PETG + PLA, bad layer adhesion in PETG layers
I'm trying to understand why this happens.
I'm printing PETG with PLA in extruder 4 as support material. From the looks of it, it all prints fine. The only issue is that the layer adhesion on my PETG is a disaster. I can simply peel the layers apart. If I print the same print with 1 extruder printing PETG the layer adhesion is perfect.
What might cause this?
Re: PETG + PLA, bad layer adhesion in PETG layers
FYI I print PLA at 230 degrees, PETG at 245, and I checked to make sure the hotend is at 245 before printing on top of the object on the build plate.
RE: PETG + PLA, bad layer adhesion in PETG layers
Bump. I want to know too.
RE: PETG + PLA, bad layer adhesion in PETG layers
From the info you provide, I am assuming that the same exact settings result in good adhesion in single mode. The only parameter that changed is thus the presence of PLA filament.
Based on this assumption, the first thing that come to mind is that your purging may be sub-optimal and your PETG layer could be contamined with PLA. I would try to increase the purging volume when going from PLA to PETG, and also keep a close eye on how the temperature change during the purging process. I guess it's desirable to start purging at 230 and continue for a while after it reached 245.
RE: PETG + PLA, bad layer adhesion in PETG layers
I print mostly in PLA, but when I switch to PETG I often find that it prints fine, but the bottom layers just de-laminate/crumble and can be pulled off in strands.
I have always assumed that PETG and PLA don't mix and traces of PLA cause this.. As such, I do extra purges when I switch from PLA to PETG or even an sacrificial print to clear out all the PETG.
So if you are doing this with an MMU, i wonder if you can purge for longer when you switch to PETG? But better still, I would look note to mix PETG and PLA in the same print.