Tally counter

Fully 3D printed mechanical tally counter. Parts that usually rely on metal springs are built into the model as plastic cantilevers. Since PLA slowly warps under consistent force, I designed this so no forces are applied when it's not being used.

Most mechanical 3D prints are large so they can get away with very loose tolerances that work for most printers out-of-the-box. I wanted a more compact device, which means it needs tighter tolerances - the kind you can only get by tuning your slicer to your specific printer setup. There are no tolerances designed into the CAD model, fine-tune the horizontal expansion settings in your slicer for your printer. Here's a YouTube video showing how to do this. I used -0.05 horizontal expansion and 0.05 hole horizontal expansion in Cura, but the right numbers will probably be different for you. You will to experiment for your own printer and do some cleanup and sanding.

Print two of the carry gear, three of the wheel reset pawl, and one of everything else. Sorry there's no detailed assembly guide, hopefully the Onshape model helps to show how it works. Sliding everything into the frame can be a bit finicky, but once it all slots into place the whole thing should be pretty solid.

Keep in mind this model is quite small and has some delicate parts. If you're having trouble with parts breaking or not fitting together due to tolerance issues, try scaling everything up or switching to a smaller nozzle. Know the limits of your own printer and don't manhandle the parts.

Video of it in action: https://youtu.be/BWP-0wes78c

Onshape model: https://cad.onshape.com/documents/c295638f8d4b83155530eae2/w/dfc5a8f2e985d5d8f6ba5083/e/116331ffcd07a19a1f2706c0

Edit 2021-02-07: Lever broke, made it slightly thicker.

Edit 2021-02-08: Fixed wheel reset pawls having different thickness, thanks to leloctai for pointing this out!

Edit 2021-02-18: Reoriented the parts to how they should be printed.