The Othermill Is Something Else


I’ll admit. When I saw the Othermill for the first time I thought it was just another mill with cheap Chinese hardware inside sold as a premium. I’m ashamed to say that I even trash talked it a little bit. It gave me another chance to relearn that I should always do my research before being a jerk, check my assumptions thoroughly, and even then it’s not recommended. Other Machine Company was kind enough to let me swing by the office in Berkeley California. [Danielle], the CEO, led me through the design of the mill as well as the challenges in running the operation.

The Othermill is a serious machine, and with the recent release of the Othermill Pro, it’s only getting better. The components are not bargain basement. This is something that could be more obvious, but it’s almost entirely made from US sourced parts, including the custom stepper motors. There aren’t any ball bearings that will start to make strange noises in a year. It can now cut 6mil traces in a PCB all day long. To put it into perspective. The Othermill Pro costs a third of the price of an equivalent machine from LPKF and has the same capabilities.

History:

IMG_0347The Othermill started as a DARPA grant researched at Otherlab. They wanted a cheap, long-lasting, and easy to understand CNC for every classroom, something with the same capabilities as a laser cutter but none of the toxic gasses or fire hazard. It resulted in a rather odd-looking machine. The machine worked exactly like a vinyl cutter with a spindle rather than a blade. Sheet stock was fed into the rollers and it moved the material back and forth until it was finished. I have some doubts about the design but, [Danielle], assured me it ran pretty well. Since she has a PhD and is the CEO of a CNC machine company, I was inclined to believe her.

However, this machine is not the machine we see today. The government, capricious as always, saw a newer, shinier button on the floor and waddled over, dropping the Othermill research project from its sticky fingers as it ran. With nearly all their funding gone, Other Machine Co should have given up, instead they restructured, took on some jobs just to keep the lights on, and worked towards a Kickstarter.

The first version of the othermill was fastenerless.
The first version of the Othermill was fastenerless.

The next iteration of their machine, and the one that was shown in the Kickstarter video, began its transformation into the Othermill we see today. Interestingly, the machine was fastenerless at the start. This was a cool design choice, and had some advantages, but not enough over the use of fasteners. The machining was more expensive and the machine was harder to service.

Throughout the development to final Kickstarter release the machine got a lot of upgrades. It grew handles. It got an enclosed build volume. The wires were nicely managed. On top of that they added a really nice software stack. The level of polish is impressive.

In the end, this worked. Other Machine Co didn’t go under. It worked its way to enough financial independence to split off from Otherlab and get its own facility in Berkeley.

What’s The Difference? Low-End vs. High-End?

To the hobbyist  stumbling onto the Othermill it’s hard to get a grip on why it costs what it does. Ebay is flush with those 3020 CNC mills from China for one-third of the price. Why should someone drop the extra cash on a machine with very similar on-paper specifications? Those specifications are nice, but all specs are written when the stars are all aligned, the head engineer has just spent three days tweaking the device, marketing is a little drunk, and the CEO is irritable.

Paper specs will give you an indication of what to expect, but evaluating the real world performance will give you the truth. Even top-of-the-line CNC machines with exactly the same specifications can be behave differently in cutting, noise, vibration, surface finish, speed, and more. If this wasn’t the case they wouldn’t spend endless hours pestering companies with salesman. They’d just post the lowest price and people would buy.

Vibration:

http://www.thingiverse.com/thing:277394
http://www.thingiverse.com/thing:277394

Vibration is a subtle thing in CNC machines. By its nature, the machine makes a lot of noise, flings chips around, and generally makes a mess. If you put a good CNC beside an equivalent bad one and run them side by side with the same settings, you’d often be hard put to spot a truly obvious difference right off the bat. However, when it’s time to fit two parts together or inspect the surface finish of the part the truth becomes obvious. Vibration matters.

It’s really easy to see the effect of vibration in a 3D printer, a sister machine, as the picture to the right shows.  The dynamic forces on the frame all add up to a repeatable ringing in the plastic. You can actually see the nodes and antinodes in the wall of the print. By changing the speed and acceleration settings the user can reduce these forces on a printer until the print comes out smooth.

Now, add in a spinning endmill seeing an intermittent load of varying magnitudes depending on a whole bucket of variables, from material type to the phase of the moon, and the problem with vibration in a CNC mill becomes easier to see.

Mentioning the 3020 mill again, here’s a great slow motion video of the spindle occasionally deflecting and vibrating back to zero. It would be very difficult to spot this behavior with an unaided eye. Keep in mind, this device is promising practically the same positional accuracy as the Othermill, however, it is often deflecting by more than .01 inches from the loads on the spindle.