3 Fundamentals of press design

166 Sheet metal forming and blanking
Example:
A cup with a conical outline and flange is to be produced. The base diameter is
60 mm, the upper diameter 100 mm, the outside flange diameter 120 mm and
the can body measurement 75mm. The required diameter of the blank piece is
calculated according to formula 20 from Table 4.2.1:
d = 60 mm, d = 100 mm, d = 120 mm, s = 75mm
1 2 3
2
2
D= d1+ 2 ⋅s⋅ ( d1 + d2) + d3 – d2=
60 + 2 ⋅75 ⋅ ( 60 + 100) + 120 – 100
D= 32, 000 = 178. 9mm
Therefore, for deep drawing this cup, a circular blank of 179 mm diameter is
required.
Draw ratio
The draw ratio � is an important numerical value for cylindrical draw
parts in determining the required number of drawing steps. The draw
ratio is the ratio of the diameter of the initial blank form to the diameter
of the drawn part. For the first drawing process, that is to say for
only one drawing operation, the draw ratio � [–] results in the following
equation:
Blank −∅ D
β =
,
Punch −∅ d
β =
β
β
1
2
D
d
D
=
d
1
d
=
d
1
2
with one drawing,
for the first drawing,
or
2 2 2 2
β 3
= d
2
d 3
,
and so on. In subsequent drawing steps, d 1 represents the diameter of
the draw punch in the first drawing operation and d 2 the diameter of
the second, etc. The total draw ratio � tot is calculated as the ratio of the
diameter of the blank to the final diameter of the drawn part:
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998