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#078 Method of Using Standard Components (27) Stripper Guide - 6: Method of Using a Stripper Guide Bush

Category : Die Design
May20, 2011

When using stripper guide bushes, it is necessary to take care about the two gaps shown in Fig. 1. These are the gap between the post and the bush (the bearing gap) and the gap between the bush and the plate (the adhered gap).

Fig. 1 Relationship among the bush, the plate, and the post

The bearing gap changed basically based on the viscosity of the lubricating oil, or on whether it is a no oil lubrication type. When used over a long time, this gap becomes wider due to wear. Periodic replacement is necessary in order to maintain the accuracy. This gap directly affects the accuracy of the relationship between the top mold and the bottom mold. In the blanking of thin plate materials, this means that this directly affects the blanking clearance. If this gap is made unduly small, it can cause fusing problems.

The adhered gap is very frequently determined by the characteristics of the adhesive material used. In an adhered type bush, very often the assembly is made taking the post as the reference. The assembled condition is as shown in Fig. 2.

Fig. 2 Relationship between the asymmetry of the adhered gap and the plate

It is not certain that the adhered gap is uniform with respect to the bush. It is very common that the gap is large in some places and small in other places. Therefore, there will be shifts between two plates. Since the shift is also linked to the holes in the plates, there will even be a shift in the relationship hole of the two plates. When a penetrating part (a punch, etc.,) enters this hole, it cannot maintain verticality and gets pushed to one side, thereby making the mold accuracy and life poor. Care should be taken about the relationship between the mold parts and the plate hole and the relationship with the estimated amount of shift of adhered gap with the blanking clearance, etc., and it is necessary to take measures regarding the method of assembling the bush and the mold.

Although extremely good results can be obtained when used correctly, the structure of the inner guide can get damaged when used wrongly. A major part of the problem is that of gap management. This point should be understood well, and techniques should be used in the method of use that match with the punch and die accuracy.

When the production volume is small but accuracy is needed, the technique shown in Fig. 3 is also used in the punches and dies.

Fig. 3 No bush is used

Although this decreases the cost, it decreases the number of gaps to be managed by one, and it can be used to aim at increasing the mold accuracy.

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