Analysis of product defects in a typical aluminum extrusion facility

Aluminum extrusions are popular in the automobile, aircraft, and construction industries. They are highly versatile, have relatively modest prototyping costs, possess good strength and corrosion resistance, and yield a high benefit-cost ratio. Technical and economic viability of an extrusion plant depends on the minimization of defects that lead to product rejection. Attempts at improvement of extrusion quality and productivity thus translate straightaway into an analysis of product defects. Product rejection may be traced back to material defects, tooling defects, processing anomalies, and postextrusion and surface finishing defects. The first part of the current paper gives a brief description of extrusion defects generally encountered in a commercial setup. The second part deals with collection and categorization of real world rejection data (spanning 9 years) from a local aluminum extrusion facility, plant activities being divided into three major cost centers: press, anodizing, and painting. The last part presents a statistical analysis of defects from three different viewpoints: (1) plantwise defects breakdown, (2) annual rejection scenario, and (3) defects breakdown in each cost center. Rejection and acceptance percentages at each cost center have been worked out relative to individual cost center production and in relation to total plant production.