Problem with long relef cut

I am having a problem with a relief cut that I am doing, I did a test cut in in pink foam and it worked just fine. I next loaded a piece of Maple and started the cuts. The first was a roughing cut that went for 3.5 hours and all was well. Then next was the finishing cut. It should take about 13 hours. I have tried it two time now and sit have a problem with the MPCNC start missing steps.
It looks like something happens with Z dropping to deep and then ever thing from there is off. Need to get some suggestions on what to check before I load a third black into my MPCNC.

That is a drag, after a long job! This happened to me once and it was the bit coming loose in the collet, and slipping down. I had not tightened it enough. It may help to use a sharpie to draw a line on the bit just below the collet nut to see whether it is slipping.

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I checked and that is not the problem.

Of the many ways to lose steps, the ones that stand out as possibilities (beyond Steve’s suggestion) are:

  • Grubs screw loose on connector between stepper motor and the lead screw loose.
  • Feedrate too high for the Z axis (it cannot move as fast as the X and Y axes).
  • Stepper driver overheating.

None stand out as the answer, and figuring out the problem when it takes hours to reproduce is painful. Personally I’d try to reproduce the problem without wasting material by starting from a know height with the router off and making a dry air run to see if there are issues. Next I’d attempt a carve of foam board and/or MDF.

The feedrate being too high can be particularly hard to find. Consider limiting the feedrate in the firmware. See the M203 g-code and the M500 to save the new setting.

One thing to consider is that Maple is one of the hardest woods you can use. You could just simply be taking too deep of a cut and it just takes a while for the extra forces to cause issues.

You could break up the second gcode into multiple parts so that you’re not running the machine so long.