Extrusion facts for kids

This is an extruded aluminum piece. It has hollow parts and special slots that let you connect other bars to it.

Extrusion is a cool way to make things that have the same shape all the way through. Imagine pushing a material, like play-doh, through a shaped hole. This hole is called a "die." The material comes out on the other side with the exact shape of the die.

This method is super useful for two main reasons. First, it can create really complex shapes that are hard to make with other processes. Second, it can work with materials that might break easily. This is because the material is mostly pushed (compressed) or slid (sheared), rather than pulled. Extrusion also makes parts with a very smooth surface.

How Extrusion is Different from Drawing

There's a similar process called drawing. Instead of pushing, drawing pulls the material through the die. Because it pulls, drawing can only change the shape a little bit at a time. This means it's usually used for simpler shapes, and you might need many steps to get the final product. Drawing is the main way to make wire. Metal bars and tubes are also often made by drawing.

Types of Extrusion

Extrusion can be done continuously, meaning it can make very long pieces without stopping. Or it can be semi-continuous, making many separate pieces. The material can be extruded when it's hot or cold.

Many different materials can be extruded. These include metals, polymers (like plastics), ceramics, concrete, modelling clay, and even food! The things made by extrusion are often called "extrudates."

Making Hollow Shapes

Making hollow shapes inside an extruded material is a bit tricky. You can't just use a flat die with a hole in the middle, because the center part of the die wouldn't have anything to hold it up.

Instead, the die is designed like a block with some depth. It starts with a shape that supports the center part. As the material moves through the die, the shape changes inside. The center pieces are held up from the back of the die. The material flows around these supports and then joins back together to create the hollow shape you want.

Extrusion can also make metals stronger.

Images for kids

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  HDPE pipe during extrusion. The HDPE material is coming from the heater, into the die, then into the cooling tank. This Acu-Power conduit pipe is co-extruded - black inside with a thin orange jacket, to designate power cables.

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  Extrusion of a round metal through a die.

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  A horizontal hydraulic press for hot aluminum extrusion (loose dies and scrap visible in foreground)

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  Two-piece aluminum extrusion die set (parts shown separated.) The male part (at right) is for forming the internal cavity in the resulting round tube extrusion.

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  Plot of forces required by various extrusion processes.

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  Sectional view of a plastic extruder showing the components

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  Sectional view of how a caterpillar haul-off provides line tension

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  Elbow macaroni is an extruded hollow pasta.

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  Front side of a four family die. For reference, the die is 228 mm (9.0 in) in diameter.

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  Close up of the shape cut into the die. Notice that the walls are drafted and that the back wall thickness varies.

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  Back side of die. The wall thickness of the extrusion is 3 mm (0.12 in).

See also

In Spanish: Extrusión para niños