Welding method solves plastics jointing problems

Added : ( Fri Jun 13 2003 )

Transmission laser welding of plastics is already used in areas including electromechanical devices, food packaging, medical, scientific and automotive applications. In each case, the application is looking to exploit different benefits offered by transmission welding. The most enthusiastic adopter of the new process is the automotive industry. A recent application, developed by Herfurth Laser Technolgy, involves a direct diode high power transmission welding system for the welding of a new, electronic throttle control (ETC). The pedal will be fitted initially to certain Ford models but it has wide-ranging application in the automotive industry. The new method of welding allows the production of a more compact, economical and tamper-proof throttle. Because two different grades of glass-filled nylon, with two different melting points, are used for the two components, it is not possible to use other joining techniques.

Transmission laser welding seeks to exploit the differential absorption and transmission characteristics of polymers and the additives used with them by using a joint configuration that employs an overlap. With careful selection of materials, one half of the joint can transmit the laser beam while the other half can be engineered to absorb sufficient energy to cause melting at the interface and thus allow welding. All this sounds very trivial. However, complex decisions considering the material mix, the lasers as well as the installation of the system have to be taken into account in order to achieve the desired results. Only a tiny change could ruin the whole process. Supported by personnel from the University of Warwick, Herfurth Laser Technology has access to the research facilities of a leading university with an international reputation for academic and industrial excellence.

In its latest projects, HLT's engineers have been able to overcome limitations encountered when using established joining techniques of plastics such as ultrasonic welding, hot plate welding or adhesion. This has been achieved through the use of high power diode lasers. Laser transmission welding offers several advantages over the more established plastic joining techniques. Unlike vibration/ultrasonic welding it is a non-contact process and is less likely to damage sensitive component assemblies, such as those containing electronics. Furthermore, it eliminates the problem of tool contamination and product location and requires minimal dedicated tooling. The high power capability and the wide beam permit the welding of large areas - there are virtually no limits to the size of the weld. Furthermore, the beam's controllability and the very precise nature of the beam delivery ensure the welding of very delicate parts if required. The results of a bursting pressure test showed that failure of an automotive component, whose two parts were welded together using Herfurth's technology, occurred through material and not joint failure. Other advantages include the high speed, the repeatability of the process, the high electrical efficiency (greater than 30%) and the compactness of the laser head (a 250W device measures only 260 x 125 x 125mm, for example, and weighs 5kg), which allows direct robot mounting, giving multi-axis capabilities.

Herfurth Laser Technology offers a full range of services - including consultancy regarding the selection of the most suitable materials and joint configuration, installation of laser systems that are exactly tailored to the needs of the customer, training and service support as well as total project management.

For more information contact:
Mr. Richard Icke
Herfurth Laser Technology Ltd
Barclays Venture Centre, University of Warwick Science Park
Sir William Lyons Road
Coventry, CV4 7EZ
Tel: +44 (0) 24 7632 3088
Fax: +44 (0) 24 7632 3087
Email: enquiries@herfurth-laser.com
Website: www.herfurth-laser.com
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