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Filament stopped at thinnest part of print

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I recently had a print that started with a great base, but filament ran thin and stopped extruding at the thinnest part.

Printer is an Ultimaker 2. I usually have to run it a little hot (about 235 degrees) to get PLA to flow consistently. Has a new nozzle that has only been used with PLA.

Underextrusion seems like a really tricky problem, but was hoping someone could point me in the right direction. Pressure too high? Too low?

Thanks for your help!





Edited by Guest

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Thanks for your replies!

No, I did not change the coupler- you think it's gone bad?


If you have ruled out everything else, then yes. It is hard to check and swap out, so it is always the last thing you check for.

Clean nozzle?

Quality material?

Clean knurled thing in the feeder?

Tangle free spool?

Easy spinning spool holder?

Same settings you have had success with before?

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If it's an UM2 (not UM2+) with the old PTFE coupler then I would definitely change it. I would make sure that you replace it with the new one in the UM2+ as they last a lot longer. You could also print a spacer to replace the spring as the spring presses to much over time and deforms the end of the coupler.

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Thanks! This helped, though I think there are a few things wrong with this machine.

PTFE coupler definitely helped the heating issue. I ordered some replacements, but in the meantime I trimmed off the burned edge as recommended in another thread. This worked very well. It's easily putting out PLA at 210C like the day I got it. So thanks for the awesome advice.

Probably should have mentioned, but the printer has a replacement filament extruder stepper. It was running hot and melting filament, so I'm running it at a lower current (advice from Ultimaker Support), and it did the trick.

Even after trimming the coupler, the job was failing at the same point. I reduced the retraction from 4mm to 2mm (started at 0.5mm and raised it up during the print). Print came out looking nice. Probably not a great recommendation for anyone else, but worked for my machine in it's weirdo condition.

I ordered a factory extruder stepper motor (got my current one from a 3rd party)- hoping to get this thing back in ship shape. It was a rental printer for a while, and got pretty beat up.

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