New laser welding technology for plastics

Citation

(2001), "New laser welding technology for plastics", Assembly Automation, Vol. 21 No. 1. https://doi.org/10.1108/aa.2001.03321aaf.010

New laser welding technology for plastics

New laser welding technology for plastics

Keywords: Lasers, Welding, Plastics

A range of laser welding units, employing radically new plastics welding technology, is now available from Herfurth Laser Technology of Coventry. The new technology offers potential throughout the industrial sector and particularly in the automotive, packaging and medical industries. It can be used to replace conventional techniques such as vibration and hot plate welding, with significant user benefits (see Plate 7).

Plate 7 A robot-mounted, direct diode laser unit from Herfurth Laser Technology carrying out laser transmission welding

Laser welding relies on the fact that a joint, whose strength exceeds that of the parent materials, can be produced between two plastic components, if one component transmits the high power laser energy and the other absorbs it. Conventional laser welding technology uses fibre optics, with the result that beam width is restricted to around 1mm, making the welding of large or complex geometry workpieces a long and difficult process. The new Herfurth high power direct diode laser units can generate a beam width of around 20mm, so that it is now possible to join a wide range of thermoplastic materials, including coloured transmitting joint components. The technology has been successfully applied to acrylics, polycarbonates, film material and to welds between combinations of matererials, including foams to film and plastic mouldings.

As the new technology is a non-contact technique, it eliminates the problems of tool contamination and product location associated with other conventional techniques. The laser beam from a direct diode system is also highly controllable and the output, which can be typically up to 400 watts for plastics, is both stable and predictable, allowing consistent reliability. The high power capability and the wide beam permit the welding of large weld areas, with virtually no limit on size or complexity of component, while the beam controllability and the very precise nature of the beam ensure that very delicate welding operations can be carried out, using thin film materials.

In the automotive industry, successful trials for a leading manufacturer of automotive lamps have already demonstrated the capability of the technology to weld polycarbonate, ABS and acrylic and PC and ABS materials across the spectrum of colours used in the production of front and rear light clusters. Similarly, the high level of laser beam control, which the equipment allows, has permitted the welding of retaining features to a finish painted component of 1.65mm thickness without any degradation of the finish.

In the food, packaging and medical industries, transmission laser welding offers the opportunity to produce seals and containment by a non-contact system, so reducing the risk of contamination and eliminating the need for solvents or adhesives.

Herfurth laser welding systems are available in a range of sizes. They have a small footprint, within, typically, a 300 x 130 x 160mm housing, offering practical design capability on the production line. No bespoke tooling is required and Herfurth can design and supply robot-mounted laser systems to make laser welding extremely cost-effective, even on short run production lines, where changeover times must be minimal. For volume production, typically, at speeds above 1.5m/min, the energy generated by a high power direct diode laser welder is sufficient to generate a weld of 10mm width continuously at 150 watts average power. The new laser welding technology also provides significant energy savings, as the conversion efficiency (from electrical energy to laser power) is around 37 per cent and energy is used only during the actual welding operation.

Herfurth Laser Technology is staffed by personnel from Herfurth UK Ltd, UK's leading plastics welding authority, and the University of Warwick Manufacturing Group, one of the UK's premier research establishments for high power laser diode technology and a centre of excellence for automotive engineering. The company offers a specialist engineering team 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, while keeping production and material costs to a minimum. It also undertakes materials testing to determine the suitability of the materials for transmission welding. It can provide prototypes for trials evaluation and offers a cost/benefit analysis to demonstrate the financial viability and advantages of laser welding technology.

Contact: Richard Icke, Herfurth Laser Technology Ltd, Barclays Venture Centre, University of Warwick Science Park, Sir William Lyons Road, Coventry CV4 7EZ, UK. Tel: +44 (0)2476 323088.