The Hook of Death!!!  

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terry.h7
(@terry-h7)
Active Member

Hello Prusa community. I have a very annoying issue that has plagued me for a while. I have a MK3S/MMU2S and when I manually unload the filament, do a 1st layer calibration, or stop a print, the filament always gets hooked as it's coming out of the extruder. Take a look at this image.

It makes a hook that grabs right above the gear.

It very tedious to resolve when it happens. I have to cut above the MMU2 grind, remove the extruder idler push filament back through so I can cut the hook off and pull the ~1m of filament from the PTFE tube. This happens every time I manually stop a print or do a 1st layer calibration. I do this multiple times a week. I have cut off hundreds of these hooks. It doesn't happen during filament swaps while printing. 

This happens when I use the default configurations with any filament. I have replaced the entire extruder assembly and it still occurs. If anyone has any ideas, I would really appreciate the feedback. 

Thank you.

-Terry Hudson

Posted : 22/06/2020 11:56 pm
john.w80
(@john-w80)
Active Member

@terry-h7,

You are not the first person to see this issue. Take a look here:

https://forum.prusaprinters.org/forum/original-prusa-i3-mmu2s-mmu2-hardware-firmware-and-software-help/mmu2s-single-unload-fails/

https://forum.prusaprinters.org/forum/original-prusa-i3-mmu2s-mmu2-assembly-and-first-prints-troubleshooting/load-unload-durign-print-fine-unload-at-end-fails/

For the first post, you will get to enjoy quite a bit of philosophical discussion between me and @steve-e3 regarding the MMU itself, but there are a bunch of good ideas hiding in there.

I wanted to loop @steve-e3 back into this conversation because your picture is an excellent clue to what may be happening and is much better than I was able to capture.

I was having the exact same issue but have fixed it. I will update the post at the first link above with my experience shortly. Don't get your hopes up - I was not able to isolate the issue to a single root cause.

Posted : 23/06/2020 3:56 pm
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