This file is 1/2 of a massage ball, designed in Fusion 360. I designed it for self-applied trigger point massage. Print twice, then connect the two halves using either heat, epoxy, or by adding your own connectors. This ball is designed to be large enough to provide pressure to the back, even when sitting against softer cushions. The first version of this ball used an insert and twist lock pattern, but I removed it because of how weak the joints were. In my experience, heat fusion has been enough to keep the parts together.
Monoprice Maker Select V2
Average speed works fine for the lower half, but once the spikes start finishing as independent circles, consider lowering the print speed for better quality spikes.
Spikes near the top of the print may need sanding due to print orientation.