HOME  > Press Dies Tutorial  > #149 Design of Hole Punching Dies (9) Design of the Backing Plate
Press Dies Tutorial

#149 Design of Hole Punching Dies (9) Design of the Backing Plate

Category : Shear Forming
March15, 2013

A force equivalent to the machining force acting on the punch is also generated on its back face. This force is received from the face of the punch holder, etc.

In the case of a punch with a small cross-section, as shown in Fig. 1, this force cannot be received sufficiently by the surface of the holder and the punch may dig in to the plate.
In the case of a punch with a small cross-section, as shown in Fig. 1, this force cannot be received sufficiently by the surface of the holder and the punch may dig in to the plate. In the case of a punch holder material such as S50C that is used without heat treatment, as a guide, when the average surface pressure on the back face of the punch (the load per unit area when the force is considered to be received by uniformly distributing the machining force over the surface of the punch flange) becomes more than 16Kg/mm2, the punch is likely to dig into the punch holder.
Fig. 1

When the average surface pressure becomes close to or exceeds this value, a heat treated plate (about 56HRC) is placed at the back of the punch.
Such a plate is called a backing plate. It also called a back-up plate (this may be correct), a back plate, backing, etc.
Although we explained a backing plate taking the example of a punch, when an insert type structure is used for the die or stripper, very often there are insert components having small cross-sections. Similar to the backing plate of a punch, it is safer to use a backing plate for these also.
Fig. 2

Although the common method of using a backing plate is to put a plate with the same size as other plates, it may be wasteful to put a plate over the entire area in the case of a large die or when there are only very small numbers of thin punches. In such situations, as shown in Fig. 3, the plate is put only for the required part.
In such cases, although a small backing plate is put in a pocket hole, it is good to make their top surfaces all in the same plane taking care about undulations and to design them to be on the thicker side since thin plates can break easily.
Although slightly different from the originally intended purpose, sometimes the height of the die is adjusted by adjusting the thickness of the backing plate.
Fig.3

MISUMI India eCatalog