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PLA from £6 inc. UK delivery on letter-sized prints. We slice, print on a calibrated Creality K2 / Bambu A1, QC and post.
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.
The parts should have a close fit. There are no tolerances designed into the CAD model. 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 may have 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…
