Process parameters optimization and airflow analysis of green sand mould to minimize the mould related defects in iron castings

Abstract

In the fast-growing industrial scenario, the foundries have to supply a high volume of good quality iron castings at the least cost in a short time. In order to improve the quality and productivity of the castings, nowadays the modern green sand iron castings foundries are equipped with sand plant, automatic moulding machines, auto pouring system with conveyors and fettling machines. When the moulds are produced in the automatic high-pressure moulding machine, the mould production rate increases due to automation (150 to 200 moulds with minimum mould height of 130mm) and the densely packed moulding sand improves the casting quality like dimensional accuracy and surface finish. Because of higher mould productivity in automatic moulding machines, vent holes are not provided in the moulds. Also nowadays, the blind risers are widely used in sand moulds to increase the casting yield percentage. The densely packed mould, lack of vent holes, usage of blind riser and high mould height reduces the mould permeability. This results in more mould-related casting defects (the mould-related casting rejection rate is nearly 35 % to 45 % of the total casting rejection in most of the green sand iron casting foundries), especially in more thickness castings. newlineIn this research work, an attempt is made to improve the permeability of the high-density moulds (hardness value of more than 90) produced in an automatic horizontal high-pressure moulding machine without man-made vent holes. For this the two important green sand mould properties such as permeability and hardness (output responses) are improved by optimizing the influencing process parameters (input variables) such as a number of ramming, mould wall thickness and western bentonite percentage using Taguchi-integrated Grey Relational Analysis (GRA) and Multi-Objective newline newline