The significance of calculating blanking work and verifying blanking work
Blanking work refers to the energy required to separate the material during the stamping process. Calculating and verifying this work is a crucial step in stamping process design and equipment selection, directly impacting production safety, economic efficiency, and equipment life. The amount of this work is closely related to factors such as the material’s mechanical properties, the contour length and thickness of the part being stamped, and the blanking speed. Accurate calculation and verification can ensure the selected press has sufficient power, preventing equipment damage due to overload, while also optimizing process parameters and improving production efficiency.
The primary significance of calculating the punching work is to provide a basis for the selection of the press. The nominal pressure of the press reflects the maximum force it can withstand, while the punching work reflects the energy it requires, and both must meet the requirements at the same time. For example, the punching work of a large cover is 500kJ. If a press with sufficient nominal pressure but insufficient power is selected, it will cause the motor to overload and the speed to drop during the stamping process, or even cause the punching to fail. By calculating the punching work, the minimum power requirement of the press can be determined to ensure that the equipment can stably output sufficient energy and ensure the continuity and reliability of the punching process. For continuous stamping production lines, it is also necessary to calculate the average power based on the punching work and stamping speed, and match the power supply system with the corresponding capacity to avoid voltage fluctuations that affect production.
Calculating blanking work helps optimize blanking process parameters and reduce production costs. The formula for blanking work is: W = K × L × t × τ × s, where K is the correction factor (generally 0.6-0.8), L is the blanking profile circumference, t is the material thickness, τ is the material shear strength, and s is the blanking stroke (generally 1.5-2 times the material thickness). By adjusting parameters, such as reducing the blanking speed (reducing the rate of change of stroke s) or optimizing the part shape (shortening the profile circumference L), blanking work can be reduced, thereby reducing energy consumption. For example, reducing the blanking profile circumference of a part from 1000mm to 900mm, while other parameters remain unchanged, can reduce blanking work by 10%, saving tens of thousands of yuan in annual electricity costs. Furthermore, blanking work calculation can be used to rationally arrange the order of multi-station blanking operations, distributing processes with high blanking work across different stamping cycles to avoid concentrated energy consumption.
Verifying the punching work can proactively identify potential process issues and ensure production safety. During verification, the calculated punching work must be compared with the press’s rated power to ensure it does not exceed 80% of the rated power, with a 20% safety margin to prevent transient overload. When punching thick materials (t > 6mm) or high-strength materials (σb > 800MPa), particular attention must be paid to the peak punching work. These materials experience high and volatile punching work, potentially subjecting the press’s drivetrain (e.g., gears and crankshafts) to excessive impact loads. This verification allows the equipment’s load-bearing capacity to be assessed, and if necessary, measures (such as adding buffers or reducing the press speed) can be implemented to mitigate impact and protect the equipment. For example, the peak punching work of a high-strength steel part exceeded 120% of the press’s rated power. By reducing the press speed by 30%, the peak work was reduced to 90% of the rated power, preventing equipment damage.
The calculation and verification of blanking work also provides guidance for mold design. Excessive blanking work means that the mold is bearing a large load, and the rigidity and strength of the mold need to be strengthened, such as increasing the thickness of the die base, selecting high-strength materials (such as Cr12MoV), or installing reinforcing ribs. At the same time, uneven distribution of blanking work may lead to increased local wear of the mold. By calculating the blanking work of each station, the force layout of the mold can be optimized to evenly distribute the load. For example, in a multi-station progressive die, the blanking work of a certain station accounts for 60% of the total work. The thickness of the pad at this station needs to be increased to improve the local load-bearing capacity and avoid mold deformation. In addition, the amount of blanking work also affects the heat dissipation design of the mold. The greater the work, the more heat is generated, and a cooling system (such as circulating water cooling) is required to prevent the mold from overheating and causing a decrease in hardness.
Calculation and verification of blanking work in special circumstances require additional consideration. For beveled or stepped blanking, the blanking work is 20%-30% lower than for flat-blade blanking, requiring the appropriate correction factor (K = 0.4-0.6 for beveled blanking, K = 0.5-0.7 for stepped blanking). For high-speed blanking (speeds > 300 times/min), the influence of inertia must be considered, and the blanking work must be increased by 10%-15% to ensure the equipment has sufficient energy to overcome inertia. During the trial punching phase, the blanking work must be measured and compared to the calculated value. If the deviation exceeds 10%, the material performance parameters or calculation method must be re-examined, corrected, and re-verified. Through scientific calculation and verification, energy optimization of the blanking process can be achieved, ensuring the safe and stable operation of equipment and molds, and improving the economic efficiency and reliability of production.
