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theisp
(@theisp)
Active Member
Extruder motor skipping steps

Hi

The extruder motor has started to skip randomly in the middle of prints. Sometimes it will skip just once, other times it will keep skipping until I use the 'change filament' option to unload and reload the filament again. I will try and list all the possible solutions I've already tried:

I have tried to take the extruder apart and
- ensured that the gear is tight on the motor shaft
- pulled the ptfe tubing out - no material is stuck in there
- insert a small wire in the nozzle to clean out any partial block

I have also tried to do a cold pull with the filament several times and adjusting the tension on the gear with the spring-screw arrangements.
I have tried adjusting the Z (thinking too close to the bed could cause a block)
Often when printing I will leave the printer and come back and see a layer is missing.

The problem began when I was printing with PETG for a few weeks. I have tried with a fresh spool of PLA but I experience the same problem.

Ideas are greatly appreciated

Posted : 14/03/2017 9:58 am
StephanK
(@stephank)
Reputable Member
Re: Extruder motor skipping steps

Some more ideas:

- are you still using the crappy original spool holder that came with the printer? It sometimes creates friction, filament doesn't unspool properly -> extruder skipping

- keep an eye on your hotend fan, if it fails or has "dropouts" or is cooling insufficiently, heat will creep up the hheatbreak and extrusion will get difficult leading from skipped steps up to a full clog.

- if you are printing a part with extreme amounts of retractions, weird stuff like this could happen as well..

Posted : 14/03/2017 10:56 am
Jakub Dolezal
(@jakub-dolezal)
Member Admin
Re: Extruder motor skipping steps

Hi,
if you tighten everything and the nozzle is free, try to print Prusa logo (without any changes) to see if the issue is with the printer or the model.

Assembly manuals

/ Knowledge Base
The guy behind Prusa assembly manuals...

Posted : 14/03/2017 11:00 am
janis.j
(@janis-j)
Trusted Member
Re: Extruder motor skipping steps

Check the cable, mine had couple of wires broken. To check I was constantly turning extruder and moving head left and right until I found spot where everything was bad and extruder movement was suddenly not even. Replacement of the extruder cable helped immediately.

Posted : 14/03/2017 12:15 pm
theisp
(@theisp)
Active Member
Topic starter answered:
Re: Extruder motor skipping steps

Thanks for all your input. The problem also happens when there is no strain on the filament spool (me rolling it out manually).

Seems the problem has gone worse, just now the hotend was completely blocked, I couldn't press any filament through manually. Trying some cold pulls again and maybe taking the hotend apart if that doesn't work..

I have tried printing different models (but all sliced by me) but I'll give the prusa logo a go when I have filament running through again.

Posted : 14/03/2017 2:05 pm
theisp
(@theisp)
Active Member
Topic starter answered:
Re: Extruder motor skipping steps

Took the whole hotend apart. Removed as much plastic residue as possible. Didn't really notice anything which could be blocking (but I could be missing something). I cleaned the thermal compound off the heat-break threads and applied new thermal compound before putting it all back together. Trying to print again later..

Posted : 14/03/2017 5:30 pm
theisp
(@theisp)
Active Member
Topic starter answered:
Re: Extruder motor skipping steps

Just after reassembly I wasn't able to load filament. I removed a small block with some wire in the nozzle and then filament could be loaded.

Printed a prusa logo without any skipping. Trying some other prints now to see if the problem is gone.

My best guess is that reassembling the hotend ensured that everything was tightened. The thread from the heat block might not have been fully tight with the heat sink. Lets see how things go..

Posted : 15/03/2017 11:32 am
matthew.s12
(@matthew-s12)
Active Member
Re: Extruder motor skipping steps

Am having the same issue making me pull my hair out thinking this printer can't reliably print PETG. I have not been able to complete a print as it skips skips skips skips & now looks like the pulley is stripped. Did you buy chance just upgrade to the new 3.0.10 firmware?

Posted : 16/03/2017 2:44 pm
theisp
(@theisp)
Active Member
Topic starter answered:
Re: Extruder motor skipping steps

No I'm still on 3.0.9.

