So now that we covered the basics of what Computer Numerical Control (CNC) is (See Introductory Article Here), we can dive a bit deeper into CNC milling. CNC mills are very powerful and versatile machines, and have been growing in popularity due to the large variety of materials they could cut, and the declining cost of these machines. For instance, the Shapeoko machine that Winston Moy uses can cut wood, aluminum and plastic all with relative ease — that is if the material is held well enough to the cut-bed so the vibrations from the router don’t mess up a milling operation.
A typical CNC mill follows an X-, Y-, and Z- positioning system that allow for great accuracy in cutting, however, CNC Mills can have up to five axis’s for more complicated and intricate shapes. The X- and Y- coordinates are where on the horizontal plane the router is, similar to graphing points in math, and the Z- coordinate is how deep the router will go into the material. The actual way a CNC mill works is rather simple, and it is common for a dedicated maker to build his own from scratch, however, even after the machine is completed, you could spend years tinkering in software and on the machine hardware, and still barely scratch the surface.
There are several major considerations when designing a file for a CNC to use, as you need to design not only the object, but also, the steps and order of operations the machine will follow to complete the cut. A user needs to ensure that with every cut the machine makes, it will not mess up a cut further along in the build process. A second consideration is what end mill — the bit that goes into the router — will be used for each cut, as different end-mills have different properties. Some end mills remove a lot of material in a relatively short amount of time, while others leave a fine surface finish. Another consideration is the “Feeds and Speeds” the machine should follow — the speed used to cut a given material on each individual pass. Feeds and speeds are a rather complicated issue, so I recommend that if you’re really interested, to check out Winston’s video on it here.
But now there is the question, why would someone choose a CNC mill over a 3D Printer? Well, I believe that Winston put it the best, “While you can design objects that are geometrically amazing with a 3D printer, you'll never admire their beauty the same way you’d look at a piece of furniture.” There are uses to a 3D printer, but for a traditional maker, you can’t replace the feel of traditional materials — wood and metal — in decor or functional projects. You can 3D print with filament made with wood, metal and carbon fiber — stay tuned for my article on it.
CNC milling is far superior to 3D printing in structurally sound projects, as there are no layers to delaminate from one another, and there are no skipped layers. also great for building structural sound projects, as the construction material is solid, rather than a layered print. This is important for projects, such as Slingshot, because, as Winston put it, “You don’t want that breaking in your face.”
CNC milling is also great for large objects with simple shapes, while 3D printing is great for quick prototypes. And for batching relatively large objects, it is far more economical and time efficient wise to use a CNC mill, rather than a 3D printer. There are three major drawbacks to CNC milling, however: it’s loud. It’s messy, and it is relatively dangerous, like any power tool is, however, if you use appropriate caution, it is significantly less dangerous.
Authors Note: I had a great time interviewing Winston, and he provided valuable insight for the upcoming articles. If you want to learn more about Winston and his projects, the links for his YouTubeand Instagram are as follows:
All project photos, and CNC photos, were taken from Winston's Website with his permission. If you would like more information on any of his projects, I highly recommend you check out the links about.