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]