[sdiy] Molding your own keycaps for tactile switches?

[jgrisso at det3.net]

See below...

> I don't know why everyone here seems to think the only way to make
> molded parts is injection molding. It's injection molding for gods sake!
> If you really want cheap custom knobs, not a batch of 500k i mean,you
> have a lot of other options. For starters, you could make a relatively
> cheap silicone mold and cast knobs in a resin of your choice.
> The downsides to that are the longevity and shelf life of the mold -
> silicone molds develoup cracks after a certain amount of use, so its not
> permanent. One of the upsides is that you can you whatever casting
> material you bloody well want.

Well, I don't think the only way to make caps is IM - there are plenty of
other ways to do it, but since I'm an EE (not an ME), it's the only one
I've seen in my work. :-) I was personally thinking of making prototype
parts using stereolithography, but that's fairly pricey. I've got a
project coming up that requires 2-3 styles of button caps, and a two piece
encoder knob. All the button caps plus the encoder knob requires a
lightpipe to get LED light from the PCB up to the front of the panel - and
that makes things even more tricky because I don't know how clear the
substance would be at the end of a resin cast from a silicon mold.

> For example, a couple months ago i made a massive army of counterfeit
> Space Marines ( Warhammer 40k - little plastic men, for the squares) out
> of BONDO. An army of bondo brand auto body-filler space marines! It was
> fantastic. Honestly you could make the casts out of anything. Hot glue.
> Wood putty. I also did a run of fiberglass resin men and they were a lot
> nicer.

Heh. Very cute. :-) Have you made transparent men yet? That would be the
ultimate, especially if you wanted to do something like attach an LED to
the bottom side of the character and have their eyes glow, but I
digress...

> If you are looking for pretty knobs  you'd want to stick to the resin,
> but both the bondo and the resin are available at home depot. The
> silicone mold material usually comes in two parts and you would probably
> have to search the cyberspace for it. Heh. To make the actual mold you
> could either fashion your own design from modeling clay, or use an
> existing knob.

Very true - but if you're using a CAD application, it would be tough to
generate a positive from something like an IGES file. Maybe something like
a plastic CNC part... hmm... that got me thinking.

> This is a nice book on the subject:
> http://www.amazon.com/exec/obidos/tg/detail/-/1558701281/103-4606066-3939849?v=glance

I'll have to check it out.

> erm thats all i can think of this instant. but the idea of custom
> pimped-out translucent knobs sounds pretty neat to me.

You know, since IM is so expensive, it might behoove the SDIY community,
if we were so inclined, to design our own custom button cap or something
like that. If we got several folks together who wanted to buy a few
hundred of these beasties, we could probably amoritize the tooling and get
the cost of the switches down to something affordable. It might be worth
looking into down the road.

Best Regards,

Joe Grisso
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