On second contour path, z axis plunged straight down into table


I just purchased a Shapeoko Pro XXL. My cnc program consists of two contour paths. The first cut just fine. Then when the second contour started the z axis plunged into the table. See photo. The burn marks are from the collet nut on the router. That is how far it plunged. I shut down the machine mid program. Then started the machine back up and initialized. The cnc failed to home. The z axis would go down instead of up to the limit switch. The machine finally homed after multiple attempts to restart the machine, manually push the router to home position, and various other things. The z axis switch wires are not crossed. Not sure what steps were the solution to get the machine to home properly.

The machine is not wired backwards. It has been running just fine up to this random moment.

Attached is the g-code too.

What happened? What did I do wrong? The help is appreciated.

My dust collector, Supermaxx 1.5 HP, was connected to sweepy dust boot. It has a lot of power and I noticed as the flex hose contracts (not collapses) under the suction it exerted force towards the head unit. The dust collector is behind the cnc.

zero set.nc (1.3 KB)

I would start by carefully checking the wiring to the Z stepper motor. If you have a bad connection, the remaining connection can make the Z travel in unexpected ways.

Check the connectors for discoloration or burnt looking (indicates arcing), and for loose wires. If you do find a connector that is bad, I would cut it out and direct connect the wires.

Thanks for the help. The Z stepper motor connector at the motor is rather warm. The other x,y stepper connectors are not. When the z connector at the motor is moved I can hear faint squeaking like noise (arcing maybe?) / clicking noises in the motor. The noises are not experienced when move the other x,y stepper connectors. So I think you are right. When I get a chance I will direct connect the wires.

Contact us at support@carbide3d.com and send us photos of your Z-axis motor wiring and connector and the connectors to the wiring extensions and at the controller and we’ll do our best to assist.

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