Electro-deposition painting process improvement of cab truck by Six Sigma concept

Abstract

The case study company is a manufacturer of trucks and currently facing a high rework cost due to the thickness of the electro-deposited paint (EDP) of the truck cab is lower than standard. In addition, the process capability is very low. The Six Sigma concept consisting of 5 phases (DMAIC) is applied to determine new parameter settings for each significant controllable factor. After the improvement, EDP thickness of the truck cab increases from 17.88μ to 20μ (i.e. standard = 20 ± 3μ). Moreover, the process capability indexes (Cp and Cpk) are increased from 0.9 to 1.43, and from 0.27 to 1.43, respectively. This improvement could save the rework cost about 1.6M THB per year.