Can an EDM be made?

[fr0st]

Thanks again
You guys have become my best source of information

Modern edm’s have provisions for both suction and pressure flushing. They also cut submerged, i.e.; the tank fills to a level above the work piece. This serves several purposes, to thermally stabilize the machine, fixturing, and work piece, to prevent fire by denying oxygen to the sparks, and to allow for “no flush” burning.

I was planning on fully submerging the workpiece, it seems the safest and easiest way. I don't think perspex will have any reaction with oils that I know of.

In Europe they use a lot of copper electrodes. This eliminates the hassle of machining dusty, abrasive graphite. It burns slower, and with less wear, but adds the potential problem of de-burring what you machined on the electrode.

I think copper would be the best option in my case, the reduced wear at the cost of slower burn rates isn't really a problem. It'll be a good experiment once the machine is running.

Wear rates on modern edm today are about 0.1% on roughing (greater than 32VDI). Parafin is still commonly used for EDM, but beware it is a fire hazzard. So take precausions.

Really? Paraffin?
I never would have guessed that. Is it any different from the candle wax variety?

Are you able to tell me some information about the frequencies and currents you use?
I havn't been able to find much info about the capabilities of many of the machines power supplies apart from the general information. A higher frequency results is a smoother cut, likewise lower currents at the sacrifice of some speed.

Thanks again
Matt

[euroedm]

The most basic of machines with regards to a power supply is the Eurospark. The power supply is 66VAC 3 Phase recified to DC giving approx 90V using 3ph recitifier and approx 1000uf of capacitance. Was made in 25A, 50A and 100A versions.

The output is via a bank of resistors (12ohm) and transistors wired in series and driven to form a pulse width modulated output. Duty cycle normally about 90%. Oscilator is basically a 555 IC driving a series of transistors to boost the power level. For currents of 5Amps of more I would recoment a ON time of 400 to 800 microseconds and an OFF time of 40 to 80 microseconds. Too much off time reduces removal and increases wear. Too little can result in arcing.

The parrafin used is illuminating parrafin as is used in parrafin stoves.

Regards

Paul

[fr0st]

Thanks for the advice.
My plan for the power supply is to have a mains transformer bring the voltage down to ~150v which may be adjustable if I find a low loss way of swiching high voltages easily.
Pulse lengths will be controlled by a microcontroller attached to a lcd for setting the timing and current.
I think I have everything sorted now
Thanks very much for all your help

Matt