Thermoforming

Forming techniques are widely used in industry, from stamping and forging metals to thermoforming plastics.

Alongside extrusion and injection molding, thermoforming is one of the most important plastic transformation processes. However, unlike these other two processes, which use raw materials in granular or powder form, thermoforming is based on a plate or sheet [AM 3 644] , i.e. a semi-finished product which is itself the result of extruding a raw material from granules or powder.

Producing a thermoformed object is therefore a two-stage process, which can take place in-line or in a rework operation; the thermoforming operation itself corresponds to the second stage. It enables us to produce objects of widely varying thicknesses, from a few dozen micrometers to more than a centimeter, and to work at very high production rates, with low-cost tooling that compensates for the handicap of the cost of the raw material, a semi-finished product.

Thermoforming has a very broad field of application, covering markets as diverse as food and non-food packaging, household appliances, sanitaryware, the automotive industry and more.

Most thermoplastic materials (PS, ABS, PE, PP, PMMA, PVC, PET, PLA, etc.) are easily thermoformed, as are lightweight/expanded polymers [AM 3 343] and multilayer semi-finished products [AM 3 659] . Some lightly cross-linked thermosetting materials can be thermoformed, but to much lesser depths than thermoplastics: for example, polyurethane foam used in car door trim applications.

To understand the thermoforming process, you need to know not only the classical engineering sciences, based on industrial and laboratory experience, but also polymers. In the following presentation, we have endeavored to relate practical observations to a more scientific viewpoint.

The variety of...