Southfield. MI—To ensure the reliable deployment of side and head airbags in case of an accident, even years after installation in an automobile, airbags are covered by special wraps.

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Innovative laser process for airbag wraps

Southfield. MI—To ensure the reliable deployment of side and head airbags in case of an accident, even years after installation in an automobile, airbags are covered by special wraps. These wraps have to meet exacting safety specifications. In the past, their production involved several process steps; suppliers stacked airbag wrap material sheets, laser cut the parts, and manually sewed them. The materials are expensive and there was a significant amount of labor involved. Now, Schreiner ProTech has developed a technology that enables the production of airbags to be accomplished in a one-step process.

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A new machine prints a warning text on the non-woven material (eliminating the need for separate labels) on a continuous web of polypropylene non-woven material, laser die-cuts it using a Rofin-Sinar 100W CO2 laser, folds the material in half, laser spot welds the wrap at 50 welds/s, and cuts it to length. All of this activity is controlled by vision systems and run by one operator.

This comprehensive, forward-thinking solution delivers maximum process reliability and cost efficiency. Optionally, the laser cut parts can be produced as non-welded "open" stock with a laminated self-adhesive strip. This "open" stock is used to create the wrap during the customer's assembly process where the material is bonded by means of the self-adhesive strip. The wraps are processed in a continuous process that exceeds the requirements for performance, cost, reproducibility, and complexity reduction. Several prominent airbag suppliers use this process.

For the automotive industry, laser technology enables the definition of any desired cutting or welding contour. This means that very complex geometries and customer-specific processing requirements can be implemented quickly and flexibly without additional tooling costs. Schreiner ProTech develops tailor-made value-added solutions as needed. For example, such solutions enable in-process monitoring of safety-relevant parameters like dimensions and break-open forces of the tear seams, ensuring reliable production results at the highest level of quality. The company's innovation has already proven its viability in the automotive industry.

For further information on this laser process, please contact Schreiner ProTech North America Inc., Southfield, MI, www.schreiner-usa.com, or e-mail pasbjerg@schreiner-protech-na.com.

Laser assisted joining of plastics and metals

Aachen, Germany—Plastic is increasingly being used as a construction material, which poses the problem of joining dissimilar material classes. Plastic-metal hybrid components could be manufactured using a variety of techniques. The LIFTEC laser-assisted joining process developed at the Fraunhofer Institute for Laser Technology ILT offers an efficient solution (see Figure 1). This patent-pending process works by heating a component, or a part of it, by laser radiation which passes through the plastic joining partner. The component is pressed onto the plastic part under mechanical pressure, then heated, and finally pushed into the plastic by further mechanical pressure. Provided that a suitable component geometry has been selected, a solid, positive bond is formed after cooling. It is essential to the process that the component should have a higher melting point than the plastic joining partner. Suitable materials include metals, ceramics, and temperature-resistant plastics.

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FIGURE 1. Laser bonded hybrid components using the LIFTEC process.
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Another approach is being investigated in the context of the Cluster of Excellence "Integrative Production Technology for High-Wage Countries" at RWTH Aachen University. In this approach, researchers are examining several irradiation methods, materials, beam sources, and pre-treatment methods. A first series of tests is being carried out to determine the influence of structural density on the joining process. This is being done by producing surface structures with dotted, lined, and checkered patterns in stainless-steel samples using Nd:YAG laser light.

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FIGURE 2. Quasi-simultaneous welding
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Subsequently, the structured samples are bonded to the transparent plastic samples by diode laser light in a contour or quasi-simultaneous joining process (see Figure 2). The resulting bonds are very strong and generally very promising.

Welding with fiber lasers

Aachen, Germany—Medical products and components in the bio-engineering and bio-analysis sector have to be made from highly bio-compatible materials that are inert vis-à-vis a variety of media. The joining method employed also has to meet special requirements. It has to get by with as few additive materials as possible, and should under no circumstances influence or contaminate the materials. As an alternative to conventional joining techniques, laser welding offers a number of innovative solutions featuring high welding speeds, narrow weld seams, and special process variants for joining transparent plastics.

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Welding of two transparent components without an absorber.
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A series of new beam sources enables laser characteristics to be specially adapted to these tasks. Highly advanced microsystems with complex welding contours for medical engineering and biotechnological applications, such as a new type of microfluidic chip with very narrow and closely spaced channels, make great demands on joining technology. The chip has to be furnished with a cover film, for which the welding seam must be no more than 100µm wide.

The new TWIST (Transmission Welding by Incremental Scanning Technique) contour-welding method developed by the Fraunhofer Institute for Laser Technology ILT meets these stringent requirements, producing high-quality welding seams at high process speeds. Based on fiber lasers, this innovative irradiation method can produce 100µm-wide seams at a rate of up to 18 m/min. Any potential degradation of the material due to the high intensity of the focused fiber laser light is avoided in the new process. For the welding of transparent plastics, the new beam sources enable the laser characteristics to be adapted to the polymers' absorption behavior, thus obviating the need for additional absorbers (see photo). This improved irradiation strategy preserves the advantages of laser transmission beam welding without influencing the surfaces of the components. It can be used for transparent and translucent polymers.

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