Just a simple tiny switch to fidget around with that satisfying clicky sound and feedback. There is virtually no in-between position and until it latches at the very end of travel to the other state, it tries to return to its previous one. AAA and AA baterries for scale
WARNING: It is a bit loud. Mechanical keyboard users approve.
Before Printing
NOTE: There might be some adhesion issues as the parts are relatively small, I had no issues on my Ender 3 with stock bed though. Brim should be OK to use.
Set the case on the side with the cavity ("top", this should be already done), there are ugly overhangs if printed up-side down. I can make a version if you had problems with adhesion. It's just a bit more pleasant to hold in hand this way.
Place other parts on any of their flat sides
Make sure to mark seams to not interfere with mechanism:
I used 0.3mm layer height (0.2 first), 3 perimeters (at 0.45 mm), no infill and 5 layers top and bottom. no supports needed.
I used fuzzy skin on the outside of the case to increase grip. Other parts need to be as smooth as possible
Post-Process
Just check that all contact sides are smooth, clearance gaps sufficient and remove brim if used.
Assembly
Other than printed parts, you will need one piece of 12x7mm coil spring. I bought it in the boxed set of coil springs. Any fitting spring is OK. I can make version for “pen spring”
check if everything moves and latch can go inside with no clearance issues, it is very hard to disassemble after it's done
put spring in the case. It should fall into the cavity
put “finger” part in, round side first. You can lube the side that will be in contact with the latch
check clearances again
press the latch in. Bit of force will be needed. it should not fall out afterwards.
Future
I am planning to make also version with printed spring or rubber band. Please let me know you want one to make me do so :)