Thermoforming Glossary

VACUUM-FORMING: In this process, a sheet of heated plastic is positioned over a male or female mold. The mold is then moved into the sheet, creating a seal, and vacuum suction is applied to draw out air between the sheet and the mold. After a walter-cooling system in the mold cools the formed plastic, air is blown back through the mold to separate the part from the mold.

TWIN-SHEETING: Using a combination of pressure-forming and vacuum-forming, this process is used as an alternative to structural foam and blow molding to create parts of superior strength. Two sheets of plastic are formed on separate molds, then brought together and form-welded at multiple contact points, sealing the parts together. This allows hollow areas to remain throughout the completed part. These areas can then be filled with rigid foam or inserts can be placed between the two sheets to provide additional strength.

PRESSURE-FORMING: This process uses compressed air to “push” on the backside of pressure-formed material to create a greater level of detail on the outer surface. This offers the ability to add texture, form sharper corners for better logo or letter definition and create a tighter fit from part to part. Pressure-forming often offers a superior, more economical alternative to injection-molding.

VACUUM THERMOFORMING: Any process of forming thermoplastic sheet that is heated and forced to contact a mold surface and cooled to retain its shape.

HEAVY GAUGE: Commonly, a sheet with a thickness of 120 mils (0.120 inches or 3 mm) or greater.

MEDIUM GAUGE: Commonly, a sheet thickness between 60 mils (0.060 inches or 1.55 mm) and 120 mils (0.120 inches or 3 mm).