Thermoforming

Thermoforming is a manufacturing process for thermoplastic sheet or film that involves forming thermoplastic sheets or films into three-dimensional shapes through the application of heat and pressure.

In general terms, vacuum forming refers to all sheet forming methods. Basically during vacuum forming processes, plastic material is heated until it becomes pliable, and then is placed over a male or female mold. The mold then moves towards the sheet and presses against it to create a seal. Next, the application of a vacuum draws out the air between the mold and the sheet so that the plastic conforms to the mold exactly. This is accomplished through venting holes in the mold that are joined to vacuum lines. The mold also has a water cooling system integrated into it that brings the temperature of the plastic to the set temperature needed. When the curing temperature is reached and the piece is formed, air blows back into the mold and separates the new part from the mold.

Pressure forming is a variation of vacuum forming that utilizes both vacuum and compressed air to force the plastic sheet against the mold. As the platens are closed, the vacuum pulls on one side of the sheet and compressed air pushes on the other. This compressed air pressure reduces the cycle time and makes it possible to run at lower temperatures, it also improves the distribution of the material creating a more even wall thickness and enhances the detail of the part to a nearly-injection-molded quality.

This process is mainly used for parts that require styling and aesthetic qualities because pressure forming creates greater detail, allowing for textured surfaces, undercuts and sharp corners, which are not as easily created with vacuum forming.

In general terms, vacuum and pressure forming produces plastic parts for various industries, such as the food, cosmetic, medical, electronics, entertainment, household products, toys, athletic equipment, appliance, automotive, office supplies and clothing industries. One of the most important industries that thermoforming serves, however, is vacuum packaging. Products like blister packs, inserts, trays and clamshells are used to house other products and are important for both preservation of the items they hold and the aesthetic designs they can provide.

Thermoforming advantages

The greatest advantage to vacuum forming is that it involves less parts and tooling than injection molding, and therefore is more cost-effective. It is an economical choice that can be used for small and medium production runs, with low cost tool modifications. There is great design flexibility available, from a variety of prototypes to custom made designs that can be used to cover almost any product. Time of production is generally short, which frees up time to do more detail-oriented aspects of production. Sharp, precise detail is available for many products, which makes vacuum formed plastics an attractive alternative to other molding processes.