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Atomic Pull Diagnosis

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Hey all,

I have recently been having some extrusion issues with my UMO+ and upon completing some atomic pulls noticed some issues right away. I figured it might be interesting to try to diagnose the hotend via atomic pulls as this is something I have not seen anyone do.

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In the first image you can see a nice atomic pull tip in the exact shape of the nozzle followed by a necked region. The necked region has a "collar" in the center which I believe corresponds to where the nozzle and throat meet inside the heater block. I do not think this would be causing any clogs as there is no foreign material present in here and I have not had any filament leaking from the heater block.

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Next you see another necked region as you move to the top of the throat. Here you can see a large lateral jog in the filament which should be happening where the PEEK meets the throat (aka the transition zone, temperature wise). This is where I could use some help: I have taken my hotend apart and the throat threads quite nicely into the PEEK. I have even replaced the throat with one I got from robotdigg and the issue persists in the exact same shape. This indicates to me that this has to be happening where the PTFE coupler meets the PEEK insulator, however there should not be any molten filament in this area as far as I know. I have ordered replacement PEEK and PTFE parts so it will be relatively straightforward to troubleshoot when they come in.

Let me know if you have any ideas for further testing and if this helps you in any way. Go ahead and post some images of your atomic pulls for analysis if you're interested!

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DSC_0674.thumb.JPG.8933a82ba3d31c451f4616519351d9c4.JPG

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I think you have two problems

Ptfe coupler is deformed due use, compressed on itself, leaving a small gab that goes between the coupler and the barrel. Even if doesn't look burn, couplers deform and compress on itself, making it smaller. Easy way to check this is to remove it and check how perfectly round is the circle (the small one, not the one that holds the bowden).

Second, I think your nozzle and barrel have a small gap. That's quite common since the assembly manual is quite poor on how it should be really assembled. @amedee made a post I can't find, maybe he can link it to you aince he explanains quite nicely how to properly assemble it.

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I think you have two problems

Ptfe coupler is deformed due use, compressed on itself, leaving a small gab that goes between the coupler and the barrel. Even if doesn't look burn, couplers deform and compress on itself, making it smaller. Easy way to check this is to remove it and check how perfectly round is the circle (the small one, not the one that holds the bowden).

Second, I think your nozzle and barrel have a small gap. That's quite common since the assembly manual is quite poor on how it should be really assembled. @amedee made a post I can't find, maybe he can link it to you aince he explanains quite nicely how to properly assemble it.

 

The former is a little concerning seeing as the ptfe has seen only a couple hundred hours of printing. As far as assembly, I heated the nozzle up and tightened it down as hard as I could without snapping the brass tube - the last thing I want is a chunk of the throat sheared off and seized in the block! I would appreciate advice from @amedee!

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Coupler 50-200h tops, so I would not really surprised if is dead/halfdead. Umo+ extruder is quite strong and it can push trough a damaged coupler, but ofc not without side effects on print quality.

3dsolex sells a umo coupler made of tfm, the same um uses (or that's what I think) on um2+, and that couplers should last a good 500-2000h.

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That's quite common since the assembly manual is quite poor on how it should be really assembled. @amedee made a post I can't find, maybe he can link it to you aince he explanains quite nicely how to properly assemble it.

 

I have this one for the nozzle and this one for the shims...

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