Small CNC - Z Axis Drop

A member reported an unexpected drop on the Z-axis on the small CNC while cutting a pocket. We’ve checked the machine and lubricated the screw. It’s possible the bit was slipping in the collet, but the member checked and the bit seemed firmly in place. The red tagged has been removed, but please ensure the collet and nut are clear of debris and dust before tightening.

Please share any other issue noticed while using the small CNC do we can diagnose if the problem shows up again.

Z-axis dropping on Small CNC has been an intermittent problem for a while. I recently encountered the same problem myself and was able to reproduce the failure on a consistent basis. While doing a 2mm deep pocket the Z-axis will drop during the cut.

Left side is nominal and the right side shows the failure mode. The cut starts in the center and Z height drops as the cut proceeds to the outside edge. Z height ends up dropping a total of around 4-6mm in this case.

As far as I can tell the end mill is not slipping nor is the spindle motor. I checked continuity on the Z stepper wires while also moving the cables around. Everything looks good all the way back to the stepper driver. Opened the stepper driver with nothing obvious. Put everything back together and spent some time testing. And now I can not reproduce the fault : (

So, beware of the issue and please let us know if you see a problem so that we may continue to trouble shoot things.