EXPERIMENTAL STUDY ON EFFECT OF MODERN METHODS FOR DEWAXING CERAMIC SHELL FOR INVESTMENT CASTING PROCESS

Abstract

investment casting is the process well known for achieving excellent finishing of surface, accuracy of dimensions and intricate shapes development. The process parameters behind the preparation of wax blends and ceramic slurry make the investment casting process laborious and troublesome. Due to the thermal expansion, shrinkage of material of pattern, material of mould and solidification of alloy being casted, there are changes that occur between pattern and its corresponding part of casting. Composition of the wax plays a vital role to optimization of the expansion, shrinkage and maximization of hardness of pattern. The ceramic slurry, composition also plays an important role to improve and stabilize the ceramic slurry. The most crucial step in investment casting is the 'dewaxing' of investment shells. It describes the nature of casting because the surface and dimensional traits of the wax are transferred to the shell of ceramic and it leads to the final stage of casting. In the present work, experiments were conducted with different type of waxes namely paraffin wax, microcrystalline wax and carnauba wax, varying their proportion. The dewaxing of wax from shell was done in microwave and infrared ovens. Using the data obtained from the experiments an attempt has been made to find out the set of input parameters, which could offer a set of ideal properties of wax blend and ceramic slurry. Taguchi method was used to optimize the process parameters. The Orthogonal Array which represents the matrix of number of parameters those are to be varied gives the number of tests to be conducted. Taguchi method has successfully suggested the set of input parameters which could offer the desired properties. The changes in properties like linear shrinkage, volumetric shrinkage, surface roughness and hardness have been calculated by dewaxing the shell in microwave and infrared ovens