Prusa-firmware: [BUG]Extruder motor is getting very hot, after pausing a print

[m50008]

Printer Type: MK3S
Printer firmware version: 3.9.0
Print via SD card

When pausing a print and letting it sit for a while, the extruder motor is getting so hot, that it can not be touched anymore (feels hotter than the 60 degree warm heatbed). After pausing the print, the extuder motor made some strange noises.
The hotend was switched of and the temperature of the hotend was at 26 degree.

After resuming the print, the temperature of the extruder motor stayed the same and I had to stop the printer, to prevent any damage.

[leptun]

The Extruder stepper is run at a very high current. Oddly enough, the faster you move, the less heat is made, so fast prints should be better than very slow ones. When the motor isn't moving it has to pass through one of the two coils all the current continuously.
I'd say what you wrote here is a duplicate of this issue #1757. Can you confirm and close the issue if that's the case?

[mkbel]

It doesn't look like duplicate. This issue is more specific than #1757. In #1757 E motor is said to be too hot in all modes of operation. In this issue only pause print mode is mentioned. Root cause of the issue may be but doesn't need to be the same. I could imagine, that when X axis moves, E motor is better cooled because of air movement around motor.

[m50008]

Yes exactly. The question is whether it is necessary to leave the motor switched on during a paused print? The hot end is switched of, so should the E motor as well?

[3d-gussner]

@m50008 Switching off the extruder motor could change the pressure in the hotend, as the filament isn't hold in position.
This could cause:

• extra oozing
• or missing filament when it starts again.

A pause should be always as sort as possible. So if you have a pause in your gcode add some sound code to it so you get kind of notified that your attention is required.

[m50008]

@3d-gussner Thanks for the response, but imagine you print several hours and want to pause the print, because the printer is to loud and you have to do something important in the same room as the printer.
Here it would be very nice to pause and disable the E motor and when starting again, we extrude a little filament and ask the user, if anything went out. If we accept, we can resume the print.