Big blobs of previous filaments ?  

Eminent Member

Hi there,

3D printing rookie here... I have an MK3S printer since a couple of weeks. First prints with the provided PLA went pretty smooth. I switched to the orange "PPE" PETG without too many trouble. Now I have bought some additionals spools from Prusament and have been toying with them...

I now have a lot of trouble, up to the point that I can't finish nearly any print more... The problem is that I get big (5 and more mm)  "blobs" of material that show up randomly. Often that material is from the previously used filament, in one ocaacion even from two colors before... It shows up randomly... Sometimes after I first successfully printed one object with the new material, it will come up in the second object... See pictures below...

I have come to the point that I missed three "Buddy" prints in a row (see last picture). What can I do about this?

This topic was modified 9 months ago by Jiheffe
Posted : 21/05/2020 5:49 pm

Hi JF,

It would be useful to find out where the blobs were comming from, 

the Most common fault, is to have a gap between the top of the nozzle and the bottom of the heatbreak, 

this often occurs after changing the nozzle

there should not be any filament on top of the heatblock... 

unfortunateely this pproblem also happens after a Blob of Doom. 


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 : 21/05/2020 8:27 pm
Eminent Member

Hi Joan,

I didn't change the nozzle but from what I understand from the KB article the position of the heatblock is important. I will check if it correctly aligned.

Yesterdy I did a series of cold pulls, see picture below. Compared to the photo in the KB article on cold pull, my extracted filaments all have this thickenend segment (circled on photo), which is absent from the photo in the article. Is this normal?

Posted : 22/05/2020 6:21 am
Active Member
Posted by: @joantabb

unfortunateely this pproblem also happens after a Blob of Doom.

Agree with all of what Joan suggests. I hit this exact problem yesterday after removing a blob and not adequately cleaning afterwards. It just kinda plopped off the back of the nozzle or bottom of the heatbreak onto my print while I was watching a critical part of the print. And that was after doing 3 quick test prints to make sure it was working after removing the blob. So it won’t always happen on the very next print.

Edit: I just noticed your other thread. I’d sure expect that to ooze off into your prints until it’s clean.

This post was modified 9 months ago by Kaiede
Posted : 22/05/2020 3:34 pm
Eminent Member

Yes, in the meantime I spent a lot of time educating myself on the knowledge base and better understand how the different parts are supposed to work 🙂

I noticed a lot of residues in the gap between the hotend and the heat block. I did a cold pull and then heated the nozzle up to 280° C and was able to remove all that dirt and have a clean looking hotend/hearblock unit again 🙂

Just finished printing Buddy succesfully, after... 6 (!) failed attempts 😉

3D printing is fun and rewarding... when you invest in understanding how things work !

Posted : 22/05/2020 4:31 pm

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