Application of Six Sigma Methodology for Enhancement of Soft Plastic Extrusion Process

Abstract

The gasket manufacturing process in “Company A” faced significant challenges and inefficiencies because of high rejection rates and variation in extrusion machine, magnetic insertion machine and welding machine’s performance. All three machines were consistently generating major rejections on a daily basis including a high volume of purging rejections from the PVC soft extrusion machine, excessive trimming of oversized magnets during the magnetic insertion process, and significant rejection due to poor joint strength in the welding process of PVC profiles. In order to address these underlying issues, Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) methodology was employed in order to decrease rejection/waste, increase process efficiency and decrease defects of all three machines. The study involved process mapping, cause and effect analysis, quality function deployment (QFD) and statistical process tools such as ANOVA, regression and Cp/Cpk analysis. Root causes were identified and targeted improvements based on the data were introduced including optimized production planning, machine parameter optimization and standardization, improvement of production execution planning and storage availability, temperature controls on welding machines and encoder wheel knurling for magnetic insertion machine. The main objectives were to deal with problems including material waste, variance in magnetic strip size, issues in welding machines and frequent machine stoppages caused by improper production scheduling because of improper availability of storage space for batch production independent of door pre-assembly plan. Following implementation, results show a considerable decrease in extrusion machine rejection %age from 12% to 4.06%, a reduction in purging waste from 17 kg/day to 6.9 kg/day and an increase in machine efficiency from 50.1% to 83.3%. Furthermore, welding machine rejection %age fell from 7% to 3.7% as a result of enhanced temperature management and equipment maintenance. Size variation issue in magnet insertion machine was resolved by knurling of encoder wheel. Overall, these changes resulted in an annual cost savings of roughly 1.5 million PKR for the extrusion process and 1.2 million from magnet insertion machine. The significance of this project originates from its potential to streamline the gasket production process by reducing waste and faults while increasing machine efficiency. The results offer a replicable framework that can be employed across wide range of manufacturing industries for quality improvement and cost optimization.