Introduction to Vacuum Forming
Vacuum forming, or sometimes thermoforming, is the process by which plastic molds are made. The general process is as follows:
Heat plastic to a point at which it becomes soft and flexible.
Put the plastic over the top of the object (model) you wish to make a mold of.
Use a vacuum source to suction out the air between object and the plastic.
As a result of the vacuum suction, the plastic will take the shape of the object.
Turn off the vacuum and let the plastic cool.
Separate the plastic from the object.
In order to vacuum form, you need a vacuum forming machine. A vacuum former, or thermoformer as it is also called, is a special type of machine that consists of a forming area (the place where you put the object to be molded), a device to hold or manuever the plastic, and usually a heating element. There are many different types of vacuum forming machines ranging from simple ones that you can make at home for less than $20, to very large and expensive industrial size machines. Several different companies are selling machines on the internet that are clean, work well, and can be used in the home or small business. The price ranges from $100 to $900.
There are many different types of plastics that can be vacuum formed. The type of plastic used will depend on the application. If you are making chocolate or candy molds, you need to make sure that the type of plastic you use is FDA approved for contact with food, also called food-grade plastic. Generally, hobby grade chocolate molds are made with PETG and more expensive molds are made with polycarbonate, but there are many other types of plastic that can be used. Your plastic supplier will be able to tell you which materials meet this critieria. There are several vacuum sources that can be used. In its simplest form, you can use your home vacuum or shop vac for suction. These are good for pulling air out quickly and are really all you need for forming objects without much detail. If your object has alot of detail, such as when trying to form letters or logos, you may want to use a vacuum pump or air compressor. These objects pull air more slowly, but they can pull more air out, and thus capture more detail. The more expensive vacuum forming machines have built in vacuums. These work the best, but it is really hard to find one without making an substantial investment.