To improve the first pass yield rate of polish line in an automobile paint shop, this paper focuses on the critical top coat defects such as crater, other paint, paint runner, solvent spot and paint sludge. The research diagnoses the root causes of various defects systematically through Manufacturing Report System (MRS) quality analysis system and "human, machine, material, methodology, environment" real reason analysis method combining infrared spectrum, element analysis and production verification. There are some targeted countermeasures to solve the defect issues such as changing the fluorine-containing lubricating grease of high temperature zone, optimizing top coat color sequence, strengthen equipment pre-maintenance, adjusting process parameter and changing fault part. The first pass yield of polish line increases from 79% to 91% and the average daily line downtime is reduced by 62% due to the countermeasures implementation. The research shows that systemtic root cause analysis and precise process impoovements are the key to enhancing coating quality and production efficiency.

Polish  /  First delivery rate  /  Top coat  /  Defect  /  Quality