Abstract—The performance of a machine tool is eventually assessed by its ability to produce a component of the required geometry in minimum time and at small operating cost. It is customary to base the structural design of any machine tool primarily upon the requirements of static rigidity and minimum natural frequency of vibration. The operating properties of machines like cutting speed, feed and depth of cut as well as the size of the work piece also have to be kept in mind by a machine tool structural designer. This paper presents a novel approach to the design of machine tool column for static and dynamic rigidity requirement. Model evaluation is done effectively through use of General Finite Element Analysis software ANSYS. Studies on machine tool column are used to illustrate finite element based concept evaluation technique. This paper also presents results obtained from the computations of thin walled box type columns that are subjected to torsional and bending loads in case of static analysis and also results from modal analysis. The columns analyzed are square and rectangle based tapered open column, column with cover plate, horizontal partitions and with apertures. For the analysis purpose a total of 70 columns were analyzed for bending, torsional and modal analysis. In this study it is observed that the orientation and aspect ratio of apertures have no significant effect on the static and dynamic rigidity of the machine tool structure. Keywords—Finite Element Modeling, Modal Analysis, Machine tool structure, Static Analysis. I. INTRODUCTION ACHINE tool structures must exhibit high static and dynamic rigidity for obtaining better surface finish and accuracy of work piece. Thus, care must be taken to minimize structural deformations in the machine tool. The need for high dynamic stiffness results from two separate aspects of the machining process. In the first case inadequate dynamic stiffness will result in poor surface finish of the machined parts. In the second case low dynamic stiffness can have more serious consequences when under heavy machining conditions the resulting vibration might be sufficiently high to cause the process to be terminated in order to prevent possible damage to the machine [1]. Currently the widely accepted method of analysis prior to manufacture of an actual machine tool is the model analysis. Based on the results of analysis and experiments on the scale model, suitable modifications are made, by a process of trial and error, to satisfy the design requirements. The complete study of the scale model experimentally only would be quite impractical in view of the large number of variables involved. Hawassa University is with the Institute of Technology, Department of Mechanical and Industrial Engineering, Ethiopia (phone: 251-916866978; e- mail: megbar458@yahoo.co.uk). The other suitable and sound method of analysis prior to manufacturing is, by making use of either lumped parameter technique [2] or Finite Element Method with computer aided technique [3]. The main advantage of these techniques is that it provides information similar to that obtained from actual tests to the designers which saves considerable time and expenditure involving in building and testing models. Martin [4] was the first to demonstrate the suitability of reduced scale plastic models for predicting the static and dynamic characteristics of machine tool structures. His studies on a quarter scale perspex model of a knee type horizontal milling machine revealed weak points in the actual structure that needed modifications to obtain a sound design. By using classical beam theory J.C. Maltbaek, [5] calculated the natural frequencies and mode shapes of the radial drilling machine structure. The first publication describing a formalized digital computer method for calculating static and dynamic characteristics of machine tool structures appeared in 1964. In this paper, Taylor and Tobias [6] described the application of a finite-element program to represent the structural part of a radial arm drilling machine and a lathe and also performed tests on a series of perspex models of radial drilling machine and lathe structures to verify the accuracy of the numerical technique developed by them and to predict the behavior of the structure at the design stage itself. An excellent agreement between experimental and computed modal shapes and natural frequencies of vibrations was reported. Badawi, Mohsin and Thornly, [7] developed analytical models to predict the bending and torsional stiffness of ribbed beams. These models have further been used to study the influence of various geometric dimensions and ribbing configuration on their stiffness characteristics with a view to obtain their optimized proportions in terms of stiffness per unit weight as the criterion. N. Ganesan and his coworkers [8] present the analysis of prismatic columns for their torsional behavior. Such columns are widely used in the design of machine tools. In this work the prismatic column was treated as a closed thin-walled beam and the problem is solved by using variational methods in conjunction with the finite difference technique. Cowley and Fawcett [9] analyzed a plano-milling machine structure for static deflections, natural frequencies and mode shapes and studied the effect of flexibilities between joints on the natural frequencies and mode shapes. The main portal frame is comprised of two 12ft (3.6576m) tapered columns spanned by a 7ft (2.1336m) cross-beam and carries an adjustable height cross-slide. The cast iron structure supports three traversing 50hp ram type milling heads with provision Modal Analysis of Machine Tool Column Using Finite Element Method Migbar Assefa M World Academy of Science, Engineering and Technology International Journal of Mechanical and Mechatronics Engineering Vol:7, No:4, 2013 699 International Scholarly and Scientific Research & Innovation 7(4) 2013 scholar.waset.org/1307-6892/9997091 International Science Index, Mechanical and Mechatronics Engineering Vol:7, No:4, 2013 waset.org/Publication/9997091