Laser transmission welding with part adapted temperature fields

Abstract

Thermoplastics are present in a wide variety of industrial applications. Different welding techniques like vibration, resistance and laser welding are used to join these materials. Laser transmission welding is known for high flexibility and extraordinary possibilities of process automation. Today, there is rising interest in joining large thermoplastic parts with three-dimensional formed weld seams. To successfully obtain these seams, the parts have to be clamped in such a way that is nearly gap-free. Gaps could result in processing issues such as welding failures, poor achievable process speed and low weld seam strengths. To overcome these problems, a new laser transmission welding technique was developed to achieve part adapted temperature fields based on a combination of contour and quasi-simultaneous welding. In addition, the authors are investigating the effectiveness of this strategy with a thermal finite element model. This model focuses on the heat affected zone geometries, temperature gradients and simulated melt pool geometries depending on the parameters creating part adapted temperature fields dynamically. The results from the model were verified by experiments with a diode laser. Furthermore, process control strategies were developed, which can later be used to ensure a constant weld seam quality. The process control is carried out by an on-axis pyrometer, which allows online temperature detection within the weld seam.Thermoplastics are present in a wide variety of industrial applications. Different welding techniques like vibration, resistance and laser welding are used to join these materials. Laser transmission welding is known for high flexibility and extraordinary possibilities of process automation. Today, there is rising interest in joining large thermoplastic parts with three-dimensional formed weld seams. To successfully obtain these seams, the parts have to be clamped in such a way that is nearly gap-free. Gaps could result in processing issues such as welding failures, poor achievable process speed and low weld seam strengths. To overcome these problems, a new laser transmission welding technique was developed to achieve part adapted temperature fields based on a combination of contour and quasi-simultaneous welding. In addition, the authors are investigating the effectiveness of this strategy with a thermal finite element model. This model focuses on the heat affected zone geometries, temperature gradients ...