Six Sigma Applications to Reduce the Cycle Time of Sub-Assembly Line in the Bicycle Manufacturing Process


  • W.N.M Wejesiri
  • R.A.S.A Perera
  • T.S.M. Amarasena


Bicycle manufacturing, Cycle time, Operator, Six Sigma, Sub-assembly line


Six Sigma is a project-driven approach to improve business performance error-free. This study is an applied and mixed-method study that focuses on applying Six Sigma Methodology to improve the sub-assembly line of a bicycle manufacturing system. The main objective of the study is “To improve the assembly line production system by reducing the cycle time, applying Six Sigma Methodology in the bicycle production system in ABC Company” To achieve the main objective of the study, two sub-objectives are addressed. “To identify the relationship between the contribution of the operator's delay time to the total production time to reduce the cycle time of the sub-assembly line.” and “To identify whether there is a significant difference between the cycle time of the sub-assembly the line before and after the Six Sigma application.” Primary data are collected for the 30 sample units, related to the time performance of the sub-assembly line operators and interviews are conducted with 05 employees to get an idea about the current process. The direct observation method is used to collect data from the sample. DMAIC methodology (D-Define, M-Measure, A- Analyze, I-Improvement, C-Control) which is discussed in Six Sigma is applied and under it Correlation analysis, Pareto analysis, range chart and mean chart, Cause and effect diagram are used to analyse the data. Analysis data revealed that the current process can be found with random and assignable variations, and it is not under control. The viewpoint of Men, Methods, Materials, Machine causes are affected by the higher cycle time of the sub-assembly line and make a deviation to unbalance the assembly line. All the operators positively contributed to generating delay time to the total production time of the sub-assembly line. By applying the Six Sigma methodology, the sub-assembly line is redesigned and balanced with reducing one operator and providing more facilities to the sublime. By applying the Six Sigma methodology the Sigma level increased from 0.8 – 8.5 level to 2.2 to 2.3 levels. One tail sample t test indicates that the cycle time is reduced due to the Six Sigma methodology. It can be concluded that Six Sigma methodology can be successfully applied to improve the sub-assembly line production system by reducing the cycle time of the bicycle manufacturing process of ABC Company.