Precise filling time calculation of thin-walled investment casting in hot mold

Abstract

The production of thin-walled investment castings causes severe difficulty during mold filling by liquid metal due to small opening and proportionate large galloping width in annular molds. The filling time calculated by employing mass flow rates using classical Bernoulli’s energy conservation equation obviously deserves certain modifications. The first factor introduced comes from the restriction imposed by small opening in the wide channel in terms of the frictional head loss operating during metal flow. The second one is the kinetic energy factor normalizing the actual velocity of the flowing liquid in the annular channel with its average velocity. The third resistance comes from pressure drop due to the capillary action of the liquid with its vapor phase. The only saving grace though negligible for the ease of filling arises from the suction by the Torricellian vacuum created within the mold. On this basis precision filling time mathematics has been developed for the thin-walled investment casting. Simulation experiments were conducted with liquid mercury, and actual metal castings of aluminum alloy and copper alloys in hot clay molds were produced to verify the developed mathematics. In both occasions, the results were encouraging for justification of the model in regular use.