Dent in 3D Benchy bow
I'm trying to tune settings for Polymaker PC Max filament and need a bit of help. I printed two relatively common test models, treefrog and 3D Benchy, with slightly non-default settings (see below). The treefrog turned out fine, however I get this odd dent on the lower part of 3D Benchy bow:
https://photos.app.goo.gl/enGNfXeCos3E1Ktg7
What might be causing this dent?
The prusa slicer comes with a preset for Polymaker PC Max filament, which I used as starting point. 270C extruder, 100C bed first layer, 115C bed all other layers. I decreased max volumetric speed to 3.5 mm^3/s. I also enabled auto-cooling with min/max cooling speed set to 10% and 20%, enabling it if layer print time is under 10 seconds. Without auto-cool, the chimney ends up crooked; AFAICT chimney is the only area where auto-cool kicks in. The same artifact on the bow appears with or without auto-cool enabled. All other filament settings left to defaults.
In print settings, I started with defaults for 0.2mm layer height quality preset, then increased perimeters to 4, and enabled extra perimeters (when needed), ensuring vertical shell thickness, detection of thin walls, and detection of bridging perimeters. The rest is left to defaults.
RE: Dent in 3D Benchy bow
I used to have cooling issues in that area. Have you tried rotating the model to see what happens? You could could cut a model just above that level and put a few of them on the bed to see if different orientations yield different results.
RE: Dent in 3D Benchy bow
[...] The treefrog turned out fine, however I get this odd dent on the lower part of 3D Benchy bow:
That part of the Benchy print is intended to test overhang and cooling. Common solutions include reducing speeds, temps or increasing cooling. Lower layer heights can help. You are undertaking a challenge with PC Max, so this is something you'll have to experiment with for your filament. As @Allen-m2 notes, the orientation of the part will change the airflow from the cooling fan. Orient it on the print bed with the bow facing front and see if that helps.
RE: Dent in 3D Benchy bow
Orienting bow to face forward helped to reduce the effect significantly. Now when you told me to do so, it looks as obvious thing to try :-). Especially since the irregularity was much more visible extending from the bow on the port side, than on the starboard side.
Lowering "bridge fan speed" from 30% to 10% helped a bit further. By comparing what's displayed in the "feature type" view, and observing when the fan kicks in during printing, AFAICT, this low on the model, the fan kicks in for the "bridge infill" for the bottom of the cargo box, and few layers later for another "bridge infill" for the deck. IMO, the bottom of the cargo box and deck would probably print just fine even without any cooling on the bottommost "bridge infill" under them. Since they'd get few more solid layers anyhow. But since Prusa Slicer has single setting for both "real bridges" and "infill bridge layer", I likely can't completely turn it off. I could try and see how bad actual bridges towards the top of the model end up.
I already reduced speed significantly from the defaults. I set max volumetric speed to 3.5 mm^3 (default preset was 11 mm^3, so this is significant reduction already), which should effectively limit linear speed to low 40's mm/s (assuming 0.4 mm nozzle and 0.2 mm layer height). Since "bridge infills" tend to be printed at this maximum speed, I could see if increasing or decreasing either volumetric or linear speed further would make additional difference (since it would change for how long the fan is on at those two layers where "bridge infills" are printed).
Said that, it would be nice if Prusa Slicer had "cooling" view to visualize when the cooling fan will be on, and at what intensity the cooling will be.
RE: Dent in 3D Benchy bow
I'm trying to tune settings for Polymaker PC Max filament and need a bit of help.
What build-plate were you using? Smooth PEI or powder-coat? How was the adhesion (too much? too little? just right?)
I'm trying out pc-max today (parts for an e3d toolchanger) and I see that they warn "must use buildtak". I don't want to mess up my bed with overadhesion.
RE: Dent in 3D Benchy bow
@paul-m27
I used powder coated plate, with bed temperature set to 100C for the first layer and 115 thereafter. These were defaults from PC Max preset that comes with Prusa Slicer (and that I used as starting point for my adjustments). I did not treat the bed with anything. Just printed straight onto a clean bed. Cleaned the bed with paper towel and alcohol every few prints. Good adhesion while printing, and the model pops off soon after the bed started cooling down. I didn't feel there was need to adjust bed temperature, so I just left it at preset's defaults (which are a bit higher than the tech sheet for the filament says). I'd be interested to hear your experiences with this filament once you have a chance to print with it.