If you’re into CNC, you’ve probably seen a 4th axis, or rotary axis on a machine before. This is usually an add-on to a machine, like an upgrade. Bob’s CNC has put out a desktop machine that cuts away everything else and just delivers on that rotary goodness with the Revolution.
The concept of a rotary cnc mill isn’t new, not even remotely. However, if you look at the desktop cnc market for amateurs, makers, or even pro-am, the 4th or rotational axis is typically an upgrade or afterthought. The Bob’s CNC Revolution delivers a solid rotary experience in the same price range that you’d find most other desktop mills.
You can get a machine like this, with all options for just under about $1200
If you’re unfamiliar with Bob’s CNC, you’ll immediately see what makes them easily identifiable. The kits they sell all use these flatpack wooden frames and gantries. At a glance, you wouldn’t think that the laser cut plywood would be rigid enough, but after seeing a few of these in action, I can tell you they work just fine.
The assembly process is not complicated, though it can be a bit time consuming with all those little screws and nuts. However, the result is fairly light weight, and of course very budget minded.
Software is one area that I’d say Bob (and many other desktop cnc manufacturers) could improve. In this case, there’s an option to buy Vcarve, or simply use whatever youre comfortable with for toolpath generation. Feeding Gcode to the machine is done through Universal Gcode Sender.
While this workflow technically does the job, it’s clunky and unintuitive. For example, to even use Universal Gcode Sender with this machine you have to manually add a bunch of macros to be able to manually move the rotary head. This really isn’t the end of the world, after you settle into a workflow, you can do the job just fine. My complaint is somewhat more of an industry wide complaint more than one pointed at Bob. If people are at the beginning of their CNC journey with the cheapest access points available, I’d love to see the software workflow streamlined.
As you can see in the video above, the machine is fully capable. There were no issues with rigidity or missed steps or anything. While I may moan that Bob didn’t invent a clever and easy new way of doing the software, he and his team really have done a great job at designing a cost effective machine that actually works. Some little nice features that didn’t make it into the video are things like an optional support system for doing long slender items that need a little additional stability, as well as jigs for setting your zero points without having to wrestle with your material.
If you’re wanting to focus on sculpture or table legs, this machine could really be a perfect fit.
Rotary Mill vs Lathe
I had a surprising number of people commenting that “this is just a lathe! “. If you’re a beginner and haven’t used either of those things much, I could see making that mistake. A lathe and a rotary mill are very different. The speed that you work at specifically is a major telltale sign of the difference. There are cnc lathes, but this is not one.