RE: need help with rapid tooling

From: Prof P. M. Dickens (
Date: Wed Jan 06 1999 - 21:07:00 EET

I think you will be wasting your time with trying to make electrodes with
metal spraying.
When I was at the University of Nottingham we tried to make electrodes by a
number of techniques.
I give a summary of the results:

Metal Spraying - There are two big problems here. The first one is the
distortion which occurs in the copper coating and in the SL pattern. It is
hard work to get the copper coating to adhere to the pattern without
distortion/cracking. Even if you do overcome this problem then the coating
is not fully dense and when you use the electrode in the EDM machine you
get a very high electrode wear rate. If you want further information it
might be worth contacting Joel Segal who is now at Rover Group.

Electroformed copper - This can be used quite successfully but there are
severe limitations on the geometry of the electrodes. It is very difficult
if not impossible to plate down into deep slots. As corners have a higher
current density then the slots close off before you have filled them. This
leads to an electrode with in built faults. It is probably much quicker to
machine the electrode!!

Copper plated SL models - This can work very well. The SL model needs to be
made conductive. The easiest way to do this is to paint a very thin layer
of silver loaded paint (like electrodag). This can be at 10 microns thick.
The quality of the plating is crucial. Make sure it is plated in one go.
Sometimes the plater will take the part out for some reason and then
restart the plating. This gives delamination when the electrode is being
used. The thickness of the coating is very important. With a coating of 175
microns then they can be used for finishing/ semi roughing. For a roughing
cut you will need at least 300 microns. This then provides a problem
because as you increase the copper thickness you start to lose control over
the geometry. I think the main application for this type of electrode is
where you have a hand crafted part and there is no CAD data. We plated some
plaster of paris parts and used these with success. If you need any help on
this then contact Dr. Alan Arthur who is now at the University of
Birmingham ( His Ph.D. was on this subject.

SLS electrodes - We did some limited work with one of the EOS materials but
found a very high electrode wear rate.

Keltool electrodes - Most of the Keltool parts are used as inserts but they
can also make Copper/tungsten electrodes. The erosion rate and electrode
wear rate seem to be about the same as with conventional copper/tungsten.
This is probably an ideal application for small complex electrodes. If you
need any more info on this I suggest you contact Jose Marafona at the
University of Nottingham ( He is
doing his Ph.D. on these electrodes.

Hope this helps!

Prof. Phill Dickens
De Montfort University

-----Original Message-----
From: Peter Martin []
Sent: 06 January 1999 01:51
Subject: Re: need help with rapid tooling

Thanx to all who replied to my queries about RP EDM electrodes. Many of
the suggestions were to use metal spraying on the epoxy/ABS part. I am
now exporing this possibility. Before I start physical trials, I need a
ball park figure for the coating thickness for the electrode to
withstand spark erosion. One try already ended in failure, when the coat
eroded off before the cavity was completed!


Peter Martin
Anna University-FRG Center for CAD/CAM
Chennai, India

>From Sun Jan 3 20:47:25 1999
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>From: "Mr. Tushar R. Mahale" <>
>To: Peter Martin <>
>Subject: Re: need help with rapid tooling
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>Try Epoxy/Spray metal tooling. Let me know if u require any help
>Tushar Mahale
>Senior Research Engineer
>Rapid Prototyping Cell
>Indian Institute of Technology-Bombay
>On Mon, 28 Dec 1998, Peter Martin wrote:
>> dear rp-ml'rs,
>> season's greetings and happy new year to everybody. i'm an
>> engineering student in india and i have a small problem regarding
>> Tolling.
>> i have been asked to standardize a
>> method to produce press tools using RP/RT techniques. so far, the
>> were produce by generative machining of a graphite electrode, which
>> then utilized for EDM machining of the punch and die set.
>> i'm trying to further reduce the lead time by using RP/RT. a
>> FDM 2000 is available to me. what would be the best method of
>> the considerations are tool-life of the electrode,the surface quality
>> the part and obviously the accuracy of the final part.
>> Can anyone suggest any solutions? cost-effective ones would be
>> we are on a most miserly, Scrooge-like budget.
>> Peter Martin
>> Anna University, Chennai
>> South India
>> AU-FRG Center For Cad/Cam
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