Z motors wont move together

dc42

@nophead said in Z motors wont move together:

It is actually behaving like one of the sockets is shorted. The motor plugged into that one would not spin but the other would.

I agree. Check that there are no solder bridges between pins of the Z motor connectors on the underside of the Duet. I recall seeing a report of a board with this fault recently. It didn't get picked up during testing because the boards are tested with the 2 jumpers in the Zb position, just as they are shipped.

Xandrel

@nophead said in Z motors wont move together:

It is actually behaving like one of the sockets is shorted. The motor plugged into that one would not spin but the other would.

@dc42 said in Z motors wont move together:

I agree. Check that there are no solder bridges between pins of the Z motor connectors on the underside of the Duet. I recall seeing a report of a board with this fault recently. It didn't get picked up during testing because the boards are tested with the 2 jumpers in the Zb position, just as they are shipped.

I took a quick look at the board this morning, front to back, and cant see anything visual. I inspected the motor wires and connectors and cant see anything wrong. I trust the next step would be to check the pin headers with a meter for shorts?

Should I be running the motors off their own driver anyways at this point? There seem to be more benefits that way anyway?

jckray

I have been having a slightly different issue with my z motors, but perhaps it could be related so I'll post here too.

I have had many a successful print of the printer I built, however sometimes at the end of a print, or after a print has finished and upon starting up a new print, the z-axis motors decide to move out of sync. This seems very weird to me. As I understand it, this should not be possible since both motors are run from the same driver. I have had this issue across 3 different models of the printer shown in this video. All using the Duet Wifi, and two .4A steppers with integrated lead screws fro the z axis. The hardware and duet configuration is identical across all 3 printers. Power cycling the printer always resolves the issue.

Perhaps the motors are been driven too fast? I know the z motors are in series so this greatly reduces torque over a certain speed.

Another thought I had was maybe this has something to do with how RRF handles idle currents.

I also have a single motor with the same specs as the z motor running of another driver on the board, which is used for a multilateral system. I have had no issues with this motor at all.

[0_1541572296923_IMG_1315.MOV](Uploading 100%)

jckray

@jckray Video link

I realized I shared that video for my earlier post incorrectly. This link should work.

dc42

@xandrel said in Z motors wont move together:

Should I be running the motors off their own driver anyways at this point? There seem to be more benefits that way anyway?

As they are large motors (Nema 23), I would recommend that. But they should work in series if you don't ask for high Z speeds.

Xandrel

Just to confirm, I did finally get back to looking at this issue and have temporarily solved it. I made a splicer so that I could put both Z motors into the same socket on the Duet, and it worked. This leads me to believe that the problem is a hardware issue on the Duet itself? Would you agree?

elmoret

@xandrel Does your splice put the coils in series or parallel?

Xandrel

@elmoret It would be parallel.

dc42

I suspect you were trying to run them too fast for a series connection. Now that you have them connected in parallel, they will receive half the current each, so the torque provided by each motor will be halved.

Xandrel

@dc42 I would imagine for the z motors, speed and torque is not much of an issue as its only raising and lowering the printing gantry at a slow speed. The only fast movements it would do is during probing. Perhaps I am missing something? Either way, continuing with the project in this capacity is perfectly fine for me.