hollow ping pong ball, with a uniform thickness (0.8mm, or twice my extrusion width - can be changed in the .scad file).

about twice as heavy by default as an official ping pong ball, so actually more usable perhaps outdoors.

when combined with an actual (concrete) ping pong table, it held up for a few minutes (after taking quite a test beating earlier).

-I wanted to have a supportless hollow on the inside, and I found that Cura has a nice option for this ("touching buildplate only" support)

-support angle needed to be about 35 for me, or the bottom part would start to curl during printing

-EXTWIDTH in .scad file should be equal to your extrusion width. the outside will be twice as thick. I haven't tried going thinner, so no idea what will happen.

-I only tested this with polymax filament, which is a fantastic PLA filament. slightly disappointed that the 0.8mm ball only held up for a few minutes though, or I would have tried to make it thinner (perhaps it's because I beat the hell out of it as a test before actually playing.. :-))

-a regular ping pong ball weighs about 2.7 grams. the 0.8mm version printed with polymax weights about 5.6 grams. so we'd have to go to about 0.5mm to come close.. but that doesn't sound very strong. perhaps epoxy glue on the inside might help..?

-my settings: 0.1mm layer height, 240 degrees, 60 degrees bed. perhaps 0.1mm is not optimal for strength..

-polish to grit 320, which takes about half an hour to do nicely manually, but it's hard to see/feel the difference with an official ball after that.

-I still hope to try slic3r's 3d-hex infill at some point, just because it's so nice.

CHALLENGE:

can you make a stronger and/or lighter ping pong ball that is actually usable for a long time??