Abstract

Quality is a standard requirement needed by foundries to survive in the market and rejection due to defects is the prime setback for such industries as it decreases the credibility of that specific industry. Depending on the type of foundry and other factors such as type of sand, casting material, molding methods, etc. there are specific defects that are more prominent than the others. It is observed in the industry that core shift and sand drop defects are the major reasons for most of the rejections of casted parts. Considering these facts, it is proposed that the generation of defects may involve single or multiple causes, hence it is studied through a systematic procedure using cause effect, Pareto analysis and Why-Why analysis of each and every defect existing in the product, which in turn helps to point out the root cause of the major defects. A study of sand parameters in relation to the defects gives the means of correction in the molding sand. Sand parameters include moisture, permeability, compactibility and green compressive strength. Analysis for core shift and sand drop was undertaken on the product Crank Case 3000 with the help of quality improvement methods.

Keywords: casting defect reduction, core shift, sand drop, DOE & ANOVA

#### 1. Introduction

Sand drop and core shift are defects based on molding sand properties. Sand drops are inappropriately shaped crests that occur when the loose sand breaks away from the mold and falls into the cavity. Core shift occurs when the position of the core changes from the required place due to misalignment of cope and drag. These defects occur when the required strength of sand is inadequate. Dirty casting surfaces and inaccurate measurements of hollow parts in castings are causes of sand drop and core shift respectively.
