Design & Technology Resources
Vacuum forming is a method of forming plastics into a particular shape. The process involves heating up a thermoplastic, usually HIP (High Impact Polystyrene) and sucking it over a mould until is cools.
The first process involves manufacturing a mould. In school we generally use MDF but other heat-resistant modelling tools can be used. It is important that the sides of the moulds are drafted otherwise it would be very difficult or impossible to remove the mould when the process is finished.
The description below shows us how to make the hull for a model boat
Turn the vacuum former on.
Place the mould onto the table.
Place the HIP (High Impact Polystyrene) sheet on top of the machine. HIP is a thermoplastic, this means that it softens when heated up and goes back hard when it cools.
Pull the clamp frame down and secure using the clamps.
It is important to make sure that the plastic covers the whole of the top of the machine. If it doesn’t then it won’t be able to develop a vacuum.
Pull the heater box over the plastic using the two handles. This will then start to heat up the plastic.
You must be extra careful as the heater box gets very hot.
After about five minutes push the heater box back and check how soft the plastic has become by touching it with your finger or a piece of wood. If the plastic is hot enough it should dent slightly when pressed. If the plastic is too hot it will sag and smoke a little, it is unlikely that the process will work in this case.
If the plastic isn’t warm enough or sufficiently flexible you should pull
Once the plastic is warm enough, pull down the table rise/fall handle. This will lift the table and therefore the mould so it touches the plastic.
Switch on the vacuum pump and you should see the warm plastic form over the mould.
After about ten seconds you can switch off the pump.
Lift up the table rise/fall handle and the mould should lower back into the machine. Once the clamp is released you should be able to remove the finished product.
The moulded plastic can now be cut to size.