On-line optimisation and experimental design analysis for the investigations on the surface roughness produced by roller burnishing: a thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology in Manufacturing and Industrial Technology at Massey University

Abstract

This thesis describes the improvement of the Surface finish of metals by a cold working, non-metal removal and plastic deformation process called roller burnishing. Roller burnishing is a popular finishing process. Surface finish has a positive and prolonged effect on the functioning of the machined parts. In this work roller burnishing is used to get a high quality surface finish on different materials like aluminum, copper, mild steel and brass. A roller burnishing tool was designed and fabricated for the project. A test rig was set up on a center lathe to conduct experiments. The angle of approach and radius of the roller burnishing tool were checked for optimisation. Number of passes of the tool was also one of the factors under study for the optimisation. The surface finish of the roller burnished cylindrical surfaces was examined for the soft materials like Aluminum and Copper and also for the hard materials like Mild Steel and Copper. The optimum values of feed, speed and depth of penetration were suggested by conducting a number of experiments varying one factor-at-a-time holding the rest constant. Since all the factors are interdependent, varying one-factor-at-a-time and keeping the rest constant method of experimental optimisation technique will not give accurate results either for the main effects or any interactions present. At same time it is not possible to vary more than one factor at a time experimentally. Hence a theoretical approach focused on the computer based, process parameters and surface quality data acquisition from the shop floor was suggested. The collected data was then analysed by Design of Experiments method, an advanced statistical quality analysis method, to determine the significant process parameters influencing the surface finish. The basic design and analysis of the process was carried out by full factorial and ANOVA for the two level three factor ( 2 3 ) experimental design. More experiments for roller burnishing process were conducted for collection of data using experiments designed by the Central Composite Design (CCD) method. These experiments were used to determine the interactions among the factors. The analysis was carried out by the Response Surface Methodology (RSM) to find the optimum values of the more significant process parameters. The final surface finish for mildsteel was found to be 0.32µm with a feed of 85µm/rev and depth of penetration of 70µm. The results of both experimental and theory were compared.