The Belomo lens triplet is one of the best (if not the best) and merits some care. I therefore designed this protective case.

The triplet is held in place by a small magnet (6 mm diameter, 2 mm height). Press it into its seat from underneath the bottom (see pictures with vise and large screw as counter-fixation). The slot above the magnet is used in case you need to push the magnet out from above with the help of a screwdriver. The 1 mm rim at the top protects the Belomo in case it is dropped inverted.

I added a slightly wider version (in my OpenSCAD source file: d_belomo=37, x1_offset=101, x2_offset=79) to adapt to your slicer/printer/filament tolerances.

As always I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD from https://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the file or even amend the code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
• Slice and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs