In my last project, I built a large, high-torque magnetic gear, but I couldn't help but wonder: could I make a miniature version? The answer is yes, and it turns out to be super easy to make. I'll show you how to build a tiny, 3D-printed magnetic gear that works surprisingly well.

The Outer Rotor and Magnets

First, I 3D-printed the outer magnetic rotor. This piece has eight small holes for the magnets. I used eight 8mm x 5mm x 2mm strong magnets for this.

1. I started by adding the first four magnets to alternating holes. It's crucial that all of these have the same magnetic orientation.

2. Next, I added the remaining four magnets to the other four holes, making sure their magnetic polarity was the exact opposite of the first set. This creates the alternating North-South pattern needed for the gear to work.

The Concentrator and Inner Rotor

After the magnets were in place, I printed the magnetic flux focusing layer. This component is a ring with five holes that will hold the iron pins. I simply clicked this layer into place over the outer rotor. It should sit securely, but still allow the outer rotor to spin freely.

Next, I inserted five 3mm x 8mm iron pins into the holes on the focusing layer. It's important to use soft iron or steel pins for this, as their purpose is to concentrate the magnetic field. I avoided using stainless steel because its magnetic properties are not as suitable for this application.

Finally, for the inner rotor, I used a 10mm x 10mm diametrically magnetized cylinder magnet. This type of magnet has its North and South poles on opposite sides of its curved face, which is key to how the magnetic gear transmits torque. Once the inner magnet is in place, the miniature magnetic gear is complete and ready to spin!