Die production needs to rely on punch (press) to provide power, different die size, structure type need to choose different punch to match. Reasonable selection of punch can reduce cost and save resources.
The main standard of die selection punch is measured by tonnage, which is usually obtained by the sum of blanking force, forming force, pressing force and stripping force. The main one is blanking force.
The blanking force is not fixed, and its change in a stamping process is as follows: when the punch starts to contact the stamping product, the blanking force is always in an increasing state. When the punch enters about 1 / 3 of the material thickness, the blanking force reaches the maximum value. Then, due to the appearance of material fracture zone, the force will gradually decrease. Therefore, the calculation of the blanking force is to calculate the maximum blanking force.

Calculation of blanking force
Calculation formula of ordinary blanking force: P = L * t * KS kg
Note: P is the force required for blanking, in kg
L is the overall contour perimeter of the blanking product, in mm
T is the material thickness, in mm
KS is the shear strength of the material, in kg / mm 2
In general, when the blanking product is made of mild steel, the specific value of material shear strength is as follows: KS = 35kg / mm2
Example:
Suppose the material thickness t = 1.2, the material is soft steel plate, and the product needs to punch a rectangular plate with a shape of 500mmx700mm. What is the blanking force?
Answer: according to the calculation formula: P = l × t × KS
L=(500+700)×2=2400
t=1.2 , Ks=35Kg/mm²
Therefore, P = 2400 × 1.2 × 35 = 100800kg = 100t
When selecting the tonnage, 30% should be added in advance. Therefore, the tonnage is about 130 tons.