Title

A dynamic study of the plunge centerless grinding process and its effect on workpiece out-of-roundness

Date of Completion

January 1994

Keywords

Engineering, Automotive|Engineering, Industrial|Engineering, Mechanical

Degree

Ph.D.

Abstract

The work described investigates the lobing and chatter behavior, and approaches to suppress lobing and chatter in order to improve the workpiece roundness in centerless grinding. The problem of workpiece out-of-roundness is one of the main limitations for the applications of centerless grinding as a high rate precision machining process. Lobing and/or chatter most often is the source of the problem. This work models the centerless grinding process as a causal system between the potential grinding disturbances and the resulting workpiece out-of-roundness, and develops approaches to set up a centerless grinding operation such that the workpiece out-of-roundness is kept minimum under the potential grinding disturbances.^ A general centerless grinding process model is proposed. The model can be simplified for lobing and chatter analysis. A Bidiagrammatical method is proposed to investigate the lobing stability. It was found that the upper and lower lobing growth rate can be estimated through the Bidiagrammatical method, and the lobing growth exhibits periodicity over the lobing frequency. A relative stability diagram is thus developed to provide guidance such that a proper setup angle $\beta$ can be selected to suppress lobing.^ During grinding, two types of workpiece surface waves can be generated: (1) standing wave; and (2) precessing wave. It was found that the standing waves are less stable, therefore, often cause significant workpiece out-of-roundness problem. A work-speed regulation method is proposed such that only precessing waves are generated during grinding, therefore, reduce the workpiece out-of-roundness.^ Chatter stability is investigated by using a similar Bidiagrammatical method. It was found that chatter stability can be approximately assessed through lobing stability. Therefore, approaches to lobing suppression can be equally applied to suppress chatter. ^