RotoMill Three-Axis Rotary CNC

I had the pleasure of attending the World Maker Faire in New York this weekend. There were many amazing displays, such as the Hand of Man picking up and dropping cars with hydraulic fingers, and Prusa anouncing their SL1 resin printer. One exhibit that was perhaps a bit more subtle in its appeal was the so-called RotoMill. This device appears, on first glance, to be a lathe of some sort — yet instead of a traditional cutting tool, it features a router attached to a linear slide system.

After inquiring about this well-made “product,” I was told that this was not actually for sale, but a senior engineering design project by a team at Carnegie Mellon University. The idea behind it is that, while a professional turning center would potentially cost tens of thousands of dollars, the RotoMill simplifies things down to three axes, each actuated by NEMA24 stepper motors, controlled with an Arduino Uno running customized GRBL firmware.

Rather than X, Y, and Z axes, the RotoMill only moves linearly in X and Z directions, while the third “A” axis is the spindle that you would associate with a traditional lathe operation. Code for the machine is generated in such a way that the cylindrical part to be cut is thought of as a linear surface wrapped around a cylinder. This type of machining would have its restrictions when compared to a true turning center, fourth axis for a CNC machine, or even a manual lathe as the rotary axis turns at only a few RPMs. However, considering it the build’s cost of around $2,000, it could be a very interesting and cost-effective solution for many operations.

Plans for the RotoMill will be made public, but whether they decided to manufacture and sell a version of this CNC device is to be seen.