WASTE REDUCTION IN THINNER CONTAINER CAP STAMPING PROCESS USING 7 QC TOOLS

Abstract

    This study aimed to investigate the problems and root causes of defects in the stamping process for thinner-container caps at a case-study factory and to develop appropriate defect-reduction measures. Data collected from February to May 2025 revealed that the production of thinner-container caps incurred the highest defect-related cost, amounting to THB 68,112.45. The seven basic quality control tools (7 QC Tools) were therefore applied to analyze and address the identified problems. The analysis showed that the trimming and piercing operations were the critical stages, together accounting for 88.47% of all defects. The principal defect types were dented parts, double-stamped parts, and incompletely stamped parts. Two corrective measures were implemented. First, the operating procedure was revised by reducing the number of parts stacked in each loading column from 80 to no more than 32 to minimize compressive force. Second, a preventive replacement interval was established for the pneumatic valve controlling the part-ejection airflow, requiring replacement every seven days or after the production of 160,000 parts. Following implementation, the number of dented parts decreased from 11,468 (1.05%) to 2,401 (0.20%). The combined number of double-stamped and incompletely stamped parts decreased from 6,520 (2.37%) to 1,354 (0.77%). These improvements effectively reduced the number of defects and brought the production process back under statistical control.