Laser polishing technology: development of engineering and scientific fundamentals

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Surface finish is one of the most important quality characteristics of fabricated components. In general, after the primary manufacturing process, components which require optical/semi-optical surface quality are polished manually. However, the manual polishing process requires advanced technical skills and is performed at slow processing rates resulting in high production costs. Also, finishing by milling always produces scallops, ridges, and valleys. No matter how narrow and close the tool’s cutting-trajectory becomes, the resultant machined surface will always exhibit a degree of form error, waviness and surface roughness. Laser polishing (LP) is one of the surface finishing techniques recently developed in Germany and USA. Our team is pioneering the development of this highly original and innovative technology influentially important to broad academic and industrial communities in Canada and abroad. The main challenge is to achieve good surface finishing without deteriorating the overall structural form. LP implies surface smoothing by melting and redistributing a thin layer of molten material over the surface through surface tension attempting to minimize surface energy. Since there is no material removal, the form of the given geometric feature is preserved. LP as one of the disruptive, knowledge-based technologies opens new avenues in cost effective manufacturing of value-added components with complex 3D geometry eliminating manual or other types of finishing operations. Further development of this highly innovative and original technology has potential for groundbreaking advances in manufacturing. From a scientific point of view, LP is a complex thermo-physical process involving several multidisciplinary phenomena accompanying rapid heating, melting, solidification, solid-state transformations cooling processes. However, LP does not have fully developed engineering and scientific fundamentals this limits using it as a conventional technology. The main limitations are: 1) a large number of process parameters, which are not systemized for predictable use and their selection and optimization requiring a highly skilled operator and large number of experiments; 2) uneven and time-dependent geometry of the laser beam as a material melting tool contributes to undesirable changes in surface geometry; 3) no reliable predictive models exist; and 4) CNC technology has not been adopted for LP process yet. In this context, the main objective of the proposed research program is to develop fundamental knowledge, thorough understanding, and engineering foundations of the LP technology. The emphasis will be on understanding and development of engineering/scientific fundamentals, process planning and optimization, where several thermo-dynamic processes in the laser-material interaction zone will be considered. Three research topics will be investigated: a) thermo-dynamic modelling and experimental verification of the formation of a pool of molten material and the rapid solidification and surface geometry change, b) modelling and experimental verification of the dynamic melting-solidification processes when a pool of molten material is moving along a tool path trajectory, and c) process parameter optimisation, system identification and process planning to achieve reproducible surfaces with desired quality. Undertaking this synergetic groundbreaking research will pursue new scientific and technological ideas with expected influential significance in the development of an original and strategic technology that will enhance competitive advantage of Canadian companies through the development of innovative, knowledge-based, cost-efficient manufacturing technologies for fabrication of the high-value components and products.