Basic Structure of Dies

Basic Structure of Dies

Punches and dies are very important items in press working. The next item would be strippers. Naturally, the structure of dies is centered on these three elements. Figure 1 shows the orderly arrangement of these three elements.

The details of Fig. 1 are summarized by the following two items. The corresponding structures are explained below.

1.Positions of the punch and die

Forward placement is one in which the punch is above and the die is below, and the reverse placement is one in which the punch is below and the die is above.

2.Presence or absence and placement of a stripper

This is whether the stripper is on the punch side or on the die side, and whether it is of the movable type or of the fixed type.

（1）Forward placement - Structure without a stripper

This is used for work in which the material pressure plate is not necessary and there is no worry of the material biting the punch. This is used in quite a large number of applications. For example, this is used in V-shaped bending dies, extruding and dropping type dies that do not need a wrinkle preventing pressure plate, etc.

（2）Forward placement - Fixed stripper structure

This is a structure in which the stripper is on the die side and is fixed to the die. A typical use of this type of structure is the die for blanking work. This is used when a material pressure plate is not necessary but the material is likely to bite the punch. This is also used in dies for progressive bending or extruding work. Although the structure is simple and easy to use, but since the working part of the material cannot be seen because it is covered by the stripper, the unnecessary part of the stripper is cut out thereby making the working part visible.

（3）Forward placement- Movable stripper structure

This is usually called the movable stripper structure, and is a very well known structure. This is the type in which the stripper is movable and is on the punch side. This structure is used when a material pressure plate is required and also the material bites the punch. This structure is used very frequently in hole punching dies or progressive punching work. This is also considered to be a type of die structure for precision work. In a die for precision work, the stripper is guided by a stripper guide post (pin) thereby restricting the movement of the stripper. Further, the punch tip is guided by the stripper thereby enhancing the relationship between the punch and the die.

（4）Forward placement - Bottom type movable stripper structure

This is a structure in which the stripper is movable and is on the die side. This structure is used during bending work when a material pressure plate is not required but is necessary to take out the product that has gotten stuck to the punch. This is because it is possible to create a space for inserting the material into the interior of the die by making the stripper movable. This is also used for progressive extruding work.

（5）Reverse placement - Structure without a stripper

This is a structure in which the punch is below and the die is above. In a reverse placement structure a knock out is always necessary in the die. A knock out is a part for the purpose of ejecting a product from the die that has gotten inside the die. This structure has no stripper and is frequently used in trimming dies for extruded products

（6）Reverse placement - Movable stripper structure

This is a structure in which a movable stripper is attached on the lower punch side. This structure is used for work requiring a material pressure plate. In addition, since the material passes by sliding over the top surface of the stripper, this surface is also used as a material guide. Since a knock out can also be used as a material pressure plate, it is frequently used for work requiring flatness, or in dies for extruding work.

Even with the same work, the quality changes when the die structure is changed. This is in cases such as when a material pressure plate is not used although it was necessary. On the other hand, care should be taken because the die can be made expensive by pressing the material when a material pressure plate is not required.

The structure should be designed to match the functions necessary for the work.

From.www.misumi.co.jp