Hybrid Laser Welding of PP and PC
In hybrid laser welding of plastics, both laser beams and radiant heaters are employed as an energy source for the welding process. The upper component has already been preheated by means of radiant heating when both components are irradiated by the laser beam. As a consequence, less heat is required to melt the material and form the weld. In addition, the transparent component is less rigid and can better conform to irregularities in the shape of the lower component. The processing speed of hybrid laser welding is about five times faster than that of conventional laser welding. The process was developed jointly by the plastic welding division of LPKF Laser & Electronics AG, Erlangen and the Bavarian Laser Center in Erlangen.
When it comes to production of automotive taillights, hybrid laser welding has become an accepted process. However, it was previously not possible to employ the process for headlights, because chemical incompatibility prevented welding the PP housing and PC lens. For this reason, the front lens had to be bonded to the headlight housing by means of special adhesive systems. The adhesive bonding process required long cycle times and the adhesive bonds were often found to be the weak spot in headlight systems. To address this issue, A. Schulman GmbH, Kerpen, developed Polyfort LH 400, a modified PP that bonds to various polyesters. Housings molded from this material can now be bonded to PC lenses by means of hybrid laser welding. The weld seams exhibit excellent appearance. The cumbersome adhesive bonding process used to date can be eliminated. Polyfort LH 400 also bonds to polymethylmethacrylate and can thus also be used for taillights or as a material for household appliances.
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