Increasing the Sigma Level and Customer Value in the Manufacturing Industry: A Case Study of Cover Components

Hari Supriyanto*, Muhammad L. Reyfasha, M. F.R. Supriyanto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Motorcycles have several parts, including the cover and step floor. The cover is the part that has the most defects, with a defect rate of more than 3%. The step floor cover has three types of defects, broken, untidy classification bolts, and Point black points. Based on the Pareto Chart, the most common types of defects are untidy and broken bolts. Those defects can lead to a gap between the cover step floor and the cover floor side. To overcome this problem, the Six Sigma Define, Measure, Analyze, Improvement, and Control (DMAIC) methodology can provide alternative solutions for improvement. The purpose of this paper study is to determine the feasibility of implementing alternative solutions based on the costs of alternative solutions. In the define phase, the steps consist of identifying the defect on cover parts, the production process, and the operation process chart production of the cover step floor. The measurement phase can be conducted using a Pareto chart to measure the most prevalent defects and identify the critical to quality in the production of cover parts, use a control chart to measure the Upper Control Limit (UCL), Centre line (CL), and Lower Control Limit (LCL), and calculate the Sigma Level through Defect Per Million Opportunities (DPMO). Support from finite element analysis is needed to identify stresses on the cover step floor and create alternative solutions. The analysis phase begins with the creation of a fishbone diagram to learn the root causes of defects. At the repair stage, Failure Mode and Effect Analysis (FMEA) is used to determine improvement solutions and alternatives. An alternative solution based on the highest risk priority number is used to design a tool called a jig and fixture; its function is to hold and position the cover step floor during the drilling process. The use of jigs and fixtures can increase process efficiency; there is an increase in the Sigma value and a decrease in the Defect Per Million Opportunities (DPMO) value. This proves that the use of jigs and fixtures is effective in reducing step floor cover defects and increasing customer value. The initial Sigma value was 4.1, whereas, after the implementation of alternative solutions in the form of using jigs and fixtures, the Sigma value was 4.3. This shows that alternative solutions can increase the production efficiency of the cover step floor; there was a decrease in DPMO from 4,660 to 2,550.

Original languageEnglish
Pages (from-to)26-34
Number of pages9
JournalInternational Journal of Mechanical Engineering and Robotics Research
Issue number1
Publication statusPublished - 2024


  • Failure Mode and Effect Analysis (FMEA)
  • Six Sigma DMAIC
  • defect
  • jig and fixture


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