There are two main methods of manufacture when creating plastic parts – plastic extrusion and plastic injection moulding. Part 1 in this series of articles explaining the production of plastic parts will concentrate on the plastic extrusion method.
Plastic extrusion is a technique used to produce plastic parts that are long and of the same size / shape cross section throughout. This method is used to create items such as pipes and plastic edging.
The process of plastic extrusion involves a continuous practice where plastic is fed into an extruder and transformed into a molten material using heat and shearing force. This molten liquid is shaped by being forced through a die opening.
A more in depth explanation of profile plastic extrusion follows:
- Thermoplastic granules are fed into the feed barrel of the extruder
- The material is transferred into the barrel from a hopper
- The plastic within the feed barrel melts as it is pushed forward by a rotating screw
- The friction from the thermoplastic being pushed / dragged causes it to heat up and melt
- External heat is also applied via heater bands to further melt the material
- To create long, constant shapes, the profile (plastic) is pushed through a die which is attached to the end of the barrel
- The plastic is then extruded into a cooling tank
- The tank is filled with water which cools the extruded plastic and allows it to solidify
- Haul off units / pull rollers are utilised to pull the profile away from the die
- Profiles are then cut to the required length by a machine
The next article in this series will explain the plastic injection moulding process.