"Brian Lawson" wrote in message
news
On Fri, 02 Jan 2004 01:48:55 -0500, Gary Coffman
wrote:

BIG SNIP OF GOOD STUFF

But this is all pretty much moot since EDM isn't done with
arcs through a gas. It is done with arcs through a liquid.
little snip

Gary

Hey Gary,

I think this last part of your reply is not really correct. Most EDM
I see is set up and started in free air. After location and some
other things are adjusted to suit the operator, then the work is
flooded, either by flooding the tank to immersion, or on smallish
parts or small burn area just with direct flow of die-electric
externally or through internal created flow ports. After the
die-electirc is applied, the rate of burn is then further adjusted to
the need, which seems to me to almost ALWAYS be MAX!!

Ed Huntress says that the arc starts without actual physical contact,
and I can't argue, but if so it sure isn't obvious. I always figured
that on die-sinkers the electrode (always carbon in my cases) does
touch and then retract ever so slightly, and now-a-days maintains the
arc through sophisticated controls on the newer CNC EDM's.

Happy New Year.

Brian Lawson,
Bothwell, Ontario.


The only reason they ever touch is to establish dimensional zeros, Brian.
And that's done with the EDM power supply turned off.

BTW, I've never seen an EDM started in air. The electrode has to be
submerged before you start.

Ed Huntress