Plastic pellets are fed and placed into a hopper, from which they drop into a heated
barrel. They are moved and kneaded in the barrel by a screw until they reach a molten
state (this is then referred to as the melt.) The melt is then extruded or forced out
of the end of the barrel through a shaping die as a long, continuous line of shaped plastic.
This line is then pulled by a haul-off (puller) through a cooling trough, where it solidifies
and then is cut to length or coiled.
An animation of the extrusion process is shown above.
Advantages of extrusion
- Extrusion is a highly efficient process (high speed process, little waste)
- Extrusion allows some of the most complex shapes to be formed in high volume
- Allows for precise cross sectional dimensions to be produced.
Disadvantages of extrusion
A sample of the variety of shapes possible using extrusion.
- Parts must be cut to finished length
- The cross-sectional shape of the product must remain the same
Even highly complex shapes are possible using extrusion.
Characteristics of extruded parts are:
- Continuous cross section
- Virtually unlimited length is possible!