Concurrent optimization of operating parameters and tolerances for CNC machining processes

Abstract

This research work is concerned with the concurrent optimization of CNC machining process parameters and tolerances for manufacturing of various engineering products in order to enhance the manufacturability, reliability, quality and field performance. The stringent specification of tolerances on the dimensions of manufactured parts has a significant impact on final production cost. Considering these significances, the research work was carried out. The objective is to minimize the manufacturing cost or time for CNC machining processes without satisfying quality and to develop the concurrent optimization procedure for the manufacture of a particular component. Machining process Optimization procedure has been developed based on three popular algorithms: Nelder-Mead Simplex (NMS) method, Simulated Annealing Algorithm (SAA) and Genetic Algorithm (GA). A Mathematical model was also developed to find the tolerance level through response surface (Central Composite Rotatable Design) methodology using MiniTAB Statistical tool. Applying this model, the range of the dimension deviations for external finish grinding of the piston material spheriodal cast iron (SG 600/3) was determined. Predicated tolerance was used to calculate the Quality Loss Cost. The results clearly show that a 30% reduction in total manufacturing cost was achieved in milling process and a minimum of 10.2% reduction in machining time was achieved in turning process. The resulting operating parameters have been accepted for implementation by the industries in which the case study was conducted. For concurrent optimization process, the cutting speed, feed rate and depth-of-cut were the parameters analyzed for eight different machining processes. The actual convergence to the optimum value was at the 403rd iteration. The results obtained in this research work clearly indicate that reduction in manufacturing cost / time is achievable using GA for solving the single stage, multi-stage CNC machining and concurrent optimization problems. newline newline newline