[sdiy] Molding your own keycaps for tactile switches?

[jgrisso at det3.net]

I have some good news and bad news. First, some background:

The best way to mold switch caps is to do injection molding. This is a
process where hot molten plastic is rammed into a mold under high pressure
to form your switch cap. Designing basic switch caps only requires a
modicum of mechanical design skills and a good CAD tool.

Now, the good news:

Injection molded parts are dirt cheap. We're talking pennies in the right
quantities.

And the bad news cometh:

The major cost of injection molding is the mold itself. Sometimes referred
to a tool, or a die. It needs to be made out of high quality steel in
order to withstand the pressure that the injection ram generates when the
plastic is rammed into the mold. The cost of manufacturing the mold is the
major expense in injection molding, ranging from a few thousand dollars up
to over six figures for large, complex molds.

Assuming you can afford to get the mold made, you'd have to buy a minimum
of several hundred pieces for most manufacturers to take your order.

Now, this is just my experience - I work with a lot of large companies, so
I don't know of anyone out of their home doing anything like sand casting,
vacuumforming, or other types of plastic molding. Usually a good rule of
thumb is the NRE (non-recurring expense) is inversely proportional to the
piece price. Meaning, the lower the cost of the custom part, the higher
the cost of the tooling or what has to be done to set up manufacturing of
the part.

Best Regards,

Joe Grisso
Detachment 3 Media

> Has anyone tried this? I recently stocked up on a variety of tactiles on
> ebay, assuming that the caps wouldn't be too hard to find... Much to my
> surprise these seem quite rare, and certainly lacking in variety. Mostly
> black circles and squares, ho-hum. I remember reading about how some
> people
> were molding plastics to make their own knobs and such (on another forum,
> I
> believe) and the designs I want and pretty simple in terms of shaps, no
> embedded LED's for the most part. Has anyone worked with this kinda thing?
> What I'd really like is a soft-touch rubber material in several colors...
> But I'm clueless where to start. Elastomers?
>