Statistical Process Control in Manufacturing Quality Management at Innoson Vehicle Manufacturing, Nnewi

This study applies statistical process control methods to quality management challenges in the manufacturing operations of Innoson Vehicle Manufacturing Company in Nnewi, Anambra State, South East Nigeria, Africa's first indigenous automobile manufacturer. Statistical process control provides a rigorous quantitative framework for monitoring production processes, detecting assignable causes of variation, and reducing defect rates, and its application in Nigerian manufacturing contexts remains underdeveloped relative to its importance in global quality management practice. The study collects dimensional measurement data on selected automotive components from the body assembly and chassis fabrication lines over a twelve-week monitoring period, with measurements taken at regular intervals during each production shift. Shewhart control charts, including X-bar and R charts for continuous measurements and p-charts for attribute data, are constructed and analysed for evidence of process instability. Process capability indices, including Cp and Cpk, are computed to assess the extent to which current process performance meets engineering specification limits. Results reveal that three of the seven monitored quality characteristics show evidence of special cause variation, manifesting as points beyond control limits and non-random runs patterns. Process capability analysis indicates that two characteristics fail to meet minimum capability thresholds. The study recommends the establishment of a dedicated statistical quality control team and the adoption of real-time monitoring software. Keywords: statistical process control, control charts, process capability, manufacturing quality, Innoson