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Prusa steppers get too hot  

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oleh.k
(@oleh-k)
New Member
Prusa steppers get too hot

Hello. I bought the i3MK3S for a week, I realized that the printer steppers get too hot in my opinion. the stepper of the extruder more than all, if you touch it it is as hot as the heat bad at 60 ° C if not more. Following are the Z-axis steppers. I wonder why they get so hot, is it normal?
Furthermore the "E" stepper if it is too hot must influence the PLA printing. It becomes impossible to print.

Posted : 05/07/2019 9:05 pm
bobstro
(@bobstro)
Illustrious Member
RE: Prusa steppers get too hot

Obvious question: Are you printing in an enclosure?

Ambient temps matter for an air-cooled hotend. The E3D V6 is rated to operate in up to 40C ambient temps. If the temp approaches the glass transition temp for your filament (notably PLA) it can soften prematurely in the extruder. This in turn creates more work for the extruder, which then contributes to heat. Make sure there is a good flow of cooler air around the hotend.

Try dialing speeds back using the front knob and see if temps drop. The Prusa 200mm/s speed for PLA infill is very aggressive. You might want to reduce that in your slicer settings.

Excessive retractions can contribute. Are your printing any detailed parts with lots of isolated portions (e.g. fingers, hair)? Turn on retractions in preview to see if you've got a lot going on.

Proper tension on the extruder idler gear is important. Not too tight, nor too loose. You want it to feed but not deform the filament. Mine stick out about 1mm on the left side of the housing.

Raising temps slightly (5C) may help filament flow more smoothly if that is your problem. Are you hearing any extruder kicks or skips?

The motors are rated to 100C IIRC, so you're not going to burn them out, but you do want to reduce back pressure and feed issues as much as possible for print quality and to avoid jams.

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 : 05/07/2019 9:20 pm
oleh.k
(@oleh-k)
New Member
Topic starter answered:
RE: Prusa steppers get too hot

No, I'm not using enclousure.
I am simply doing a 3D printing test with the Prusa g-codes loaded into SD.

Those from Prusa told me to lower the temperature of the extruder.

I had to deal with an i3MK2S and I remember that the steppers did not overheat so much.

Posted : 05/07/2019 9:39 pm
Alucardi
(@alucardi)
Active Member
RE: Prusa steppers get too hot

what is to hot in you opinion? They can handle a lot of temps. I remember people mounting stepper dampers in their ender 3 printers and everyone said the steppers will burn up if not adding cooling fins. Just like bobstro said you have nothing to worry about. They are not overheating as long as you don’t burn your fingers touching them. 

Posted : 08/07/2019 10:52 am
Peter M
(@peter-m)
Noble Member
RE: Prusa steppers get too hot

On thingiverse you find a extra cooler for  the extruder,this will cool it down very good, the can now not go to the gears and melt the filament(in a enclosure and the summer).

Also if you have a enclosure, add a extra fan to cool it down, maybe at a certain temperature, this is for pla, and in the summer.

Posted : 08/07/2019 11:09 am
John~T
(@johnt)
Eminent Member
RE: Prusa steppers get too hot

That is one my questions also after stuffing all that extra wire into the enclosure before closing, May rearrange that bird nest if heat from drivers becomes an issue.  Running Wizard today, my first rodeo in 3d printing.

Posted : 08/07/2019 12:29 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Prusa steppers get too hot

the drivers emit most of their heat thru the card ( if you add heatsinks they go on the bottom of the board not on the driver chips)

Posted : 08/07/2019 1:55 pm
John~T liked
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: Prusa steppers get too hot

A resistance in the PTFE tube can also cause the motor to become hot.
If the pipe is deformed at any point, the extruder motor must work harder to overcome the resistance and it will then overheat.
At room temperature, my extruder motor rarely exceeds 45-50°C.

This post was modified 3 years ago by RH_Dreambox
Bear MK3 with Bondtech extruder...
Posted : 08/07/2019 3:48 pm
RetireeJay
(@retireejay)
Reputable Member
RE: Prusa steppers get too hot

It's worth noting that the temperature of a stepper motor is only slightly influenced by the mechanical work the motor is doing (or not doing).  The circuits that control stepper motors are designed to always send a specific total amount of current through the two coils (dividing it between the coils according to the microstepping algorithm).  This current, flowing through the ohmic resistance of the windings, creates heat even when the motor is completely stationary.  There's a bit more heat involved when the stepper is in motion and doing work, but not a lot. (For the geeks among us, the fact that the motor's coil voltage goes up when the motor is working against a mechanical load does not result directly in extra heat; that voltage is due to "reactive" impedance, like an inductor, which (ideally) stores energy but does not dissipate energy.)

This is very different from some other types of motors that absolutely will heat up a lot more if they are working against a significant mechanical load, and especially if they are bogged down and running slower than designed due to the mechanical load.

So for stepper motors, there is an adjustment in the control circuitry that determines how much current is being pushed through the motor coils.  In some older circuit boards, this was controlled by a potentiometer, but in the boards used by Prusa it's controlled by a digital signal.  In other words, somewhere deep in the firmware there's a setting that tells how much current to send to the motors.  I'm not sure if it's accessible by G-code, or whether you need to find the setting in a configuration file and re-compile to change the current.  But Prusa has worked on optimizing the current settings.  If you have too little current, the motor can skip steps (or "click") under load.  Obviously, too much current leads to overheating - so it's a tradeoff.

If the motor's heat is causing a problem, you can add cooling fins and even a dedicated motor-cooling fan.  But make your decision on whether it's "causing a problem" by looking at your prints and the machine's performance, not how comfortable it is to touch the motor.

Posted : 08/07/2019 3:55 pm
bobstro
(@bobstro)
Illustrious Member
RE: Prusa steppers get too hot
Posted by: RetireeJay

[...] in the boards used by Prusa it's controlled by a digital signal.  In other words, somewhere deep in the firmware there's a setting that tells how much current to send to the motors.  I'm not sure if it's accessible by G-code, or whether you need to find the setting in a configuration file and re-compile to change the current.  But Prusa has worked on optimizing the current settings.  If you have too little current, the motor can skip steps (or "click") under load.  Obviously, too much current leads to overheating - so it's a tradeoff.

IIRC, one of the Prusa Mk3 firmware updates addressed this very issue. I recall stepper motor current being one of the issues causing Linear Advance to be disabled back in 3.1.1 or so.

Some possibly relevant discussion here.

If the motor's heat is causing a problem, you can add cooling fins and even a dedicated motor-cooling fan.  But make your decision on whether it's "causing a problem" by looking at your prints and the machine's performance, not how comfortable it is to touch the motor.

I think when you start to encounter extruder skips and clicks and basic heat remediation fails is a good time to start. I spent some time with someone complaining that their "motor was too hot", only to find it was running at 40-45C. Having lived in Phoenix, that's not "hot"! Agreed that not worrying about it unless it causes actual problems is a good idea. The motors would only be a contributing factor. Friction and other problems no doubt contribute to actual heat-related failures.

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 : 08/07/2019 4:16 pm
macropin
(@macropin)
New Member
RE: Prusa steppers get too hot

There is no problem. Stepper motors are designed to operate at up to 100C!

Posted : 08/07/2019 10:23 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: Prusa steppers get too hot

There is no problem. Stepper motors are designed to operate at up to 100C!

Yes it may be so, but only for short periods. The life span at 100°C is considerably shorter than if the motor operates at 50°C.

Bear MK3 with Bondtech extruder...
Posted : 09/07/2019 7:30 am
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