(1) Sideward Force (F)

As shown in Fig. 1, the sideward force is the force that is generated in a direction at right angles to the forming force. When the remaining width of the material is small, the material is pressed by the sideward force and can get deformed.

The effect on the punch is that it is pushed to one side, and the clearance changes thereby changing the blanking state. The die can break if its cutting edge part is weak. The sideward force increases in proportional to the blanking process. It also changes depending on the size of the blanking clearance. The sideward force is expressed as follows.

Fig. 2 shows the coefficient (Kf) of the sideward force when the clearance is 3%. In the case of a soft steel plate, care should be taken because this can become even larger than 30% of the blanking force.

(2) Scrap Removing Force (Ps)

This is also called the stripping force. This is the force required to detach the material that has got stuck to the punch. (See Fig. 3.)

This force is indicated as follows with respect to the blanking force (P).

The scrap removing force varies between 0.03 and 0.08. The scrap removing force changes greatly with the clearance. This force becomes large as the clearance becomes small and becomes a minimum at a clearance of about 20%.
In the case of a movable stripper type die, this scrap removing force is required to determine the strength of the spring. When flatness is obtained by pressing the material using a movable stripper, the above value of Ks is insufficient, and it will have to be made much larger. The value of Ks in this case will be about 0.1 to 1.0. The more frequently used value of Ks is in the range of 0.1 to 0.3.