Curtis, I would be very interested in trying this also, do you have a
schematic of your circuit available?
How fast is brass wire used up as part of the process?
Thanks!
Dave Miller
>
> I'm working on reconfiguring the Garden of EDM to the International
> Rectifiers IPS5451 "intelligent power switch" instead of IGBTs or
> FETs. The IPS5451 chips have a 50 volt and 45 amp pulse limit. and
> built in thermal and over current protection. I'm using a 556 dual
> timer to control the pulse repetition rate and gap breakdown
voltage.
> The 555 allows pulse rates up to the 1 mHz range and the 30 amp
rating
> of the IPS is about twice the needed pulse current. I would like a
> higher voltage rating, but my initial experiments show clean traces
with
> .003 inch brass wire as the electrode with pulse rates of 30,000
per
> second. Since the IPS handles all the proteection circuitry
internally
> ( the chips are meant for automotive uses ) the Garden of EDM
circuit is
> reduced to a complexity level that matches the RC EDM circuitry.
>
> My breadboarded circuit consists of a 48 volt DC-DC converter (
too
> close to the IPS limits, but it's what I've got at hand ) feeding
a
> ~10-20 uf polypropylene cap with a SCR triggering the pulse when
the IPS
> has switched off. One half of the 556 controls the discharge rate
and
> the other half blocks the IPS while the gap is conductiong. I'm
using
> the servo circuit from Ben Fleming's _The EDM How-To Book_ ( based
on a
> SN754410NE and LM-339 ) to drive an electrode of .003 brass wire
held in
> a modified pin vise over a bath of deionized water. My initial
runs
> have burned clean .003 lines in 1 ounce copper glass epoxy board
with
> out burning the substrate at 60 inches per second. Not too bad!
>
> I'm thinking about an electrode design using .003" ( or finer )
brass
> wire feed through a plastic shield/electrolyte feed tube and the
gap
> controlled by a stepper driving a worm on a gear which would drive
a
> wire spool. The gap could then be controlled by a simple step in
step
> out sequence while the electrode chuck could be kept compact and
light
> in weight.
>
> Finally a new area of inquiry. Using microwaves to burn the copper
(
> and possibly the substrate for through holes ). See the October 18
2002
> edition of Science magazine for an article on a microwave drill!
>
> I'll try to put more time into the EDM project now that I can see
the
> light at the end of the tunnel on my Willys restoration.
>
> --
> Curtis W Richards
>
> --
> "Law and liberty cannot rationally become the objects of our love,
> unless they first become the objects of our knowledge."
> --James Wilson
>
>
>
> [Non-text portions of this message have been removed]