Homebrew PCBs

This post refers to duplicating a railroad shell, and a comparison 
between casting the part and photo-etching brass.  I have been 
lurking on both etching and casting forums, and I have been debating 
using either method for my project.

I plan to create a body shell to replace an existing body shell.  
Just picture 2 sides, front/back and roof (no floor needed).

If I were to cast the part in resin, I would have to create a master, 
and pound out each rivit.  This would be very time consuming, and I 
could possible ruin the master if I mistakenly create a rivit 
incorrectly or in the wrong place.  I would then have to create a two 
part mold then cast my duplicates.  This also seems to be expensive, 
as 1 LB of Alumilite mold in $25, 28 OZ of resin is $28, clay is $2.  
Total about $55.00 to get started.  But I can cast the entire shell 
in one part, no assembly (just cleaning up flash).

If I were to photo-etch in brass, I would use a cad program to layout 
a design of rivits, window openings, etc.  Then make a copy onto 
transparency.  Then use the transparency to expose a sheet of brass 
costed with resist.  Then let acid eat away at the brass, hoping that 
the rivit details are left standing above the surface.  Then I would 
have to piece together the shell (the brass sheet is flat - walls, 
sides and roof are done seperately) into it's final form.  Cost of 
etching: Brass sheet (4x10) $1.60, acid $4.00, developer $0.95, photo 
resist $??.  Seems much cheaper to create (if I could find someone 
selling a spray photo-resist), just more time to assemble.  No need 
to pound in rivits, just design them using a computer (rivit lines 
perfectly straignt, etc).  Downside - consistancy of etching varies 
for beginners.  Also, you have to assemble the shell, and the 
chemicals can be bad for you/environment.

Any thoughts from those who have experience in both methods?

GregC
Antioch, CA

It good that this was brought up because I am doing some casting of 
my own. Right now, I have been using the Alumlite RTV MoldMaking Set 
to create master mold of the gears found in my GBC 95P laminator. I 
also use Casting Craft Liquid resin for the duplicate part. I would 
recomend using the plastic method if you are going to make a 
duplicate item. Keep in mind that any imperfect features from your 
original will come out in a mold.

On Wed, 18 Feb 2004 05:40:44 -0000, gmanca101 <gmanca101@...> wrote:

> It good that this was brought up because I am doing some casting of
> my own. Right now, I have been using the Alumlite RTV MoldMaking Set
> to create master mold of the gears found in my GBC 95P laminator. I
> also use Casting Craft Liquid resin for the duplicate part. I would
> recomend using the plastic method if you are going to make a
> duplicate item. Keep in mind that any imperfect features from your
> original will come out in a mold.
>
>

It's not that i am not very interested in casting too (really)
but i wonder if it isn't OT and maybe there are better groups.....

To the etching:
i somehow doubt it will work very nice. you need a very even etchn and 
then
you only have 2 "heights". i doubt it would look very realistic.

ST