The term “thermoforming” refers to a process in which a film or sheet of thermoplastic polymer is heated in a controlled manner to temperatures close to the material’s glass transition temperature; the plastic sheet is then shaped into a specific geometric form using airflow, vacuum, mechanical force, or even a combination of these methods.
While in this deformed state, it is cooled to room temperature, ensuring that the resulting three-dimensional shape retains its form at the operating temperature. In industry, this process is carried out continuously, requiring multiple processing stages known as stations. These stations are arranged sequentially to produce the final product as efficiently as possible.
Film feed system.
The function of this system is to provide the rolled film with motion that is synchronized with the process from which the packaging will be produced, starting from the moment it is unwound at the front end of the machine, known as the material feed. It is then held in place by a chain system or an automatic servo-controlled feed mechanism.
At this point, it is important to verify that the film is positioned correctly, as it has a mark indicating the side where the cover material will later be welded.
Preheating Station
When the polymer material is conveyed by the transport system to the preheating station, the thermal process begins. At this station, the film is heated until it reaches the proper consistency so that, upon passing to the thermoforming station, it can take the shape of the container. Although this phase of the process may seem simple, it is important to note that it must be precisely controlled to achieve the proper temperature in the film—above the glass transition temperature (Tg) and close to the crystallization point (Tm)—both of which depend on the type of material. Before the film reaches the point where the container will be thermoformed, it must not be too hot, as it would flow and “sag,” losing important chemical and physical properties necessary to continue the process; nor should it be too cold, as in that case, the desired geometry would not be achieved, or there would be problems with the uniform distribution of the polymer within the container, compromising its aesthetic qualities and mechanical strength.
Thermoforming Station This station is the most important part of the process, not only because it is where the container is precisely formed, but also because of the complexity involved: it is here that the various mechanical, pneumatic, and electrical drives, among others, operate in a coordinated manner and are precisely adjusted to achieve the desired result.