IMPROVING CASTING PROCESS BY REDUCING SMALL PART DEFECT USING SIX SIGMA APPROACH AT PT. LOL

Abstract

The competition among company has become strict nowadays, PT. LOL as the vendor of battery manufacturing had a commitment with the quality of the product. Recently, PT LOL get a complaint by the customer. The customer complaint about the quality of small part MH that PT. LOL manufactures. Quality Control Division of PT. LOL conduct observation about casting process that leads to the high number of defect. In order to reduce the number of defect, especially in small part MH, the casting process has to be improved by using Six Sigma with DMAIC approach. After conduct the observation in casting process, it is known that most of defect is categorized as shrinkage with the percentage of 12% out of 1,072,172 units of small part MH produce on period June-September 2016 by using Pareto Chart. The root causes of shrinkage have to be analyze, and one of the root cause was parameter setting in casting process. To reduce the number of shrinkage defect, design of experiment was done. The purpose of design of experiment is to find the best new parameters, these parameters aims to reduce the number of shrinkage in small part MH. The result of design of experiment is 450oC of melted lead and 8 seconds of cooling time. Then the investigation using new parameters was conducted. The result is using new parameters shrinkage has reduce from 12% to 4% accompanied with another type of defects. The total defect percentage of small part MH has reduce to 10% from 19%. With the data from investigation it is expected that new parameters can reduce the loss 55% from before.