DESIGN AND EVALUATION OF A MACHINE TOOL COLUMN MADE OF CEMENTITIOUS COMPOSITES

Abstract

In this study, an investigation was carried out on the feasibility of using steel fibre reinforced concrete (SFRC) to replace the conventional material, cast iron, in the fabrication. Firstly, the mechanical properties of the steel fibre reinforced concrete were studied. A total of 18 mixes of steel fibre reinforced concrete (SFRC) were prepared. Based on static, dynamic and long-term dimensional stability tests, it was observed that two kinds of mixes provided the required alternative to cast iron, they were: polymer modified microsilica enhanced grout (with a trade name RENDEROC TG40) in a concrete matrix containing 1. 5% volume fraction of steel fibres and a normal mortar matrix with 3% volume fraction of steel fibres. The properties of the first mix were relatively better than those of the second one, but the inclusion of large aggregate particles could affect the flowability to fill narrow spaces in the intricate geometry of the structural components. Therefore, within the scope of the present experimental study, the second mix was recommended for the fabrication of the prototype column of a grinding machine. After the design and fabrication of the prototype column, the performance evaluation of the cast iron and the steel fibre reinforced concrete columns was carried out based on static stiffness and dynamic behaviour. Test results showed that the steel fibre reinforced concrete column was statically less rigid but dynamically much better than the cast iron column. Since the actual grinding force is very small, the deflections produced by the actual loading conditions will not be significantly large enough to have any drastic effects on machining accuracy. However, the dynamic behaviour of the structural components of a grinding machine is of great importance. With the advantages of low cost, simple manufacturing process and good dynamic properties, the steel fibre reinforced concrete (SFRC) can be considered as a suitable material to replace cast iron for fabrication of machine tool structures.