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#148 Design of Hole Punching Dies (8) Design of a Punch Plate with a Movable Stripper Type Structure

Category : Shear Forming
March 8, 2013

Some care should be taken about the design of a punch plate with the movable stripper structure.
It is a relationship with the stripper plate. See Fig. 1.

Fig.1

This is the relationship between the tip of the punch and the stripper. There is a difference between when the tip of the punch is made the guide of the stripper plate and when it is not made the guide.
When the punch is not made the guide, it is necessary to acquire the position and verticality of the punch using the punch plate. The design of the punch plate can be considered to be the same as that of a fixed stripper structure.
The following precautions will have to be taken when the punch is to be made the guide.
When the punch is lightly press-fitted into the punch plate and the tip of the punch is guided by the stripper plate, when there are several punches such as during hole punching, the problem is whether or not it is possible to create their relationships correctly.
In case that there is any error in the relationships between their coordinates, a punch may not be directly above its hole in the stripper plate. This is determined by the relationship between the diameter of the hole in the stripper plate and the punch diameter.
When any problem is likely to occur, make the hole in the stripper plate slightly larger than the punch so as to allow for the error.
By doing this, the assembling reference of the punch changes from the punch plate to the stripper plate.

Fig. 2 shows the relationship between the length of the punch and the thickness of the punch plate.
In the case of the movable stripper structure, a guide for the thickness (T) of the punch plate is about 30% of the punch length (L).
Fig.2

Fig. 3 shows the precaution about small diameter punches. The drilling of the hole becomes difficult when the diameter (d) of the hole to be drilled in the punch plate becomes less than 1/3 of the punch plate thickness (T).
In such cases, the depth (S) of the hole is made about twice the punch diameter (d).
Fig.3

Fig. 4 shows the relationship between the diameter (d) of the inner post (stripper guide pin) and the thickness (T) of the punch plate. Here, d is made less than or equal to T. Fig.4

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