A Short Diversion to CNC

I am presently blocked on the Glass 2 Cylinder project while I decide what grinder tool rest I am going to build. Boring the cylinder head, which is brass, is showing me that my hand grinding of cutting tools is not adequate. This requires a trip to a metal supplier and so need to fill up the hobby cash pile first.

In the meantime,  I decided to revisit my previous CNC efforts. For the Unimat I used Mach3 (free edition) on a dedicated small PC. This worked well enough but it seemed overkill plus the learning curve for Mach3 is steep. After a bunch of browsing I came across Grbl and SmoothieBoard. SmoothieBoard requires a processor that I don’t have (it is partly based on Grbl though). For Grbl I only need an Arduino Uno, which I already have. It took some investigating to see if the 2.5D milling/routing that we want to do is supported by the limited G Code subset of Grbl. There are enough free tools to generate the code we need. Even helical threading is possible! 2014-07-16 16.28.19

The controller board from the previous CNC effort works fine. A bit of soldering and I have the Uno connected to the printer port on the controller.

I had 2 Nema 17 motors wired up from the Unimat project. The result: a CNC controller for <$80 total cost. Plus the motors which I think were $8 each. I spent a bit of time tweaking parameters such as feed rate. I’m sure these can benefit from more adjustment but the result is quite pleasing to watch. The driver board may need some modifications as well, I found an article outlining why and how to replace a capacitor for each axis to significantly increase the step rate. I will consider that if the overall cutting rate is too slow. With aluminum it is amazing how fast you can rip a milling cutter through it.


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