2017.02.05

PCB Milling

One of my goals with the Little CNC Milling Machine was to make my own PCBs. I’ve typically made my own printed circuit boards at home by etching them with chemicals, but the mill opens new opportunities to etch and drill the boards, so I gave it a shot.

I knew the basics, but did a a quick search for posts that might explain things a bit more. (I should note I planned to use Fritzing, Inkscape, MakerCam, and GrblController, all free/open source software available on multiple platforms.)

The two useful posts I found were: PCB designing and isolation milling using only free Software and Hello World, How to Mill Printed Circuit Boards (PCB).

OpenSCAM

I wasn’t really planning on documenting this in-depth, but I got a few photos and screenshots, so I’ll share what I can. I had some bits I grabbed from eBay, 0.1mm Carbide PCB Board 60 Degree V-shape Engraving Bits and 0.8mm Carbide PCB Endmill Engraving Bits (a total of 20 bits for under $10) to work with, so that’s what I used. (I may want to try some 45 degree bits and 0.6mm bits next time.)

Milling Traces

Here’s the “isolation milling” I did with the 60 degree engraving bit. Not bad! You can also see a little mark on the copper board where I homed the machine.

Yeah, I did not have double-sided tape, so I just tapped the board down to my spoil board. The board wasn’t completely flat, and bowed slightly in the middle. I’ll use double-sided tape next time, which will also help with cutting the final profile of the board.

Set Home

I swapped the bit from engraving to drilling and drilled all the holes. It seemed to work well, so… yeah. (Sorry, no photos of drilling!) I then switched back to the engraving bit to (attempt) to cut out the board…

PCB Milled

It worked, but I miscalculated how deep it would need to cut, and ended up lowering the z home and re-running the job again. I might want to use a different bit next time. When I thought the board was cut out enough I pulled it off the machine.

Light Test

The board held up to the light. Oops! Well, the holes didn’t all work. They were close, but not quite all the way through. I ended up using my Tiny Drill Press to finish the holes, and it didn’t work very well as it was difficult to hit the center. Not great.

I also didn’t cut all the way through with the outside profile. Not a big deal for this board, as it would be easy to cut out on the band saw, but more complex boards may not have this luxury. No matter, the amount of board left was paper thin and it came right out. I’ll definitely use a different bit for the final cut next time.

Final PCB

Here’s the final board. It totally worked, but there’s plenty of room for improvement. This probably won’t be the method I use for all my boards. OSH Park does a great job and prototyping PCBs, and Seeed Studio is great for production runs, but I’ll probably mill any new boards I want to test out before sending out to a fab house. Milling also allows me to have a PCB in an hour or so, versus waiting a few weeks.

Of course I’m (sort of) limited to single sided boards, but most of my PCBs are pretty simple, so I’m not concerned yet. Also, once I master the single sided board, I’ll certainly try a two-sided board, I mean… how hard could it be!?

3 Responses to “PCB Milling on the Little CNC”

  1. This is awesome, thanks for sharing Pete.

    Couple of questions:

    1. How loud is it?
    2. How much mess does it make?
    3. How long did this take?

    I’m really on the fence about picking up something like this to mill prototype/experimental boards vs. sending them out (chiefly to save time/speed up iteration) and I’m curious as to how reasonable it would be to run this on my workbench next to other equipment, or if it’s something that really needs to be used in a more isolated/workshop environment (the kind of place you’d use a saw to cut lumber, for example).

  2. Milling copper board is not that loud (at least compared to wood or HDPE.) It’s not as loud as a table saw, and quieter than a drill press going through Aluminum.

    Mess for copper boards was not bad. Milling HDPE and wood was pretty messy. It helps to have a vacuum running to grab the dust, otherwise I use a small paintbrush to brush away the chips & dust then vacuum it up later. It messes up the workbench but not much more. I’ve thought about building an enclosure like the Nomad to contain all the dust.

    Time-wise, for milling this PCB, with three operations, maybe an hour. I definitely don’t have all the feeds & speeds dialed in, but I did document all my settings. I’ll be trying another (larger) board next week. Oh yes, this is a small board, btw. (It’s this board: http://rasterweb.net/raster/2016/11/27/attinynoisy/ )

    I’d say YES, you can definitely run this in your shop. It’s small, so if I put aside 20″ x 20″ for the machine and the dust, it’s all good. I have a computer about two feet away via USB just to keep it out of the dust path. And it’s not loud enough to be heard at an annoying level upstairs where Dr. Prodoehl is. :)

    I’m seeing it useful for when I want to test a PCB before I get it sent out to be made by OSH Park, or if I need it right now or just want to try something weird or do a one-off.

  3. Awesome, thanks for the info Pete. This is something I’ve considered for a long time but it’s easier when you know someone with hands-on experience :)

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