Form, function, and a satisfying THØNK.

The THØNK is big enough for 20+ Breville portafilter double-shot pucks at a time, and has a smoothly curved interior without nooks and crannies for coffee grounds to get stuck in. The base is slightly deeper than the top, giving it maximum stability and zero wobble or bounce. The rim is raised to prevent any splash out of coffee grounds.

There are two versions of the knock pad, depending on whether you want to print a TPU insert or not.

• If you do not want to print TPU, you should print knockbox_with_basin.stl. In this model, the area for the knock pad is cut out as a basin so you can pour an appropriately shock absorbent material in there until it is level; I don't currently have any TPU filament, so my build as shown uses hot melt glue (EVA), smoothed with a heat gun. You could use RTV silicone or similar materials as well.
• If you do want to print TPU, you should print knockbox_with_insert_cutout.stl in whatever rigid material you like, and then knockbox_soft_insert.stl in TPU. The insert may be printed without support in either orientation (depending whether you like the texture of the print bed on the visible side of the insert or not). There is 0.2 mm of clearance on the left and right sides to allow for solid contact on the bottom of the pad when gluing.

With the basin knock pad, printed in PLA with 15% gyroid infill, this knock box feels plenty sturdy and weighty, and stands up to a heavy portafilter quite well. Obviously PLA has temperature limitations, so you could use PETG, PA6, PC, or your high temp engineering material of choice if you want it to be dishwasher safe. So far, even just in PLA, there has been no deformation from hot coffee pucks falling into it, so if you're willing to hand-wash, PLA seems perfectly viable.