Cold extrusion is one of the most advanced technologies in the extrusion and plastic deformation processing. As the name suggests, cold extrusion works on the metal blanks at room temperature or slightly elevated temperatures. The technique has grown popular in manufacturing over the years because of the numerous benefits over the available plastic deformation processes. The technique can be used to produce numerous products and mass production; that’s why it has been growing popular.
Cold extrusion is simply a push-through compressive forming process that uses an extruder or extrusion machine. During the process, a punch is used to apply the pressure on the metal blades against a stationary die. The tonnage applied is determined by the product that is to be formed and the material. It is also important to note that modern hydraulic cold press machine for cold extrusion enables users to control the amount of tonnage to be applied.
Based on the die and punch design as well as the material flow, cold extrusion is usually classified into five main processes: lateral extrusion, backward extrusion, forward extrusion, compound, and forging. In forward extrusion or positive extrusion, the material and the punch flows in the same direction. This type of extrusion is used to manufacture hollow and solid parts such as rods, tubes, and pipes. For this process, rods’ and tubes’ diameter are formed by forcing the blanks through the orifice in a die.
In backward extrusion, the metal blank flows in the opposite direction of the punch. This type of extrusion can be used to obtain cup-shaped pieces of various shapes. In lateral extrusion, also referred to as radial extrusion, the material flows in a perpendicular direction to that of the punch movement. This type of extrusion can further be divided into centrifugal and centripetal extrusions. Radial extrusion is widely used for the manufacturing of flower keyboards, helical gears, and other parts.
The fourth type of cold extrusion is the compound extrusion. In compound extrusion, part of the material flows in the same direction is the punch, while the other flows in the opposite direction of the punch. This kind of extrusion can be used to manufacture various parts, including rods, barrel parts, and cups. The fifth and last type is forging extrusion. In forging, the material flows radially outward. But forward extrusion, reverse extrusion, and compound extrusion the most widely used extrusion methods.