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[on:]

Hi, I've been trying to build ECM(Electro Chemical Machining) and EDM(Electro Discharge Machining) machine using arduino but I didn't know what specifications of parts are required and how I should hook them up.
Below links are the videos that inspired me.
ECM : http://www.boingboing.net/2009/08/06/bb-video-carve-steel.html
EDM :
I hope I could build them both but I couldn't find any circuit diagram that I could make principle of. The reason why I am trying to build them is to machine materials like stainless steel and steel alloy like monel, inconel, hastelloy. I will make groove or through hole in those materials.
Could you please advise me how should I approach this project?
 

[Reply #1 on:]

If I recall correctly you will want to move the electrode forward close enough to get a spark and back if the electrode actually touches.  Perhaps sensing the current through the electrode you can pick a set points below which the electrode is advanced and above which the electrode is retracted.

Since you need bi-directional control but not absolute positioning you can choose either a stepper or (geared) DC motor and H-Bridge.  I think turning a threaded rod is the usual method of advancing and retracting the electrode since you will be moving it VERY slowly.

If you can use rectified AC as a source of fairly high voltage and current DC.  You can use a high wattage lightbulb in series with the electrode to limit current (not fry the rectifier or pop the breaker).  You could then use an LDR to sense the current by seeing how bright the lightbulb is. That way your Arduino would be completely isolated from the AC.