The Doctor was recently called in to investigate a variable-hardness issue involving rotary cutting dies. The process used to diagnose what was wrong and how to correct the problem offers a number of important lessons. Let’s learn more.
Areas of variable hardness (i.e., hard and soft spots) were identified along the blade length (i.e., cut edge) of 4150 rotary cutting dies (Fig. 1). The hardness problem had been occurring, off and on, for a number of years. Some parts came out very good, and others did not. No apparent pattern existed. For example, two mirror-image dies (same size, same material, same manufacturing method, same production time frame) yielded one good and one bad part.