Date:         Sun, 11 Jan 2004 12:36:54 -0800
Reply-To:     "J. Harvey" <jtharvey2@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "J. Harvey" <jtharvey2@HOTMAIL.COM>
Subject:      Re: casting molds of plastic/rubber/fiberglass parts? anyone done
              it?
Content-Type: text/plain; format=flowed

Are you looking to make one for your self or a couple hundred for profit?  I
know a little about making low quantities.....

I prototyped a small air pump this summer using a two part silicone mold.
The silicone was able to pick up very intricate features of the master (a
stereolithography) and the stuff is easy to work with.

Here's how I'd do it.  Build an open topped tray that closely matches the
shape of the spoiler, atleast +2" in every dimension.  Coat the master part
and tray with mold release.  Fill the tray less than half full with
silicone.  Submerge the master half way in the silicone and support it from
above so that it doesn't sink to the bottom or shift.   Let the silicone set
up (24 hours) and then spray mold release on the silicone surface.  Then
pour more silicone, filling the tray to the top.   Let that set up and then
open it up and remove the master.  Now you have a two piece mold.  You'll
also need a method of indexing and a few other things....e-mail me if you
want to hear those details.

What I can't tell you is what type of material to pour in to your mold.
Take the part to the local mold making supply house and ask them for a
material suggestion.

A few random words of warning.....the silicone isn't cheap (GI-1000
$100/gal), a lot of thought must go into the mold design, air bubbles will
drive you crazy, your part will only be as good as your mold, and don't
quote me on any of this.

John

'85 Silver Sunroof
'91 GTi 2.0 8v
'76 BMW 2002




>From: JordanVw@AOL.COM
>Reply-To: JordanVw@AOL.COM
>To: vanagon@GERRY.VANAGON.COM
>Subject: casting molds of plastic/rubber/fiberglass parts?  anyone done it?
>Date: Sun, 11 Jan 2004 12:32:59 EST
>
>im looking to reproduce a rear wing/spoiler for a vw that is no longer
>being
>made (rear spoiler for the vw mk1 cabriolet).  i have found an original
>but
>the owner doesnt want to sell it, tho he has granted permission for me to
>make
>a copy.  the spoiler is not mounted, and is a black rubber/foam type
>spoiler
>like those used on the A2 jetta or audi 4000q, and looks similar.    i was
>thinking of reproducing it.. the finished product does not have to be done
>in
>rubber/foam, it can be done in plastic or fiberglass, whichever is easier
>to work
>with.  what is the best way to make a mold, without damaging the original?
>and what is the best bedium to cast it in?  fiberglass?   anyone have any
>experience with this?
>
>thanks
>
>chris

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