Plastic thermoforming is the process of heating sheet plastic and forming it into or over a mould.

The thermoforming process uses vacuum, air pressure and/or mechanical forming to move the heated and softened plastic in contact with the shape of the cool forming mould. These forming moulds are usually made of aluminium and are water cooled.

Plastic thermoforming companies usually specialise in either thin gauge or thick gauge thermoforming.  Thin gauge thermoforming usually refers to a performing material thickness range from 0.05 to 0.080 inches. Heavy gauge continues from that point to thickness in excess of 0.5 inches.