Every Unload gets jammed because of Blobs at the end  

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thomas-7
(@thomas-7)
New Member

Hey everyone,

I've assembled my MMU2S yesterday and I'm still trying to achieve a normal print. Every filament I tried has these blobs at the end when unloading and gets stuck in the extruder/selector tube. I've tried different Filaments, temperatures and even PETG, but the problem remains. While loading, everything works fine, only the unload is broken.

Anyone has an idea how to fix it?

Thanks and have a nice day

Posted : 21/01/2020 4:34 pm
vintagepc
(@vintagepc)
Noble Member

Bump up the number of cooling moves and make sure the ID of the extruder PTFE in the hotend is 1.85mm. If you used generic stuff you'll get no end of this sort of issue... ask me how I know...

Posted : 21/01/2020 5:12 pm
Nikolai
(@nikolai-3)
Noble Member

This filament tip looks not that bad. Before replacing stuff, adjust the tension screws on the MMU2 and the extruder. Maybe a little bit more grip will solve this issue for you already.

Often linked posts:
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Real Multi Material
My prints on Instagram...
Posted : 21/01/2020 5:20 pm
wpegden
(@wpegden)
Trusted Member

I agree with nikolai-r, that tip doesn't look that bad.

When it fails and you pull it out yourself, do you struggle to get it loose?  If not, then I suspect something is wrong in the MMU2 unit (gear alignment, clean gears, etc.)  This can give you a run down of things to check, even though it is for the MMU2:

 

If the ends really are too big, one thing that seemed to helped me with PLA printing with the MMU2S was adding heat sinks to the extruder.  I got two of these:

https://www.digikey.com/product-detail/en/cts-thermal-management-products/BDN14-3CB-A01/294-1101-ND/272739

and put one on top and one on the left.

 

But like I said, your problem is likely not this, especially if it happens every time.  Also if it is not very hard to pull out when you do it manually, I wouldn't mess with settings like cooling moves yet either (as those have other consequences).

Posted : 21/01/2020 7:00 pm
magician.144
(@magician-144)
Eminent Member

Did the filament have unloading problems before you installed the MMU2?

If not, it is probably the gear alignment on the filament pulleys. Be real careful with them and also check for filament that is grinding, if it is grinding I would bet money that the pulley gears are misaligned. Take a  light and line them up, also make sure the grub screw is on the flat end of the pulley motor. Clean the dust out of the unit and try again.

Posted : 22/01/2020 1:23 am
teapack
(@teapack)
New Member

Try to change PTFE tube in extruder for new one (1.85mm diameter). Over time it gets wider and it starts causing unload problem (at least in my printer).

Posted : 22/01/2020 7:25 am
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