WARPAGE IN A STEPPED WAX PATTERN - A SIMULATION APPROACH (original) (raw)
In the process of investment casting of precision blade/vane components for aero-engine applications, generation of a precison wax pattern is the first critical step. A significant part of the dimensional deviations observed in the casting can be attributed to the wax pattern. During the process of generation of wax pattern through injection moulding, two types of dimensional deviations occur, namely shrinkage and warpage. Shrinkage deviations are predictable to a an extent as they are predominantly an outcome of the injection temperature, which is controllable. Warpage on the other hand is difficult to predict as it depends on many other factors of injection molding process. However, control of distortion is critical in order to conform to the strict dimensional tolerances of aerospace standards imposed on the turbine blade/cane castings. Simulation based studies are emerging as the preferred route for prediction of extent and location of warpage in precision wax patterns. In the present study, Moldex3D based simulation package has been utilized to anlyze the effect of injection temperature, packing pressure, cooling time and flow rate on the distortion behavior of a stepped pattern. Two types of waxes with different rheological properties have also been included to gauge the effect of change in wax on the warpage. A full factorial design of experiments has been configured and results of the analysis of variance is presented.
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