Z height drops over long jobs

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1

Machine: Longmill MK2 48x30 with SLB and Makita router

The job is vcarving text for 72 coasters over an hour or so, and by the end the text is nearly double the depth as the first coasters. For future runs, I ended up dividing the “rows” into separate files in VCarve and re-zeroed each time but would like to figure it out for the next batch.

For testing, I used a block to zero my Z off of the spoilboard and then with the router off, I let the complete job cut in mid air. When I put the router back at XYZ0, I had to raise Z approximately .025 inches to clear the block. Not a lot, but makes a big difference with a 90 degree V bit.

Things I have tried:

  • Checked Z-Axis coupler and Spring-loaded Anti Backlash nut
  • Toggling Independent Motor Holding via $37 in the firmware with $212 at the default of 35
  • Ran the Z-Axis movement tuning with setup blocks (stayed at the default of 800)

I’ll run through the movement tuning again just to be sure, but was hoping someone else may have some suggestions to check when I’m there.

Thanks

2

Browsing other threads, I found Can SLB drive a stronger Nema 23 Stepper Motor? - #11 by aarseneault which mentioned that changing the microsteps and corresponding travel resolution fixed their issue with dropping Z height.

After setting $152 to 16 and $102 to 400, I’ve run the same air-carve twice with no perceptible drop in Z height.

Hopefully this helps someone in the future.

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