#003 Chaff Rising Countermeasures in Punching Work (1)
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
- | The supply of oil to the material is made large on the side surface of the die and made small on the punch side. | |
- | -A relief is prepared on the bottom surface of the punch (the surface that comes into contact with the material) thereby making the contact area smaller. | |
- | An air hole blowing weak air is prepared. (It is better to use this along with the above relief.) |
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
- | Since the pressure reduction is proportional to the punch speed, reduce the spm of the operation.。 | |
- | Open an air inlet hole |
* | Placing a kicker pin and suppressing the rise of chaff forcibly is a countermeasure that is effective for all chaff rising irrespective of the cause. We have discussed here only other countermeasures that are possible. |


- #167 Problems in Punching and their Countermeasures (6) Scrap Processing in Punching
- #166 Problems in Punching and their Countermeasures (5) Trimming of Drawn and Shaped Parts
- #165 Problems in Punching and their Countermeasures (4) Scrap Clogging in Punching
- #164 Problems in Punching and their Countermeasures (3) Bending and Twisting of Narrow Punched Parts
- #163 Problems in Punching and their Countermeasures (2) Bending due to Punching

