Reinventing quality in foundry castings through gearbox housing optimization: A case study approach

Abstract

The Indian Foundry cluster is a key player in the production of metal castings used across various industries, including automobiles, railways, machinery, sanitary appliances, pipes, gears, earth-moving equipment, cement, electric circuits, pumps, valves, and wind turbines. Grey iron is the predominant material, constituting around 68% of all cast parts. In this context, Kolhapur plays a pivotal role in the production of diverse castings in India, primarily focusing on grey iron and SG iron castings, both of which are ferrous materials. The Kolhapur Cluster of Foundries is expected to produce approximately 650,000 tonnes annually, contributing about 7% of India's total cast iron production. However, this cluster encountered challenges related to higher rejection rates for castings due to a variety of defects. One established foundry in Kolhapur faced stricter rejection standards for specific castings. To address these issues, a comprehensive case study was conducted to reduce rejection rates in this foundry. The primary focus of the study was on a specific casting, the Gearbox Housing, which had an initial average rejection rate of 13%. In some instances, this rejection rate spiked to as high as 18% in a single month, resulting in significant revenue losses for the company. The defects observed in Gearbox Housing castings were categorized into two main types: Methoding, Filling, and Solidification-related defects, which included issues like shrinkage porosity and hot tears. Sand and mold-related defects, such as sand inclusion, sand drop, and mold quality issues. The initial step in addressing these defects involved utilizing casting simulation techniques to analyze and tackle shrinkage and porosity issues. A new gating system was designed to enhance the casting process. In the subsequent stage of defect reduction, the Design of Experiment (DoE) tool was employed. This data-driven approach helped refine and optimize the manufacturing process to minimize defects and enhance the overall quality of Gearbox Housing castings. By implementing these strategies, the foundry in Kolhapur successfully reduced rejection rates, thereby safeguarding company revenue and ensuring the production of high-quality castings for various industrial applications.