PERFORMANCE EVALUATION OF MACHINE TOOL STRUCTURES

Abstract

The properties of machine tool structure are important factors that influence the performance of machine tools. The structure of the machine tool forms the vital link between the cutting tool and workpiece on the machine. This is particularly crucial when stability against chatter is an important consideration. Traditionally, machine tool beds are made of cast iron because they have high rigidity, they can be cast into complex and intricate shapes and can be easily machined to high degree of accuracy. However, low damping ratio, high shrinkage rates during curing, high production cost, etc. have led the researchers of machine tools to look for a suitable replacement which will offer high rigidity, high damping, low cost, etc. Cementitious materials like ferrocement, etc. have been found to have quite high rigidity and damping, at the same time they are easy to cast and are quite cheap. Polymer impregnation is expected to further upgrade the rigidity and damping. An attempt will be made in this study to improve the machine tool structure both through design modification and by introducing new structural materials. Prototype bed of a lathe machine was fabricated from ferrocement and subjected to a series of tests to determine its static and dynamic properties. The study was further carried out by assemblying the bed into an actual lathe machine and its performance was evaluated on the basis of cutting test. An attempt was also made to evaluate the machine tool performance with fibrous ferrocement and polymer impregnated ferrocement.