Mathematical Modeling and Analysis of the Surface Topography Generated During End Milling Processes

Abstract

Computer integrated manufacturing systems have emerged in response to the requirements for greater flexibility, productivity, high precision and quality of the product. As the computer technology advances, the manufacturing industry is now seeking a higher degree of production automation. Numerical control (NC) machining stands out in this regard. There is pressing need for computer-based simulation models that can be used for the purpose of analyzing the machining performance during the programming stage.<P>Research has been done in this thesis to develop a system model which can describe the generation of machined surfaces during an end milling process. In the first step, an ideal surface topography is constructed based on the kinematics of a vertical milling machine tool. Building on the ideal surface topography, factors such as the parallel axial offset of an end mill (runout), tool static deflection and vibration are taken into consideration in the surface texture generation. Consequently, the developed mathematical model represents a realistic picture on how the machined surface is produced during an end milling process.<P>In order to gain a comprehensive understanding of the dynamic nature of surface generation during an end milling process, the method of design of experimentation is employed to investigate three system parameters, namely, the feedrate, helix angle, and runout, and their effects on the surface topography generation. Computer simulations based on a 23 factorial design are conducted in this thesis work to obtain the predicted values of indices such as roughness average (Ra) and Peak-to-Valley (PTV) that characterize the finish quality of machined surfaces.<P>Experimental verification has been done in this thesis work. Samples are made on a Matsuura 510 Machining Center. These samples are inspected and data are recorded at the National Institute of Standards and Technology at Gaithersburg, Maryland. For a similar machining condition, the results predicted through computer simulation are compared with the results obtained from the direct measurements taken on the samples, showing good agreements.