ENGINEERING JOURNAL CHIANG MAI UNIVERSITY

Volume 27, No. 01, Month APRIL, Year 2020, Pages 72 - 86

Defects reduction from the complaints as customer modification requirements

Somyos Phongsai and Jeerapat Ngaoprasertwong

Abstract Download PDF

This research aims to decrease faults from the complaints by the customer from the case study company’s truck modification, focusing on customer’s order truck modification. The study has shown that damaged chassis have the greatest number of complaints, which negatively affects both safety of users and the company’s image. Therefore, the researcher has applied the Six Sigma technique with DMAIC methods to improve the quality of welding modification process. The 2k-1 Factorial Design has been used to find the significantly fault causing factor and the Box-Behnken Design has been used to find the appropriate level of factors – from the five factors used in the study which are electric current, electromotive force, electrode angle, travel speed and rules of welding observing. The researcher has collected and analyzed statistical significance showing that electric current, electromotive force and travel speed have significantly caused the faults: the appropriate electric current is 230A, the appropriate electromotive force is 26V and the appropriate travel speed is 40 cm/min. This improvement has diminished proportion of faults in welding modification process from 0.23% to 0.08% which resulted in decreased repairing expenses of the case study company.

Keywords

Six Sigma, Design, Truck modification, Faults, Complaints

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