Thermoforming is one of the oldest and most widely used forming processes in the plastics industry. It involves heating a thermoplastic sheet or preform to a temperature where it becomes soft and pliable, then forming it into a desired part shape using a mold. In the U.S., the breadth of applications for thermoforming are endless. From airplane components to medical products, to lawn and garden equipment, to automotive parts and packaging, products made with thermoforming dominate the market.
Compared to other forming processes, such as injection molding and blow molding, thermoforming has a number of advantages. These include shorter start-up time, lower tooling costs and can provide design flexibility in the use of multiple materials within the same part. Moreover, thermoforming can be used to produce a wide variety of shapes and sizes, including complex three dimensional shapes.
At its most basic, thermoforming can be divided into two main processes: vacuum forming and pressure forming. Vacuum forming involves heating a sheet of plastic and forming it over a mold using a vacuum. The vacuum sucks the plastic sheet against the mold and holds it in position as the sheet cools and hardens. Pressure forming involves the same basic steps, but in addition to the vacuum, air pressure is applied to the backside of the plastic sheet in order to further define the shape of the part.
Vacuum forming is typically used for low- to medium-volume parts, where tooling costs are the most important consideration. It is ideal for simple parts without intricate details, such as flat plastic trays or clamshell packaging. Pressure forming is typically used for higher volume parts, where a more complex shape is required, such as medical device enclosures or automotive trim.
The process of thermoforming is relatively simple and straightforward. First, a sheet of thermoplastic is heated until it is soft and pliable. Next, the sheet is placed on top of a mold and held in place by either a vacuum or air pressure. Then, once the plastic is modeled around the mold, it is allowed to cool, which allows it to harden into the desired shape. After cooling, the part is released from the mold, trimmed of any excess material, and then inspected for quality.
Thermoforming continues to be an essential process in the plastics industry, with ever-increasing demands for accuracy and precision. As companies look to reduce cost and remain competitive in the marketplace, thermoforming is increasingly being used for higher volume production parts. Moreover, advances in controls, materials, tooling and process design are allowing companies to push the boundaries of what thermoforming can achieve.
