3 Fundamentals of press design

10 Basic principles of metal forming
punch
workpiece
press bush
blank
ejector
Fig. 2.1.8
Backward
can extrusion
Extrusion is used for the manufacture of semi-finished items such as
long profiles with constant cross sections. Cold extrusion is used to produce
individual components, e.g. gears or shafts. In both methods,
forming takes place using either rigid dies or active media. In addition,
a difference is drawn depending on the direction of material flow relative
to the punch movement – i.e. forwards, backwards or lateral –
and the manufacture of solid or hollow shapes (cf. Fig. 6.1.1). Based on
the combination of these differentiating features, in accordance with
DIN 8583/6 a total of 17 processes exist for extrusion. An example of a
manufacturing method for cans or cups made from a solid billet is backward
cup extrusion (Fig. 2.1.8).
Forming under combination of tensile and compressive conditions
Drawing is carried out under tensile and compressive conditions and
involves drawing a long workpiece through a reduced die opening. The
most significant subcategory of drawing is strip drawing. This involves
drawing the workpiece through a closed drawing tool (drawing die,
lower die) which is fixed in drawing direction. This allows the manufacture
of both solid and hollow shapes. In addition to the manufacture
of semi-finished products such as wires and pipes, this method also
permits the production of discrete components. This process involves
reducing the wall thickness of deep-drawn or extruded hollow cups by
ironing, and has the effect of minimizing the material input, particularly
for pressure containers, without altering the dimensions of the can
bottom (Fig. 2.1.9 and cf. Sect. 6.5.5).
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998