makercam

PCB Milling on the Little CNC

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).

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.)

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 taped 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.

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…

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.

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.

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!?

DCRL

A big part of the work I do is the process, and trying to find tools that fit the way I work, and are also available. “Available” may mean open source, or free (as it beer) or multi-platform, or some other criteria I come up with.

In my Digital Craft class we’ve used RhinoCAM to generate the G-code needed to run the 4×8 CNC router in the DCRL. RhinoCAM has a lot of options, as it should for a full-on commercial package. Meanwhile, I’ve been working on a Shapeoko2, which is a small and affordable hobby-level CNC machine. For a machine like this, I’d like to use a workflow that doesn’t require expensive commercial software, because at some point I may not have access to Rhino and I’ll need tools I can afford.

(I should note that I have used CamBam in the past, but being commercial software that is Windows-only doesn’t entice me to want to use it again.)

I’ve played a little bit with Easel from our friends at Inventables, but I’m also not a fan of hosted solutions that can disappear, or start charging for access, etc. At this point I start to sound extremely picky, but really, I’m just looking for tools I can rely on, that are not expensive, and run on the platforms I use. (Easel is actually really nice, and while it’s easy to use, I think that comes at the price of hiding some of the complexity and advanced features I want to learn. Still, if you just want to cut/carve/engrave, check it out.)

I stumbled up MakerCAM, and there’s a bunch more info about it on the Shapeoko wiki. Basically it’s a Flash application (!) that you can use online, or download and run offline, which provides all the basic needs of a CAM application. And it actually works.

Inkscape

I started as I often do, drawing a 2D vector file in Inkscape. (Oh, I should mention there is an extension for Inkscape called Gcodetools, but we’ll skip that for now.) Once I had my Inkscape file I saved it as an SVG, as you normally would with Inkscape.

MakerCAM

I then loaded the SVG into MakerCAM. Note that if you load an SVG from Inkscape you need to set the px/inch to 90 in the preferences. Once in MakerCAM it’s fairly easy to create the toolpaths and generate the G-code. If in doubt, check out the help page and the tutorial page for all the info.

GrblController

After exporting my G-code file I was able to load it into the Grbl Controller and run it on the Shapeoko. Now, Grbl Controller is no Mach3, but it’s also open source, and multi-platform, so there’s that. (Yes, I know the image above does not match the first two images, that’s because I went crazy with the hatch fill from the Egg-Bot extension for Inkscape. Just pretend you know what I’m talking about.)

Oh, if you want to “run” your G-code before you run your G-code to make sure it’s doing what you think it’s doing, check out OpenSCAM, which is a nice little simulator.

(And yes, I know of Chilipeppr for Grbl, but I’ve not dug into it yet.)