• Manganese, phosphorous, silicon and the main carbide formers were associated with a local segregation phenomenon.


rather than defect occurrence.


• Potential reasons for improved impact resistance in the bottom part of the casting include smaller ferrite grain size, lower pearlite per- centage and higher nodule count.


Presentation


Management Decision Making and the Cost/Benefit of Multiple 100% Inspections (12-049)


Author


Ted Schorn, Enkei America Inc., Columbus, Ind.


Background Tis presentation developed a model


of the cost and quality effectiveness of single and multiple 100% inspections and applied the model to management decision making in the metalcasting facility. Four specific cost cases were evaluated against a series of potential scenarios of visual inspection error and the number of inspections performed (Fig. 4). Conclusions were drawn about the advisability of 100% inspections.


Conclusions


• Repeated inspection of accepted product will improve the outgo- ing quality level. The defect rate in outgoing product will fall as the number of inspections increases.


• Repeated inspections of accepted product at poor inspection effectiveness are inefficient and susceptible to false alarms.


• Repeated inspections of rejected parts to find false alarms are not recom- mended on a cost or quality basis.


• Improving the quality of inspec- tion by reducing the miss rate and/ or false alarm rate is a valid means of reducing the ongoing cost of quality. In the cases considered in this work, an improvement in effectiveness of inspection of 12.5% was as valuable on a cost basis as a 50% reduction in the internal reject rate.


May 2012 MODERN CASTING | 57


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