Archive | 2021
Multi spot modules to improve joining processes due to tailored spot geometries
Abstract
Tactile guided laser welding of aluminum and laser brazing of zinc coated steel with filler wire are standard joining applications in body in white BIW serial productions since 10 to 20 years. Advantages like smooth and tight surfaces made these applications very successful especially in outer skin applications.In 2014, VW published an increased spatter process behavior when using hot-dip galvanized sheets for brazing the outer skin of tailgates. Within a year, Laserline developed specifically for this process the multi-spot module with Triple-Spot design (a square main spot with two little spots ahead of the main). For laser beam brazing, the module is integrated into the Scansonic ALO3 brazing optic. The collimated laser beam is divided, customized for the respective processes, transformed, and then focused. Power distribution and spot geometry can be adjusted.The new brazing process was further developed and finally qualified and released beginning 2016 within a VW production trial in China. Since that trial the triple spot module is standard for all upcoming HDG projects at VW and is installed in production lines all around the world. Spatters could be significantly reduced, and the usual maximum process speed of 4.5\u2005m/min could again reached with a reliable process.To reproduce all adjustable parameters we designed a new camera measurement tool and this year we introduced a new motorized triple spot module which is controlled by the handling device. Now the power distribution can be changed for different brazing applications or front spots even can be switched off during a process or between cars.In aluminum welding the multi spot module combines keyhole and heat conduction welding to improve the appearance of the weld in outer skin applications (Spot- in-Spot design). The module is again integrated in a tactile Scansonic ALO3 optics with smaller magnification (0.9 to 1.1) and special Aluminum features. After many trials with different triple spot designs finally the spot-in-spot design brought a big step forward. It combines reduced spatters, nice surface appearance, high penetration depth and high welding speed. The bigger spots also reduces bonding defects and number pores. Which leads to a very high process robustness. With the new automated Multi Spot Module it is now possible to shift approximately 70% of the whole laser power between inner and outer spot by the robot for each weld during the cycle.Promising results were also achieved in Tailored Welded Blanks (TWB), battery housings and in powertrain gearwheel welding.