Hot Projects List -- Nav Lights

cavelamb himself wrote:

Another advantage of using the clear plastic is that it is possible to
get AR grade scraps. The AR grade is scratch and UV resistant. I
also found it to be much less brittle that any plexiglass or lexan
I've ever worked with in the past. I was able to cut the 1/8" sheet
very effectively with a pair of sheet metal shears (then I cleaned the
sides up with a belt sander, followed by a 400grit sanding block).


Nice for flat parts, but how does it heat form?


I haven't tried it yet, but it sounds like a "hot project" that I need
to get around to.

"cavelamb himself" wrote

Nice for flat parts, but how does it heat form?

Do some googling over in rec.models.rc.air. The subject comes up fairly
often, as it has around here, as I seem to recall.

There is a need to get a very smooth mold, and cover it in felt, or have a
very perfect hard plug. Any cloth with texture will transfer the weave to
the plastic.

You mound the plastic in a frame, and either pull mold it onto the plug
(which is sticking up off the table, so you can pull well past the bottom of
the mold) or vacuum mold it. Wait until the material starts to sag pretty
good, and stick it over the mold and pull, or use the vacuum table method,
if it is a complex part.

The only major difference (other than a slightly different heat requirement)
between plexi and lexan, is that you need to bring the lexan up to over 250
degrees and keep it there for an hour or so , to drive the moisture out of
the plastic. Weird, that there can be water in plastic, to me! g

You just have to look at the material and get the right timing when it sags
just right. Also, that your part will only be as good as your mold.

Also, sports fans, remember to fix up a special drill bit before you drill
the plastic to mount it. Use a dremel, and grind a couple degrees negative
angle on the bit, so it scrapes the plastic, rather than pulling through the
plastic, and cracking it.
--
Jim in NC