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# 120: Terminology and Surroundings (14) Width of Blanking Bridges

Category : Terminology
April13, 2012

The bridges in blanking are the feed bridge and the edge bridge as shown in [Fig. 1] The minimum values of common bridge widths in blanking operations are shown in [Table 1] The reason why the width of edge bridge is larger compared to feed bridge is the relationship with the material width guide. The material width guide is made slightly wider than the material width so that the material can move smoothly. Although the edge bridge width changes because of this, it is made wider than the feed bridge so that the minimum bridge width is maintained even in the most oblique state.

[Fig. 1] Bridge width

[Table 1] Standard bridge widths in blanking

When the bridge width becomes close to the limit to product formation or becomes so narrow as to exceed that limit as shown in Fig. 2, a constriction or twisting occurs due to the effect of bending or droop caused by a sideward pressure. This effect is large in soft materials. When this phenomenon occurs, the state of the cut cross-section will no longer be normal, and the external appearance of the blank becomes poor. In addition, the wearing out of the punch and die becomes faster speeding up the generation of burrs, and also shortening the maintenance interval of the dies.

[Fig. 2] Limits to the bridge width

However, there are also times when a narrow and long object is to be prepared by blanking. The phenomena described regarding the bridge width in blanking operations occur as they are in such situations. This means that we are expecting contradicting things from the point of view of blanking. The reason is the same phenomena that occur in the bridge width during blanking. It is effective to observe well the phenomena that occur in the bridge width, and to take countermeasures to prevent deformation. As shown in Fig. 3, it is most effective to make the material pressure pad stronger. It is also possible to think of restricting the blanked part in order to prevent slipping. In addition, it is also effective to use a smaller clearance than normal.

[Fig. 3] Restricting narrow blanked parts

Even the bridge width in blanking becomes useful for a different purpose depending on the viewpoint.

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