Numerical optimization approaches of single-pulse conduction laser welding by beam shape tailoring

• A pulse of a shaped laser beam can cause a different, unexpected weld shape.
• Competing heat flow mechanisms are difficult to quantitatively capture.
• Suitable indicators from heat flow simulation can guide beam shape optimization.
• Accordingly beam shape improvement has stepwise led to an acceptable weld.
• The approach enables effective optimization of Diffractive Optical Elements.

While circular laser beams are usually applied in laser welding, for certain applications tailoring of the laser beam shape, e.g. by diffractive optical elements, can optimize the process. A case where overlap conduction mode welding should be used to produce a C-shaped joint was studied. For the dimensions studied in this paper, the weld joint deviated significantly from the C-shape of the single-pulse laser beam. Because of the complex heat flow interactions, the process requires optimization. Three approaches for extracting quantitative indicators for understanding the essential heat flow contributions process and for optimizing the C-shape of the weld and of the laser beam were studied and compared. While integral energy properties through a control volume and temperature gradients at key locations only partially describe the heat flow behaviour, the geometrical properties of the melt pool isotherm proved to be the most reliable method for optimization. While pronouncing the C-ends was not sufficient, an additional enlargement of the laser beam produced the desired C-shaped weld joint. The approach is analysed and the potential for generalization is discussed.