M2 Extruder stepper motor not turning

[b8smat]

My son went to change out the filament last night after a successful print and the extruder refused to back out the filament.

Now I can't get the extruder motor to turn at all. Hot end is up to temperature and Prontoface says its sending the command to extrude 5mm.

I disassembled the head to be sure that nothing is jamming the extruder, and even with it completely removed the extruder gear does not turn. It is locked solid until you turn off the printer. Then it turns freely by hand. Any ideas?

[Toby]

When you disassemble, is the extruder still at temp? By default the Marlin firmware won't allow the extruder motor to run if the temp is not up to a certain amount.

You can force it to allow a cold extrude with the command M302, but obviously only do it with the hot end off the machine.

[b8smat]

When you disassemble, is the extruder still at temp? By default the Marlin firmware won't allow the extruder motor to run if the temp is not up to a certain amount.

Yes it was still at temp. There was no warning message about cold extrusion.

[b8smat]

I fiddled around and reseated some connectors and now it's working again.

[b8smat]

Well that fix didn't last long. It's stopped working again. Turning off and then back on again and then heating up the hot end, then trying to extrude just results in a small clunk from the motor and then nothing. It's like the gearbox is locking up?

[jimc]

it is a possibility. pull the filament drive and fans off the front, unplug the motor and remove it from the mount. remove the small allen screws that hold the cover on the gearbox. you dont need to remove the filament drive gear off the shaft. remove the cover and inspect the gears. there are 3 planetary that rotate around a pinion gear off the motor. look at all the teeth. the pinion sees the most wear.

[b8smat]

Thanks, I will try disassembling the gearbox tonight to see if that is the issue.

[jimc]

Remember if the motor is powered then it wont turn by hand and seem locked up. Befor you disassemble, with the filament drive off, unplug the stepper or hit the reset button on the rambo board and the see if it turns. It will have some resistance but should turn with your fingers.

[b8smat]

Remember if the motor is powered then it wont turn by hand and seem locked up.

Yes I checked that. With the printer powered off, the motor turned freely by hand. Doing that might be what "fixed" it and freed up the gearbox.

Both times this has happended now, it is when we have gone to change out the filament which obviously involves driving the gearbox in reverse.

[b8smat]

Same problem happened again tonight. But now I can't get it running at all.

When I power up the printer, the extruder is free to turn by hand. As soon as I ask it to extrude or reverse there is a small clunk from the motor and then it locks up until I reset the printer again. When it's locked up you can feel the motor vibrating a bit, like it is trying to turn.

I took the cover off the gearbox, it looks just fine inside.