Pedal power through laser transmission welding
Keywords: Laser welding, Automotive
A high power, direct diode laser transmission welding system, from Herfurth Laser Technology, of Coventry, is being used by Birkby's Plastics Ltd in the manufacture of a new, electronic throttle control (ETC) pedal assembly for motor vehicles. The pedal, which is manufactured as a glass-filled nylon moulding, is being fitted initially to certain Ford models but it has wide-ranging application in the automotive industry (see Plate 4).
Plate 4 The electronic control pedal, which is assembled with the aid of direct diode laser transmission welding from Herfurth Laser Technology
Birkby's Plastics, of Liversedge, has an international reputation as a designer, manufacturer and assembler of plastic components for the automotive and business electronics markets, using state-of-the-art technology. Its new ETC pedal features an integrated, rather than a bolt-on, sensor, making it compact,economical and tamperproof compared with competitive systems. When it is operated by the vehicle driver, a demand signal is transmitted to the engine management system, which compares it with the ignition map, allowing the engine to be precisely fuelled to optimise efficiency, in terms of economy, performance and emissions.
The integration of the sensor within the pedal housing relies on welding the electronics "pot" precisely in position. Because the pot needs to be exactly located and zeroed, it was impractical to achieve the weld between the two plastic components by vibration welding. Furthermore, because two different grades of glass-filled nylon, with two different melting points, are used for the pot and the pedal, it was also impossible to weld the components together using heating techniques and ultrasonic welding.
The solution to the problem was found in direct diode, laser transmission welding. This technology relies on the fact that a joint can be produced between two plastic components if one component transmits high power laser energy and the other absorbs it. In many cases, the strength of such a joint can exceed that of the parent materials. In addition, unlike conventional laser welding techniques for plastics, which employ fibre optics, high power direct diode laser welding can generate a beam width of up to 20mm. Furthermore, the diode array ensures that sufficient, evenly distributed, controlled energy can be delivered across this beam width to achieve the weld required.
After successful trials at Herfurth Laser Technology's development centre at the University of Warwick, a direct diode laser transmission welding system has been supplied to AB Precision Ltd (ABP), one of the UK's leading automation specialists, for incorporation into an automated assembly, weld and test line,which they have purpose-designed and built for Birkby's. The welding system carries out the welding of the two glass-filled nylon components of the electronic control throttle pedal assembly. It produces a 3mm wide weld and also hermetically seals the pot within the pedal. It is robot-mounted to ensure replicability of the welding operation and requires no bespoke tooling.
Enquiries: Richard Icke, Herfurth Laser Technology Ltd, Barclays Venture Centre, University of Warwick Science Park, Sir Williams Lyons Rd, Coventry CV4 7EZ, UK. Tel: +44 (0) 2476 323088; Fax: +44 (0) 2476 323001.
