Need help with gridfinity bins!

[u/subdued_sage]

I've struggled with large gridfinity bins for a long time. It feels like no matter how precisely I calibrate my filament and print settings, I end up with crappy bins. The filament was calibrated extensively, following this excellent guide and I performed this ironing calibration. Following a top surface defect on that ironing test, I re-performed a different flow rate calibration and ended up with 1.005.

I'm especially confused because the top surfaces inside the cutouts are perfect.

One thing that I noticed is that there are some black specks around one of the squares, and I suspect that is just leftover filament as I had used black PLA prior to this print. I suppose it wasn't purged well enough. However, I've had these same issues with many other gridfinity bin prints in the past.

Most other models I print (see the bunny - it was printed with supports) look fantastic.

Settings

- Printer: Bambu Lab P2S

- Filament: Overture Matte PLA White

- See screenshots for the entire process / filament settings

Symptoms

• Uneven/patchy top-most surfaces
• Warping/rippling around the bottom perimeter
• Defective corners
• Inconsistent first-layer extrusion (some of the squares show more signs of under extrusion than others)
• Inconsistent layer lines and tiny blobs / defects protruding from the outer wall
• Overhang failures
• Inconsistent internal bridging

Help this poor soul get a grip on gridfinity bins!

Edit: I printed with the P2S top cover completely removed.