Vacuum Forming

What is Vacuum Forming?

Vacuum forming is one of the oldest methods of processing plastic material into desired shapes; and are used on some of the most common items we see around us each and every day, such as yoghurt pots shower trays, and vehicle dashboard parts.

Vacuum Forming

Vacuum Forming Process

The first part of the process is making the mould which, dependent on the level of detail required, could be simply cut by hand from a wooden block, or machined in its own right using CNC Milling methods.

The mould is then placed into the machine and clamped down, along with the sheet of plastic material. The clamp and frame of the machine needs to be powerful enough to ensure this is firmly held in place and not moved during the forming process; else the final product could be distorted.

Vacuum Forming
Colagor, Public domain, via Wikimedia Commons

Heaters, usually with infra-red elements and reflectors, evenly heat the sheet over the entire surface area to ensure the best forming results. Any areas which aren’t heated to the correct temperature could be more rigid and not form correctly over the mould.

Once heated, the sheet of material (on some machined) is pre stretched to ensure the wall thickness of the final product is uniform and then draped over the mould; while a vacuum pump draws out the air between the sheet and the mould to form the desired shape.

Once formed, the plastic must be allowed to cool before it can be released from the machine. This is often done through the use of fans or though a cold spray mist to speed up the cooling process.

Secondary machining can be completed on the formed product to trim the excess material and add in any slots, holes etc.