Extrusion

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Extrusive means to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. This is opposed to intrusive rock formation, in which magma does not reach the surface.

Cross-sections of extruded aluminium

Extruded when talking about an artificial material like soft metals like aluminium, plastic or glass means that it is pushed out of a nozzle when the material is in a soft state. The shape of the nozzle will vary depending on the shape required in the finished product