EFFECT OF PROCESS VARIABLES ON CASTINGS PRODUCED BY CERAMIC SHELL INVESTMENT CASTING PROCESS

Abstract

In the current competitive environment, casting industry has several challenges such as production of intricate castings, near net shape castings, decrease lead-time from product design to production, improved casting quality and to control costs. Casting of metal part closer to its final specification in relatively shorter lead-time shows a greater promise to wards the survival of small and medium scale industries. Ceramic shell investment casting is one of the near net shape casting technologies which has the potential to satisfy the above mentioned challenges. The Ceramic Shell Investment Casting Process uses an expendable/ disposable pattern (usually wax) which is coated with ceramic slurry and allowed to harden to form a disposable casting mold. Very fine details and thin sections can be produced by this process, because the mould is preheated before pouring. Possibility of complete elimination or substantial minimization of costly machining operations on castings may make the process very cost effective. The process is very specialized and has not gained much commercial grounds in India. Since the investment casting process is relatively complex and expensive compared with other casting processes (e.g., sand, permanent mold, etc.), total reliance on the old-fashioned trial-and-error approach in selecting various process parameters is generally found to be tedious, time-consuming, expensive and inadequate. In this investigation, indigenously procured materials were used and the process of making the ceramic shell investment casting was established. The effect of process variables on various characteristics of the castings produced was also studied. The investigation to quantify the relative influence of these variables and their individual contribution in affecting the shell mold and casting characteristics would help in determining optimal sets of process variables. The present research was undertaken with a main objective to study the effect of process variables on various characteristics of the castings produced by ceramic shell investment casting process. The objectives of the present investigation are summarized below: • Design, development and fabrication of experimental setup for Investment casting process. • Fabrication of wax injection machine with a provision to prepare wax patterns at different process parametric conditions • Selection of best wax blend for pattern making and selection of shell mold materials