Pedal power through laser transmission welding

Pedal power through laser transmission welding

Pedal power through laser transmission welding

Keywords: Laser welding, Plastics

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 (Plate 7).

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 tamper-proof 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.

Plate 7 A Herfurth Laser Technology direct diode laser transmission welding system

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 the 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 20 mm. 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 3 mm 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.

Herfurth Laser Technology is a company within Herfurth Holdings, Britain's leading plastics welding authority. It has an exclusivity agreement with the world's sole manufacturer of diode array lasers in the power range 250-750 W and is, consequently, the only company in the UK which has the resource, capability and expertise to offer high power laser transmission welding throughout the industrial sector. The company offers a specialist engineering team, backed up by the resources of the University of Warwick Manufacturing Group, to assist manufacturers during the initial design and development stages for new components, to ensure that any solution is optimised to meet the required specification. It also undertakes materials testing to determine the suitability of materials for laser transmission welding. Typically, the technology has been successfully applied to acrylics, polycarbonates and film materials and to welds between combinations of materials including foams to film and plastic mouldings.

For further information, please contact: Richard Icke, Herfurth Laser Technology Ltd, Barclays Venture Centre, University of Warwick Science Park, Sir William Lyons Rd, Coventry CV4 7EZ. Tel: 02476 323088; Fax: 02476 323001.