Goofy Behavior With Multi-Extruders & Brims (Possible Bug?)

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username48

(@username48)

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Goofy Behavior With Multi-Extruders & Brims (Possible Bug?)

PrusaSlicer 2.9.0

So I just printed a part on my dual extruder XL out of PLA (Extruder 1) with PETG supports (Extruder 2). I had Extruder 1 set as the extruder for the part in the right hand menu, and then set both the supports and support interface to Extruder 2 in the "Multiple Extruders" print settings. The support material sliced in PETG as expected. The part has a small footprint, so I needed to add a brim. This stayed as PLA (Extruder 1), which is what I wanted.

Then I went to reprint the part with the extruders and materials reversed. So PETG (Extruder 2) for the model and PLA (Extruder 1) for the supports. Just reversed all the same settings I discussed. Everything behaved as expected, except the brim, which was suddenly being assigned to the support material (Extruder 1). Not what I want since they're dissimilar plastics and the brim won't do anything. I searched Google but there's no separate setting I was missing for the brim extruder. Annoyingly, I had to physically swap the filaments in my printer so I could use Extruder 1 for the PETG. When I swap the extruders back in PrusaSlicer to the original configuration, the brim once again is assigned to Extruder 1.

Not sure what would cause this behavior? Is there some deeply hidden setting I'm missing, or is this just a bug?

Posted : 06/03/2025 4:22 am

BaconFase

(@baconfase)

Reputable Member

RE:

Doing some testing. Looks like "Support material/raft/skirt extruder" is the parameter to affect brims, but not directly. Looks like the slicer compares that parameter's extruder number to the extruder number for the model set on the Plater's model list and it will use the smallest number as the brim extruder.

Model is 3; parameter is 2. Brim is 2.