Hi. I tried to make a homemade EDM. This is inspired by savarin and brino, who appear to have made some successful ones. I wanted to start with the solenoid actuated design because it is simple and it would make a good foundation for a proof of concept. The starting point was the circuit that savarin posted. I tried it out, and it did not work so well with my available components. I think that the problem is that all the charging current must go entirely through the solenoid. This results in the solenoid being engaged too much of the time, and also it restricts the total amount of power that can get into the circuit. My initial machine was able to make a hole in a 1.5 mm piece of steel sheet in about 10 hours. It was very fiddly and jammed or stuck continually. Part of the problem was the top of the shaft getting distorted where it attached to the solenoid, but even with that addressed, it still seemed kind of anemic.
One thing that really helped was changing the circuit diagram. The original diagram is posted for reference. If you run the resistor directly to the capacitor and connect the solenoid across the resistor, the operation becomes quite a bit more aggressive. In this case, the capacitor is being charged through the resistor and the solenoid in parallel instead of in series. When the voltage drop across the resistor becomes too high, presumably due to the electrode being stuck, the solenoid will actuate, pulling it free. Now the problem became that flimsy chemistry lab stand. The support rod is anchored in plastic, and the retainer screw is also threaded in the plastic. That makes it very floppy, and causes the electrode to jam in the hole once it has been drilled a bit. Still, it reduced the time to get a hole considerably. A hole appeared in 1 hour in the same piece of metal. It seems that this small change is a major improvement. The stand should probably be replaced with something custom fabricated. Even a wood setup with a piece of square tubing like savarin posted would be much more solid. Any amount of slop causes movement which wallows and binds the hole, which will be especially deleterious for tapping.
I will post a picture of the original circuit and the first prototype.
One thing that really helped was changing the circuit diagram. The original diagram is posted for reference. If you run the resistor directly to the capacitor and connect the solenoid across the resistor, the operation becomes quite a bit more aggressive. In this case, the capacitor is being charged through the resistor and the solenoid in parallel instead of in series. When the voltage drop across the resistor becomes too high, presumably due to the electrode being stuck, the solenoid will actuate, pulling it free. Now the problem became that flimsy chemistry lab stand. The support rod is anchored in plastic, and the retainer screw is also threaded in the plastic. That makes it very floppy, and causes the electrode to jam in the hole once it has been drilled a bit. Still, it reduced the time to get a hole considerably. A hole appeared in 1 hour in the same piece of metal. It seems that this small change is a major improvement. The stand should probably be replaced with something custom fabricated. Even a wood setup with a piece of square tubing like savarin posted would be much more solid. Any amount of slop causes movement which wallows and binds the hole, which will be especially deleterious for tapping.
I will post a picture of the original circuit and the first prototype.
