Giant glob of plastic on the print head  

New Member


I have had MK3 for a few months and everything has been working great. it's all original. Yesterday I started a 23 hour print. I left for work this morning and all was well. I get home and find disaster struck. It looks like the last layer it printed (not the top layer) delaminated. The prints look good up to that point.  From there it managed to build a huge glob on the bottom of the print head. See the pictures.

As far as filament, it was Sunlu PETG which I have had good luck with, and this roll was about 2/3 used when this occurred.

So two questions:

What is the most likely cause?

Is there any realistic technique to get the glob removed, or am I stuck with tearing it all apart to see what can be salvaged?



This topic was modified 1 month ago by ti-10
Posted : 22/09/2020 1:01 am
Veteran Member Moderator

I heat the nozzle, and use a temperature controlled soldering iron, to carve the blob off

be very careful with the thermistor and heater wires!

regards Joan


I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 23/09/2020 12:32 am
ti-10 liked
New Member


Thanks Joan. Something along those lines had occured to me, but maybe I was looking for some validation. The glob is about the size of a golf ball and almost completely surrounding the heater and thermistor wires.

I will give that a try!

Posted : 23/09/2020 12:36 am
Prominent Member

As far as cause, it's most likely a bed adhesion issue causing the print to break away while in progress.  It can also be such things as warping causing a nozzle crash, again breaking away the print from the bed.

The worst I had is shown below.  I walked in (fortunately) to see a blob forming around the nozzle and the extruder dragging what was left of the part around the printbed kind of like a futile attempt to walk a cat on a leash.  😉

I was fortunate in that getting the nozzle good and warm and applying some gentle pressure caused the blob to cleanly drop away.

If you want to see some examples of what can happen with this, you can visit the Blob Of Doom gallery here:

If you want to have a photo of yours added to the gallery, just post it here or PM me.

Posted : 23/09/2020 1:16 am

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