[FanFan]

Hello, Recently, I have been moved to a different area that has some EDM machines. I am more use to working on chip making machines. EDM's are kinda new to me.
I have been out on a couple of trouble calls for no output. I would like to know if there some type of tester that I can use to check the output of the machine. Is there a dummy load that I can substitute an expensive part for? Seems to me that the EDM is outputting a DC pulse. Would a large power resistor work or do I have use something that mimics the part being cut (varying load)? Any information would be appreciated. FanFan

[jmullett]

You could probably use an oscilloscope to look at the wave form. In fact many older EDM machines had an oscilloscope built into them for set-up purposes. Some EDM waveform examples can be viewed at the following link:

A look at the waveforms from a CNC EDM | Steve?s Junk

[FanFan]

Thank you for your reply. I took a look at that link. It was interesting. None of our machine seem to have a oscilloscope for viewing wave forms but we can always drag and an oscope out to the machine to take a look. It is a good idea. But I also would like to able put a simulated an load on the edm output. I wonder if it could be as simple as two pieces of metal with a gap of say .200 or even maybe just a spark plug. Maybe I am over thinking the matter. I was thinking that I had to simulate the effect of the dilectric solution and how it reacts to the cutting pulses. Thank again, FanFan

[graflex]

First, there are two basic types of EDM systems. 1. Pulse generator types and 2. capacitor discharge types. The pulse generator models use a transistor switching circuit to generate a square wave pulse of variable pulse to width ratio to vary the power level. The second type relies on a capacitor discharge circuit which in its simplest form charges a variable capacitor bank through a resistor limited DC supply. The square wave pulse generator output waveforms are somewhat complex during discharge across the dielectric gap and are modified by the action of the servo system controlling the gap width. The capacitor discharge waveforms are exclusively a product of the discharge across the gap. When the head is raised off the workpiece, only a DC potential is present between the workpiece and the electrode. Hope this may help.

[xrdcarbon]

agree to graflex