EFFECT OF PROCESS VARIABLES ON THE QUALITY OF Al-7% Si ALLOY CASTINGS PRODUCED BY EPC PROCESS

Abstract

Casting industry has several challenges. These are to control costs, decrease lead-time from product design to production, production of intricate and near net shape castings and improved casting quality. Evaporative Pattern Casting (EPC) process is one such process which is capable of facing the above challenges. EPC process was introduced as an innovative technology giving rise to improvement over the existing conventional casting methods. EPC process was invented and patented in 1958 in the United States of America. The first commercial casting produced by this process was on June 26, 1963. During the 1960s, the use of EPC process was limited to casting of machinery bases, dies and work of art. EPC process is a sand casting process that uses expandable polystyrene pattern. EPC uses a cavityless mould with the pattern remaining in the sand mould during metal pouring. The polystyrene pattern is replaced by molten metal, producing the casting. It is a binder less process and no physical bonding is required to bind the sand aggregates. Advantages of EPC process, as compared to conventional bonded sand casting techniques, are numerous. No cores are required. Sand is reusable and need for sand additives are eliminated. As a result of these advantages, EPC process offers reduced moulding time, tooling cost, fettling cost, and machining cost. However, the castings produced by EPC process have blow holes. The blow holes and/or gas porosity in EPC castings is because of the non-escape of the gas produced as a result of burning of polystyrene pattern in the sand mould.