so sometime it would be to high, sometimes to low, so I don't think this is it
- cumulative error from back lash, You would need to do a bunch measurements to see if you have some backlash that is affected by gravity causing your axis to creep
- trying to drive your Z to fast and missing pulses, try cutting the feedrate in half and see if the issue goes away
Let us know the result of your testing and we can suggest some fixes.
edit: Also add a few pics of your machine, and it's Z axis, someone may spot something else to look at