out of the vacuum formed part you can use compressed air and blow some air
between the formed part and the mold, this will make it easier to separate the two
in some cases. Chalk dust or other release agents can also be used on the mold
to make the separation easier (Not on clear plastics).
If you need help or have questions we can be contacted at :
General Comments and tips
·
If your mold has undercuts you might have to cut the plastic to get it out.
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You can easily use common items as molds for practice or make custom
molds from plaster, metal (any kind), wood or experiment with different
materials. Some molds will require a hole to be drilled from top to bottom
so air can go through. This is usually needed in areas where vacuum will
have a hard time pulling, like recessed parts in a mold.
·
You can also make a duplicate mold by vacuum forming a part and
pouring plaster of Paris/liquid plastic/2 part polyurethane in the mold and
letting it cure. In order to get a crystal clear part (using clear plastics) the
surface of the mold has to be very smooth.
·
Please make sure your mold has the correct geometry for vacuum
forming. The picture below shows the general shape of a mold that is
suitable for vacuum forming.
Plastics:
In General most plastics are vacuum Formable. The type of plastic you decide to
use should depend on your application. Some are harder than others and some
form with better detail. One important thing to remember is that some plastics
will absorb moisture if they are stored improperly or if they are old pieces. If you
get bubbles in the formed part(s) then the plastic has absorbed moisture in it.
Polycarbonate or Lexan may need pre-drying first in a circulated oven before use
for about 1 hour (at 150-200° ) or more depending on the thickness and moisture
level. Some other plastics may also need pre-drying before use, please check
with your plastic supplier. For food related or other products that need to be
clear PETG (FDA approved) is the most common plastic used and it forms
around 300 -330°. You can also use it for packaging, sign making, chocolate
molds and almost anything else. ABS and Styrene are great for all around use
and from around 350-390°. There are many other plastics but these 3 should be
on the top of your list. Polycarbonate is a tough plastic but it is also hard to
vacuum form. It requires a very strong vacuum, the sheets need to be pre-dried,
