Help on Z depth issues

For some time I’ve been trying to solve inconsistency in z depth.

I went through the process of calibration for belt stretch and I get a really good result - using my Mitutoyo calipers I get within 0.004" over a 2 inch span.

But when I go to actually cut material, I’m way off in final depth, even when using Bitzero. For example, today I was cutting 1/16 aluminum. My calipers measured it at 0.064" but I couldn’t cut through it until I set CC depth to 0.078". But the X and Y features are nearly perfect, to within 3-4 thou.

Is that normal? Any tests that I could run to help diagnose?

Please add a little more. Like what Z axis you have, standard belt, ZPlus, HDZ. Sounds like you are losing steps if you have a standard Z axis and the solution is usually tightening the belt and/or checking your set screws on the Z axis pully.

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I have just the standard Z axis.

I thought about the tightening issue. I didn’t think it seemed loose because when I press down on the spindle mount, I don’t seem to get much flex. But maybe “not much flex” translates to 0.010’’ discrepancies?

I think you should first check whether manually jogging on Z, in the air, moves the axis by the right amount (i.e. jog 1 inch with a ruler near the router mount, and check how much it actually moved)

If that is not spot on, you may want to calibrate Z steps per mm (GRBL param $102)

If that is ok, it may be that your plunge rate is a bit high and/or that the Z belt is (still) a bit loose.

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