Vacuum forming of plastics
In vacuum forming, a heated thermoplastic sheet is pressed against the mould by a vacuum. The result is a formed part that reproduces the mould’s shape exactly. Masterplast, Aikolon Group’s production plant in Vantaa, has five vacuum-forming machines, which can be used to produce items of varying sizes. Our largest machine has a forming area of 1,800 × 2,800 mm.
The process involves heating a plastic sheet with the plastic-forming machine’s electric resistors. Once the plastic has reached its forming temperature, air pressure is applied to stretch it into a bubble. Simultaneously, the tool table containing the mould is raised, so that the mould is positioned inside the bubble. Then, air is sucked out of the bubble through introduction of a vacuum, after which the item is cooled and released from the machine. To complete the process, excess material is trimmed off, and any necessary holes or slots are drilled in the formed part by means of CNC technology.
The moulds used in vacuum forming can be made from a variety of materials, such as wood, aluminium, or polyurethane resin (for example, ebalta materials, Cibatool, or SikaBlock). The choice of the mould material depends on the quality required of the end product and the batch size.
Materials used for vacuum forming
Numerous thermoplastics are suitable for use in vacuum forming. Some plastics (such as PC and PP) must be pre-heated before the vacuum-forming process begins. Sheets used for vacuum forming usually are 1–10 mm thick.
The most commonly used materials: