This evening Matt and @Elliot_Wells spent some time hacking on the old Shapeoko (small-scale CNC mill). Documented progress on the Wiki here. We eventually got it to engrave a rectangle in a piece of scrap wood. I think maybe next week I’ll bring in some copper clad material and we’ll try and etch a circuit onto it. /cc @abe
In a follow-up post to this thread, some research indicates you have to be careful, for the health and safety of yourself and others in the space, when it comes to milling common copper-clad materials. Typically copper-clad is adhered to a substrate, and the composition of that substrate is the main concern.
Most commercially manufactured printed circuit boards are produced on a substrate called FR-4, which is essentially a fiberglass substrate. As such it is not really is not suitable for DIY circuit milling without some pretty significant precautions that we are really not set up to allow for at IG. In open air, milling into that kind of material basically causes fine glass and glue fibers and particulate to become airborne where humans can readily breathe them in.
I’m not an expert in the health effects of that, but you get a pretty varied response on the internet regarding the topic in the context of this post. It seems to me like there’s a reasonable contingent of people who essentially say it’s really only a concern on a chronic exposure basis, and it might cause some irritation acutely without causing lasting damage.
That being said, if we’re going to be regularly using CNC milling equipment to cut circuit boards, we should probably come up with some safety precautions which might include using substrate material alternatives to FR-4, like FR-1 and doing a good job of vacuuming swarf. I’m mostly informed by this website’s discussion of FR-1, an excerpt:
Is FR-1 safe?
Unlike FR-4, which is fiberglass-based and generates dangerous glass-shard dust when milled, FR-1 is safe to use if you keep it away from your eyes, lungs, and skin. We recommend vacuuming up the debris after you’re done milling (never blow on it).
Based on that, I would recommend we discard, or otherwise give away to a responsible home, the copper-clad squares of unknown provenance / pedigree / origin that are currently in the IG space, and expressly prohibit the use of FR-4 (or uknown, or maybe anything but FR-1 even) copper-clad for milling purposes as a matter of policy.
Suitable ventilation, like a hood or enclosed ventilated container, would probably be more than fine for cutting FR4. After all, we often cut acrylic, wood, polyester and rayon on the laser cutter, we solder components using solder and flux, we cut wood, use kilns and weld in the space. I’ve heard a good rule of thumb is that if you can smell it, it’s probably not too good for you.
That being said, I think cutting FR4 is fine on a CNC mill without ventilation if you insist that a layer of oil is put on the surface when cutting. This has the two major benefits of capturing all the fiberglass and copper shards in the oil instead of kicking them into the air and it also dissipates heat to give cleaner cuts. Common household vegetable or olive oil will do. I’ve done this before, successfully and never had an issue with “smelling” any fiberglass.
There’s a blog entry from 2009 on Openmoko about PCB milling with oil which is what I used as a reference way back when. I also see a demo video on Prometheus PCB milling that looks like they do the same thing.
It’s up to folks at the space, of course, but I would ask that since I was the one that donated those materials that if you do decide to throw them out, you let me take them back.