Metals, especially steel and aluminum, are among the most useful materials in construction and manufacturing. Their durability and high strength makes them very versatile and suitable for many applications. For thousands of years, people have developed many different ways to shape and form metals and other materials. One of the techniques perfected over the years is a process called extrusion.
What is Extrusion?
If you played with modeling clay before, you may have a good idea of what extrusion is. In extrusion, material is pushed through a die using force, heat, or compression. Extrusion results to a continuous object with a fixed cross-sectional profile.
Extrusion is very useful for materials like beams, rafters, railings, and other objects that need to have a consistent cross-sectional profile. Unlike other ways of shaping materials like rolling, press-dies, or using controlled explosions, extrusion has many advantages:
Consistency and uniformity. Many long objects like beams, rails, and posts need to have a uniform cross-section profile. Extrusions do away with the inconsistencies of other shaping and metalworking methods.
Smooth surfaces. Smooth surfaces in metals are very important to preserve its strength, and improve its visual appeal. The consistent, smooth look of an extruded piece of metal makes it look good for a very long time.
Strength and durability. Before extrusions, metals were joined or pounded together to make a continuous length. Welds and joints are always the weakest point of any structure. Extrusion eliminates this problem by processing an entire continuous length of material.
Speed and efficiency. Welding and soldering are time-consuming, and put a lot of stress on the metal. Many sophisticated and advanced extruding machines can shape and process metal in the same amount of time needed to weld pipes and bars together.
Types of Extrusions
There are two kinds of extrusion processes used by machinists and metalworkers:
Hot extrusion processes metals heated to a very high temperature to prevent deformities and weakening over time. A hydraulic press is used to process the metal. The key is not to melt the metal, but to soften it enough to pass through the die. Temperatures can range from 850 to 4,000 degrees Celsius, and pressures range from 5,000 to 100,000 pounds per square inch. To keep the extruded metal smooth, lubricants like graphite or glass shards are used in the press.
Cold extrusion is used for processing metals that require high strength and a smooth finish, like engine pistons and plumbing pipes. The material is pushed through the die at room temperature. While heat makes metals easier to process, it also weakens the material. Cold extrusion is faster than hot extrusion, because the material does not need to cool and cure before being shipped off to customers and companies that need them.
Extrusion Tools
There are different types of equipment used for extruding material:
Direct presses have stationary dies, and the ram moves to push the material.
Indirect presses have stationary rams, and the die moves to the material to cut and shape it.
Vertical presses extrude material downward, using gravity to aid the recovery of waste material and the extruded materials themselves. Vertical presses are especially useful for extruded objects like gear blanks.
Horizontal presses extrude material sideways, and are useful for long, continuous building supplies like rails, rods, and beams.
Hydraulic presses use water and pressure to drive material into a die.
Mechanical presses use a system of machines to move material and push them through the press.
Other Applications of Extrusion
Extrusion can also be used for other materials besides steel. Many foodstuffs are processed through extrusion, like cookie dough, pasta, and sausages. Plastics are also extruded, especially if the material is used for film, filaments, or tubes. Glass is extruded to make scientific instruments. Clay and terracotta are sometimes extruded to make complicated and decorative bricks, and other construction materials.
When a balance between strength and shape is needed, building and construction don’t demand a compromise. The extrusion process ensures that you get the absolute shape of the material you need for the exact specifications of the task at hand.