In automotive engineering there is a growing trend towards touch-sensitive control logic as an interface between man and automobile. By combining a thermoplastic base support, a capacitive sensor foil and a functional coating of polyurethane (PUR), such hybrid parts can be realized. And in order to bring these products to market, a cooperation between Hennecke GmbH, Engel Austria GmbH and the Plastics Institute in Ludenscheid focuses on the issue of painting in the mould, taking advantage of many years of experience from the Clearmelt and Clearrim process.
In the Clearrim process, a thin layer of PUR is introduced under high pressure into the mould cavity in order to finish thermoplastic support elements with natural surfaces. The work required for post-processing and the level of emissions are significantly reduced in comparison to painting. Through the use of special polyurethane raw material systems it is even possible to create self-healing surfaces, where the focus is not only on the surface feel, but also on functionality. A further advantage of the Clearrim technology is its ability to be combined with accompanying processing methods. An example is the Clearmelt technology, a process resulting from the collaboration between Hennecke and Engel Austria GmbH. In this process, thermoplastic mouldings are combined with decorative film overlays or wooden inserts by means of injection moulding. The actual finishing process using the transparent PUR system is carried out in the same production cell.
With the additional integration of a capacitive foil, an elementary added value has now been incorporated into the new product. A cockpit centre console can serve as an example: the thermoplastic base support is injection-moulded using a turnplate device made of PC/ABS, while at the same time on the second side of the mould the premoulded part produced in the previous cycle is coated with polyurethane. The capacitive foil is inserted into the mould before the first component is injected. In this part, the PUR layer fulfills several functions at the same time. The main focus is on protecting the high-class surface against chemical and mechanical attack. One important side effect is the high degree of gloss of the coating and the depth effect that is achievable, which produces the impression of extremely high quality.
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Effective protection, a high degree of gloss and impressive depth effect: PUR layer on the thermoplastic base support of a cockpit centre console (photo: Hennecke GmbH)
