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Really hot x motor while on pause  

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sanch2003
(@sanch2003)
New Member
Really hot x motor while on pause

Hey guys. I've became lucky owner of MK3S. Recently,  I tried pause mode to check how safe this option is. After the hotend decreased its temperature to stable 39 (and fan was turned  of,  I spotted that the x stepper motor became very hot. It feels like 70 - 90 degrees Celsius. All the other parts of printer and especially extruder,  are warm,  but not hot,  indeed.  

Can someone explain - why it heats up? Anyone else saw this issue? How safe is to keep the printer in this mode for 8-10 hours  in a row 

This topic was modified 5 years ago by sanch2003
Posted : 01/06/2019 11:10 pm
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(@)
Illustrious Member
RE: Really hot x motor while on pause

X and Y steppers are typically 50c or less operating. Uncomfortably warm to the touch. My E stepper has reached 58c, hot to the touch. This is dependent on ambient of course, and how much motion is going on.   But at idle, the holding currents should not cause a lot of excess heat - nothing near 70c which will burn, nor 90c which i think is high enough to blister skin.  If you are seeing these high temps, something is probably connected wrong.

 

As for printer reliability - I've printed continuously (one part) for almost 100 hours.  And have had filament sensor issues where the printer has paused half the night.  No issues with the printer motors over heating.

Posted : 04/06/2019 10:57 pm
sanch2003
(@sanch2003)
New Member
Topic starter answered:
RE: Really hot e motor while on pause

Thank you for your answer. Indeed, this looks like something is wrong here. And sorry, I messed up. I meant E stepper motor.

BTW, I tried to pause the print and hold it for 5 hours to see the results. I didn't finish that print later on. The PTFE tube got clogged with a piece of melted plastic and it just stopped extruding, while the print was going on. Eventually, it started to make clicking sounds and I had to stop the print and replace the PTFE tube. So, I suggest that this was idle extruder motor's high temperature, which caused the plastic to melt inside the tube. 

I had to find the what is causing this temperature issue. Anyone has any idea what can be connected wrongly?

Posted : 05/06/2019 12:41 pm
DarcShadow
(@darcshadow)
Trusted Member
RE: Really hot x motor while on pause

Just a side note. Stepper motors are always drawing power even when they're not moving. So pausing the print, while it will turn off the heaters, the motors themselves are still active and drawing almost as much power as they would if they were moving. It's only when a stepper motor is disabled that it stops drawing power, however, a disabled stepper motor can also be easily moved and therefor not an option for a pause situation because there would be no way to ensure that when it resumed the stepper motors would be in the exact same position as when they were disabled.

Posted : 05/06/2019 1:21 pm
bobstro
(@bobstro)
Illustrious Member
RE: Really hot x motor while on pause

Ah, this sounds like the "extruder clicking" and "heat creep" posts that spike as we approach summer. Extruder motor heat can have many causes. The most obvious is ambient temperature. If you're printing in a warm room or using an enclosure, be aware that the E3D V6 hotend is air cooled, and rated to operate in max. 40C ambient temps.

Other possible factors:

  • Partial nozzle blockage.
  • Obstructions in filament feed path (filters, over-tight extruder screws, Bondtech gear in extruder idler loose or stuck)
  • Excessive retractions (check preview mode in slicer)
  • Excessive speeds for parameters (try just slowing down using the front knob)

I've put a dump of related issues that we commonly encounter in my online notes that you can skim for ideas. The heat break Prusa uses is known to cause some problems as well, so research that issue. Mostly, observe what is going on. Adding an extruder visualizer can help see when the motor is working hard.

 

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 05/06/2019 1:40 pm
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(@)
Illustrious Member
RE: Really hot x motor while on pause
Posted by: darcshadow

Just a side note. Stepper motors are always drawing power even when they're not moving. So pausing the print, while it will turn off the heaters, the motors themselves are still active and drawing almost as much power as they would if they were moving. It's only when a stepper motor is disabled that it stops drawing power, however, a disabled stepper motor can also be easily moved and therefor not an option for a pause situation because there would be no way to ensure that when it resumed the stepper motors would be in the exact same position as when they were disabled.

While somewhat true, a stepper at idle is using far less power than one in motion.  Currents are high, but voltages across the motors are low.  When the motors start to spin, higher EMF is required to build the additional torque.  Voltages rise accordingly, and power is Volts time Amps with a bit of phase thrown in.  Driver power dissipation on the other hand can actually decrease as the motor spins up.  

That said, the motor - generally speaking - will be hottest when providing the highest torque/HP/we ... 

 

Posted : 05/06/2019 9:40 pm
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