Abstract
PT. PQR produces casting for automotive products. Based on data from the Quality Control department, there are several products with high defect levels and most of defect products are categorized as scrap that make the company's efficiency decrease. This condition is very detrimental to the company because it will add costs that should not be spent. Therefore, this research is conducted on the causes of defects for finding the solutions. The results of the observation showed that the data during January - March 2017 knuckle arm steering products had a defect rate of 20.04% with macro shrinkage as the biggest contributor. In March-July 2017 improvements were made with the concept of lean manufacturing with the PDCA method. The results of these improvements provide improved quality of knuckle arm steering products so that defects are reduced by 15.01% to 5.03%. Then the cost incurred before improvement is Rp. 2,626,160 and after improvement is Rp 2,224,890