Help with PETG print

jasonI

jasonI

jasonI

Associate
Joined
17 Jul 2024
Posts
3
Location
Essex
Hi all,

I am trying to print a vase lid with clear PETG, i have been successful with getting the print to come out really clear however I keep getting this weird burn mark and filament line across the print, can anyone help me why this might be happening?
I am guessing it's where the nozzle finishes a layer and moves to a new position then strings filament along the same path each time, but can't understand why that bit burns. The first few layers had no burns at all.

Temp 225c
PETG
Speed 30mm
Bed 80c
100% aligned rectilinear infill
0.4mm nozzle
width .48mm
layer height .15mm
Cooling off
I changed Z offset to 1.04 as before it wasn't sticking to bed properly.



https://flic.kr/p/2q4Fh2w
 
It's most likely as you say that it's travelling across that part when it's finished. Do you have a web cam or can you watch what it actually does and how it happens?
It looks like there's more brown in other places in that picture too...but your temperature doesn't look too hot. Could be build up of PETG on the nozzle that slowly gets baked and then deposited rather than it buring directly. Cleaning the outside of the nozzle when hot might help - obviously being aware that it's 200+°C! I find that metal ESD tweezers (not that they need to be ESD, that's just the set I have) are quite good for that.
You may also find a setting in your slicer something like "Avoid crossing wall". That makes it travel around the model rather than across it. That might help a bit.
Worth moving the model to another part of the bed too...just on the off-chance there's some contamination in that spot that's causing it - unlikely but easy to eliminate.
 
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