Extruder Motor getting too hot  

Re: Extruder Motor getting too hot

My observation . . . I have a Full MK3 kit and also an MK3-clone; the clone is built with extruded aluminum rail, it has the latest firmware (.hex version 3.3.1), Einsy-RAMBo 1.1a, MK52 HeatedBed, latest version of the MK3 extruder w/E3D, BondTech gears, PINDA, Optical sensor, everything except Prusa's stepper motors and PSU. So . . . In the same room printing the same models simultaneously the MK3 extruder gets really hot . . . the clone extruder does not get hot, ever !!!! I actually have 4 3D Printers, one is a Delta so it's not relevant in this discussion, but my Rigidbot-Big doesn't have a crazy hot extruder either.

In my 40 years of electronics / engineering experience, anytime mechanical and electrical devices get really hot they tend to provide marginal results, and typically fail sooner than expected. So I disagree with the people saying it's OK, things aren't designed to run at or near max temps constantly.

Also this confirms that it has nothing to do with the BondTech gears, in fact they're the best hobb'ed gears I've run so far. If you tightened the bolts too tight and your squeezing the crap out of your filament then yes that might cause extra current / heat, but that's an assembly / calibration issue. Here's a test . . . do a test print with no filament . . . does your extruder still get hot ??

Can anyone provide actual electrical information for the Prusa MK3 extruder stepper motor ?? I've seen some posts online saying they're OEM'd from LDO, but LDO doesn't show a "stock" 4 wire NEMA-17 with similar coil resistance. If it is a custom motor why isn't it better; to match the capabilities of the Trinamic's and the BondTech gears? I'm measuring the coil resistance at 6.5 Ohms which if it is an LDO stepper might put it in the 0.8 amp category with 25Ncm of holding torque. In contrast my Clone has a 17HS16-2004S1 with a 2.0 amp rating and 45Ncm of holding torque, the coil resistance is 1.1 ohms. Not hard to see the difference here, we're possibly running a lower rated motor near it's limits. I plan to make an adapter cable so I can attach my O-Scope and also take some current / voltage measurements. Does anyone have any real scientific information to share ????

Re: Extruder Motor getting too hot

My scientific experiment on cr10 was thus: I changed the lousy steppers rated to 0.8A to 2.0 A - overheating stopped, working noise went away. Everything runs better - smoother - quitter.

Prior to that I did try to adjust voltages following few tutorials on the tube - no result any way i changed them except worse.
Now they are at 0.6 to 0.7. Fairly standard.

Re: Extruder Motor getting too hot

So you think that overheating is due to a voltage problem?
I also noticed that after a few minutes of use the engine becomes very hot!

Re: Extruder Motor getting too hot

No. Because - as i said - adjusting voltage doesnt do anything.

Its due to bad, lousy stepper motors that are too weak.
Buy several rated for 2A, same nema 17 model, replace old ones and solve that problem and several others.

They are fairly cheap anyway.

Re: Extruder Motor getting too hot

I should have stated above that I do love my MK3, it's an amazing machine for the money, when you consider all the innovations and then the print consistency, it's definitely comparable to much more expensive machines. Prusa has done an amazing job ramping up to meet the demand, that's not an easy thing to accomplish and still maintain product quality.

So back to the business at hand . . . I agree with sinia.k, it's not a voltage issue, it's most likely a current issue coupled with the wrong stepper motor. I'm not saying the motor is bad, just the wrong motor for the application; which is quickly becoming the consensus here. I'll know more once I take the readings I mentioned above.

Also I'm gonna try an MK3 print with no filament in the extruder (filament sensor off of course) and see if it still gets hot, that would be a tell-tale test.

Re: Extruder Motor getting too hot

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As already stated in this thread, feel free to adjust the current with a gcode:
Holding currents: M911 X16 Y20 Z35 E26
Running currents: M912 X16 Y20 Z35 E26

You can try to go even lower. The bondtech gears require more torque from the motor and depending on your speed settings it requires more or less power. Current Prusa default should work for most of the people, so I assume that's why they increased a little bit the current.
The Prusa motors are pretty good quality and you barely see user posting here this things failing.

Re: Extruder Motor getting too hot

So, if a underpowered motor is the issue, what would a good higher powered replacement option be?

Re: Extruder Motor getting too hot

I don't know if it affects any of you having heat issues, but when I was printing with flexible filament I had symptoms similar to yours. What caused mine was that I had the filament tension screw too tight so the extruder motor was working too hard. When I unscrewed the screw a bit to relieve tension the heat issues went away.

Re: Extruder Motor getting too hot

I did release the tension a lot, but still gets hot. Also the weather is more hot here now (30 - 35C) .
I also made a cabinet, but I'm afraid to close it because of the hot extruder. It will get even more hot!

I can't print low melting temp filaments like PLA, they keep jamming, but I can print PETG.

I might do a test printing without filament to see is motor keeps getting hot even without load

Re: Extruder Motor getting too hot

Last night I tried several prints . . . in my case the extruder motor was reaching it's peak temp about 30% in to my hour long print. So I used this as the sampling point for all 3 tests.

1) With PETG filament reached 55c, could not hold on to the motor. Bed 90c / HotEnd 240c
2) No filament, still reached 55c, Bed 90c / HotEnd 240c.
3) BondTech 2nd gear flipped up, so there was zero drag on Extruder Stepper, reached 52c, Bed was at 30c and HotEnd at 240c, I should have kept the bed at 90c, but wanted to get a good IR pic of the stepper. Will try it again tonight with the Bed at 90c.

