Distorted burn mark same location every time  

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Darrell
(@darrell-2)
Eminent Member

Strange distortion & burned spot in the same place every time.  Not a random nozzle goo blob.  Any ideas what could be causing this?

blob examples

Posted : 26/10/2020 7:55 pm
Darrell
(@darrell-2)
Eminent Member

Here's my crackpot theory:  A leak has developed where the heatbreak enters the heater block.  As the print starts, the goo outside the heatblock heats up and begins dripping.  This acts as a timer, and when the print is about 6mm off the bed, a drop large enough to be wiped off on the print has formed. Why it chooses that same X-Y position to be removed, I don't know.

I ordered the Bondtech upgrade kit because the original plastic parts have become droopy.  While replacing those parts, I'll heat & reseat the hot end.

Thoughts? 

Posted : 28/10/2020 7:34 pm
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 -2
(@-2)
Illustrious Member

It looks more like a problem with the model that is printing in mid-air around that level. Filament collects on the nozzle and is pushed around until fried, then adheres at the next convenient spot.  A failed support is common for this sort of thing, too.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 28/10/2020 7:39 pm
Darrell
(@darrell-2)
Eminent Member

Problem solved: 

Was running without a fan since the printer's parts closest to the hot end were starting to melt and sag - in particular, the PINDA probe and the part fan support.  Had to remove the support & fan since it they were drooping too far.  To fix this problem, I replaced the entire PETG extruder assembly with Bond Tech's Nylon alternative.  This put the part cooling fan back in service.

Testing after replacing the extruder showed the problem still exists.  Since the fan is now usable, I turned it on at 50%.  Also dropped the temp 5 degrees to 250.  Problem gone.

Posted : 02/11/2020 9:45 pm
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 -2
(@-2)
Illustrious Member

Nice to post a question and not mention you have disassembled half the hot end... lol.  Seriously?  Officer, why no, I didn't know I was speeding; I took out my speedo because I was always getting tickets.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 04/11/2020 5:24 am
Darrell
(@darrell-2)
Eminent Member

The brown globs problem developed slowly over time. Everything mentioned happened after the globs, except the melting/sagging of the original parts which I didn’t notice until some of them fell off.

Posted : 04/11/2020 5:21 pm
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 -2
(@-2)
Illustrious Member
Posted by: @thetipgiver

The brown globs problem developed slowly over time. Everything mentioned happened after the globs, except the melting/sagging of the original parts which I didn’t notice until some of them fell off.

Yeah, I understand.  I have never known a screw to instantly come completely loose on its own, either.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 04/11/2020 6:49 pm
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