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3 Fundamentals of press design

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Methods <strong>of</strong> forming and cutting technology<br />

embossingpunch<br />

workpiece<br />

Fig. 2.1.6 Coining<br />

During free extrusion, a billet is partially reduced without upsetting<br />

or bulging <strong>of</strong> the non-formed portion <strong>of</strong> the workpiece (Fig.2.1.7 and<br />

cf. Sect. 6.5.4). Free extrusion <strong>of</strong> hollow bodies or tapering by free extrusion<br />

involves partial reduction <strong>of</strong> the diameter <strong>of</strong> a hollow body, for<br />

example a cup, a can or pipe, whereby an extrusion container may be<br />

required depending on the wall thickness.<br />

In extrusion <strong>of</strong> semi-finished products a heated billet is placed in a container<br />

and pushed through a die opening to produce solid or hollow<br />

extrusions <strong>of</strong> desired cross-section.<br />

Cold extrusion <strong>of</strong> discrete parts involves forming a workpiece located<br />

between sections <strong>of</strong> a die, for example a billet or sheet blank (cf.<br />

Sects. 6.5.1 to 6.5.3 and 6.5.7). In contrast to free extrusion, larger<br />

deformations are possible using the extrusion method.<br />

punch<br />

workpiece<br />

<strong>press</strong> bush<br />

Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998<br />

Fig. 2.1.7<br />

Free extrusion<br />

<strong>of</strong> shafts<br />

9

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