Strange mpcnc stair artefacts

Hi I’m fairly new to this whole mpcnc thingy :wink:
My dad and i build a mpcnc and tried after some successfull tests (with pen) cutting our first parts.
But unfortunately we get some really strange stair case artefacts. Cuts at the top of the part are awesome, but the cuts further down are offset. We’re absolutley clueless what might cause such offsets.

Here’s a list of possible culprits that I can think of:

  • Belt tension too loose
  • Depth of cut too large
  • Feed rate too high
  • Using a dull cutter

Sorry I couldn’t be more helpful.

Are the dimensions of the cut spot on, or are they oversize on top?

With the left side perpendicular and the right side sloped (with increasing DOC) then is this a gear-lash issue, i.e. a loose grub screw on the stepper motor shafts?

That’s what I’m thinking (and why I asked about the dimensions). If it was a printer, the whole thing would be slanted, but the bit is cutting away the evidence on one side…


It looks like it skipped steps on the way down. Something is making the load a lot higher deeper down. IDK how many passes you took. But as it went deeper, it moved the whole pattern, so it was cutting too far to the left.

I also think one or more steps were skipped. Looks like one step on of just before the second-to-last layer, and then another step on or just before the last layer.

Depth of cut doesn’t seem to be that large (2mm or so perhaps?). Feed rate could be too high, stepover could be too high, or the cutter could be dull.