Abstract

The Computer Numerical Controlled (CNC) Precision Chucker is a machine tool (lathe) indigenously designed and manufactured by HMT machine tools ltd. widely used in precision manufacturing Indian industries. This machine enables machine finishing to higher level which replaces grinding machine usage in some applications. The rigidity of the machine tool is very important aspect in determining the precision and surface finish accurate representation of individual components I parts of the whole machine tool is very essential i n predicting the behavior of the entire machine tool when it is subjected to the actual working condition. The joints like spindle-bearing, linear motion guideway-LM bearing is also another area of interest since these joints influence the rigidity of the entire machine tool. The finite element method is chosen for the modellingbecauseof its flexibility in reasonably accurate modeling of various parts of the machine tool[l]. SESAM [2], finite element analysis software, opted for the modelling of the machine tool since it has superelement technique to model the individual components of the machine tool separately. The machine tool consists of several components and each component has varying size of crosssections. Hence line (beam), surface (shell) and solid (brick) finite elements are used to get reasonably accurate model of the whole machine tool. Though these elements have different degrees of freedom, coupling of these elements are properly considered at element interfaces by using shell-solid and beam-solid connectivity. several components are modelled separately as two sub-assemblies; the stationary equivalent cutting loads are applied on the machine tool spindle and reactive forces on the tool post; the deformation results. major components of the entire machine tool with worst cutting load conditions are analyzed., the machine tool was re-designed to increase the rigidity and to reduce the weight of the machine tool. Finally, the dynamic behavior of the machine tool is considered. By analyzing the defection of the structure, better rigidity of the machine for facing, turning (general cutting) and parting off operations from rear has been observed. The result shows the increase in the rigidity of the machine for these operations from rear as compared to front. From this one can conclude that machining from rear side is always better based on the rigidity.