Investigation of Product Defect Rates in a Glass Bottle Manufacturing Company in Ogun State

This research investigates product defect rates and root causes at a glass bottle manufacturing company in Ogun State, South West Nigeria. Glass bottle manufacturing involves complex interactions among furnace temperature, gob weight, mould condition, and forming machine timing, all of which must be precisely controlled to minimise defects such as birdswings, stones, checks, and dimensional non-conformances. This study employs a defect measurement and root cause analysis approach, combining systematic defect inspection and classification of five hundred bottles sampled daily over six weeks with Pareto analysis and fishbone diagram construction for the three highest-frequency defect types. Production parameter data were extracted from process control records and cross-referenced with defect occurrence patterns. Results show that birdswing defects, arising from incompletely formed glass in the lower section of the bottle, account for thirty-nine percent of total defects and are strongly correlated with gob weight variability exceeding plus or minus two grams. Stones, inclusions of unmelted batch materials, constitute the second most frequent defect category and are traced to insufficient batch homogenisation time in the mixing stage. Recommendations include tightening gob weight control tolerances, extending batch mixing time, and establishing a defect monitoring dashboard for real-time production floor visibility. Keywords: glass bottle manufacturing, defect analysis, Pareto analysis, Ogun State, quality improvement