Sheet Metal Forming

Shearing Velocity.
As in the case of blank-
ing, shearing velocity has an influence on the 
quality of the sheared edge. Higher shearing ve-
locity gives a better sheared edge. 
Ram incline
is the angle of the upper blade, 
as shown in Fig. 1.22 (left). During shearing, as 
the ram and upper blade descend at an angle 
into the material, the blade moves down and 
away from the lower blade, ensuring that the 
material falls away without binding between the 
back gage and the blade. It also can prevent the 
blades from rubbing against each other. The in-
cline of the ram varies from 0.5 to 2.5
°
. A 0.5
°
incline angle provides greater edge squareness 
than a 2.5
°
incline angle.
1.9 Finite-element Simulations
Finite-element (FE) simulations of blanking 
have been carried out to predict the part edge 
quality, that is, the ratios of the various zones 
(similar to the schematic shown in Fig. 1.24). 
Conditions such as punch and die corner radii, 
punch shape, and blank material affect the part 
Fig. 1.23
 
Penetration during shearing. Adapted from Ref 1.21

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16 / Sheet Metal Forming—Processes and Applications
edge quality; these can be predicted by simula-
tions. Punch force and stresses on the tool can 
be predicted by modeling elastic tools. 
An example of an FE simulation model for 
blanking a circular part is shown in Fig. 1.24. 
Part at fracture and the various zones, such as 
the rollover, shear, fracture, and burr, are shown 
in Fig. 1.25. When the tools are modeled as 
elastic, the stresses on them can be predicted 
using FE, as shown in Fig. 1.26. Finite-element 
predictions have been found to give reasonably 
accurate estimations (Ref 1.23). 
Finite-element analysis has also been used to 
study the influence of various parameters, such 
as punch-die clearance, tool wear, stripper pres-
sure, and blanking speed, on part edge quality 
and tool life. However, FE modeling of blank-
ing alone is not sufficient to predict the part 
quality and dimensional and geometric accu-
racy of the parts. There are several other factors 
that affect the dimensional accuracy of the part, 
such as the dynamics of the tooling and press, 
misalignment of tooling due to deflections, and 
elastic deflections of the tooling and press. 
These factors are not incorporated in blanking 
simulations. Ongoing studies in incorporating 
the effect of these factors in forming simula-
tions show improved accuracy of results during 
blanking. Finite-element simulations can also 
be used to estimate the forces and tool stresses 
in shearing.