Analysis of Car Body Paint Glossiness Using Statistical Process Control Method

Abstract

High quality paint glossiness for exterior body panel of a car is critical to the success of automobile sales because it influences the purchasing decision of potential car buyers. A study was performed in a local automotive manufacturing factory to analyze paint glossiness. Incidentally, the company was experiencing reworks to some of its products, where it was estimated about RM1100 a month or RM13200 annum spent for bad quality coating. This project used statistical process control (SPC) method for analysis purpose. In particular, x and R charts, Cp and Cpk indices were utilized in this study. The Cp index shows how well the process spread is compared to the specification spread or tolerance and the Cpk index shows whether the process is producing reject or not. Meanwhile, 4M cause effect factors; Men, Machines, Methods and Materials were analyzed to determine sources of variation. Analysis shows that the painting process is in out-of-control situation; control charts show unnatural runs and existence of some outlier points. Cp value is found to be 1.22, lower than de facto standard of 1.33 while Cpk value is 0.94, lower than de facto standard of 1.00. It was found that rework percentage is 1.84%. Preventive actions and countermeasures are proposed in order to get the process in control and back on its target. The proposed solutions are expected to improve the quality of paint glossiness and reduce the amount, as well as costs of reworks.