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Extrusion is a manufacturing process that involves forcing base metal through a pre-shaped die to create objects with a specific shape and profile. As the metal passes through the die, it’s shape changes to reflect the die’s shape. There are different types of extrusion processes, however, including cold, hot, friction and micro.
Cold Extrusion
With cold extrusion, metal is forced through the die while at or near room temperature. The metal used in cold extrusion typically comes in slugs, which are poured into the die’s feeder where pressure joins them together to create a solid object in a new shape.
Some of the most common metals used in cold extrusion include the following:
- Aluminum
- Copper
- Niobium
- Steel
- Lead
- Tin
Hot Extrusion
Hot extrusion, on the other hand, involves heating metal at high temperatures and then forcing it through the die while in a molten state. Depending on the type of metal, temperatures may range from 650 degrees Fahrenheit (magnesium) all the way to 1,300 degrees Fahrenheit (steel). It’s important for manufacturers to use the right temperature when performing hot extrusion. If the base metal isn’t heated to its recrystallization temperature, it may struggle to pass through the die. When heated the metal is heated to the appropriate temperature, however, hot extrusion is an accurate and effective way to reshape metal.
Some of the most common metals used in hot extrusion include the following:
- Magnesium
- Copper
- Steel
- Aluminum
- Nickel
Friction Extrusion
There’s also friction extrusion. Invented by The Welding Institute in the 1990s, this modern extrusion process involves the automatic rotation of the metal slugs or billets based on the position of the die. As the die rotates, it produces heat from the metal-on-metal friction around the entry of the die. This heat allows the metal to pass through the die more easily. Friction extrusion is an effective, efficient process that’s gaining popularity among manufacturers.
Micro Extrusion
Finally, micro extrusion is a relatively new type of extrusion process that’s characterized by the ability to create small, micro-sized objects. Specifically, the cross-section of the die supports base metal measuring just 1 millimeter. Like friction extrusion, it’s a modern process that was invented in the 1990s. But because of the highly technical nature of creating such small dies that can withstand such pressure, it hasn’t gained the same level of popularity as its friction counterpart. Of course, this may change as new advancements are made with micro extrusion.