“Machining” copper parts using Cupric Chloride

[Ben Ardwin] was asked by a friend to help fix an old motor. It needed a new set of brushes. They’re just thin pieces of copper that mount on the motor housing and contact the commutator. The metal is so thin he thought he’d try fabricating replacements by dissolving copper stock.

This is not copper clad board; the raw material used in PCBs that has a copper-covered fiberglass substrate. It’s just thin sheets of copper stock. [Ben] started by covering top and bottom with painter’s tape. This will act as a resist for the chemical etchant. He headed over to the laser cutter to remove the tape mask around the outline of the parts. From there it’s into the Cupric Chloride for about two hours.

The etched parts are a bit rough around the edges so he cleaned them up by hand using a file. When writing to us about the process he suggests a few improvements. The tape used for masking wasn’t ideal and he would try a different method. He would also remove less area around the parts to help speed up the process.

This technique is a really becoming popular as a home-fabrication tool. Recently we’ve seen etched copper used to make a faceplate for an enclosure, and a translucent template for a clock.

Comments

  1. Keith says:

    Ok, that’s great, but couldn’t you just have used tin snips or a nibbler and a drill? LOL

    I figure that it would probably have been cheaper and faster, but I applaud you’re creativity.

    • Spork says:

      I have tried tin snips/nibblers on metal that thin. It usually doesn’t survive. Even a drill is iffy unless you have something to hold down (eg between two sheets of wood or plastic)

      This is a great way to do it. I used the same method with toner transfer to make a solder stencil for a Macbook Pro ribbon cable.

  2. Jay says:

    If you’re interested in this, research Photochemical Machining. It’s the preferred alternative to laser-cutting thin sheet metal for stencils and stuff when you don’t need very small apertures.

  3. tyco says:

    he could have used black spray paint as a resist, and then selectively burned that resist away with the laser cutter.

    • Ben Ardwin says:

      Good recommendation. I had tried spray paint in an earlier version of this process, but was using paper as the masking for the spray, so I had over-spray issues. Will have to try cutting through the paint next time. Wonder how narrow I can get away with for exposure to the etcher. I think the beam is only about 0.005 inches wide, though there is usually some degree of overburn.

  4. TheFabricator says:

    There is a much simpler way of doing this, and a very similar method for steel sheet.

    First you paint the copper or steel sheet, a couple of good coats on both sides. Then you trace around the original part, or use a printed drawing, to scratch the outline into the paint, exposing bare metal.

    With the copper you use the cupric chloride. For steel you use electrolysis, with your painted sheet as the cathode.

  5. ( ! )hat says:

    If he already had a laser cutter couldn’t you just repeatedly trace the outlines and eventually get through the copper (or is the heat dissipation too great for copper so it wouldn’t be able to cut through it?)

    • Ben says:

      Sadly, no. The laser we have available at work is only a 50W CO2 laser, not enough power to cut through even very thin sheet metals, though I have used it to cut metal screen before. We do have a more powerful fiber laser around, but in previous attempts with that, the cut has been a bit messy. Need to convince someone we need a waterjet table.

  6. Ken Quast says:

    Question: In the photo it looks like Radio Shack Ferric Chloride, FeCl3. Did you actually use H2O2 and HCl to do the etching?

  7. cgimark says:

    I keep all my etchant for just this reason. No point throwing out perfectly good copper. Use a low current DC to speed up the process.

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