Homebrew_PCBs

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]