Does anyone know a reason why the PETG interface layers might be curling up and sticking terribly to the PLA supports?
I’ve been thinking it might be simply due to PETG and PLA being so “unsticky” to each other that the printer simply can’t lay down the PETG first layer of the interface properly on top of the PLA supports, but many people here and elsewhere have had success, so I’m wondering if it’s something I’m doing wrong?
The settings I’m using are:
Support interface speed: 10mm/s (have tried from 10 to the default of 80mm/s)
Top and Bottom Z distance: 0mm
Base pattern spacing: 1mm (have tried from 1 to the default of 2.5mm)
Top interface layers: 3 (have also tried the default of 2)
Interface pattern: Rectilinear (have also tried the default of concentric)
Top and bottom interface spacing: 0mm
Support/object xy distance: 0.5mm (have also tried the default of 0.35mm)
Purging volumes: 800mm3 both ways between PETG and PLA (although I think in this case this isn’t a factor for the interface layers not sticking to the PLA and curling up, because if there were any residual PLA left in the nozzle, then it would make the interface to support adhesion better not worse)
I’m using snug supports in this case, but I’ve had issues with other support types as well.
I’m printing with a Bambu Lab A1 using Bambu PLA Basic White and Bambu PETG Basic Black, which has been dried for 8 hours at 55C in a filament dryer before printing.
Temperatures are the default of 220C for PLA and 255C for PETG.
Here’s some pictures of what I mean by the terrible interface layer quality:
2nd interface layer:
3rd interface layer:
1st layer of the main print on top of the 3rd interface layer:
1st interface layer:
2nd interface layer:
As you can see, there are a ton of PETG blobs and spikes sticking up from the interface, which will inevitable get printed on by the main white PLA, which means lots of bits of PETG get trapped inside the main PLA print which will weaken it. Also because of this, the surface finish is not great on the overhangs printed on top of the interface layers, and the supports do not come off fully cleanly, with little fragments of PETG left behind that need picking off individually with pliers, and even then there are some trapped bits of PETG that are impossible to remove.
Also, this level of quality is only because I slowed down to 10mm/s and added a 3rd interface layer. Using the defaults, the results are even worse, and sometimes result in complete print failure from the PLA not being able to be laid down properly on the PETG interface due to the blobs, and the nozzle then catching the curled up PLA and PETG mess.