eroding Wire EDM fixtures

[Rivet head]

I make fixtures for one of my customers that has a wire edm machine. The problem we're having is that the fixtures are slowly eroding away where the parts being cut touch the fixture. I'm using 17-4 Stainless steel and heat treating it to H900. Anybody know how to prevent this erosion???

[kevh]

Hi rivet head

I have sodick A320 and it is eroding away gradually my expensive hirschmann tooling the reason for this i have been told is due to secondary sparking from charged particals in the tank. Possible cures are:


1 Keep filters regularly changed

2 Older machines tended not to have EF11 or equiv Reverse polarity

3 lumps of zinc in the tank which tend to get attacked first.

Out of interest what machine is the fixturing for ??

What kind of fixturing do you make?? Might be interested ??

Cheers kev

[roysol]

I will add to this any movement of the part in the fixture creates it's own gap which a spark can jump across.

[Xterrian]

Why not use a non conductive material?

[roysol]

That is a valid technique which would require grounding cables directly to the part in order to complete the circuit. Secondary grounding such as this can help mitigate the arcing problem, even without changing the fixture material. The stumbling block is often the configuration, size and shape of the parts and their relationship in the fixture, often do not lend themselves to this approach.

Regards,

Roy Solomon