INTERIORS AND EXTERIORS | AUTOMOTIVE
provides the required protection for the wheels. Automotive exterior components have to display high scratch-, weather-, ageing and chemical resistance properties, says Covestro. For wheel blades there is the additional requirement of high heat resistance during braking. In combina- tion with the coating system, the composite wheel blades have withstood rigorous safety and perfor- mance requirements, such as impact, chemical and weather resistance. The Makrolon PC on which Maezio is based has high thermal stability qualities so the wheel blade insert can survive braking- induced temperatures of up to 150°C. Maezio compounds can be easily joined with functional components during processing, for example, through back injection moulding. In the case of the wheel blade inserts, they are joined with the aluminium spokes of the wheel through back-moulded screw bosses made of PC. The common resin material makes it easy and secure to bond the two parts. Maezio compounds can be cut and re-melted for reuse at the end of life, or reground into short fibre compounds and used in an injection moulding process, making them a sustainable material choice for EV manufacturers, says the company. PC compounds from Covestro have also been used for a new range of roof spoilers for automo- tive exteriors. The spoilers are equipped with numerous functions. These include sensors, cameras and 5G antennas. The antennas perform important tasks in driver assistance systems. Rear lights and elements for ambient lighting are also integrated into the spoilers. Some of them are designed using black panel technology, which means that they look like flat, dark surfaces if the LED elements concealed behind them are not activated. The 3D surfaces of the spoilers can be designed in different colours and with adjacent high-gloss and matte areas. The components are optimised for low weight through low wall thick- nesses and the low density of the engineering plastics, as well as using sandwich structures with a lightweight foam core made of expanded Makro- lon (E-PC), providing good thermal insulation. Covestro adds that the spoiler materials are tough, which is maintained even in cold temperatures, benefiting safety. The dimensional stability of the thermoplastics is also high when exposed to heat, so that narrow gaps between adjacent components (zero joint optics) can be achieved. Continuous fibre-reinforced thermoplastic from
Lanxess is being used for lightweight car design as an insert for structural reinforcement for A-pillars. These lightweight applications for the design of
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Lightweighting road sweepers in the UK
Injection moulder Broanmain Plastics has assisted street cleaning vehicle manufacturer Johnston Sweepers in the UK in switching from metal fabricated components to plastics moulded parts. For some time, Johnston Sweepers had considered switching from metal fabrication, predominantly steel, to plastic components for vehicle components, such as caps, levers and water outlets. However, low production volumes combined with the initial capital outlay for mould tooling, made the investment hard to justify. Addi- tionally, with vehicles exported globally, components needed to be able to withstand extreme hot and cold temperatures, and perform in wet, dry, dusty and sandy environments. Speeding up the manufacturing process for parts and address- ing weight constraints is increasingly important, according to Steve Hurst, Head of Purchasing at Johnston Sweepers. Starting with the filler cap, Broanmain collaborated with Johnston Sweepers’ in-house design and purchasing teams to develop an initial prototype and trial the strength and durability of plastic materials. “Changing the process from metal to plastic means that the part has to change subtly. It isn’t a one-for-one comparison, so it was important to have our design team working closely with Broan- main,” says Hurst. “The thickness of the components also proved to be a key challenge,” says Wilf Davis, Broanmain’s Managing Director. “We worked with material suppliers to source a dimensionally stable thermoplastic that would meet the tolerance requirements, opting for glass-filled PA for the thicker components that required strength and ABS for the ascetic components.” Johnston Sweepers estimates that switching from aluminium to plastic for the caps has reduced the part cost by half. Since then, Broanmain has helped convert more than 30 metal parts to plastic, among them a complex suction water outlet integral to the road sweeping operation that required extensive welding and powder coating. Broanmain’s most recent development is a holster for the pendant that enables a driver of a sweeper to walk outside of the cab and operate the machine to lift and tip the body.
November/December 2019 | INJECTION WORLD 61
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