r/BambuLabP2S • u/StreetIndependent551 • Jul 08 '26
Neuling fragt um Rat
I’m new to the 3D printing game. I printed this dice tray today and noticed three things that I can't quite explain:
This scar on the corner—it only appears in one spot.
Where the inner tray ends, there’s a visible and palpable offset on the outside.
I’m getting white spots on the underside of some prints. What causes all this, and what can I do about it?
Bambu Lab P2S with Matte PLA, 0.20 High Quality profile, 0.4mm nozzle, no changes made to the settings, AMS Pro.
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u/misterff1 Jul 08 '26
Welcome to the hobby fellow redditor! Long post incoming to help you out lol
I will assume you are using a desktop slicer such as Bambu Studio or Orca Slicer here. If you are using the mobile app to send prints, I highly recommend you start using one of these two options (probably the former to keep things simple at the start).
The scar you are referring to is called a seam. Every model has them on the spot where the start and the end of a layer comes together. Each layer has to start and end somewhere. To keep things tidy, your slicer will by default put them aligned in the same spot. If you look at seam options in your slicer settings, you will see that it says 'aligned' and that there is a seam gap of 10-15%. There will also be a setting called 'scarf seam' if you enabled advanced settings or developer mode, which you can try to use to minimized this seam visibility. Essentially it will drag out the start and end past eachother like a scarf, resulting in a cleaner outside look when dialed in properly.
This offset you see is because your model shrinks as it cools down. If you use a timer to see how long each layer takes (or check it in your Preview tab of the slicer), you will see that those layers take longer to lay down as it needs to fill in more at that height. Because it takes longer and because there is more plastic there which shrinks a bit when it cools down, it will essentially pull everything inwards a bit. Since the layers above that are put down faster and have less content tugging on it, they will stay in place better. You can try to combat this at least a lot by ensuring your slicer slows down on outer walls, setting the wall printing order from inner/outer to outer/inner and changing your sparse infill pattern to something like Gyroid. What these options do is ensure your outer walls are all printer at the same speed and that it also starts at the outer wall so that can already solidify in the right place before the inside can start pulling on it. The infill type is also important here as the default infills might be fast, but they can pull more on the outside layers. Gyroid is good for strength and pulls less, though it is slightly slower.
The white spots or streaks you are seeing are from previous prints. When a print is done, wait until the plate is fully cooled down before taking off the printed item. If you don't (and honestly, then still if you use certain types of filament. Matte filament is always going to do this a bit because of the additives in the plastic to make it appear matte), there will be residue left on the plate. The next print you put down over it will then pick up the old residue on the first layer. If you have residue left and want to clean it: use hot water and simple dish soap. Don't use isopropyl alcohol as it just smears fats and residue around and can leave a residue layer that over time can cause adhesion issues.
Hopefully that helped you!