This article describes my homebuilt AC/DC electro etching device. It's built from plans I got online -- I got the original plans from http://www.knives.mlogiudice.com/knifeshop/etcher/index.shtml . During the design phase, this site was the most helpful for the hardware building. I now know I can go ahead and use any basic power supply design pretty easily, so the next one will surely be a circuit of my own design.
The etcher is mounted in an aluminum case salvaged from a parallel printer sharing switch from the 1980s.
This is the second build of this circuit that I have done. This one has a much better case and a larger capacity transformer than the first, but the components are all salvaged from the first build except for the case and transformer. Total cost was <$30 -- it's only that high because I bought almost everything new the first time around. Just about any power supply will do -- I have used a wall wart transformer with the plug cut off and a couple of alligator clips soldered on to do etching and plating. Stick to lower voltages like 6-24v for sharper results, since the image tends to bloom with higher voltage for longer time. Make sure you get the biggest current rated tramsformer you can, since this circuit can easily put out over 1000 mA of current through your workpiece and a smaller transformer will definitely overheat or short out in an exciting manner. I would recommend looking for at least 1 amp output to avoid overheating.
The plans at
You can probably use any fabric to protect the probe surface from direct contact. I've used t-shirt fabric and synthetic felt to good effect.
A spot probe with a stainless mesh and a felt pad, all on the end of a 3/4" or 1" plastic dowel, will come next.
HOOKING UP THE PROBES:
The workpiece is attached to the positive terminal with a spring clip or wire hook. Stainless steel or titanium are best if the piece is to be immersed in electrolyte. No copper should be exposed to the electrolyte anywhere, or else you risk polluting your solution and plating your workpiece or probe.
The probe is at a negative voltage to the workpiece during DC operation -- so clip the probe on the negative or ground of your output terminals, and the workpiece to the +12 or +5 side. The metal from the workpiece migrates toward the negative terminal, is my understanding.
Avoid touching the probe's metal to the workpiece directly; this maximizes current and minimizes electro-etching action, heating your circuit and possibly shorting components.
You can clean the probe off when it gets gunked up by reversing the voltage and DC-etching the probe; the cruft will collect on your sacrificial workpiece. This is also the basis of a larger electrical de-ruster; plans and pics of our 35 gallon de-rusting device to follow.
I am going to be adding a voltmeter / milliammeter to avoid having DMMs clipped in all over the place, but it runs stable and cool at 10.5VDC out sending about 500mA through the circuit.
Also making more smaller spot probes would be nice, for doing a small touchmark or logo on a tool or knife handle.
I'll be soldering the whole thing permanently together and removing most or all of the spade connectors.