The printer is working after I tightened the hotend parts

Posted : 18/03/2017 9:32 am
michael.e3
(@michael-e3)
Eminent Member
Re: Extruder motor skipping steps

I found this while trying to fix a similar problem. My issue is that the extruder motor cable is damaged where it connects to the extruder assembly. Try moving the head to the position on the board where the issue most occurs and run a long extrusion command (like settings > move axis > extruder) or just load filament, and while it's doing it, move the cable harness around. If the extruder stutters, you have the same issue I have. I was just looking to see if there's a way to remove the motor w/o disassembling the whole thing. lol

Posted : 08/04/2017 11:50 pm
Starlynk
(@starlynk)
Trusted Member
Re: Extruder motor skipping steps

If all you are having is a wiring issue due to a broken wire, you may not have to remove the motor. NEMA motors commonly have a connector that can be removed. To replace that connector, remove the hotend fan and you have access to remove the extruder cable easily.

Posted : 09/04/2017 12:59 am
kenneth.o
(@kenneth-o)
New Member
Re: Extruder motor skipping steps

Had the same problem recently and nothing helped. Tried S3D, Slic3r, nothing worked. Changed nozzle still no luck.
Then I moved the extruder wheel a little on its axel and also saw some marks on the plastic, like the small bearing that pushes on the filament was toughing the plastic. Used my cutters and removed a little material and since then its working. Hope this helps.

Posted : 13/06/2017 10:16 pm
mdj
 mdj
(@mdj)
Active Member
Re: Extruder motor skipping steps

In my case, the reason for the extruder motor skipping was that the extruder spring screws were tightened too much. The manual says it is alright to tighten these with higher force (than what is obtain by the 13 mm:s, I guess), but this caused the skipping. Possibly, it could also have been due to the force being uneven between the two screws.

The skipping was kind of random, much as has been described in this thread.

This is all very tricky, because it is easy to think of tension from the spool holder, etc,.

Posted : 19/06/2017 12:09 am
Antonis DSAW
(@antonis-dsaw)
New Member
Re: Extruder motor skipping steps

Last couple of days i was struggling with a similar skipping issue on my MK2S. Took everything apart, cleaned, reassembled, even made a new PTFE from Capricorn material. The problem was completely random.
Since due to winter the printers are in an enclosure i decided to stay on top and watch as it would potentially happen and it did.
Noticed that my printed Prusa tensioner was slightly bend as if the springs were took tight and they had warped the part. But at the time my springs were 14mm since for me this is the tension of choice. After checking and checking once more i realized that the tensioner bearing was slightly touching the PTFE holder. Trimmed it with an exacto knife about 1mm on the same angle as the bearing and now i already have two flowless prints on which i had to also decrease flow (since i saw overextrusion during the print).
Maybe my solution might help another person also. Happy printing!

Posted : 17/02/2018 1:51 pm
hanjos
(@hanjos)
Active Member
Re: Extruder motor skipping steps

Loosen the extruder tension screws 1.5 turns helped for me. First I thought that I needed to fasten them, but then it got worse. The problem started after a wood filament test, changing back to PLA. But al right now! Thanks for the info guys

Posted : 23/03/2018 12:10 pm
digibluh
(@digibluh)
Reputable Member
Re: Extruder motor skipping steps


Am having the same issue making me pull my hair out thinking this printer can't reliably print PETG. I have not been able to complete a print as it skips skips skips skips & now looks like the pulley is stripped. Did you buy chance just upgrade to the new 3.0.10 firmware?

I've printed at least 5kg through it and swapped between PETG, PLA,ABS... it's capable. make sure you cold pull every filament change, because old stuff / residue can get stuck there... if it was PLA then you prep the temp for PETG/ABS at 240c and leave it sit, it will burn that PLA and it can get stuck to the sides of the nozzle making it smaller inside. I have some purge filament and even when i THINK it's clean and looks clean, it keeps pushing out black flakes...

Posted : 26/03/2018 12:32 am
chexone
(@chexone)
Eminent Member
Re: Extruder motor skipping steps

I was having the same issue. Loosening the extruder tension screws seems to have resolved the skipping issue. I don't get it but I'll take it! Thanks for the suggestions on this thread.

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Prusa I3 MK3S

Posted : 19/12/2018 11:57 pm
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