Incorrect Z axis on Shapeoko 4 XXL

My Z axis is changing every so often on the cutter. It runs perfectly for a few passes and then changes the level slightly. This happens on a flat face and a curved surface. I have include a pic of the test piece of the curve. This clearly shows the issue. I increased the tension of the anti-backlash spring on the drive shaft, but to no avail.

Is this issue solvable?

Thanks,

Shaun

Is that extruded or cast acrylic? Acrylics are notorious for inconsistent thickness. Just an idea…might not be your z changing but the depth of cut due to thickness issues. How are you setting your Z… top of stock or machine surface? A little more information would help the community help you.

This is milled out of a flat piece of 0.47 inch cast polycarbonate, with a close to perfect thickness. The Z is zeroed on the top of the stock. This issue is identical in aluminum.
Please note that the Z error is consistent along the curve, while the stepper motor is moving.

It seems to me that the stepper motor is giving the wrong feedback to the controller… is there a way to check/correct this?

Could you post your file and a wider photo showing the context?

The Z-Plus has a steps/mm of 200 — if you chart that against the different heights/depths wanted do you see any sort of interaction?

Perhaps try on an HDZ which has a steps/mm of 320?

Sorry, no HDZ machine out here on Orcas Island, but the resolution of my Z-Pluss machine is more than adequate, it follows the curve perfectly… just jumps a little up or down occasionally.

Not sure how a “wider” pic will be more clear, it will just show more of my kitchen counter… :slight_smile: Would you like a different angle?

Swan SP03-FC-1-0-17.zip (240.3 KB)

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