Integrating injection and thermoforming is a hit for moldmaker at K Show

One of those is Georg Kaufmann Formenbau AG, a Swiss mold manufacturer that developed and debuted at K a molding technology it calls GK LIPfibre (Georg Kaufmann Lightweight Integrated Process fiber). The process demonstrated at K combines the injection molding and thermoforming processes to produce lightweight structural components from glass fiber reinforced thermoplastic composites. The resulting components have high strength and rigidity and are 25% lighter than comparable metal components. Special interest is being shown by the automotive and aviation sectors, but the company says it has application in many other market segments.

The system at K was a collaboration of GK with Audi, Krauss Maffei, Lanxess, Bond-Laminates, and Jacob Composite, all Germany-based.  To produce the component, a passenger car side-impact modifier, a flat pre-heated sheet of fabric and glass fiber reinforced thermoplastic is thermoformed, and remains in the closed mold. In a second step, in the same mold, the part is enhanced by the injection molding of reinforcement ribs, corners and edges. The material for the ribs is a glass-fiber-filled polymer.

The innovative combining of thermoforming and injection molding requires a production system in which the individual processing steps are closely synchronized in order to guarantee the required quality and process reliability. The first stage of the process - the thermoforming of the glass-fiber-reinforced thermoplastic composite sheet - begins with a special cavity insert pressing the sheet onto the core and holding it in place.  Orientation of the fibers in the formed sheet is critical.

The mold remains closed at the end of the thermoforming process and the melt for the overmolded ribs, consisting of a glass-fiber-reinforced polymer, is injected via a hot runner system and bonds completely with the thermoformed sheet. Additionally, the melt flow endures that all sections of the part are fully formed and filled.

To develop this two-process mold the research production mold was equipped with several pressure and temperature sensors to monitor the various process stages, shaping of the glassfiber reinforced sheet during thermoforming, injection of the polymer melt, and complete filling of all corners and edges of the part. Future production molds will be equipped similarly but with fewer sensors to monitor the different steps in the process.