Design Approach for Quality Improvement and Cost Reduction: A Case Study of Cable Manufacturing
Chukwuebuka M. U- Dominic *
Department of Industrial and Production Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
Harold C. Godwin
Department of Industrial and Production Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
Nkemakonam Igbokwe
Department of Industrial and Production Engineering, Nnamdi Azikiwe University, Awka, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
In this study, an extrusion process was studied in a cable manufacturing company located in Southeastern Nigeria. The critical-to-quality (CTQ) characteristic considered in the study was the cable diameter and the design effort was to reduce the possibilities of having cables with inconsistent dimensions. Taguchi Orthogonal Array Design L16 (4˄2) was used to achieve the optimum parameter settings after statistically investigating the assumed correlations between the process parameters in relation to cable dimension. Thereafter, an appropriate engineering tolerance interval for the improved process was designed to tighten the existing tolerance of the process from T±0.185 to T±0.032, thus reducing the engineering tolerance by 82.7% from the initial tolerance limit. After the process improvement, the Taguchi loss function approach was used to estimate cost attributed to deviations. The loss function estimation result has shown that the cost attributed to cable diameter deviations from the nominal value reduced from the initial value of ₦7.34/coil to a reduced cost of ₦2.08/coil. The sigma level increased from 0.6 to 5.2 at the project termination stage and the estimated annual loss decreased by 72% from the baseline value.
Keywords: Cable manufacturing, engineering tolerance, loss function, sigma level, Taguchi design.