Stability analysis of boring bars with asymmetry

Stability analysis in machining systems is often based on linearized models of the cutting forces, and it is common to assume that chatter is due primarily to relative tool/workpiece motion normal to the workpiece surface. Reasonable agreement between theory and experiment has been noted in previous studies using these types of cutting force models, combined with machine tool structural models. In Parker's work (1), a boring bar was used which had dissimilar stiffnesses in the directions tangent and normal to the workpiece surface. While good agreement between theory and experiment was found for many spindle speeds, poor agreement was noted for certain speed ranges. In these speed ranges, the relative tool/workpiece motion was primarily tangential to the workpiece surface. It has been assumed by Parker, and others, that additional terms may be required in the cutting force model to account for the tangential motion effect and to accurately predict chatter in some boring operations. This paper presents an analysis of Parker's system, and shows that conventional cutting models can explain the tangential motion effect he encountered, without any additional terms.