Calculation for Punching Force

 

Punching force is the total force required by the machine to punch a particular hole based on the material thickness, type and hole shape. Calculating the punching force is very important for checking whether the machine has enough tonnage to do the job without damaging the machine itself. This is especially true if a large tool is used in thicker material or harder materials such as stainless steel. The most common formula to determine the punching tool is by multiplying the material shear strength with the material thickness and the perimeter of the punch tool.

The general Punching force formula;

Open Area for perforated metal calculation

Open Area for perforated metal calculation

If the tool shape is round or circular shape;

Open Area for perforated metal calculation

Here is the sample to calculate punching force for rectangle tool with the dimension of 40mm x 60mm, the material is 4mm thick Stainless Steel T316L.

The rectangle perimeter, P = 2 x (40 + 60) = 200mm = 0.2m

The material thickness, t = 4mm = 0.004m

The shear strength of Stainless steel T316 = 482.63 Mpa =  4.921487 x 10^7 Kg/m^2

The Punching Force, F =  0.2 x 0.004 x ( 4.921487 x 10^7 ) = 39370 Kg = 39.37 Ton

Besides this basic and general calculation, a big company like Wilson Tool International (www.wilsontool.com) has its own calculation that is streamlined but based on the general calculation above.

The difference is that they use some coefficient factors that reflect particular material type and thickness. 

More information about Wilson Tooling’s punching force calculation can be seen in their tooling handbook (http://www.wilsontool.com/pdf/prodLit/Tooling_Maintenance_Manual.pdf ) on page 34.

 


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