The chaff rising is a defect phenomenon in which the chaff does not remain in the die but rises along the surface of the die. Unfortunately, the fact that countermeasures against burrs have improved and the punching conditions have became better has decreased the frictional force between the punching chaff and the side surface of the die therefore making it easy for punching chaff to rise along the surface of the die.

Cause of chaff rising

The above figures show the main cause. Apart from this, although there are other causes such as magnetism or springing back, etc., their effects are small.

Cause of oil adhesion

The machining oil applied to the surface of the material makes the bottom surface of the punch come into close contact with the material, prevents the inflow of air from the periphery, and raises the material.

Oil adhesion countermeasures

Cause of suction

During the process in which the formation is complete and the punch is returning, the material inside the die becomes a base and the punch becomes a piston, the pressure decreases in the space between the material and the bottom surface of the punch and hence the material is lifted up.

Suction countermeasures