Can monitor stepper temperature?



  • Hi,

    since a days ago, here, where i live, the temperature its high... i am having problems of underextrusion, i think the extruder stepper it loosing steps by temperature.... when i touch the stepper its very hot, i dont know, but 60º, aprox....

    There is some sytem for monitor the motor temperature... ex:

    • Create a new extruder with a termistor asigned... the stepper its the extruder stepper, but the termistor, its a termistor attached to stepper that measures the temperature.

    or... easy.

    • Duet can ask the stepper the actual temperature....?


  • See this posting from a year ago for a detailed discussion on the topic: https://forum.duet3d.com/topic/6054/help-configuring-pwm-fan-in-thermostatic-mode-for-duet-drivers



  • @peirof Stepper motors don't come with temperature sensors built (at least most don't) so if you want to measure the temperature of the motor, you'll have to attach a temperature sensor to it as I did in the thread that @oliof linked to. Here is a link to my post on my own blog (but it's an old post and firmware has changed since then). https://somei3deas.wordpress.com/2017/04/18/stepper-motor-and-electronics-cooling/

    For info, it is common for stepper motor to run hot and most are rated at around 85 deg C. The easiest thing to do to reduce the motor temperature is to reduce the current, if that is possible without causing movement issues.



  • Also, although the winding resistance increases significantly the torque should stay the same because of the constant current drive as long as the supply voltage is significantly more than the motor voltage. The top speed will reduce though.



  • I don't know what kind of extruder you are using, but it's usually not necessary to run so much current that the motor gets very hot. If the filament drive gear is mounted on the stepper shaft, the gear will get almost as hot as the motor. If you're printing PLA, the filament may soften when it contacts the hot gear, and that can cause extrusion problems. If the motor mount is printed PLA, it may soften when the motor gets hot.

    Geared extruders typically require less current than ungeared extruders because the gear reduction multiplies the motor torque. That means you can reduce the current a bit to keep the motor cool and still have plenty of push to get the filament through the hot-end.



  • hi,

    i am using a Bondtech extruder in Bowden (short, 15 cm) setup



  • In that case you can probably reduce the current quite a bit which will keep the motor cooler. My printer has a heater enclosure, so I run the extruder current as low as I can that still drives it reliably. The motor barely gets above ambient temperature.



  • Hi,

    I have find a provisional solution... HIGH TECH.... NO, ULTRA HIGH TECH.

    I printed a medium size piece... And when the print progress reach aprox 50%... I have use a bio termistor... I have touch with hands stepper motor of extruder... Its really hot... Over 70 degrees... How I can know the stepper temperature.... The temperature of the steeper was similar to bed temperature, 70 degrees...

    After this I have touch config.g and change the current of extruder stepper from 1800 ( I know... Was very high voltage) to 900 and I have do the same print... When the print reach the same point than before... I have used the same biotermistor... Touch with hand.... And stepper was much cooler, and the print looks great, don't loose steps.. Seems



  • @peirof Yes if you halve the current then you halve the torque but you quarter the temperature rise above ambient, so it makes a huge difference.



  • @peirof I refer you back to my post of 13:19 today where my final sentence read.............

    "The easiest thing to do to reduce the motor temperature is to reduce the current, if that is possible without causing movement issues."



  • @deckingman You can lead a horse to water, but sometimes he'll insist on touching a hot stepper before he'll drink.



  • To be fair it is a bit counter intuitive to reduce the stepper current when it it under extruding.

    I have seen people add fans to their steppers to stop them skipping but as they are rated for at least 80C I am not sure why it helps. Does the expansion cause the bearings to bind? Or is it the increase in resistance reducing the high speed performance? I run my steppers at 65C and never have a problem.

    As pointed out if you have direct filament drive or metal reduction gears it can cause PLA to go soft and lose traction. The machines I run hot have ABS drive gears so the heat doesn't get to the filament and it wouldn't matter with ABS anyway, which is what I mostly print.



  • @nophead I've seen some servo motors that have the entire casing finned and made of aluminum. That will surely help cool the motor, but do stuck-on heatsinks/fans really do any good on a stepper? Steppers are mostly steel. Sticking a heatsink on one side/end may drop that side/end a few degrees, but I have doubts that it will have much effect on the rest of the motor. It's a lot like sticking those tiny heatsinks on the plastic IC package on those little stepper driver modules used on so many printer controller boards.

    We need a thermal image of a stepper with a heatsink on one end... My printer has aluminum motor mounts bolted to aluminum plates- essentially a heatsink on one end of the motor. I'll see if I can get an image.



  • @mrehorstdmd

    It's not like the heatsink side will be cold and the non heatsink side hot. Thermal conduction in metal will occur much faster than the convective and radiative heat transfer that the heatsink provides, so the heatsink and the source of heat will likely be in equilibrium, even assuming a less than perfect mating surface.

    Heatsinks need a fan to be truly effective. By themselves they increase the thermal mass of the object which will delay thermal saturation as heat conducts into it, and weak convective forces will transfer some heat to the air, but without forced convection from a fan and an ambient air temperature delta, it only delays heat saturation.

    That said I'd be very interested in seeing a thermal image.



  • I can't give you a thermal image but I can say that putting a heat sink and fan on the top of a stepper motor is quite effective at cooling the base of the stepper as measured by a thermistor stuck to the stepper, close to the bottom. I can also say that fixing a stepper to an aluminium mount attached to an aluminium frame is even more effective. I know this because I have tried both methods.



  • @phaedrux said in Can monitor stepper temperature?:

    @deckingman You can lead a horse to water, but sometimes he'll insist on touching a hot stepper before he'll drink.

    I was thinking of the other proverb. "Catch a Vegan a fish and he will refuse to eat it. Teach a Vegan how to fish and he will ignore you. But give him the rod and line and sooner or later, hunger will prevail and he'll work it out for himself". The slightly annoying part is when he comes back to you and says "Hey, I cured my hunger problem - I ate a fish". 🙂


 

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