Reliability and performance evaluation of extrusion dies

Extrusion dies are made of hot working tool steels and they can fail due to a variety of failure modes, such as wear, cracking and mechanical and thermal fatigue. Important features of the die damage processes are identified and approaches to minimise the tool damage are highlighted in this paper. Inservice performance evaluation is done using industrial data of time to failure of dies of different complexity. It shows a significant variability around its average value. Keeping in view the average value and dispersion in the die life, the nature of their failure rate is explored and appropriate reliability characterisation is provided. Based upon the reliable life modelling, an interpretation of tool quality and its performance in view of Taguchi's loss function is also provided to compare dies produced by two competing manufacturers, die materials or heat treatment processing cycle. Finally, some recommendations to enhance die life are provided.