DEFECT REDUCTION IN PLASTIC PIPE EXTRUSION PROCESS

Abstract

This thesis focuses on the study of defect reduction strategy for a plastic pipe extrusion company in Thailand. The objective of this research is to lower the plastic defect production in the company’s main plastic pipe extrusion line. The main methodology revolves around the Six Sigma’s DMAIC method of defining, measuring, analyzing, improving and controlling the defects created within the company. Define phase studies the Cause-and-Effect Diagram, Risk Analysis, and Pareto Analysis to identify the causes leading to defects production. The Measure phase involve the Failure Mode and Effect Analysis to study the key input factor affecting the causes of defects production. In the Analyze phase, the Design of Experiment (DOE) and Analysis of Variance (ANOVA) are used to determine optimal level for each critical key input factor. For the Improve phase, optimal level key input factors will be implemented and post-improvement data will be collected, followed by cost analysis. Finally, in the Control phase, strategy to sustain and control the optimal level key input factors will be discussed. In the end, the research identifies four key input factors that are mainly responsible to creating defect within the company’s main extrusion line. By finding the optimal parametric input, this research allows the company to reduce manufacturing defects from 8.8% to 5.25%; this 3.55% drop in defect production allows the company to save up to 3,600,000 million Baht on an annual basis.