Extruder engine will not turn gears in housing

Extruder engine will not turn gears in housing  

Active Member

I'm having an issue where the extruder engine isn't moving the gears.

This is a result of resistance in the filament (it was knotted on the spool) that prevented the extruder from pulling filament off the spool. the printer probably ran 10 minutes or more with no filament extruding from the nozzle.

I've done the following troubleshooting steps:

cut the filament at the spool end and attempted a load, unload, purge filament. filament didn't move

manually removed the filament.

3 cold pulls on the nozzle to confirm no blockage

checked the extruder access panel for debris

released tension and manually fed filament through both ends of the extruder housing.

manually ran filament through the hose connecting the nozzle and extruder housing.

tightened the tension to be flush with the housing and attempted another load filament.

regardless of tension setting the gear visible from the access panel does not move on a load / unload filament. the engine does make sound.

looked for manuals on how to dissemble the extruder housing (haven't found any).

emailed Prusa.

anyone else run into this issue or have any suggestions?

Posted : 24/04/2020 10:30 pm
Active Member

further troubleshooting abounds.

I've removed the tension screw entirely in order to open the idler hatch.

then I attempted to load and unload without filament in the system. I did put a small piece of filament in the PTFE tube to fool the filament sensor. I can see the extrusion engine shaft turning yet the extruder drive gear (which can be seen from the top by opening up the access panel) doesn't move at all. If I manually move the extruder drive gear I do not get any sort of resistance. this tells me that either the teeth on the gear attached to the extruder engine are broken or blocked. has Prusa or the community provided instructions on removing the extruder engine? that is a troubleshooting step that I'm fastly approaching.

Posted : 25/04/2020 9:18 pm
Active Member


I had to remove the Extruder Engine side of the block. there are 3 bolts on the orange block in which the extruder engine attaches that can be removed.

once removed there are 4 bolts on the back side of the block that also need to be removed as well as the idle tension bolt. this back plate lifts off and allows access to the idle gear and the extruder engine shaft and gear.

the extruder engine gear had come lose and slide back away from the idle gear. so I had to remove the extruder engine from the block which is held on by two bolts and readjust and retighent the Extruder gear.

put everything back together and it's good to go.

you do not need to touch the 4 screws that are part of the extruder engine, nor do you need to do anything on the X-axis engine side of the block to get to the gear.

Posted : 28/04/2020 1:05 am
Active Member

images of the bolts


Posted : 28/04/2020 1:35 am
bebored, alvaromontoro, jonas.gerdes and 2 people liked
New Member

I had exactly the same issue, day one after my mini arrived. Thanks for the steps, the grub screw holding the cog to the extruder motor was completely loose. Took some random photos as I did it.


It's quite simple if anyone else needs to do it. The instructions are basically: take out all bolts you can see from the extruder end until the motor comes free, then align the cog, tighten the grub screw and put it all back together again.


Posted : 28/04/2020 2:07 pm
alvaromontoro, Olef, alexanderkraus66 and 3 people liked
New Member

I had the same issue with my new Mini after around 1-2 hours of printing. Thanks to your explanations it was an easy fix 🙂

Posted : 13/06/2020 9:40 pm
New Member

I had the same issue as well.    joehaines fix above worked for me.  thankes  joehaines for the solution and detailed photos.

Posted : 15/06/2020 2:45 am
New Member


Thank you so much! I had the same problem. Extruder motor was turning, but the gears didnt. The little gear on the extruder motor shaft was loose and didnt catch. 

I had a couple of other issues - i guess prusa was having trouble to catch up to the high amount of orders, so they diverged from their qc standards. Fine to me - i just hope they include your fix to their troubleshooting faq. It took me quite some time to find this post 🙂

Posted : 15/06/2020 11:57 am
New Member

Thank you for posting this!  I just had the exact same issue with my Mini too.  Easy fix, a little intimidating, but not so bad to do.  

Posted : 23/06/2020 8:06 pm
New Member

Thank you, the extruder drive gear on my mini was spinning on the motor (engine) shaft after three prints.  The pictures posted by joehaines  were very helpful.

Posted : 03/08/2020 12:03 am

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