Reducing Cutting Force Induced Bore Cylindricity Errors by Learning Control and Variable Depth of Cut Machining

Abstract

In this paper, a method for on-line compensation of cylindricity errors in machined bores is formulated and demonstrated. The cylindricity errors addressed are those caused by the elastic deformation of the bore wall due to forces applied to the workpiece both during and after the machining process. Compensation is achieved using a piezoelectric boring bar servo capable of varying the depth of cut rapidly for on-line compensation at acceptable industrial machining speeds. Control of the boring bar servo consists of both learning and repetitive control. Learning control is used to determine the cutting tool reference trajectory required to achieve compensation, and repetitive servo control is used to accurately track the reference trajectory. The stability and convergence of the error dynamics of the learning control system are analyzed using a model for the flexure-induced machining errors. Experimental results demonstrate that the proposed method can significantly improve bore cylindricity in machined components.