Coffee Grinder

Coffee Grinder An old friend asked for help developing a new type of coffee grinder. It's an ongoing side project.
I started out by creating a material model that could represent crushing / grinding of a coffee bean, based on this paper.
Then I did an explicit dynamics simulation of a few beans entering the grinder. This showed that the inlet geometry wasn't good enough, and I improved it. The rotor is hidden here. This took 4 days to run, and was limited to 32k nodes+elements count because it's the academic version.
The first iteration of the grinder was just two cones that I actuated by hand to grind beans. It was surprisingly effective given that it was entirely made of plastic.
The next iteration had some bearings and was a complete assembly.
You can adjust the grind size by switching out a plain bearing.
Two grind settings magnified 10x.
One of the most recent iterations with drivetrain. The plastic worm heats up too quickly and is not stiff enough to avoid skipping; an aluminium one is on the way. The final design will be stainless steel on brass or nylon.
A drawing I used to define the requirements of the shaft (in addtion to 3D geometry). I ordered it from Xometry; we'll see how it turns out soon.
A rendering of a cross-section of the grinder.