Model system for thermoformed packaging

Thermoforming represents a cost-effective and resource-efficient process for manufacturing plastic parts. A high level of process stability is needed to ensure that production is economical. This is based on precise material characterization/selection, state-of-the-art machine technology, and optimum interaction between the two. The focus of the work being done at Fraunhofer IVV in this respect is on the investigation, description, and optimization of mechanical engineering solutions and the overall process.

A detailed specification of thermoformability is a basic prerequisite for the targeted selection, further development, and quality control of thermoforming materials, processes, and equipment.

Despite intensive research work by numerous institutions, however, there is still no generally valid and industrially applicable test method available for quantifying the thermoformability of a thermoplastic.

As demonstrated by an already completed project at Fraunhofer IVV, thermoformability is described with the aid of a thermoforming test rig using sample molds. Forming parameters (temperature, time, etc.), achievable forming depth, and wall thickness distribution (WTD) are recorded and analyzed on the basis of thermoforming tests. Nevertheless, it is only possible to make limited claims regarding the molded parts.

In a planned research project, specifying thermoformability depends on a large number of individual optical, functional, and forming criteria, which are evaluated one by one using simple substitute tests. This approach makes the qualitative assessment of thermoplastics possible with regard to their thermoformability based on the requirements for the end product.

Performance

To investigate the thermoforming behavior of plastic films, the parameters of heating time and temperature and of forming time and pressure are freely definable. The test rig’s modular design allows a wide variety of mold inserts to be used. One investigational emphasis is evaluating the forming behavior under reproducible conditions.

Control and Setting Parameters

• Sample dimensions 150 mm x 150 mm x 0.05 – 2 mm
• Max. mold insert size 100 mm x 120 mm
• Heating temperature up to 160 °C
• Heating time as of 1 s
• Forming pressure up to 6 bar
• Forming time as of 250 ms