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Laser transmission welding is a relatively new technique for joining thermoplastic components in the automotive industry. Laser energy is passed through a laser-transparent part and dissipated as heat in a laser-absorbent component. There is currently no standardized test to assess the strength of laser transmission welds made using thermoplastic materials. A properly-designed test allows the weld strength of the joint to be measured accurately and rapidly. This paper reports on a technique for measuring overlap shear strength. This study compares two weld orientations (weld line parallel and perpendicular to assembly loading) using polycarbonate, polypropylene, polyamide 6, polyamide 6 reinforced with 30% glass fibres and polyamide mXD6 reinforced with 50% glass fibres. Assemblies were made using a range of laser powers. In order to simulate industrial conditions, artificial gaps were also introduced between the transparent and absorbent parts.

An all-nylon intercooler for automotive applications has been shown to be possible. The heat rejecting element (cooling core) can be made employing the latest developments in plastic tubing, and the joining of the tanks to the tubes can be accomplished by advanced plastic welding techniques. The resultant part is similar in performance and environmentally robust compared to the aluminum parts made today. This paper will discuss assembly techniques and thermal performance, including test data and results. Increasing the robustness of the design is the recent development of extrusion grade polyphthalamide plastic tubing. The feasibility of production has been enhanced by the commercialization of laser welding of plastics using diode lasers.

Three different pairs of high melting temperature and low melting temperature nylons have been welded together using three different design of experiment welding process parameter matrices. An unorthodox analysis of these has revealed that there is a general increase in strength as the total welding sliding distance of the two surfaces increases. This is not surprising. The analysis also reveals that, for a given sliding distance, the vibration amplitude should be large, which shortens the welding time. This strategy produces shorter cycle times and stronger welds, according to the data obtained in these test sets.

The objective of this study was to compare mechanical properties of lab-scale vibration welded test specimens with those of a complex automotive component using several different materials. Different laboratory specimens (butt, Tee, cup-plate with/without flash trap) were made under different vibration welding conditions (weld pressure, meltdown) and then tested in tension. The tensile properties of the specimens were then compared with the burst pressure results from a prototype air intake manifold. 30% glass reinforced nylon 66 and polypropylene compounds were used. The lab scale specimens and manifolds showed similar trends: (i) all parts failed at the weld; (ii) increased weld pressure generally caused decreased weld strength (iii) meltdown was observed to have little effect on part strength (iv) the ratio of lab specimen strength to burst strength was comparable but not equal for the materials tested. Flash traps significantly affect weld strength when over filled.

The effects of varying laser-welding parameters were studied for the welding of the thermoplastic elastomer EPDM to glass filled polypropylene. Through-thickness scanning transmission welding (contour welding) was carried out with a diode laser with a wavelength of 940 nm using various power levels up to 150W and line speeds up to 2500 mm/minute. The observable weld attributes: weld strengths, weld widths, and failure modes, have been tabulated and discussed.

The effect of laser welding parameters such as laser power, laser speed, working distance and weld pressure on the weld strength, microstructure and meltdown of modified T-joints were studied using a diode laser and a contour welding technique. Specimens made of 30% glass reinforced nylon 6 were used in this study. A regression model was fitted to the data based on a central composite experimental design. The model showed that low levels of laser power at lower laser speed gave the maximum weld strength. It was observed that increases in weld pressure had a negative effect on weld strength. Meltdown was found to increase proportionally to the line energy and weld pressure.

Hollow polymer-based automotive components cannot, in general, be directly injection molded because they cannot be ejected from the mold. The common practice is to injection mold two or more parts, and then join these together with a welding process. Of the many joining process available, laser welding has an advantage in geometric design freedom. The laser weld joints are also generally stronger than those of vibration welds because the weld joints are located in the walls rather than on external flanges. Eliminating the external flanges also makes the part more compact. In transmission laser welding processes, the laser beam passes through a transparent part to its interface with an opaque part. The beam energy is absorbed near the interface in the opaque part, and heat flows back across to the transparent half to make the weld pool. So successful laser welds are possible only when there is a continuous interfacial fit between the parts.