Laser beam welding with CALAS software-supported process planning and control

Software supported process planning and quality assurance are of main importance for the realization of a manufacturing method in laser beam welding. A novel software tool for process planning and prediction of the properties of laser welded seams named CALAS, i.e. Computer Aided LASering, is presented. Its structure, handling, simulation capabilities, and performance are described in detail. The software tool connects a physical model of welding with C02 laser radiation to an interactive man-machine interface by simulation and visualization. The model considers five fundamental physical processes, absorption of laser radiation at the keyhole surface (multiple reflection), heat conduction in liquid and solid phase, melt fluid flow, fluid flow and heat conduction in the vapor phase, and absorption of laser radiation inside the keyhole volume (plasma absorption). The effect of process parameters and their alteration on the geometry of the welded seam are calculated and displayed. The int erface provides a three dimensional visualization of the keyhole and the melt pool. Cross sectional views and longitudinal sections may by visualized two-dimensional. Also the temperature distribution and/or hardness can be displayed in this mode. Besides typical parameters the beam characteristics, such as distribution of the intensity, and material properties, such as temperature dependent surface tension and heat conductivity, are included in the calculation, too. This is the part of simulation, which is important to process planning. CALAS allows the prediction of the micro-structure of the solidified seam and the heat affected zone. A forecast of strength, ductility, and distribution of the hardness becomes possible. This function- ality deals with quality assurance and quality planning. Therefore CALAS is embedded in a holistic structure of manufacturing in laser beam welding. Due to direct and fast prediction of process parameters and seam geometry it serves as a controlling to o l to the operator at the machine tool. Because of its planning functionality CALAS has to be located in a planning step preceding manufacturing. Hence, it covers the planning and the guiding level of the hierarchy of communication steps in manufacturing. Linking CALAS to an autonomously operating manufacturing system consisting of sensors, actuators, and a central operating computer interconnected by a field bus a manufacturing system with optimum support of the operator is built up.