25 Aug
2000
25 Aug
'00
5:47 p.m.
Though they make special materials for making molds and castings in them, I
rather suspect that this is a simple enough one that you can easily save
some hassle and use components you get at the local lumber yard and/or
crafts store rather than having to buy then from a specialty house. You're
an engineer, and you can probably figure out how to make a mold. Silastic
copies every detail. You won't believe how precisely it does it. It even
copies paint finish.
These silastic molds require two things. (1) a way to give off acetic acid,
which is the inhibitor that keeps them from curing in the container
(usually a caulk tube) and (2) a way to get the silastic out of the mold
with the model in it so you can cut the mold in half for later extraction of
the new plastic part. I personally have used a vertical milling machine
(Bridgeport) to make the molds for fairly simple models with only a couple
of bends. if your mold is in two pieces and fairly thin, you'll have no
trouble getting it out of a two-part mold.
If you cut the approximate but generously cleared shape appropriately into a
2x4 which you can later cut in half, that's worked for me. The trick is
that the two-part mold have an open top so (a) you can put the model inside
before putting the halves of the mold together, and then, having fastened
the halves together, you can introduce the silastic. If you use the clear
stuff (costs about $2 for a tube) you can see the bubbles and manipulate
your material so no bubbles turn up on the surface of your model.
There are lots of steps, but when you're done, you have a silastic mold
that's reusable, gives an excellent finish, and lets you make excellent
copies of an original that may be totally useless for anything except a
model. If you need encouragement, email me. If you want details, remember
that each job is different.
Dick
----- Original Message -----
From: Dwight Elvey <elvey(a)hal.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, August 25, 2000 10:19 PM
Subject: Re[2]: Intel PT reader
Hi
I agree that there will be a change in index but my exerience
with solvent welding is that unless done right, you get bubbles.
This is worse at blocking light.
Richards idea is a good one.
Dwight
"ajp166" <ajp166(a)bellatlantic.net>
wrote:
> >Joe <rigdonj(a)intellistar.net> wrote:
> >> I recently picked up a nice Intel paper tape reader (model
Intellec
> >> 8-90?) to go with my Intellec MDS
system. The only problem is that
the
> light pipe in it is broken. However both parts
are still there. Does
> anyone have any suggestions about how to fix the pipe or where I can
get
> another one?
I'd check the plastic to see if it's suitable for solvent weld. Epoxies
tend to build
an optical discontinuitys as they are very different form the actual
plastic.
Allison