Printer randomly extruding blobs of burnt filament  

Active Member

I have recently upgraded my mk2 to mk2.5s. Prints over the first few weeks were fine, but recently almost all prints are failing because the extruder randomly extrudes blobs of filament that looks burnt. In some cases, the print will complete, but with visible burnt spots, but in most cases, the extruder will crash into the extruded blob and cause the belt to skip.

I used the PTFE tube that came with the mk2.5s upgrade kit.

The nozzle is a E3D V6 0.4mm, also purchased from Prusa. I've checked that it is properly tightened.

Any ideas for what could be wrong and how to troubleshoot? Picture of a recent print attached.

This topic was modified 1 year ago by ahochan
Posted : 11/04/2020 7:14 am
Active Member

I forgot to mention that I am printing with Prusa PETG, standard settings in Prusa Slicer. The model in the picture has 90 % infill, but it happens for other infill settings too.

Posted : 11/04/2020 7:26 am
Eminent Member

I'm still guessing that the nozzle is leaking. The material flows down on the outside of the nozzle slowly, burns and after some time is wiped of to the printing surface. Observe the nozzle while printing or make a photo of the nozzle, or just check that material is on the outside of the nozzle.

Posted : 11/04/2020 10:23 am
Active Member


If it is the same problem which i had a few months ago. There were some blobs all over the nozzle. They fell down on my printing area.

Look on the video

Posted : 14/04/2020 5:20 am

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