A simple TPU peanut ball for back massage rolling. The sides are flat instead of round, so it's easier to print and can be stored standing. You can also add text to the flat side in your slicer as a note if you want print multiple ones and compare how different infill patterns/rates feel like.

With the config below I think the outcome is similar to a peanut ball I've bought at store before. It took about 1 hour 55 minutes in total to print with the following config:

• Machine: Qidi Q2C, 0.8 mm nozzle

• Filament: Elegoo Rapid TPU 95A, max volumetric flow rate set to 18 mm3/s

• 2 wall loops

• 0.82 mm line width

• 0.56 mm layer height

• 30% gyroid infill. This is somewhat hard, but can still be pressed in a bit, so I feel it's comfortable for the purpose of massage. For a softer ball, try reduce the infill percentage.

• (Optional) For aesthetics, consider changing the top & bottom surface layer pattern to concentric.

I also tried to print in PETG with 15% gyroid infill, it feels less comfortable because it became too hard and too slippery for massage compared to the TPU print, but still usable. Therefore I recommend to print this in TPU.

If you print with 0.4 mm nozzle, you might want to test increasing the amount of wall loops.

FreeCAD file is included for editing.