Re: [CAD_CAM_EDM_DRO] Commercial EDM capacitance ranges

Hi Larry:
My Hansvedt EDM (sinker) runs typically at about 30 to 40 volts while
sparking and 80 volts open circuit.(depends on what gap I need to flush
well)
The lowest power setting runs at about 0.1 amp, and max on my machine is 20
amps.
300 amp machines are not uncommon.
This commercial power supply does not depend on capacitors to generate and
time the spark.
I can set the capacitance from zero to about 20 microfarads (I think it's
microfarads!!) in 0.05 microfarad steps.
I almost never use this feature.
I am running copper electrodes exclusively, to keep the mess down in my
shop.
The subject of what dielectric to use and why is a complex one.
Water is a better dielectric in a number of respects, but it induces higher
wear rates than oil, and in sinker operations, the bulk of the labour is
usually in making the electrodes.
Wire, as you know, uses a consumable electrode that requires only to load a
spool to make it go.
Water will permit a faster cut than oil, so water is the better choice for
wire under most conditions.
There are oil based wire machines available; these are used primarily for
cutting carbides and exotic alloys that don't tolerate hydrogen
embrittlement, and, specifically for carbide, are adversely affected by the
dissolution of the cobalt binder in the carbide.
There have also been water based sinker machines put on the market a couple
of times, but they seem not to have been cost effective to run, and were
apparently withdrawn again.
Hope this helps.
Cheers

Marcus

----- Original Message -----
From: "Larry Edington" <ledington@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, February 09, 2003 11:39 PM
Subject: [CAD_CAM_EDM_DRO] Commercial EDM capacitance ranges


> Anybody know the range of capacitance found in a typical commercial wire
and sinker EDM?
>
> What about the adjustability of the capacitance? How many different steps
are usually available?
>
> What about voltage? I've read 80 volts max is typical.
>
> I assume if you are doing active spark control, you just put in enough
capacitance to supply your longest
> spark time and limit down from there. I'm trying to determine what those
ranges are for spark time and max
> voltages.
>
> One more question ( for now ). Why is deionized water used in wire EDM
when an oil product is used for sinker EDM?
>
> thanks,
> Larry E.