Chatter prediction from orthogonal cutting force data and stability analysis of peripheral end milling

Abstract

Machine tool chatter has been the focus of extensive research due to its adverse impact on productivity and quality of machining. The objective of this thesis is to characterize tool motion from orthogonal cutting force data, obtained from a Bridegport Discovery Torq-cut 22 vertical milling center. Nonlinear system tools are an integral part of the analysis of complex dynamic systems. State Space Reconstruction by the method of delays is used in this work to reconstruct the attractor of the tool-workpiece system. The reconstructed state space provides a tool to analyze and characterize the behavior of the machining system. The force data is processed through a low pass filter to eliminate noise from the signal. The attractor constructed for unstable cutting, repeatedly folds onto itself, indicating the presence of multiple frequencies in the signal during chatter. In the second part of the thesis, a regenerative cutting force model is used to study the effects of chatter on tool motion. Floquet theory in conjunction with perturbation method is used to determine the critical depth of cut for stable cutting. Close correlation is observed between the predicted and the experimentally determined critical depth of cut. Simulation of the model, for cutting conditions over the critical limit of the depth of cut, also shows the presence of multiple frequencies.