what can be substituted with PHOTO-FLASH capacitor?

[ghanbari]

Hi everyone,
I am going to build a simple EDM (Electric discharge machining) system and its circuit schematic is as following:

Capacitor C3, is needed for making coarse EDM cuts. This electrolytic capacitor should be a photo or strobe flash capacitor. The rating should be a minimum of 100VDC @ 80uf (Schematic and information from: "The EDM How-To Book" by Ben Fleming).
Now, the main problem is that, the mentioned capacitor is not available in my country, so i want to substitute it with an array of parallel normal capacitors that are available for me. I need to know what kinds of capacitors are suitable to be used?

[Seekonk]

I've worked a lot with EDM, even used a similar method to machine at nearly 1mhz (100% electrode wear) on a very specialized product.  Really wish you would use a switched FET to do this.  About the cap, you don't want one there should be many in parallel.  Most consumer caps are only good for a half amp.  Multiple caps in parallel will give you lower inductance and ESR.  Lower heating will greatly extend the life of the capacitors.  20uF each should work nice.  I wouldn't think a photoflash capacitor would be that exceptional.  After all they only need to flash every couple of seconds, this would be continuous.  Hope you are not expecting much performance with this.  An actual FET driven machine of 20A is only a tiny more effort and I wouldn't have a machine that couldn't at least provide a 150V teaser.

[SeanB]

You would be better off using a lot of film capacitors in parallel to make up the value. 16 10uF 400VAC motor run capacitors will give a correct value, and will have the pulse rating you need. You just need to ensure that the wires used to connect them together are all the same length, and they should ideally be 2.5mm copper wire with a large terminal to join them together. If you use values larger than about 22uF film caps they will fail with time as they are not really rated for crash discharge, but the 10uF ones will most likely not see a high enough current per unit.

[ghanbari]

Thank you wilfred, Seekonk and SeanB,
your answers were very helpful for me.