Reduction of Bit-Type Defects in Powder Coating Production:A Case Study in Thailand

In the manufacturing of polyester powder coatings at a case study factory, it was found that waste caused by pigment bit issue accounted for 49.82% of total production waste. This significantly impacted productivity and production costs. Therefore, the objective of this research is to study the factors contributing to pigment-related defects in the manufacturing of Polyester-TGIC-HG powder coatings and to identify methods for reducing the percentage of such waste. The factors affecting the occurrence of pigment bits include the method used to clean the extruder, the screw speed settings, and the extrusion temperature. This research conducted experiments to study the effects of these three variables: the cleaning method of the extruder (Open/No Open), extrusion temperatures (50, 60, and 80 degrees Celsius), and screw speeds (400 and 500 revolutions per minute). The response variable was the percentage of pigment-related waste. Analysis of variance revealed that changes in all three factors had a statistically significant effect on the percentage of waste produced. The optimal condition for minimizing pigment-related waste was found to be using the open cleaning method, an extrusion temperature of 60°C, and a screw speed of 400 rpm. Under these conditions, the percentage of pigment-related waste was reduced from 49.82% to 13.87% of total production waste. representing a 72.2% improvement in reducing bit-type defects. The implementation of the optimized conditions reduced monthly rework costs from 25,708.02 THB to 18,795.68 THB, representing a 26% cost reduction. This financial impact highlights the practical benefits of process optimization beyond defect reduction.