Re: [CAD_CAM_EDM_DRO] Die sinking power supply for Wire EDM

Hi kdoney:
Theoretically, you should be able to make the adaptation, but there are
likely a lot of details that will be a challenge for you.
First, the sinker power supply typically puts a lot of current into the
electrode, compared to a wire power supply.
A sinker trode usually has the mass to handle it, whereas a wire can't take
much.
So the power supply is set up in the wrong amperage range...should be
fixable.
Second, the sinker senses voltage agross the spark gap and directs advance
or retreat of the electrode via Moog valve and hydraulic cylinder, or
stepper/servomotor and screw.
That sensing circuit has to be adapted into the wire path.
Third, typically sinkers use oil dielectric whereas wires use deionized
water...the dielectric constants of these two media are likely different
enough that you need to tune the sinker control to get useable performance
in the wire environment, unless you stay with an oil dielectric (very slow).
Fourth, wire power supplies are pretty sophisticated in how they respond to
fast changes in the spark gap voltage.
They continuously diddle the voltage, frequency, amperage, off and on times,
rate of advance & retreat etc, etc.
They require this sensitivity because of the difficulty of maintaining
constant dielectric conditions in the spark gap zone.
A sinker power supply from an obsolete machine is not set up to do
this...you may have insurmountable difficulties maintaining a stable spark
gap just because the supply can't respond fast enough and in enough ways.
That translates into more ramming events and more arcing events, both of
which break wires.
So...it's probably doable if you've got the knowledge to poke around in the
electronics, but you ain't gonna get commercial wire cutting speeds, and
you'll likely be severely limited in the thickness of material you can cut.
Expect also to use a LOT more wire per cubic inches of cut than a commercial
machine, and expect more wire breaks.
Having said all that, a transistorized sinker power supply is a helluva lot
better than a home cooked capacitor discharge supply, so you may find a
workable solution that is better than the unaltered plans call for.
I commend your effort...keep us posted
Cheers

Marcus

----- Original Message -----
From: kdoney_63021 <kdoney_63021@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, November 15, 2003 3:48 AM
Subject: [CAD_CAM_EDM_DRO] Die sinking power supply for Wire EDM


> I just bought a Charmilles D10 with a good power supply and was
> wondering if I could use the same supply on the WEDM I am building
> from Dan Mauch's plans. I haven't gotten my schematics or user
> manuals yet so I don't know all of the specifics.
>
>
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