Reducing Warranty Claims and Defects in a Motorbike Industry of Bangladesh Using Lean Six Sigma

Mobassher Al  Hasan; NAYAN NATH; MD MAHFUZUR RAHMAN

doi:10.38032/scse.2026.4.213

Authors

Mobassher Al Hasan Chittagong University of Engineering & Technology, Chittagong, Bangladesh and Jashore University of Science & Technology, Jashore, Bangladesh
NAYAN NATH Jashore University of Science & Technology, Jashore, Bangladesh
MD MAHFUZUR RAHMAN Jashore University of Science & Technology, Jashore, Bangladesh

DOI:

https://doi.org/10.38032/scse.2026.4.213

Keywords:

Lean Six Sigma, DMAIC, DPMO, Control Chart, Root Cause Analysis

Abstract

The main goal of this study is to reduce the number of defects and warranty claims to improve quality in a local motorbike industry. Therefore, Lean Six Sigma was applied in this company at the Jashore plant. Initially, the top five warranty claims were identified and the four major defect areas: material, welding, paint shop, and assembly. Then the DMAIC was applied methodology to improve key performance indicators such as First-Time Right (FTR) and total pass rate, as well as the Six Sigma level. Various Lean tools, including FMEA analysis, DPMO, control charts, Pareto diagrams, fishbone diagrams, 5S, Poka-Yoke, and 5W+1H. In particular, root cause analysis was applied to identify the main reasons behind the increasing number of defects. As a results, The Six Sigma level increased from 3.53 to 4.0075, and the defect percentage decreased from 8.57% to 2.22%. The total number of defective parts during assembly was reduced from 28,772 to 19,174, and the overall pass rate improved from 90.21% to 97.47%. As a result of this research, the company improved quality and reduce costs by implementing the Lean tools as per our recommendations.

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