If you're familiar with 3D printing (you're reading Tested, chances are you're probably pretty familiar with the topic), it isn't too difficult to understand the basics of CNC milling. Instead of building up a form layer by layer, milling carves away from a block of stock material. Replace the plastic extruder of an FDM 3D printer with a high speed spindle turning a sharp cutting bit. CNC milling also requires CAD models of the desired form. And just like 3D printing, CNC mills have been moving from the workshop to the desktop. These machines have become affordable, small, and relatively easy to use.
Milling--subtractive fabrication--is often louder, messier, and let's be honest, not nearly as “magical” as additive 3D printing. The results don’t have the same wow factor as a Yoda bust you can make with a basic 3D printer. But this process creates more accurate and durable parts from a much wider selection of materials.
I’ve been testing several CNC mills for my work at NYU’s ITP program, and wanted to share some of my results. Some of these machines work right out of the box, some are kits (like the first home 3D printers). I’ll also discuss the difference between home mills and higher-end models designed for workshops, as well as my thoughts on the future of desktop milling. But this week, we’ll start off with a machine you may have seen on Tested before: the Othermill.
First up is the Othermill Version 1, made by the Other Machine Co. . Other Machine Co. designed this CNC mill with the belief "that regular people should be able to use professional tools". And I think they knocked it out of the park with this little guy.
The machine is ready to go right out of the box. It has easy to understand controls, just one button. The two wrenches, used to secure and remove the cutting end mills, can be secured to magnets on the front of the machine. This is such a simple little thing, but it is so handy. I'm now convinced every tool that requires a specialty wrench/chuck key/whatever should be held to the machine by a magnet. Seriously, this should be standard for all power tools.
The mill has a work area of 5.5" x 4.5" x 1.25", meaning it can work with blocks of material that size or smaller. Recommended materials--wood, metal, and plastic--are fixed to the aluminum bed using double sided tape, hot glue, or screwed down using any of the numerous tapped mounting holes.
Otherplan is the recommended free software. It is Mac only, which is practically unheard of in the CNC world, and is intuitive and easy to use, which is also pretty unheard of in the CNC world. You can be up and running in minutes--it took me longer to mount the material to the mill than to set everything up in Otherplan and begin cutting.
Otherplan has taken a lot of the things that are usually a drag about CNCing and made them easy. Determining mill feeds and speeds for a particular material is typically an educated guess/trial and error kind of process. Otherplan let’s you pick material from a drop down list with pre-set values. All of the pre-sets I’ve used have been right on the money. There is an advanced setting called "Bit Breaker" that allows you to adjust the settings. But I found out the hard way that Bit Breaker can be an apt name.
In my experience, setting the Z axis (the up and down direction) origin on CNC machines is usually a pain in the neck. The Othermill simples this too. The end mill is brought down to the aluminum bed and completes an electrical circuit on contact. The downward motion is stopped and zero is set. The only catch, you need to be fairly accurate in determining the thickness of your material. I wouldn't use this mill without a set of digital calipers close at hand.
If material is mounted to the bed by screws, you can select which threaded hole(s) you are using and Otherplan will steer clear. Fantastic.
Now I would never leave a running CNC unattended (and you shouldn't either), but the Othermill does have a "set it and forget it" kind of feel. For longer jobs, I’d have it running on my desk and keep an occasional eye on it while doing other work, so far so good.
CAD Not Required
I feel the Othermill really shines when making 2.5D parts. 2.5D parts are actually three dimensional objects created from two dimensional drawings. A 2D .svg file made in a vector graphics program (Adobe Illustrator, InkScape, etc) can be imported and Otherplan does all the heavy lifting. Shapes are set as either cutouts or engravings and multiple files can be layered on top of each other, allowing for a lot of control and experimentation. It felt a little like sketching, only I had actual physical parts when I was done.
It’s also possible to make true 3D parts with curvy surfaces (I'm envisioning a lot of self-portraits frozen in carbonite) by importing g-code, the programming language for CNC machines. But a third party CAM software will be necessary to create the code. Other Machine Co. recommends Autodesk CAM tools.
Noise and Mess
When cutting softer materials the noise and mess levels are pretty low. You could keep this guy running on your desk, still get work done, and not tick anyone off (for the most part). Cutting hardwood and aluminum is a different story. The machine can get loud, I had to take it all the way back into the workshop for the dirty looks to stop. But the mill only weighs 16.8 lbs. and has two convenient carrying handles, so it is very mobile. The mess is pretty contained, some dust might get on your work surface, but a decent shop vac is necessary to properly clean out the mill. I'm told the Othermill Version 2, the model they're shipping now, is more contained and noise and mess are even less of an issue.
I experimented cutting a wide variety of materials: wood, metal, PCB boards, plastic, even mushrooms (long story). The Othermill cuts hardwoods beautifully, I tested mostly with walnut and it produced really clean lines. I got a lot of tear out with plywood, but I chalk that up to the low grade ply I was experimenting with. In the beginning I cut a lot of aluminum, there is something incredibly empowering about making metal parts. The mill is not exactly a beast, and aluminum put a little wear and tear on the machine. The cuts were fine, but I wouldn't have this guy ripping through metal all day. But for the occasional metal part, it does the job.
The material I was happiest with is a plastic made by DuPont called Delrin. I know I'm late to the party here, but Delrin, where have you been all my life? It just wants to be machined. The milled surface finish looks incredible. Delrin is pretty much self lubricating and perfect for mechanical parts. Chocolate and peanut butter, Butch and Sundance, Othermill and Delrin.
A Good Place to Start
From my testing, the Othermill seems ideal both for first timers looking to get into CNCing and experienced makers who want to create fussy little parts. I loved how simple it is to get up and running and the price is right, compared to higher-end milling machines. Other Machine Co. has a good product here.
Photos by Ben Light. Find more of Ben's projects on his website.