A quick lesson to give you a rough idea of how it is done.
 I am going to try to tell you in as few words as possible, how vacuum formed molds are made.
The first step is making the "buck". This is the name of the piece that the forming will be done over. This has to be smooth,
strong, heat resistant, and free of undercuts. The smooth part is self explanatory. The strong part is so that it will not be crushed
when the plastic is being formed over it. The heat resistant part is because the plastic is at about 300 degrees F. No undercuts
means that you will be able to get your piece out of the mold without having to cut the mold off.
All these are of equal importance. They all must be done, and done right! This is the time consuming part of making the molds.
Once this has been done the buck is placed on he table of the vacuum forming machine.
This machine is the costly part of making molds. It makes it possible to evenly heat and then mold the plastic. The bigger the
molds you require, the bigger the machine you need. They go up in price according to the size of the plastic that they can
handle.
The machine has two basic parts,
1 - the heater - it controls the temp of the plastic within the range determined.
2 - the vacuum pump - it sucks the air out from under the sheet of plastic when it has been brought down to the vacuum
table.
The blank piece of plastic is clamped into its frame and heated.
As soon as the plastic has reached it flow temperature it is pressed down onto the buck and vacuum is applied at the same time.
The plastic forms over the buck and cools. This takes about 15 seconds!
Once it has cooled (about 30 seconds) you pop the buck out, take the plastic out of its clamp frame and trim out the mold!
That's it!! The mold is ready to use and will make about 30 or 40 castings if you look after it. You should check out these sites for
more ideas.
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Delmar Germyn
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