In the previous testing we've done we have typically hooked the electrode directly to the high voltage output of a current limited power supply. It works, but a light touch is necessary or the system purely shorts, current limits, and stops cutting. We had hypothesized that perhaps we could get better cutting by modulating the signal. In fact, it seems most commercial EDM machines modulate the voltage as well. In addition, we had hoped that this system could run off of the 12V supply on most hobby 3D-printers. Therefore, I built a quick prototype with an off-the-shelf boost converter (Amazon cheap XL6009 style) to achieve 30V+. A optically isolated solid state relay charges some large capacitors, then we can drive an optically isolated MOSFET to do the cutting. A voltage divider allows us to measure the capacitor voltage. Below is an image of the whole setup. An Arduino Uno drives the system. The input to the boost converter was 12V limited to 1A.
The test was highly successful. In the gif below, I'm pushing relatively hard onto the PCB, and it is not disrupting the cut. Best of all, the system runs from the 12V supply, reporting about 0.14A, so only 1.7W. There likely is some spiking higher that I do not see, but the power buffering seems to avoid that. This is really encouraging, that this system is:
- Simple to drive
- Low power
- Doesn't need careful force control to keep cutting
- Even with modulation, we can cut quickly