1. EXTRUSION
In the extrusion process, metal is compressed and forced to flow through a suitably shaped die to form a product with reduced but constant cross section.
Extrusion may be performed either hot or cold, hot extrusion is commonly employed for many metals to reduce the forces required.

3. EXTRUSION
Extrusion process is like squeezing toothpaste out of a tube. In the case of metals, a common arrangement is to have a heated billet placed inside a confining chamber. As ram continues to advance, pressure builds until material flows plastically through the die.

4. EXTRUSION
Lead, copper, aluminum, magnesium, and alloys of these metals are commonly extruded, because of relatively low yield strengths and low hot-working temperatures.
Steels, stainless steels, and nickel-based alloys are far more difficult to extrude.

5. EXTRUSION
Almost any cross-sectional shape can be extruded from nonferrous metals..

6. Extrusions and Products Made from Extrusions
Extrusions and examples of products made by sectioning off extrusions. Source: Courtesy of Kaiser Aluminum.

7. EXTRUSION Extrusion has a number of attractive features.
Extrusion dies can be relatively inexpensive, and one die only be required to produce a product. Conversion from one product to another requires only a single die change, so small quantities of a desired shape can be produced economically.
Major limitation of process is a requirement that cross section be uniform for entire length of product.
Extruded products have good dimensional precision.

8. EXTRUSION
For most shapes, tolerances with a minimum of in. are easily attainable.
Grain structure is typical of other hot-worked metals, but strong directional properties (longitudinal versus transverse) are usually observed.
Standard product lengths are about 20 to 24 ft, but lengths in excess of 40 feet have been produced.

9. Extrusion Methods
Extrusions is produced by various techniques and equipment configurations. Hot extrusion is usually done by either the direct or indirect method
Direct extrusion, a solid ram drives entire billet to and through a stationary die, must provide additional power to overcome frictional resistance between surface of moving billet and confining chamber.

11. Extrusion Methods
Indirect extrusion, a hollow ram drives die back through a stationary, confined billet.

12. Direct-Extrusion
Schematic illustration of the direct-extrusion process.

13. Types of Extrusion
Types of extrusion: (a) indirect; (b) hydrostatic; (c) lateral;