The grinder has adjustable ceramic burrs for ... selector for total control over how fine you want it, plus a solid ceramic ...

The grinder uses high-quality ceramic blades to efficiently grind coffee beans into a fine powder, ensuring a rich and flavorful cup of coffee. Ceramic coffee grinders offer several benefits.

Sadly the creation of a steel burr and ring was beyond his 3D-printing capabilities so those parts come from a commercial grinder, but the housing, shaft coupler and hopper are all from his printer.