A digital machining system based on mechanistic models

Hongqi Li, Purdue University

Abstract

With intensifying global competition, manufacturers are facing challenges to reduce the cost of production as much as possible and yet improve their product quality. A digital machining system, which is the kernel of a virtual machining system, is desired to design optimal process conditions and evaluate processing alternatives with a minimal cost and time before the process is implemented on the shop floor. The goal of this research is to develop a digital machining system based on mechanistic models. The system consists of integrative dynamic machining process models, which combine the machining process modules developed by the previous researchers in the author's group, a spindle analysis model, and new machining process models, such as endmilling and grinding process models developed for the integrative system. To this end, the expandable general base model is built in the system and the interfaces for extending to upper level models are provided for easy integration. A comprehensive endmilling model is developed that simulates the process under general cutting conditions. A new method to extract cutting pressure coefficients is also introduced. Time-domain dynamic models are also developed to simulate cylindrical plunge grinding, surface grinding and infeed centerless grinding processes under general grinding conditions. The models focus on the prediction of grinding chatter. Critical issues are considered in the model, including the distributed nonlinear forces along the contact length and the geometrical interaction between the wheel and workpiece based on their surface profiles. A simulation program is developed using the models to predict regenerative forces, dynamic responses, surface profiles, stability regions, and chatter thresholds. The models are validated using numerical and experimental results. The development of the digital machining system is completed by integrating the "Dynamic Thermo-Mechanical Spindle-Bearing" model (Li, 2002) through a modular interface using modal superposition methods. The digital machining system is evaluated in aspects of determining spindle related machining process constraints, predicting spindle status-dependent chatter boundaries and selecting cutting tools.

Degree

Ph.D.

Advisors

Shin, Purdue University.

Subject Area

Mechanical engineering

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