Free Forming This method of thermoforming does not use a mold. Instead, an acrylic sheet is clamped in a frame and either a vacuum or compressed air draws the material to a desired depth. An electric eye determines when the proper depth has been reached and cuts off the pressure. Since only air touches the sheet of material, there is no markoff. Free forming is used to create windshields for planes, skylights, or anything where optical quality is necessary.
Advantage is achieving high clarity.