the workpiece and the temperature is
raised until the sheet is almost molten.
At this time it is lowered onto the mould and air is
sucked out which forces the heated sheet to take the
shape of the mould.
The thermoformed sheet is then cooled with blowers and
removed from the frame.
Variations of the process includes male or female tools,
plug assistance, pre-blow, pre-stretch and rarely,
airbox pressure assistance. Materials used for vacuum
forming become thermoplastic at forming temperature and
offer little resistance against deformation.
Unlike the thermo-elastics however, they cannot be
satisfactorily de-moulded to a flat state. The majority
of tools are manufactured from hardwood, plywood and
Where long runs are planned, cast aluminium tooling or
skeleton steel tooling is used.
Owing to better heat conduction this has an effect on
the reduction in the cooling cycle and requires less
repair and maintenance.
The preferred material for tooling in vacuum forming is
There is of course an increase in the cost involved and
of lead time for tooling manufacture.