I just finished a new 4’ x 8’ LR4 build and ran into an odd issue when turning it on and doing the first moves. The X and Y axes worked as expected, I just had to flip the Y1 motor connector to get correct motion. The Z axis (either side) didn’t move and just rattled.
I tried flipping the Z motor connectors in different combinations, picking up the gantry to take the load off of the motors, and moving the Z motor connectors to the Y axis spots on the board. All had the same result and the Z motors just rattled.
I plugged in two other stepper motors from an old LR2 build and they worked properly (motion and torque) when I jogged the Z axis.
I checked the resistance on both of the new Z axis motors and found one phase on each motor was an open circuit. I have started but not fully removed the cable sleeves to check for damaged wires/connectors, but I was very methodical on the wiring/routing so am confident it’s not that. Especially since it is specifically both Z motors.
My plan is to just disassemble and put the LR2 motors in for now, I’m more just curious if anyone has experienced something like this or if there’s insight on something that I may have done to cause this.
This is either an issue with the wiring, or indicates that there is excessive friction/load on the motors (skipping steps). Your multimeter checks indicate the former.
Yes, I have seen this before, but only on the farthest (Z1 and Y1) motors. The cause was a loose connection where the extension cables and the motor wire connectors plugged together.
With yours, it is both Z motors, and presumably only one of them has an extension cable.
Did you do any crimping on the motor wires? A bad crimp could cause this.
You have a measured open. I’m not sure why folks are having you swap poles in wires.
Let’s find where the opens are.
As noted above, it could be a bad crimp anywhere there is a crimp, it could be a bad connection at an extension cable, it could be a broken or damaged wire anywhere in the run buried under your sleeves as you note.
It sucks to do, but if it were me I’d pull the motors and the wires and then carefully go through the whole harness looking for any issues.
Stepper motors themselves seldom fail internally- I’ll bet you find wiring issues.
Please post pictures of what you find, it helps the rest of us learn and eventually advise other users.
I ended up disassembling to the point that I could remove the Z motors and inspect them. Kind of an unlucky deal but I believe I figured out what the issue was.
There were no issues or visible damage to the cable extensions, connectors, or wires. Both Z motors ohmed out on one phase but the other phase was open circuit on both.
I plugged one of the bad motors into the controller and jogged it and it ran properly. I picked it up and jogged it again and it just rattled. I could move the wires right where they come out of the motor and get it to run or not run, so it seems that one of wires had a bad connection inside the housing.
Given that there’s no strain relief on the wires entering the housing, both problem motors were for the same axis, and it was even the same two wires on each one that wouldn’t ohm out, I think I must have strained them too much when installing and routing the cable through the YZ plates. I took extra caution installing the old LR2 motors, verified motion, reassembled, and have a fully operational machine now.