The blanking force required for punching can be calculated based on the punch shape and sheet thickness. Below is an introduction to punching with a punch core that has no beveled edge:
Blanking Force (kN) = Punch Core Perimeter (mm) × Sheet Thickness (mm) × Material Shear Strength (kN/mm²)
Conversion to Metric Tons (t): Divide the force in kN by 9.81
Formula: Stamping Force (t) = Blanking Force (kN) ÷ 9.81
- Punch Core Perimeter: Refers to the sum of the lengths of all sides of the punch core, regardless of its shape (e.g., circular, square, or irregular).
- Sheet Thickness: Refers to the thickness of the sheet that the punch core needs to penetrate completely during punching.
- Material Shear Strength: A physical property of the sheet, determined by the sheet’s material (e.g., carbon steel, aluminum alloy).
(To be supplemented with specific materials and their corresponding shear strength values)
For example:
To calculate the blanking force for punching a 25mm-diameter circular hole in a 2mm-thick cold-rolled steel sheet:
For a circular punch, the perimeter (circumference) is calculated as:
Perimeter = π × Diameter
= 3.14 × 25 mm
= 78.5 mm
- Sheet thickness: 2 mm
- Shear strength of cold-rolled steel: 0.3447 kN/mm²
Using the core formula:
Blanking Force (kN) = Punch Core Perimeter (mm) × Sheet Thickness (mm) × Material Shear Strength (kN/mm²)
= 78.5 × 2 × 0.3447
= 54.1179 kN
Metric tonnage = Blanking Force (kN) ÷ 9.81
= 54.1179 ÷ 9.81
≈ 5.52 metric tons
