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I've never done this before - so I'm making it up as
I go along. I really would not recommend doing this unless you are
well experienced in this kind of activity.
First some caveats: vacuuming forming involves melting plastic with a lot of
heat, so some precautions are advisable:
 | This needs to be done outside and away from things
which could burn |
| protective gear should be worn for eyes, lungs, and
possibly hands. |
| it's a good idea to have a fire extinguisher on hand
(although I haven't needed it... yet) |
| Try not to melt the shop vacuum hose (!) |
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Lighting diffuser panels are
made for suspended ceilings, and are very cheap since they are
mass-produced. There are several different patterns - I used the
"cracked ice" pattern as it looks semi-random. The panels are
available in either residential grade styrene, or commercial grade
acrylic. The acrylic are more expensive, but seem to vacuum-form only
about as well as the styrene ones.
I cut these panels in half as they come in a 2'x4'
sheet, which is exactly right for two roundels.
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First the lighting
diffuser goes in the frame.
On the first try I oiled the mould with cooking
oil to stop the panels from sticking, but it turned out that they
don't soften enough to get sticky, so this was probably not
necessary.
The frame is latched closed (below left)
Then we turn on the shop vacuum... (below) |
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It's important to heat carefully and give the
vacuum time to do its work - if you overheat an area the plastic
will melt and a hole forms. As soon as that happens you lose the
suction, and the plastic will begin to lose the mould shape.
Fortunately it doesn't stick to the mould.
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We apply heat... and more
heat...
The
heat source here is a flame weeder, which puts out a lot of BTUs -
I'm not sure how many, but more than my camp stove, and more than a
barbecue I think. The wood gets a little scorched, but doesn't smoke
or burn. |
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We cool it off with a
water spray from a garden hose with the vacuum still running so the shape gets fixed
before we release the suction.
We remove it from the mould (below left)
... And that's all there is to it (below right) done
in less than a minute. |
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