A workholding optimization model for turning of ring-shaped parts

Abstract

The ability to produce precision ring-shaped parts using the turning process depends significantly on the workholding characteristics. Workholding parameters such as the number of jaws and chucking force are known to influence the roundness tolerance of ring-shaped parts commonly used in ball/roller bearing applications. Experimental trial-and-error methods are often used in practice to optimize the workholding parameters to achieve the desired part quality. This paper presents a systematic mathematical approach for optimizing these parameters using a previously developed analytical model of ring deformation and a model for determining the minimum chucking force. The optimization approach takes as input the required roundness tolerance, geometry, and mechanical properties of the ring, cutting forces, and the coefficient of friction between the jaws and the ring. The output consists of the minimum number of jaws and the range of acceptable chucking forces that ensures the required tolerance while preventing slip of the ring. Simulation examples illustrate the use of the proposed workholding optimization approach for a turning application. In addition, the paper proposes the concept of dynamic chucking force control that promises to yield part roundness that is superior to that obtained via conventional constant force chucking.