Erratic Z axis/motor issue

Running the Pro XXL and have been cutting a number of jobs with no issues. A couple of days ago, while initializing my machine, my Z axis was acting strange, almost like it exceeded it’s limits, made some grinding noises and was on a downward travel rather than up. I disconnected the limit switch and motor, made a manual adjustment, and it initialized properly. That’s happened a couple of times in the last day or two. Yesterday, with 2 minutes left in a rather lengthy cut, I heard a slight “grind” while cutting and then heard a distinct difference in the sound of the bit cutting (a little deeper). Sure enough, my Z axis almost doubled in depth (from .120 to over .200). The bit is tight in the collet and the belt(s) appears in working order and tight. Just looking for a starting point to get this ironed out. Any input is appreciated!

Check your Z-axis motor wiring and connectors — if you don’t find anything obvious to address, please write in to

Thank William…I reached out support as I think I found my issue.

What is the issue, mine seems to be doing something similar yesterday and today

Please take photos of your Z-axis motor wiring and connectors including the wiring extension and at the controller and send them in to

I had a bad connector, but follow Bill’s lead and support will nail it down for you. If you need new extensions/wires, they’ll next day ship them…good luck!!!

I just tracked my issues down, I’m working on transitioning from Carbide motion to GSender and I’ve tested some macros the past two days. Still trying to use motion for production till I get GSender all set.

Somehow GSender set my Z steps to 250, so now my challenges all make sense with math! Basically it was adding the exact same depth with the extra steps as my stock to leave on first operations… duh… I feel stupid!

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