AN IMPROVEMENT OF THE ASSEMBLY PROCESS OF MOTORCYCLE CAP TANK WITH LEAN-SIX SIGMA CONCEPT

Abstract

This paper presents the application of Lean Six Sigma principles in improving the cap tank assembly process of the ZR650 motorcycle model with the objectives of increasing production rates and reducing associated waste using the DMAIC methodology. Two main issues were identified from the D phrase: 1) Production rates were lower than the target of 600 pieces per day, and 2) The proportion of defective products exceeded the acceptable threshold of 10,000 ppm. The M phrase indicated that the assembly cycle time was 45.54 seconds/unit, exceeding the 42.00 seconds/unit target. This resulted in a production rate of only 550 units/day, and the proportion of defective was determined to be 28,440 ppm. The A and I phrases revealed the causes of the problems and subsequently led to the rearrangement of the production line using the ECRS approach, and the revision of sampling plans for components that were purchased from suppliers. In addition, the appropriate material mix between the new and used ingots for the casting process was determined for in-house components. The results showed a reduction in assembly cycle time to 34.31 seconds/unit resulting in a production rate of 804 units/day (33.67% impressment), and decrement in defective rate to 1,997 ppm. The work instruction was established for assembly operations and the p chart was used to monitor the proportion of defectives in the C phrase. In conclusion, the application of the DMAIC methodology for the Lean Six Sigma principles led to significant improvements in productivity and quality, achieving the desired goals which can also serve as guidelines for improving others' processes.