How to calculate the tonnage of a hydraulic stamping press

Determining the correct pressing force is not only a matter of production efficiency, but is essential to ensuring the longevity of machinery and the quality of components. Underestimating tonnage leads to incomplete parts, while overestimating it can damage molds and presses.

Here are the 5 fundamental factors to analyze for an accurate calculation.

1. The shear or tensile strength of the material

The first parameter to consider is the nature of the metal. Materials such as stainless steel or high-strength alloys require significantly greater pressure than aluminum or mild steel.

2. The thickness of the sheet metal

Thickness not only affects linear force, but also determines the resistance during plastic deformation. Doubling the thickness doesn't simply double the required tonnage, but can exponentially increase the required force depending on the complexity of the shape.

3. The geometry of the piece and the cutting perimeter

The more complex the part profile, the greater the friction and resistance during the operation. When calculating stamping tonnage, the total perimeter of all holes and cutting lines must be added together. Sharp angles or irregular shapes require force distribution that must be adequately supported by the press structure.

4. The type of operation: Blanking vs. Drawing

Not all molding operations are the same.

• Blanking: It requires an immediate surge of strength.

• Drawing: It requires a constant, controlled force throughout the piston stroke.

  In the latter case, it is essential to also calculate the force of the hydraulic cushion, which can add an additional 20-30% to the total required tonnage.

5. Mold wear and the safety factor

A worn or blunt die can require up to 15-20% more force than a new die. It's common engineering practice to apply a safety factor, choosing a press that offers 10-15% more capacity than theoretically calculated, to compensate for variations in sheet metal thickness or lubrication.

Conclusion

Calculating tonnage is a balance between material physics and mechanical precision. Getting this assessment wrong can jeopardize your investment.

If you're designing a new production line, rely on the experience of those who have been building custom machines for over 40 years. Discover the range of SICMI stamping presses. Or contact our engineers for technical advice on your specific project.