Quality Control Analysis of Product Defects Using Seven Tools Method & PDCA

Quality Control

Abstrak

The injection molding industry faces persistent challenges in maintaining consistent product quality, particularly in high-volume plastic component manufacturing. At the company studied, the Tank Cold Water (CWT) OPP model product exhibited a notably high defect rate, posing risks to production efficiency and customer satisfaction. This problem necessitates a systematic quality control approach to identify root causes and formulate effective corrective actions. This study aims to analyze and control the quality of Tank Cold Water OPP model products using the Seven Tools method and the PDCA cycle. Production defect data from June 2023 to April 2024 (15 observation periods) were analyzed using checksheets, histograms, P-control charts, scatter diagrams, Pareto diagrams, and fishbone diagrams. Results show that out of 2,143,806 total production units, 79,995 defective units were recorded, yielding an average defect rate of 3.73%. Based on the Pareto diagram, Foreign Material is the most dominant defect type at 55.51%, followed by Blackdot (30.34%) and Oily (14.15%). Fishbone diagram analysis identified four main root-cause categories: machine, environment, method, and personnel. Corrective action proposals were formulated using the 5W+1H framework, covering periodic machine maintenance, production area housekeeping, SOP updates, and structured operator training. This research is expected to serve as a reference to pursuit of zero defect production.