Application of Statistical Process Control in Minimizing Defects in the Production of UPVC Sanitary Pipes

Abstract

Introduction: Plastic processing industry is considered an important industry that supported other industries in the construction of building, establishments both commercial or industrial, housing, etc. Producing quality plastic products such as sanitary pipes are essential in the sewage conveyance, rainwater drainage, waste disposal, and the like and its quality is of prime importance. In this study, the various quality controls of Statistical Process Control (SPC) were used to minimize defects and produce quality sanitary pipes.

Objectives: This study aims to determine if there are special causes of variation in the process of producing uPVC sanitary pipes using x-bar control chart. Furthermore, the study seeks to identify the causes of these variations or defects through employing pareto chart and fishbone diagram. And also, to develop an action plan to address and minimize the defects in order to improve the quality of the uPVC pipes.

Methods: The study was conducted in the plastic manufacturing industry in Davao City, Philippines. The study employs statistical process control tools such as x-bar chart to determine if the process is statistically controlled. The pareto chart is utilized to determine the types of defects and its frequency. Lastly, fishbone diagram was utilized to determine the cause and effect of the identified defects. The study also provided an action plan based on the information given in the quality control tools used.

Results: After the study was conducted, the following were the results: the uPVC sanitary pipes sizes #2 and #4 specifically on their weight and thickness were found to be statistically not controlled using the x-bar control chart. The pareto chart revealed that defects related to weight and thickness of the pipe and the fishbone diagram presented the causes of these defects with respect to machine, man, method, and materials.

Conclusions: The Statistical Process Control tools such as x-bar chart, pareto chart, and fishbone diagram were used to study and understand the complex nature of production of uPVC sanitary pipes especially when encountering special causes of variations, also in identifying the defects and causes, so as to minimize the occurrence of these defects and improve the quality. The study concluded that the combined application of the mentioned control tools was useful in determining if the process is statistically controlled or not and in identifying the causes of common defects. The suggested action plan is based on the result of the application of the Statistical Process Control tools and is helpful in detecting and in minimizing defects in the production of uPVC sanitary pipes.