Geometry Assurance of Laser Processed Metal Components

Doktorsavhandling, 2021

The manufacturing industry largely contributes to the global economy. How-ever, with the growing complexity of customer demands, stringent environmental norms, and requirements for shorter product development lead times, the industry continues to seek alternatives to address these challenges. Laser based manufacturing techniques are among the popular alternatives to address the challenges, mainly for their precision focusing abilities. Specifically, two laser assisted manufacturing techniques, namely the selective laser heat treatment of sheet metals and the selective laser melting of metal powders, have garnered attention for their ability to produce complex, and near net-shaped products that caters to the needs of industries such as the automotive and the aerospace industry.

 While great progress has been made in understanding their process capabilities, shortfalls remain in the area of geometric quality. Specifically, addressing the effect of local heating and local melting on geometric variation is scarce due to the novelty of the aforementioned manufacturing processes. As a result, the methods and tools in practice today may not be readily applicable to analyzing and minimizing the effect of local heating and local melting on geometric vari-ation. Thus, this thesis aims at developing knowledge to provide insights into the effect of the aforementioned manufacturing processes on geometric variation and, thereby, assist in establishing methods and tools for the geometry assurance process.

To this end, literature studies were performed to map the significant factors influencing geometric variation and a robust design framework was established as the first step. The focus was then focused towards analysing a set of factors that could be optimized in the early design stages. Specific to the selective laser heat treatment of boron steels, the effect of factors such as the laser heat treat-ment grid pattern dimension, laser heat treatment grid pattern position, and laser heat treatment scanning path sequence on geometric variation were analysed. Meanwhile, in the selective laser melting of 316L stainless steel powder, the effect of factors such as particle size distribution and powder layer thickness on geometric variation were analysed.

The results highlight the significance of considering the effect of the specified set of factors on geometric variation in the early product development stages and offer solutions to minimize the effect on geometric variation. Moreover, simulation techniques are presented that enable accurate decision making and demonstrate integration into the virtual product development setup. In summary, this thesis demonstrates the application of a robust design approach and the significance of considering geometry assurance in the product development process of laser processed metal components.