Extruder drive gears jamming even without filament loaded
Today I had a print fail due to the extruder clicking and underextrusion. I followed the steps in the knowledge base of doing cold pulls, checking idler tension and checking for debris in the extruder gears. All looks clean and well, but when loading or unloading filament the extruder gears will stop spinning completely and the extruder makes a load whining noise as if it is trying to drive but cant. (I watched the gears with the Z axis hatch open) This noise is very different from the clicking noise. This happens even when there is no filament at all. As far as I can tell the gears are clean and there are no obstructions. I have tried adjusting the idler tension from extremely loose to very tight and nothing seems to help.
I am aware of the ongoing discussions about the PTFE tube at the hot-end being the wrong length, however I am getting this issue even when no filament is reaching the hotend at all. I would like to deal with one issue at a time before changing out or adjusting the PTFE tube.
Everything has been printing fine out of the box for about a week until today when this issue came up. It is identical whether I am using Prusament or another brand of filament.
Any thoughts or insight would be appreciated, really not sure where to go from here.
RE: Extruder drive gears jamming even without filament loaded
I would try the following to see if it is mechanical an issue.
Can the filament be fed by hand through the extruder?
To do this, unscrew the PTFE tube, heat hot end and feed filament through the tube by hand.
If the extruder gear loose/stuck?
Try turning the extruder gear by hand when the printer is powered off. It should be burnable with some motor resistance.
Is the cables set firmly into the Body board and without damage?
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RE: Extruder drive gears jamming even without filament loaded
Alternatively you could try to dissasemble the estruder part, and re-assemble it again. It is possible something's not right there and disassembling and re-assembling will put it into correct place. If that does not help, it may be bad motor or gears, contact support they will help you replace it.
RE: Extruder drive gears jamming even without filament loaded
Loose grub screw on extruder gear.
RE: Extruder drive gears jamming even without filament loaded
@area51
I tried both of these. I am unable to feed the filament through manually, nor turn the gears by hand with the printer powered off.
Is there any instructions on how to disassemble it correctly if I want to look and see if there is something jamming the gears that I can't see?
RE: Extruder drive gears jamming even without filament loaded
@bobcousins
Where would the grub screws be located and how do I verify if they are loose?
RE: Extruder drive gears jamming even without filament loaded
@daniel-ryan-j
To my knowledge there is not an official disassembly instruction for the Mini.
I did disassemble the extruder drive by unscrewing the screws around the extruder stepper. As I remember it, the extruder drive comes free as a unit - you need to cut the two zip ties holding the cable to the hot end. The extruder drive can now be disassembled and inspected.
Maybe someone else has a better instruction for disassembling here in the forum...
It looks like the extruder hot end is clogged too, but that is strange as you did a cold pull and that should have cleaned it.
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RE: Extruder drive gears jamming even without filament loaded
@daniel-ryan-j
Here: https://help.prusa3d.com/en/article/clicking-extruder-under-extrusion-and-clogging-mini_112011
He's telling you to loosen it, not that the screw is loose. Yours may be too tight.
RE: Extruder drive gears jamming even without filament loaded
I figured I would leave an update as I think I have finally resolved this issue. I believe it was a combination of the PTFE tube issue people have been sharing on the forum as well as the extruder drive gear assembly being too tight. I changed the PTFE tube and compressed the heater block as much as possible before tightening the three screws on the side of the fan, which seemed to help a little but still got clicking and underextrusion after a couple layers.
The big fix seems to have been adjusting how tight the extruder assembly was fastened together. As @area51 mentioned, the drive gears should be able to be turned with only a little resistance from the motor. Mine would turn one or two revolutions, and then seemingly jam and I could not overcome the jam with my finger strength. I removed the extruder from the X axis, and disassembled it. With the two halves separated I could spin the gears continuously. I then reassembled and slowly tightened screws while checking I could spin the gears. Got them snug, but not tight and gears were able to be spun continuously while mounted. Midway through a print now, and have had zero issues without needing to modify any settings whatsoever.
Essentially, as @area51 said, ensuring the gears can be spun by finger strength with the unit turned off and filament unloaded is a good diagnosis tool for determining what may be causing underextrusion.
RE: Extruder drive gears jamming even without filament loaded
@daniel-ryan-j
I am happy to hear that you sorted it out and thank you for reporting back.
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