Application of Six Sigma Methodology in Reducing Defects in a Plastics Packaging Plant in Lagos State

This research applies the Six Sigma DMAIC methodology to reduce defect rates in a plastics packaging manufacturing plant in Lagos State, South West Nigeria. The plastics packaging sector is one of Nigeria's most dynamic manufacturing industries, supplying containers, films, and bags to food, pharmaceutical, and consumer goods producers; however, quality-related losses from defective products remain a significant cost burden for many producers. This study follows the Define, Measure, Analyse, Improve, and Control phases rigorously, beginning with a project charter identifying a fifteen percent defect rate on multi-layer film production as the project focus. Measurement phase activities include gauge reproducibility and repeatability studies and baseline process capability calculation. Analyse phase tools applied include multi-vari analysis, hypothesis testing, and regression analysis to identify significant process variables driving film thickness non-uniformity and seal integrity failures. Results confirm that extruder melt temperature variation and haul-off speed instability are the dominant root causes. Improvement phase interventions include revised temperature controller tuning parameters and installation of an in-line thickness gauge for real-time feedback control. Post-improvement defect rate measurement shows a reduction from fifteen percent to three-point-eight percent, representing a Sigma level improvement from approximately two-point-seven to three-point-eight. Keywords: Six Sigma, DMAIC, plastics packaging, defect reduction, Lagos State