COMPUTER AIDED ENGINEERING Modeling linear guide systems with CoFEM: equivalent models for rolling contact A. Dadalau • K. Groh • M. Reuß • A. Verl Received: 22 March 2011 / Accepted: 23 November 2011 / Published online: 6 December 2011 Ó German Academic Society for Production Engineering (WGP) 2011 Abstract Today’s machine tools are highly complex mechatronic systems capable to exert large translational and rotatory movements. In most cases rolling bearings are used to connect the moving parts to each other. As full FE models of rolling bearings can consume a large amount of degrees of freedom (DOF) efficient methods for reducing the DOF consuming rolling elements to more simple equivalent models are needed. As an example a linear guide system is used. A special feature of the considered linear guide is that the runner block consists of three sep- arate parts, which are hold together only by pretension and friction. FE simulations of such linear guide system were not reported before in the literature. Beside the full FE model three equivalent contact models are presented. The first two equivalent contact models feature novel charac- teristics. Advantages and disadvantages of the equivalent models are discussed using as reference a slice of the full model and simulation results of static stiffness. The vali- dation of the numerical models is also done using the general analytical solution of Hertz. Keywords FEM  Linear guide  Rolling contact  Hertz  Plasticity 1 Introduction Rolling bearings can have an important influence on the dynamical behavior of a machine tool. Therefore the exact determination of stiffness and damping of rolling bearings is crucial. As computer resources are increasing, simula- tions of rolling contact bearings become even more inter- esting. In general linear guides are simulated with the help of FEM (Finite Element Method). The level of detail can be very different, reaching from simple linear springs [11] up to full 3D FE models with accurate contact represen- tation [10]. Simple linear or nonlinear spring models of linear guides have the advantage of fast solution times. However finding exact stiffness parameters is an issue. On the contrary, 3D FE model of linear guides implicitly contain accurate stiffness information but the computa- tional time is enormous. In conclusion more efficient methods of reducing model size by simultaneously pre- serving the original properties are needed. In this work a linear guide system with rolling contact is considered. A special feature of the considered linear guide is that the wagon consists of three separate parts (runner block and rails), which are hold together only by pretension and friction. Due to the system complexity a new method for component oriented FE (finite element) modeling is used to model the linear guide in ANSYS. The concept of com- ponent oriented modeling is already being successfully applied in commercial CAD (Computer Aided Design) programs as a standard modeling method. By dividing a very complex model in smaller and simpler subcompo- nents, the modeling task is easier to manage, the error probability is decreasing and the model is more flexible regarding changes of subcomponents. In contrast compo- nent oriented modeling for MBS (Multi Body System) or FEM is far from being a standard modeling method. For- tunately some researchers recognized the potential and are developing the method in most cases for MBS, [1]. In this work the concept is being developed for FEM under the name ‘‘Component Oriented Finite Element Modeling’’ or A. Dadalau (&)  K. Groh  M. Reuß  A. Verl Institute for Control Engineering of Machine Tools and Manufacturing Units (ISW), Stuttgart, Germany e-mail: alexandru.dadalau@isw.uni-stuttgart.de URL: http://www.isw.uni-stuttgart.de/ 123 Prod. Eng. Res. Devel. (2012) 6:39–46 DOI 10.1007/s11740-011-0349-3