Reduction in earring failure of pilfer proof caps

摘要

This case study is concerned with a phenomenon known as earring (which may be positive or negative) that occurs in sheet metals. A reputed Indian integrated aluminium company was having a high rejection of around 5% due to this problem. The objective of this study was to reduce the rejection due to earring. A step-wise regression approach was used. Since the aim is to minimize the earring, subject to the ranges of variation of the process variables as permitted in the specification given, the problem was formulated as a linear programming minimization problem and the optimal values of the variables determined. Again, as technologically it is virtually impossible to have one fixed value for these process parameters, a sensitivity analysis was performed and the ranges over which the optimal value continues to be optimal determined. These determined ranges were within the given specifications. The plant tried with these specifications and achieved creditable results.