So it's not a stretch now to say the motor is getting very hot with zero drag !! Can someone else confirm this please, thanks

Re: Extruder Motor getting too hot

[...] So it's not a stretch now to say the motor is getting very hot with zero drag !! Can someone else confirm this please, thanks
No FLIR here for specific testing, but my extruder motor never gets too hot to touch comfortably. I've got a Mk3 running FW 3.3.1-845 and have done multi-hour prints with a variety of materials, including PLA, PETG, NGEN, XT and a variety of filled PLA materials. I have not modified the printer in any way since delivery in late March 2018. Ambient room temp is about 25C/77F. Let me know if you'd like me to check any other printer settings.

Re: Extruder Motor getting too hot

3) BondTech 2nd gear flipped up, so there was zero drag on Extruder Stepper, reached 52c, Bed was at 30c and HotEnd at 240c,

Interesting temperature. What is your ambient temperature?
I never got the extruder stepper above 48c while printing PLA for several hours. That was with the printer standing openly in a 22c room.
Now I have it in an enclosure, and while printing ABS or PETG it feels quite a bit hotter (I don't have exact measurements though).

I plan to rebuild the extruder with the new R3 parts, and at the same time I'll experiment with a higher power capable stepper. I should be getting one next week.

Re: Extruder Motor getting too hot

So it's not a stretch now to say the motor is getting very hot with zero drag !! Can someone else confirm this please, thanks
Test 3.jpg

I also don't have an IR camera (yet 😉 )
But this was my test setup for the last few day's while printing the R3 upgrade parts :

In big lines I found the following extruder temperatures :
- Printing without filament : 47°C
- Printing with PETG : 57°C
- Upgrading to R3, printing with PLA : 49°C (and replaced the PTFE tube, old one was still looking clean tough)
# ambient temp ~30°C

So the R3 upgrade and fresh PTFE tube looked promising! But I tried 3 PLA prints already, and all 3 failed around 1:30h in a print. I also noticed it is making a high squeeking noise just like scratching a knife over a sheet of plexiglass. I kinda think it might be that I have the gears pressure not high enough, so I increased it and I'm currently printing my 4th PLA print. Really hope I can print PLA some day.

I will try to measure new temperatures from PETG as soon as I print it again, now I have the R3 upgrades and fresh PTFE tube.

Re: Extruder Motor getting too hot

Increasing the gears by 1,5 to 2 full turns has solved it so far!
I did a 16hour print with the Prusa default PLA, ans switched to ColorFAB Glow-in-the-Dark PLA on about 85% of the print and finished it!

The squeeking sounds I had also went way after I had tightened it a bit more. The extruder motor didn't seem to get any hotter (43C at ambient of 27C)

Re: Extruder Motor getting too hot

I've just found this thread, so apologies if this has already been said. I scanned the pages quickly but didn't see it.

I was having a very similar issue. The problem only really became evident on prints that had many retracts and fine details. But the extruder motor was very very hot to the touch.

I found this after some googling: https://www.thingiverse.com/thing:2975582

And then I bought a fan on Amazon: https://www.amazon.com/gp/product/B00NEMGCIA/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

$13 later and my extruder motor is barely warm at all. It might not have solved the underlying problem (as I believe you all are attempting to do), but it works!

I had to tap into the existing 5v extruder fan, so its not for the faint of heart. Some fine work with an exacto knife and soldering was needed. You could probably home run it back to the RAMBO, but I opted against that.

Re: Extruder Motor getting too hot

I plan to rebuild the extruder with the new R3 parts, and at the same time I'll experiment with a higher power capable stepper. I should be getting one next week.

Now I have rebuilt the extruder with a new motor, and the short version is: Don't waste your time.

The long version:
Initially it seemed to work fine. The new motor runs noticeably cooler than the original Prusa. The motor I used was a JKM JK42HS40-1704.
But when printing with a fast profile, and large objects, the new stepper started to skip steps. I could also make it skip steps by pulling the filament. It wasn't the Bondtech gears, it was the stepper that was too weak. This makes sense as the two steppers are the same size, but the new one has lower coil resistance. Lower resistance at the same size means thicker and fewer windings. Fewer windings gives lower magnetic flux (given unchanged current).
The solution is obvious: Increase the current. After all, the new motor is built for exactly that, right? I did, and I got satisfactory pulling power without overdoing it. Unfortunately, after a 1 hour print, the new stepper was every bit as hot as the original would have been.

I will now strip down the extruder again to switch back to the Prusa motor and get rid of the custom gcode that increases extruder motor current.

Re: Extruder Motor getting too hot

So does anybody have a working solution for this problem ?

I just did a 3 hours print and the extruder motor got so hot I couldn't keep my fingers on it.

New stepper ? Heatsinks ?

Re: Extruder Motor getting too hot

So does anybody have a working solution for this problem ?

I just did a 3 hours print and the extruder motor got so hot I couldn't keep my fingers on it.

New stepper ? Heatsinks ?

If it was printing fine for you (no issues), keep it like that. Hot stepper motor in general is perfectly fine.

Re: Extruder Motor getting too hot

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Hot stepper motor in general is perfectly fine.
[/quote]

No it isn't. My extruder motor temp is about 40 C. I got higher temp only if there is something wrong:
- too low nozzle temp
- tangled filament spool
- incorrect position of bondtech gears

Re: Extruder Motor getting too hot

If it was printing fine for you (no issues), keep it like that. Hot stepper motor in general is perfectly fine.

While the motor will work just fine at the "too hot" temperature, the problem will be when that heat travels down the shaft. It heats up the bond tech gears which then softens the filament. This softened filament will then flex, deform and cause jams.