Just curious about injection molding or casting

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Sat Aug 25 12:39:49 2001

I've done this a couple of times but it isn't as useful yet as I would like.

For duplicating parts, the simplest solution is to use something called
"RTV" or, if you can convince your dentist to sell you some, dental casting
foam. This stuff is mixed, and the part is placed in it to form a mold.
When making a mold be sure and figure out how you want to fill it and take
it apart. When you're done you'll have a rubbery thing with a mold shape in it.

Next use a casting material. The two I've used are acrylic resin (two part
resin available in craft stores) and Alumilite. (www.alumilite.com)
Alumilite is harder than acrylic but less tough. Both can be dyed.

Designing your own parts is a bit trickier but certainly doable if you know
a machinist. Generally you get a machined "blank" and use that to create
the molds from which all parts are made. Stereo lithography is a good way
to make the blank.

--Chuck

At 10:28 PM 8/25/01 -0500, you wrote:
>Don't recall this ever coming up before. I don't need to do it with
>anything now, but might in the future so thought I'd solicit any ideas
>from the listmembers.
>
>For small plastic parts, say - switches and actuators and the like - that
>get broken or are missing from systems or peripherals. Is it within the
>realm of the home hobbiest to forge duplicate parts? For example - a
>switch on a DEC PC04 where you have 3 switches but are missing one. Can it
>easily be done to make a casting of the part in some kind of clay, then
>work with dyes to get the color right and pour in a plastic or resin and
>thus create another identical switch?
>
>I'm sure there's a lot of side issues that come up. Some parts need to be
>hard, some ever so slightly flexible. Others need to be a solid material,
>and still others would need to be somewhat opaque to let light shine
>through. I'm thinking of like front panel switches or light covers.
>
>Anyone ever try this route or is it silly to even attempt non-professionally?
>
>Jay West
>
>
Received on Sat Aug 25 2001 - 12:39:49 BST