Vibration Analysis and Stability Prediction of CNC end-milling

Abstract

This Master's Thesis investigates the process of stability prediction for milling process.Stability prediction for a given tool-workpiece combination can maximize materialremoval rate while maintaining vibrational stability. Milling is modelled as atime-delayed system with single degree of freedom. Temporal Finite Element Analysis& Spectral Element Analysis algorithms have been prepared to solve those. TFEAalgorithm is then customized for milling process to prepare stability charts for a givensystem.The algorithm is verified by experimental means. A compliant system is designedand manufactured for cutting tests. Impact modal tests are performed to extractmodal parameters, which are used to produce stability charts. Milling test passes aredone on the workpiece for various combinations of spindle speeds and depths of cut.Real-time workpiece displacement and spindle speed data is used to identify stabilityof the cuts. These are then analyzed and compared with stability predictions.The findings of this work indicate considerable agreement of theory with experiment.TFEA algorithm was able to predict stability accurately for low spindlespeeds. They also suggest the need to consider dynamics of the cutting tool and tomodel a second degree of freedom for more accurate predictions.