Must-have PDP-11 ... GOLD PLATING AND SWITCH HANDLES

[vrs]

> I've done some 2-part rubber silicone resin moulding for military
> encapsulation-
> pretty well the only well we could get the bubbles out was to cycle vacuum
> in a bell jar and purge ..took half a dozen cycles to get a reasonable
> smooth finish..

The molds are not having a problem with bubbles.  The resin does tend to
trap bubbles.  Partly that is because it sets up so darn fast.


> you using an anginate mould? I was thinking perhaps wax or plaster might
> be more tolerance accurate... the mould is the issue  - it's hard to get
> the 'axle' bits without make two half moulds and filling them, unless one
> goes with a one piece mold and metal pin axle.

True; the axle bits can be done by over-sizing the mold indentations for the
pins.  Then they still trap air, but you just trim off the bubbles (before
things get too hardened).

I actually like the metal pin axles.  They seem more robust.  Making little
plastic axles is fussy work and it feels like it is propagating a design
problem from the originals.

    Vince