The Quickmill 5000 has hybrid/plastic gears on the high-speed/low torque side of its gearbox, that failed after 30 years in my machine. I have printed replacements in PETG, that have held up so far, but SLS Nylon gears would come very close to the originals.

One could also print ALL gears in metal. One would then need to use the hybrid_gear_as_monomaterial model instead of the hybrid_gear model.

The gears have a module of 1mm and a pressure angle of 20°. The axles have a 4mm diameter.