dielectric conductivity & wire cutting aluminum

I am running a charmilles 290 cutting aluminum with .01 brass. Most of the work we have done has been in steel so aluminum is a new experience. It cuts ok, just dirtier than steel judging from the filter useage, but we noticed that the conductivity of the water is falling. Normally this machine runs at 15 micro siemens when cutting steel. The level goes up due to cutting steel and the resin system brings it back down to the preset level of 15. We started cutting a block of aluminum 6.0 thick with about a 16 inch total burn length. By the end of the rough cut the level had fallen to 10 ms. At the end of the second pass we were down to 6 ms. Does anybody out there with experience in aluminum know if cutting it will cause the conductivity of the dielectric to go down instead of up like it does when cutting steel? Tech support is closed for the weekend or we would ask them all about it.

My Mits DWC110H has cut quite a few aluminum parts. The conductivity does move around more than when cutting steel. I never really payed that close attention to it over time of cut, but it did not seem to hurt sizing or speed. The only thing I can say is that my edm has a "sludge tank" in line to the dielectric pump unit. water comes out of the machine, into a "tub in a tub" The first tub must overflow into the second tub, which when full enough overflows into the "scavenger pump" that flows thru the filters to the resoivor that the flushing pump is in. It has my filters lasting 3 times as long. really "gomer pyle" engineering, but seems to work well. Unless it is affecting size I'd keep right on a burning.

[This message has been edited by WILLEO6709 (edited 12-22-2002).]