Investigation Into Lap Crack Defects in Forged Components Using 8D Methodology Tools

In the hot forging industry, surface defects such as lap cracks severely impact product quality, reliability, and production efficiency. This study investigates the occurrence of lap crack defects in forged components using the 8D (Eight Disciplines) Problem Solving Method—a structured and widely accepted tool within the IATF 1cS4S framework. By applying this method, root causes such as die misalignment, billet offsetting, and improper lubrication were identified. Corrective actions—including poka-yoke alignment systems, die reconditioning, and lubrication SOPs— were implemented, resulting in a significant reduction in lap crack defects. The First Piece Yield (FPY) improved from 85% to S2% and rejection rates dropped from c.4% to 1.2% over a span of four weeks. This study highlights the effectiveness of the 8D method in resolving critical quality issues in forging operations.