The binary image that results from the above actions is
shown in the top right of Fig. 11.
From the binary image two windows (shown in the bottom
left/right of Fig. 11.), containing the two extremity “lines”,
are selected to apply the algorithm that calculates the
springback angle: the algorithm starts finding two horizontal
lines that intercept the white “line” near the bottom and top
extremities; then the median point of the white “line”, that
has the same line index, is found for both top and bottom
horizontal lines. The value of H and L, shown in Fig. 12., is
consequently calculated and used to find the angle between
the white “line” and the vertical plane:
R2 = atan(L /H )×180/ Q . In order to reduce the error the
same procedure is repeated with two different horizontal
lines near the previous ones. The angle is calculated and then
the mean value is used as the value of R2 . The same
procedure is applied to calculate R1 using the left window
image. Thus the value for the springback angle is:
R = R1 + R2 . In the example of Fig. 12. the angles are:
R1 = 29.4º , R2 = 27.7º and R = 57.1º .
The springback effect is expressed as the difference
between the angle R after unloading and the minimum angle
that occurs when the punch reach the die extremity (see Fig.
9.). In the present example the minimum angle is 30.6º , thus
the angle difference is R 30.6º= 26.5º .
The angle R , measured with the above described method,
was compared with manual angle measurements. The
comparison proves that the automatic method is very
accurate. In order to evaluate springback evolution the angle
shown in the top right of Fig. 11.
From the binary image two windows (shown in the bottom
left/right of Fig. 11.), containing the two extremity “lines”,
are selected to apply the algorithm that calculates the
springback angle: the algorithm starts finding two horizontal
lines that intercept the white “line” near the bottom and top
extremities; then the median point of the white “line”, that
has the same line index, is found for both top and bottom
horizontal lines. The value of H and L, shown in Fig. 12., is
consequently calculated and used to find the angle between
the white “line” and the vertical plane:
R2 = atan(L /H )×180/ Q . In order to reduce the error the
same procedure is repeated with two different horizontal
lines near the previous ones. The angle is calculated and then
the mean value is used as the value of R2 . The same
procedure is applied to calculate R1 using the left window
image. Thus the value for the springback angle is:
R = R1 + R2 . In the example of Fig. 12. the angles are:
R1 = 29.4º , R2 = 27.7º and R = 57.1º .
The springback effect is expressed as the difference
between the angle R after unloading and the minimum angle
that occurs when the punch reach the die extremity (see Fig.
9.). In the present example the minimum angle is 30.6º , thus
the angle difference is R 30.6º= 26.5º .
The angle R , measured with the above described method,
was compared with manual angle measurements. The
comparison proves that the automatic method is very
accurate. In order to evaluate springback evolution the angle
