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Filament Head Diameter  

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tdub415
(@tdub415)
Eminent Member
Filament Head Diameter

I am nearly there getting everything working fairly intervention free, but the biggest hurdle I'm facing currently is with the unloading of filament (mainly during single mode prints) at the end of a print.  The filament head, while having a good tip, is too wide and getting stuck in the orange PTFE tube between the extruder and the selector.  I can pull it through by force, but when I take my calipers to the tip, i'm getting a 2.1mm diameter, which the MMU2 just doesn't seem to be able to reliably pull through the 2.0mm inner diameter of the tube.  almost every time I wind up with a groove ground in the filamennt when it tries to unload it by itself due to this. 

I've tried 1, 2, 3, and 4 cooling moves, but none of these seem to help with the filament head's diameter, just the tip quality (3 seems to work best for me in that regard.

Is there another setting I should turn my attention to in order to minimize the size of the filament head?  My undersanding is it shouldn't every really be larger than 1.85mm, due to that being the inner diameter of the PFTE tube in the heat sink, but I'm very much having consistant issues 🙁

Posted : 08/07/2019 4:16 am
jprintmk3smmu2s
(@jprintmk3smmu2s)
Active Member
RE: Filament Head Diameter

I had this *exact* problem, did you measure your PTFE hot end tube?  Try a 1.85mm internal diameter PTFE tube for your hot end as it may be 2.0mm.  They come standard with MK3S and MMU2S kits, and may be available on the prusa site (or you could buy and make your own). 

This post was modified 2 years ago by jprintmk3smmu2s
Posted : 08/07/2019 6:31 pm
tdub415
(@tdub415)
Eminent Member
Topic starter answered:
RE: Filament Head Diameter

I'm 99.9% sure that I used one of the 2 1.85mm inner diamter PFTE tubes that came with my mmu2s upgrade kit (I went straight from my MK3 to MK3s MMU2s.  The MMU2s "electronics" bag lists 2 on the label, and only one was still in the bag.  I plan on taking the extruder apart tonight to confirm for sure to rule that out though.

Posted : 08/07/2019 6:33 pm
jprintmk3smmu2s
(@jprintmk3smmu2s)
Active Member
RE: Filament Head Diameter

The MK3 extruder likely had a 2.0mm hot end ptfe tube, so unless you did swap it with 1.85mm from the MMU2s kit, it's likely the or at least an issue.

As an aside, I wonder what the expected lifetime of that hot end PTFE part is.  I mean, it should egg out or widen over time right?  Certain abrasive filaments may shorten that MTBF too.

Posted : 08/07/2019 6:37 pm
tdub415
(@tdub415)
Eminent Member
Topic starter answered:
RE: Filament Head Diameter

I definitely swapped the tube when I upgraded the exturder (the original MK3 tube was longer than the MK3s and MK3s MMU2s tubes). I will be making 100% sure this evening that it's not the MK3s tube, and was indeed one of the MMU2s tubes, because that's really the only thing I can think of that it could be.

 

Posted : 08/07/2019 6:42 pm
Jorge S
(@jorge-s-2)
Active Member
RE: Filament Head Diameter

I had a similar experience with the tip heads.I used one of the PTFE tubes provided with the s upgrade, for whatever reason, the internal diameter of one of the provided tube was 2mm(I could fit the shank of a 2mm drill ), after checking and fitting the spare PTFE tube the tip issue has been resolved.

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Posted : 09/07/2019 4:29 pm
tdub415
(@tdub415)
Eminent Member
Topic starter answered:
RE: Filament Head Diameter

That was indeed exactly my issue.  I had absolutely used a tube from the electronics bag with the IR sensor for the mmu2s upgraded for the extruder, but for whatever reason one was a 2mm inner diameter (the one I used) and the other the 1.85 mm inner diameter.  So far my test print I started this morning has been going with only one initial intervention at the start (I hadn't cut the filament at a 45 angle when I loaded it initially.

 

Posted : 09/07/2019 4:32 pm
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