Vacuum forming is the process that moulds sheet plastic into the desired shape through vacuum suction of the warmed plastic onto a mold. Vacuum forming can be used for many thicknesses of plastic sheet and can provide great strength in its finished moldings. Fairly complex moldings can be achieved with vacuum forming. Vacuum formed plastics are invariably thermoplastics because thermosetting plastics assume their final shape through heat and so can not be molded with this process.
Thermoforming is the process that moulds sheet plastic into the desired shape through the pressing of formers into the warmed plastic. Thermoforming is used primarily in low-cost applications for the simple embossing of thin plastic sheet and cannot be used to form as rigid shapes as vacuum forming is capable of.