How to choose a good punch should be considered from several aspects?

There are many types of punching machines, and the selection of the type is mainly based on the material, specification, size, size and requirements of the finished stamping product. The punch itself is a large collection of processing equipment. Therefore, customers should make targeted selections according to the finished products to be manufactured, the type of stamping die, the characteristics of the stamping process, the production efficiency and the investment budget when purchasing to ensure that the purchased punch can really exert its actual production efficiency. Then the selection of punches needs to pay attention to two aspects? Here I will briefly introduce one or two.
First, the first is the choice of punch type
Normally, open punches are recommended for small metal blanking, bending or shallow drawing. The elastic deformation of the body of the open punch press will destroy the uniform distribution of the gap of the punching die, affect the accuracy of the punched product, and reduce the life of the punching die. However, its fuselage is open on three sides, easy to operate, easy to install molds, feeders, and automatic mold changing devices to achieve automatic production, and the price is economical. Therefore, it is recommended to use open punches for stamping small and medium parts.
 
For large and medium-sized or high-precision stamping products, portal punches and double-shaft punches should be used. For special stamping processes such as leveling, correcting bending, and shaping, a punch with high strength and rigidity should be selected.
 
Second, the second is the selection of punch specifications
The selection of punch specifications involves four aspects: punch tonnage, maximum closed height, punch speed and punch table size:
1. Selection of punch tonnage
The tonnage of the selected punch must be greater than the stamping pressure during actual stamping production, and it must be ensured that the load curve of the workpiece cannot exceed the allowable load curve of the punch. Usually the tonnage selection principle is as follows:
When punching and correcting bending, the maximum punching force is not greater than 80% to 90% of the tonnage; when deep drawing, the maximum drawing force is not greater than 50% to 60% of the tonnage; when shallow drawing, the maximum drawing force is not greater than 70% to 80% of the tonnage.
When punching and bending or punching and drawing, the tonnage value should be determined according to the specific situation and the allowable load curve of the machine tool used.
For thicker stamping parts, not only the allowable pressure of the punch, but also the power of the punch should be considered.
2. Selection of punch table
The punch table should be determined according to the size of the actual installed mold. If the mold is large, the size of the work table can be increased according to customer needs.
3. Selection of the maximum closed height
When selecting a punch, the closing height of the stamping die should be between the maximum closing height and the minimum closing height of the punch.
Because the connecting rod will be shortened after wear, and the mold repair will reduce the closed height of the stamping die in the future, so the height of the stamping die when designing the stamping die is generally close to the maximum die height of the punch press.
4. Selection of punch stroke and punch speed
This is usually determined according to the actual stamping process. When manual feeding is performed, do not use a punch with too many strokes; when automatic stamping, choose a punch with as many strokes as possible. When deep drawing, a punch with too many strokes cannot be used, because the drawing is too fast, the material cannot be fully deformed, and the parts are easy to crack.