Six Sigma Methodology for Reducing Warpage Defect of Sanitary Ware Production

The purpose of this research is to apply DMAIC approach of Six sigma methodology to reduce the loss of sanitary ware in the production line. The warpage problem is one of defectives usually found in production after firing process. The warpage is the deformation of shape and dimension of sanitary wares which cause them look nonconforming and poor appearance. The toilet bowl, AC19 Model, highly demand model, is the case of this study since it has high warpage problem consisting of 17% of total defectives. Six sigma methodology associated with Shainin DOE are used to investigate the root causes in order to increase production yield. The primary area is variation in forming process and the design of plastic mold. The location of warpage is frequently found near the back of sanitary ware that is used to connect to the wall. After some experiments are taken to find the causes, the first important factor is the flatness of base clay ware and the second is the flatness of clay batt, a support sheet. The redesign of a base day ware and quality control of a clay batt are implemented as practical solutions. The warpage defect problem is reduced from 10.94% to 2.56% during the control phase that can prospectively improve production yield of this AC19 model almost 10%.