Y-Axis Motor Randomly Turning In Wrong Direction

Hi All,

I have a strange issue with my 30x30. I’ve had it for over a year now and it’s been working fine. Last month I built a new table and moved the CNC to it about a week ago. When I connect everything up and jog the positions, the right side Y axis motor will sometimes turn in the wrong direction, or not at all. At first I thought I was loosing my mind, but to confirm, I jogged the mill to the back where both sides make the ‘grinding’ noise. Then, I jog it back again (using Gsender) and I can see the lead screw turning in the wrong direction…sometimes.

To troubleshoot, I updated Gsender, checked the dip switches, checked the tightness of the lead screw (seemed about same from left to right) and swapped the Y1/Y2 cables at the controller. The problem seemed to stay the same, so I suspect a bad stepper motor? The last thing I checked was the motor itself by uncoupling it from the lead screw, electrically disconnecting the left side motor, and watching the right side motor when I jogged from Gsender…the problem seems the same. This leads me to believe that the problem is not mechanical.

One thing different on the new table is the way I ran the wiring, I put a piece of panduit on the back and side, running all the motor wires through it. At one point I had the power supply output wires (low voltage) in there too. I’ve taken the power supply wiring out just in case it’s a case of electrical interference. The 120V wiring is under the table and not really near the same channel.

Can anyone thing of anything else that could be causing this? What I find so puzzling is that it was working fine on the old table. Now I’ve got some customer work waiting while I troubleshoot this. On the plus side, I can’t wait to start using the t-track for work holding (the reason I built a new table).


The symptoms you’re describing sound like one of the four wires that power the motors might be disconnected or have a poor connection. I would double-check along the wires and controller and see if there’s anything loose at the connection or the motor side.


Thanks Andy,

That seemed to be it. The Y2 motor pheonix connector blue wire was tightened down on the insulation.



As the original issue has been addressed, I’m closing this topic. If anyone else has a similar concern, feel free to start a new topic, which will ensure that it is addressed promptly.