3 Fundamentals of press design

372 Sheet metal forming and blanking
b = 60
3
90°
Fig. 4.8.4 Bent workpiece (cf. example)
5
a=30
3
45°
d=20
Bending force and bending work during V-die bending
V-die bending is a production technique that is widely used. Here, bending
takes place between the bending punch and die (Fig. 4.8.5). This is
generally followed by the application of pressure on the die, which
serves to relieve residual stresses (reducing springback).
When bending angles in the V-die, the bending force F b [N] required
for forming depends on the die width w [mm], as this determines the
bending moment. In contrast to this, the magnitude of the bending
radius plays only a minor role, provided that the corresponding die
width w has been correctly selected. Generally speaking, the dimension
l[mm] of the die is selected in accordance with the sheet metal thickness
s[mm]:
When using a conventional die in which the sheet metal is positioned
at a distance w on both sides while the punch presses centrally onto the
sheet metal, with a coil stock width of b S [mm] the following bending
force is obtained:
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
l = 6 ⋅ s [ mm
]
10
135°