Reduction in Welding Defects and Rejection Rates through Implementation of Six Sigma DMAIC Methodology

Abstract

Six Sigma is being Implemented all over the world as successful Quality Improvement Strategy. This thesis is conducted at a welding Facility to decrease the defect rate of different welding processes used in various Projects of the Welding Facility. The Industry selected is Pakistan Welding Institute (PWI) which is Islamabad Based Welding Industry equipped with modern Welding and testing Equipment. The Scope of the Thesis includes statistical Analysis to evaluate and optimize the welding processes settings; this will improve the yield and sigma value of individual Welding Process and overall Welding Facility. As there are different methodologies Six Sigma adopt to improve Quality of Processes so Define, Measure, Analyze, Improve and Control (DMAIC) was selected for implementation at welding facility. In the define phase first the Project Scope and Charter was clearly to reduce the defect % up to 0.25%. Measure phase includes comprises of measuring the Sigma values of individual processes and establishing the Base line for Project which includes Targeting the Welding process with least sigma level and selecting the target of sigma Level to be obtained, Shield Metal Arc Welding Process was selected as the target Process with Sigma Level of 3.3 Sigma. Base Metal frequently used was Stainless steel. In Analyze Phase Different Screening Experiments were performed to Analyze Source of Variation in Shield Metal Arc Welding Processes. From Analyze Phase Findings an Improvement Strategy was formulated and further on implemented to bring the Welding Process in required Sigma Limits. Further on in the Control Phase of Project the Control Plan was established and Cost of Quality after Improvement was measured which showed major Cost Savings by Improvement in Sigma Values of shielded Metal Arc Welding Process from 3.3 Sigma to 4.3 Sigma and Overall Welding Facilities Sigma Level from 4.0 to 4.3 Sigma.