Thermoform or Vacuum
In the vacuum or thermoforming process, a sheet of hot plastic is draped over a form or mold and the air is sucked out from between the form and the plastic, causing it to take the shape of the form, then the sheet is cooled and removed.
Vacuum forming molds may be less expensive and can be made from various materials. The required cooling time means that it can be a slower cycle time to produce parts than injection molding.
However, if large thin parts are needed in small to medium quantities, vacuum forming is an ideal process.