CNC Gadgeteer modules

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As I mentioned in another thread I’ve recently been playing with a CNC mill (at the Sydney Hackerspace) to create circuit boards. At the moment I’m only playing with simple single-sided designs, but if/when I get more reliable results I might try double-sided - because the double-sided aspect needs very fine accuracy in aligning the top and bottom sides, some people suggest using two thin boards that you cut separately and laminate them together. Anyway, single sided design means that you inevitably face issues where you can’t route your traces without crossing some other signal, so you need to use actual wire to join those signals.

Yesterday I spent a bit of time playing around with the mill and cut this one - it’s a simple breakout of the 10 pins on the Gadgeteer socket to solder points or screw terminals. Much like the Breakout TB10 module GHI have on offer, it has spots for 10 screw-down terminals. I wanted to make one because (a) freight to/from GHI is costly to AU, and (b) because I needed a more square footprint for connecting buttons to. Turned out pretty well I think !

Lessons learnt: it takes longer than you think to learn to cut PCBs on CNC. I really need a lot of “play time” to tweak settings, re-export the CNC instruction code (GCode), cut another version. But once you know the settings, it’s pretty simple (although if you share a CNC with others, it’s obviously possible that the machine reliability can drift without your knowledge, and in a hackerspace setting that can be easy to have happen). You also need a height probe to ensure that the engraving across the entire circuit board is to the same depth. I have yet to finish the mod on the hackerspace CNC to get that working, but it really needs to be the next thing I do. The larger the board you want to make, the more critical that becomes.

Next PCBs for me to make: I need to re-cut my relay board from the coffee roaster control. Then I need a three-button Gadgeteer module (with LED indicators). Then I have a WS2812 sample board I want to cut - it’s a little larger so I am not going to try it until I have the height probe finished.

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Very cool. One of the next things I want to do next with my 3D printer is build an effector to hold my Dremel and attempt making PCBs with it. Are you using the PCB-GCode software to convert your schematics to GCode or something else?

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Cool. I few month ago I was also playing with CNC and milling Gadgeteer boards. I even was able to route a track between gadgeteer connector pads! But eventually I gave up. Cutting a track as narrow as 0.08mm introduces lots of new problems, like:

  • one can only cut along X or Y axis — diagonal lines introduces vibrations;
  • laminate has to be polished before routing, as it initially has bumps, hills and valleys that, combined with high rpm and gyroscopic effects, makes the endmill wiggle perpendicular to cutting direction;
  • and then a few others.

Of course, anything wider than 0.2mm works just fine.

Oh, and I was using eShapeOko. A brilliant machine, I must say.

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Yes, PCB-gcode is the software du jour for getting an Eagle design into GCode. Then, once the probe setup works, I’ll use the leveller from autoleveller.co.uk to create the calculated/relative GCode.

PCB-GCode is a beast that takes some time to decipher. Depth of cut and isolation values really affect the way it looks.