There are two factors propelling the use of thermoplastic composites in automotive applications, says Norbert Müller, head of Engel’s Centre for Lightweight Composite Technologies.
First, a consistent thermoplastic approach makes it possible to efficiently integrate the forming and functionalisation of fibre-reinforced prepregs, which reduces unit costs; second, the use of exclusively thermoplastic polymers makes it easier to develop recycling strategies.
To meet these needs, Engel developed the organomelt process, in which fibre-reinforced prepregs with a thermoplastic matrix such as organic sheets and tapes are heated, inserted into the mould, formed there and directly overmoulded with thermoplastic. This has since become a well-known process, used in high-volume manufacturing for the fully automated production of items such as front end carriers.
Now, Engel is collaborating with its customers and partners on the production aspects of designing composite components with a targeted load distribution. At the upcoming K show, a moulding process developed in partnership with automotive supplier Brose, will be demonstrated. A production cell will show how different prepregs can be combined to tailor the lightweight construction characteristics to a component’s specific shape as well as the different stresses on individual areas inside the component, said Müller.
One of the challenges with processing organic sheets is the heating of the prepregs. The time they take to heat and cool depends on their thickness. The organomelt production cell at K will demonstrate how three organic sheets of different thicknesses - 0.6mm, 1 mm and 2.5 mm - can be heated at the same time. To that end, the cell, based on a duo 3660/800 injection moulding machine and including three easix robots, will feature two integrated IR ovens: a vertical IR oven positioned directly above the clamping unit to heat the 0.6mm thick organic sheet; and a standard, horizontal IR oven on a pedestal above the moving platen for the two thicker organic sheets. This high degree of integration make this complex cell one of the most sophisticated systems on display at K 2019.
Two of the robots, mounted next to one another above the clamping unit, handle the organic sheets; the third, located next to the clamping unit, removes the moulded part, while at the same time moving one of the three organic sheets into the mould for the injection moulding process. The IR ovens and the three easix robots are fully integrated with the IMM’s CC300 control unit and can be centrally controlled via the machine’s display.
Kingfa is supplying the PP glass-reinforced organic sheets, which are formed when the mould – built by Georg Kaufmann Formenbau – closes. Immediately afterwards, they are overmoulded with glass fibre-reinforced polypropylene in the same mould. Designed with reinforcing ribs on the back of the component, the visible side features a leather-look grain, something hitherto considered impossible, said Müller. “In that regard, we’re laying the foundation for producing large structural thermoplastic door structures using the organomelt process in the future.”
Engel can be found at K 2019 in Hall 15, stand C58