Optimum end milling tool path and machining parameters for micro Laval nozzle manufacturing

Cutting tool path has significant effects on the performance of micro nozzles manufactured by micro machining. Different tool paths induced different directions of surface roughness. As for it, the manufacturers need to obtain optimal cutting tool path and cutting parameters. In this article, optimum machining parameters for the fabrication of micro Laval nozzle with two different end milling tool paths are presented. First, surface roughness models for different types of cutting tool paths are proposed. A case of machined nozzle surface is then given to verify the applicability of the developed roughness model. Second, theoretical profile geometries for the Laval nozzle to be manufactured are designed. Third, the influences of surface roughness on the nozzle performance parameters including total pressure, average outlet velocity and thrust are investigated through computational fluid dynamic analysis. Simulated performance parameters are contrasted with their theoretical values. It is found that for different tool paths, the nozzle of axial tool path has larger total pressure and average outlet velocity than that of circular tool path. Moreover, with surface roughness increasing, thrust decreases obviously when surface roughness R_z is larger than 4.8 μm. Micro end milling experiments based on axial tool path are then performed, and the optimum cutting parameters are obtained. Finally, a nozzle was manufactured with the axial tool path as well as the optimized cutting parameters.