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#027 Basics of Die Structure (2) Structure of Blanking Dies - 2

Category : Shearing work
February 5, 2010

The purpose of blanking work is the same as that of a die of the fixed stripper structure. In the fixed stripper structure, since the fixed stripper is covering the die plate, some people say they do not like it because they cannot see the condition during working. Further, if a thick plate is blanked, gradually it may get warped making it difficult to carry out the work. Because of this, a movable stripper may be used because it is possible to press down the material. A blanking die of this type of structure is called a "movable stripper structure blanking die".


Compared to the fixed stripper structure, in the movable stripper structure, there are additionally the stripper bolt, spring, and the guide plate. Because of this, the cost will increase to some extent relative to the fixed stripper structure.

If a simple die is required, it is also possible to substitute the movable stripper by tying a urethane spring or rubber around the periphery of the punch. This is used very frequently in the case of small quantity production such as prototyping, etc.

The product gets bent to some extent in blanking work. This is due to the effect of the bending moment that acts on the material at the time of blanking. This cannot be eliminated in ordinary work. Although there are some people who use the movable stripper structure with the purpose of improving this bending, but that is wrong. The bending becomes somewhat larger in the case of the movable stripper structure.

The blanking chaff sticking to the punch is removed from the punch by the force of the spring of the stripper. The size of this force need only be about 3 to 5% of the blanking force when a standard clearance is used. This force is called "stripping force" or "chaff removing force". The stripping force can be made larger when the clearance is smaller, and on the contrary, it can be made smaller as the clearance becomes larger.

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