Depth is deeper at end of pass than at beginning

Not sure where to start troubleshooting this. It’s not really causing an issue with the type of stuff I’m carving, but I noticed that the end of my carve passes are deeper than the beginning of the pass. Anyone experience this before?

There are a few possible causes:

  1. the bit is slipping in the collet
  • Just be sure the bit is very tight in collet
  1. the Z axis is missing steps
  • check the voltage pot for the Z axis on the Gshield
    – The Z axis may also be binding so check to be sure the ACME rod spins easily (turn it by hand – with the power off) for the full travel length of the Z axis
  • check to be sure the pulley is not slipping on the motor shaft
  • check that the Z axis belt is tight and not slipping
  1. the wasteboard is not perfectly perpendicular to the spindle.
  • Surface the wasteboard by using a large diameter end mill and cutting about a mm off the top over the entire working surface (you may want to screw down a secondary "sacrificial’ piece of half inch MDF on top of your “nice” wasteboard and then surface that.