15. Experimental Investigations on Mould Dilation Characteristics of Synthetic Greensand Systems Using Factorial Design

Greensand systems are known to suffer in the problem of mould dilation which results in dimensional inaccuracy and unsoundness of casting. The problems involved in the manufacture of dimensionally accurate casting have received constant attention of both the scientific investigators as well as the engineers actually facing the problem in the industry. It still remains a living problem in spite of many strides already made towards its solution. In the present study, it is planned to investigate the mould dilation characteristics of river bed sand. Higher compression strength of moulded sand implies higher stiffness or rigidity of mould wall which resists mould dilation better. Binders and additives which improve the mechanical properties of moulds also help to decrease mould wall movement. In order to obtain practically a relationship between mould dilation and mechanical properties of the sand system, the bentonite as a binder is employed in different amounts. The experimental investigations are determined to obtain the optimum range of mould hardness, compressive strength, bulk density, permeability and grain-size distribution which have a greater influence on minimizing the mould wall movement of the moulds prepared by selected sand. Factorial design methodology has been followed in order to obtain the significance of optimum parameters on mould dilation which is monitored by the volume of shrinkage pipe formed on castings. Further, the developed relationship was validated using analysis of variance (ANOVA) technique.