Take any 3D printer, throw on this modular head, and use it as an EDM machine to do precise metal carving. Exciting stuff!

What’s EDM?

Electro-Discharge Machining or “spark erosion” is a fairly specialized field that not many hobbyists are familiar with. The technique flips traditional electrical design upside down by trying to maximize a phenomenon that most designers seek to minimize — contact erosion. Every time a switch is switched or a relay is triggered, as the two ends are physically brought together an arc eventually jumps the air gap right before actual contact is made. This burst of electrical plasma vaporizes a tiny spec of material on the impacting side.

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If the ends were brought close enough to arc but never touch — like in a TIG welding arc — electricity would continue to flow between the electrode and the workpiece in the same spot. This is because plasma has only a tiny fraction of the resistance of air. In EDM that’s not useful, so the power is rapidly pulsed on and off (Khz) such that the microscopic bit of dust is vaporized from a different point every time. Since the last part vaporized will now be farther away due to the bit that was eroded, on a flat surface the next-closest point is next to be vaporized. This repeats tens or hundreds of thousands of times a second.

What good is it?

Traditionally if one wants to machine hardened materials like tool steel, they must be machined in a softer state, then sent to be expensively heat-treated. Since EDM is a thermal, not mechanical process, the hardness of the workpiece has almost no effect on the cutting rate. One can begin with pre-hardened steels and machine them directly. Another use is making stamping dies, a graphite or copper electrode is easily machined then burned into the workpiece with all its features transferred. A third common use is tap-burning. Any hobbyist who’s done some metal work will eventually break a tap off in a workpiece and be stuck wondering how to remove it — you can’t drill it out, the tap is harder than the drillbit. Most shops use an EDM to rapidly carve the tap out of the workpiece.

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But there’s more to this than typical shop stuff. Most hobbyists and makerspaces have 3D printers but lack access to common industrial metalworking tools like lathes and mills. Even machining softer metals is not within reach. A Dremel or other tool could be mounted in place of a 3D printer print head, but 3d printers lack rigidity by an order of magnitude or two to act as mills for anything other than plastic or soft woods. That’s where this modular EDM head comes in.

What’s new about this project?

Just like with 3D printing, there are practically zero mechanical forces when using EDM because the sparks do the cutting. Rigidity is not an issue. The two machines are practically soulmates!

By swapping an extruder head with an electrode and building a fancy pulsing machine, small parts can be created by spark erosion without building a whole new CNC.

The technology is not new, back in 1968 Popular Science published a simple design that uses only one diode, two capacitors, a pair of lightbulbs (resistors), and almost zero concern for safety.

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Popular Science, March 1968, p151-152.

Simple burning is easy, but different parameters yield different removal rates and finishes: voltage, current, frequency, on-time, off-time, flushing methods, pulse shape, etc. The past five decades of experimentation with these parameters have led to closely-guarded trade secrets and not much that the rest of us can use.

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The project’s creator, who goes by the name ArduinoVsEvil, has a plan to open this up and is forging a new kind of crowdfunding to make it happen. His philosophy is that making something requires motivation, time, and money. He is happy to produce his regular edutainment on machining and hacking for free, but aims for crowdfunding to pay for the costs of some of his new project tutorials. He has assembled a fairly unique following of like-minded individuals and wants to take things to the next level and explore new territory. “Nothing on the internet that walks you through the design steps for small scale manufacturing,” like How-Its-Made “Are interesting because you can see how it’s made, but they never show you how it was designed.”

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His 3D printer EDM head is a pilot for the new approach and the prototype is already working. If you’re interested, watch his pitch on why things like these matter. (Warning: Language).