Extrusion is the process used to make metal rods and shafts of varying sizes and shapes. A hydraulic ram is used to push the molten substance through a shaped die, forming the custom rod or shaft. Aluminum and copper, as well as their respective alloys, are commonly subjected to the extrusion process as raw materials for finished parts or products.
Extrusion can either be direct or indirect. The more commonly-used direct extrusion pushes the substance out with direct force. In an indirect extrusion, a pair of smaller rams push the substance the opposite direction of the rams. Indirect extrusion is considered more efficient due to reduced friction and displacement.
Extrusion can also either be hot or cold. For brass, however, hot extrusion is involved, done at temperatures 50 to 75 percent of the metal’s melting point, and at pressures between 5,000 and 100,000 psi. Cold extrusion is only reserved for metals that can withstand greater stresses from the extrusion process.
The resulting rods and shafts can be used in a wide range of applications, from architecture to roofing to sculpting. There’s a good chance that these materials will undergo separate processes, perhaps even a second extrusion, as preparation for their applications.