I bought a foot spa for my wife's birthday (commercialized as HoMedics (not the most clever brand name) FM90), but the motorized rollers that came with it were a real pain, as it was covered in small spikes, and was made of hard plastic.
I removed the original rollers, and designed new ones, made of PLA for the roller "inside", and TPU for the part that comes in contact with the skin.
Tested and approved, the gift is saved!
Print the roller as pictured, supports on, touching buildplate. Add a large brim to ensure that the part will not detach.
Print the rubber part in TPU, and try to get the “blobs” empty (with infill at 0%, or concentric infill for example) for maximum softness.
Simply slide the TPU part around the other part. Pay attention, one side of the inside of the roller is angled, and one side of the TPU part is also angled; make it match.
It may be difficult to slide one part into the other one, if so some water could help.
The author marked this model as their own original creation.