Optimization of Seam Sealing Process Parameters Using Statistical Process Control for Waterproof Outerwear Production

Abstract

The seam sealing process is a critical stage in the production of waterproof outerwear because it seals needle holes created during sewing, thereby preventing water penetration and ensuring the waterproof performance of the garment. At PT X, leakage defects were identified in the neck, shoulder, and armhole areas, causing the products to fail to meet the buyer's zero-defect quality standard. This study aimed to identify defect patterns and root causes, control process variation using Statistical Process Control (SPC), and determine the optimum seam sealing parameters as a basis for process standardization. Previous studies have primarily focused on evaluating materials, seam construction, or seam sealing process parameters independently. This study extends previous research by integrating SPC with process parameter optimization to identify sources of process variation, determine the root causes of defects, and establish optimal process parameters for quality improvement. This study employed a quantitative, descriptive, and experimental approach using check sheets, histograms, Pareto diagrams, p-control charts, and fishbone diagrams, followed by experiments with sealing temperatures ranging from 450⁰C to 490⁰C and machine speeds of 3.5–4.0 ft/min at a constant pressure of 0.6 MPa. Water resistance was evaluated using an HTM-2225A waterproofness tester. The results showed that 75 of 90 inspection points (83.33%) experienced leakage defects. Pareto analysis revealed that the armhole and shoulder areas accounted for 72% of the total defects, making them the primary priorities for process improvement. Parameter optimization demonstrated that a sealing temperature of 480⁰C reduced the defect proportion to 33.33%, while the combination of 480⁰C, 3.8 ft/min, and 0.6 MPa achieved the best sealing performance with no leakage observed at any inspection point. These findings indicate that integrating SPC with process parameter optimization provides an effective basis for standardizing the seam sealing process, reducing process variation, and improving the quality consistency of waterproof outerwear.