This is a massager for your muscles/back. It's official product name is “lunar rover massager” that used to be quite popular in China.

We had one in the family for 20+ years. Recently my mom broke my grandma's, and asked me to fix it. Instead of just fixing the broken handle, I just recreated the entire design in Fusion 360, and optimized it slightly for FDM printing.

Printer Settings: 

• 0.4mm nozzle
• 0.12mm layers
• 4 perimeters
• Gyroid infill, 15%
• Tree support for the handle
• Normal support for everything else

Print Parts:

• 1x handle
• 16x wheels
• 8x short leg
• 4x long leg
• 4x long peg/pin (used for attaching long leg to the handle)
• 16x short peg/pin (used for wheels)
• 8x peg/pin with protrusion (rotation limiter for short leg attachment to long leg)

Assembly Notes:

• Make sure the parts fit losely/turns - trim/sand slightly if not (designed with 0.5mm gap)
• gently hammer/tap the pin/peg into place
• Use some lubricant (silicone or whatever you use to lubricate your printer screws) would make the wheels spin more freely if your printer's tolerance isn't as good
• Wheels have an inside and outside - the side with shorter “bearing” faces outside so the pins sit flush

Updates

• Feb 22, 2024: new version with significant updates to how the pins/pegs work, now stronger and more “round” for better tolerances and wheel spin.