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What Causes This?  

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ARAMP1
(@aramp1)
Eminent Member
What Causes This?

I don't know what to call this but it just deposits a blob and the print will crash.  I'll be able to pull it off and resume the print most of the time, but what causes this and more importantly, how do I avoid it?  Printing in PETG.

 

Posted : 19/09/2023 1:11 pm
Extra Fox
(@extra-fox)
Reputable Member
RE: What Causes This?

In my experience that comes from build-up on the nozzle depositing on the nozzle, dropping off, and then getting in the way of the ongoing print.

Aaron

Posted : 19/09/2023 2:33 pm
RedDawg
(@reddawg)
Reputable Member
RE:

My experience has been similar to @Extra Fox's. Make sure the outer surace of the nozzle is clean before starting the print, and, for long prints, pause every 15 minutes or so and remove any buildup. Seems to happen mostly with PETG. Lowering the nozzle temperature a bit MAY help. YMMV. Does the blob appear at the same location every time?

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Posted : 19/09/2023 2:47 pm
ARAMP1
(@aramp1)
Eminent Member
Topic starter answered:
RE: What Causes This?

 

Posted by: @reddawg
Does the blob appear at the same location every time?

Nope, just randomly.  Seems like it's doing it every couple hours.  

 

 

Was wondering if it's because the bed isn't level and the nozzle is dipping into the print, but there's no rhyme or reason as to where it's doing it.  I clean it every new print or when it crashes.   

Posted : 20/09/2023 2:37 am
Hello
(@hello)
Noble Member
RE: What Causes This?

 

Posted by: @aramp1

 

Posted by: @reddawg
Does the blob appear at the same location every time?

Nope, just randomly.  Seems like it's doing it every couple hours.  

 

 

Was wondering if it's because the bed isn't level and the nozzle is dipping into the print, but there's no rhyme or reason as to where it's doing it.  I clean it every new print or when it crashes.   

Is the nozzle tight

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Posted : 20/09/2023 3:27 am
RedDawg
(@reddawg)
Reputable Member
RE: What Causes This?

Once the print is that high, bed levellness (or not) means little. Yes, do check the nozzle tightness. Minute amounts of filament could be working their way through the threads and eventually winding up on the outside surface of the nozzle, then driping onto the print. It looks as if the blobs are discolored (darker) than the rest of the filament, evidence that it has been "cooked" by extended (time) contact with the hot nozzle. Check the tightness and pause at least once an hour to remove any filament build-up on the outside of the nozzle with a fine steel or brass bristle brush.

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Posted : 20/09/2023 2:12 pm
nighthawk
(@nighthawk)
Eminent Member
RE: What Causes This?

My experience has been the nozzle tightness causes this. The threads leak and the material is dropped onto the print.

I take the temp to 280C and tighten with a torque ratchet: https://www.matterhackers.com/store/l/3dverkstan-olsson-nozzle-tool/sk/M3FMF8XC

My issues with blobs have pretty much disappeared.

Posted : 20/09/2023 3:32 pm
RedDawg
(@reddawg)
Reputable Member
RE: What Causes This?

I would pretty much agree with you with one small mystery: I have only had this happen with PETG, no other filaments. And my nozzles ARE tight. 

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Posted : 20/09/2023 7:19 pm
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