3 Fundamentals of press design

4 Sheet metal forming and blanking
4.2 Deep drawing and stretch drawing
4.2.1 Forming process
In deep drawing operations forming is carried out with tools (rigid and
flexible), active media (e.g. sand, steel pellets, liquid) or active energy
(i.e. a magnetic field). The following section covers possible applications
for stretch and deep drawing processes with rigid tools as a first
and subsequent operation (cf. Fig.2.1.10 to 2.1.12). Sections 4.2.4 and
4.2.5 will cover deep drawing with active media (cf. Fig.2.1.13).
Unlike in deep drawing, in stretch forming the sheet metal cannot
flow because it is gripped by clamps or held in a blank holder. The forming
process takes place with a reduction in the thickness of the sheet
metal. Pure stretch drawing is a forming process conducted under tensile
stresses (cf. Fig.2.1.18). Mostly large-scale work pieces such as, for
example, body panel components used in aircraft or automotive manufacturing,
are produced on special production lines. This is certainly
true in producing low volume or large size parts, as, for example, with
the wing elements of an aircraft. The advantage of this process is that
the tooling and machining costs are relatively modest in proportion to
the size of the part being produced.
Deep drawing is a compression-tension forming process according to
DIN 8582. The procedure with the greatest range of applications is deep
drawing with rigid tooling, involving draw punches, a blank holder and a
female die (cf. Fig.2.1.10). The blank is generally pulled over the draw
punch into the die, the blank holder prevents any wrinkling taking
place in the flange. In pure deep drawing, the thickness of the sheet
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998