Towards the Development of a Model for Nonlinear Elements in Machine Tools

Abstract

Machine tool structures contain a number of joints which provide for rotation or translation of connected structural elements. These joints add significant nonlinearity to the system thus making overall performance difficult to predict. Linear guides have been identified as a particular connection which exhibit significant nonlinearity. Linear guides are thus very difficult to accurately model into a dynamic simulation. Linear guideways have predominantly replaced box ways in industrial machinery to facilitate linear directional motion. As opposed to box ways which are scraped to obtain the most contact area possible, linear guides depend on theoretical contact patches between the guide, rail, and rolling element train. Linear guides exhibit complicated dynamics, the accurate prediction of which is necessary for a high-fidelity model of a machine tool. A fixture was developed to study linear guides. This paper highlights some of the properties of linear guides and begins the process of creating a model by studying the form of the nonlinearity using the Acceleration Surface Method (ASM). Future work will involve the comparison of the derived model against other popular linear guide models and the parameterization of the model found here.