Vacuum molding is a type of manufacturing method that takes thermoplastics and forms them through a molding process into a wide variety of plastic products. It offers low tooling costs, quick start-up and cost efficiency for small to medium production runs.
The food and beverage, sporting goods, electronics, medical, appliance, automotive, cosmetics, telecommunications and commercial goods industries all use vacuum forming processes that heat a sheet of plastic material and shape it through a mold, adhering it by use of a vacuum pump system that rids the molding area of air.
The most common products made from vacuum forming processes are plastic packaging. The three different types include blister packs, clamshells and plastic trays, all of which are used to protect, transport and display many different commercial products for sale. Many different plastics are used, including polyester (PET), used for packaging, high density polyethylene (HDPE), which makes bottles and bags, polyvinyl chloride (PVC), used for food wrap, vegetable oil bottles and blister packaging, polypropylene (PP) food containers and caps, high grades of polystyrene (PS) which are best for products like disposable plastic silverware, CD cases and cartons. Other materials that may be used in plastic forming services include acrylonitrile butadiene styrene (ABS), acrylics, polycarbonate and Kydex, which is a PVC-based thermoplastic.
There are different methods of plastic forming, the most popular of which is vacuum forming. Vacuum forming, also called thermoforming, is one of the oldest plastic forming techniques. The process begins when a plastic sheet is fed into an extruder, heated in an electric, infrared or natural gas heater and then transferred to a forming station where two mating molds made of aluminum enclose the sheet.
A vacuum removes all the air from the molding environment, forcing the sheet of plastic to adhere with the two molds. After the newly formed part has dried and cured, it is ejected from the mold and trimmed if necessary.
Pressure forming and twin sheet thermoforming are slightly different techniques. Pressure forming uses the vacuum environment and additional air pressure to increase the tightness of the sheet to the mold to create more detailed products. Twin sheet thermoforming takes 2 separate sheets of plastic, forms mirror images of each other, and then welds them together, forming a hollow product with a small seam running down the middle. Most plastic parts formed through all of these processes must have a shallow depth and are 3 dimensional.
Vacuum Molding Informational Video