Wood game piece being carved by a CNC mill with a hacked rotary axis

This $12 CNC Rotary Axis Will Make Your Head Spin

May 15, 2023 by Michael Shaub 19 Comments

[legolor] brings us a great, cheap rotary axis to add to your small 3 axis CNC mills. How are you going to generate G-Code for this 4th axis? That’s the great part, and the hack, that [legolor] really just swapped the Y axis for the rotation. To finish the workflow and keep things ~~cheap~~ accessible to all there’s a great trick to “unwrap” your 3D model so your CAM software of choice thinks it’s still using a linear Y axis and keeps your existing workflow largely intact. While this requires an extra step in Blender to do the unwrapping, we love the way this hack changes as little of the rest of your process as possible. The Blender script might be useful for many other purposes too.

The results speak for themselves too! We thought the 3D printed parts were suspect in a CNC setup, but for the small scale of game pieces and milling wood, the setup is stable enough to produce a surprisingly accurate and detailed finish. If you want to try the same approach with something larger or a tougher material, [legolor] has a suggestion of a tailstock setup that’s still under $100 USD. Continue reading “This $12 CNC Rotary Axis Will Make Your Head Spin” →

A Rotary Axis CNC Machine

September 24, 2018 by Brian Benchoff 20 Comments

There’s a certain class of parts that just can’t be made on a standard 3-axis mill, nor with a 3D printer or a lathe. These parts — weird screws, camshafts, strange gears, or simply a shaft with a keyway (or two) — can really only be made with a rotary axis on a CNC machine. Sure, you could buy a rotary axis for a Haas or Tormach for thousands of dollars, or you could build your own. That’s exactly what [Adam Zeloof] and [Matt Martone] did with their project at this year’s World Maker Faire in New York. It’s the Rotomill, a simple three-axis CNC machine, with a rotary axis, that just about anyone can build.

The design of the Rotomill uses a standard, off-the-shelf Makita rotary tool for the spindle, and uses leadscrews to move the X and Z axes around with NEMA 24 stepper motors. The A axis — the rotary bit — is driven through a worm gear, also powered by a NEMA 24. Right now this provides more than enough power to cut foam, plastic, and wood, and should be enough to cut aluminum. That last feat is as yet untested, but the design is open enough that a much more powerful spindle could be attached.

The software for this machine is a bit weird. For most CNC machines with a rotary axis, the A axis is treated as such — a rotary axis. For the Rotomill, [Adam] and [Matt] are generating G Code like it’s a normal Cartesian machine, only with one axis ‘wrapped’ around itself. This is all done through Autodesk HSM, and a properly configured Arduino running GRBL makes sense of all this arcane geometry.

It’s a great looking machine, and the guys behind it say it’s significantly less expensive than any other machine with a rotary axis. That’s to be expected, as it’s basically a five axis mill with two axes removed. Still, this entire project was built for about $2000, and some enterprising salvage and hacking could bring that price down a bit.