Application of “8D Methodology" for the Root Cause Analysis and Reduction of Valve Spring Rejection in a Valve Spring Manufacturing Company: A Case Study

Abstract

The Eight Disciplines (8D) is a problem solving technique intended to identify the root cause of a problem.8D is a phenomenal first step to enhancing Quality and Reliability when the product is defective or not satisfying the customer. The study was conducted in a manufacturing company producing springs & stampings. The data was collected for a period of Six months from January 2014 to June 2014, to identify defective percentage of valve spring components and they were found to be high at the average rate of 17.07%. In this work the objective was set to reduce the rejection level to 5%. In order to achieve this, 8D problem solving technique was used to analyse and solve the problem. Then, Pareto analysis was done to identify vital causes contributing defectives. From the Pareto analysis, it was found that functioning length variation (L2) is the major cause for rejection. Further brainstorming sessions was held to identify the root causes. After the brainstorming session, cause and effect diagram was constructed and 5why analysis was carried out and it was found to be variation in the pitch distance at the begin-end side leading to negative helix in the functioning length of the valve spring. The suggestions to reduce the rejection percentage were to make pitch distance equal at begin-end side of the valve spring and to gradually increase the pitch up to 2 coils. After implementing the suggestion the pitch distance were equal at the begin-end side of the spring which reduces the negative helix in the functioning length reducing the percentage of rejection to 4.91% in July 2014, from average rejection of 17.07% (6 months data).