Development of process metodology for optimization of machining of turbine blades on turn-mill machine tools with Ti6Al4V applications

With the development of technology and increasing production requirements, high precision production processes especially for the parts in aviation, energy and automotive industries gain importance everyday. In the manufacturing processes of workpieces with complex geometry and high precision operations, energy efficiency and high quality compromise have always been influential on process output. Making production processes feasible both with high quality and high energy efficiency contributes to sustainable production practices. Turbine blades are components having a critical importance, especially in the aviation and energy industries. For this reason, they need to be produced with high productivity, low energy consumption and excellent surface quality. In this thesis study, a methodology has been developed for the optimization of machining of turbine blades on turn-mill machine tools. The developed methodology includes the steps as CAD/CAM, experimental design, collection of data by machining, analysis of results with Response Surface Methodology and obtaining Pareto optimal solution set by Multi-Objective Particle Swarm Optimization. The manufacturing strategies were determined through the Pareto optimal solution set obtained at the end of the multi-objective optimization and the models were confirmed with the optimal process parameter values required for these specified strategies. This methodology has been put into practice by two different applications. The applications were carried out with Ti6Al4V material which is a special titanium alloy, with high mechanical and thermal properties. In the first application, using the process parameters as depth of cut, stepover, feed per tooth and cutting speed, machining processes are examined for rough and fine machining of turbine blades. Specific cutting energy, material removal rate and average surface roughness were investigated as process responses. As a result of the application, Pareto optimal solution sets were established for roughing and finishing. The optimal process parameters for the three different manufacturing strategies identified through these solution sets were determined and the models were verified with these values. Ball nose solid carbide end mills are used for finish flow milling. The ball nose end mills have to be machined with an angle to perform an efficient chip removal operation. These cutting tool angles are lead and tilt angles. In the second application, firstly, the effects on the surface quality of the lead and tilt angles in the finish flow milling process are investigated with a wide range of examination. Then, for the second application of methodology; lead angle, tilt angle, stepover and feed per tooth have been specified as process parameters for finish flow milling and developed methodologyfor the machining of turbine blade has been applied. The effects of the cutting tool inclination angles and basic machining parameters on specific cutting energy, metal removal rate and average surface roughness were investigated. From the Pareto optimal solution set obtained as a result of multi-objective optimization, optimal process parameter values are selected for the three manufacturing strategies and the verification process has been carried out.