US Patent 7594417 Apparatus for wiper die monitoring

In a rotary tube bender, a first set of pressure sensors is located between the normally disposed mating surfaces of a wiper die insert and its wiper die holder; and a second set of pressure sensors is located between the axially disposed surfaces of the wiper die insert and the wiper die holder. Signal outputs of the first and second sets of pressure sensors over the course of bending cycles are compared to previously determined nominal signal outputs for drift indicative of whether a realignment or replacement of the wiper die should be performed.