Extrusion, whether used to create shapes in plastics or alloys, is a method that has been used for centuries in a variety of different forms. The actual first development of a plastic extruder was in the early part of the 19th century, although these were crude devices by the standards in use today.
The Extrusion Process
The basics of extrusion for any material involves the heating of the material to the melting point and then, using a set force, pushing this material through a die. In standard profiles or for custom plastic extrusion, the process is more complex and can include mixing in colorants and other additives to the resin before the heating process.
As the melted plastic passes through the die, it is under a specific pressure, which creates a uniform, continuous feed. Once through the die the plastic, now shaped to the specific profile, moves through a water bath and vacuum system that is in a tube. The water bath allows for cooling while the vacuum in the system prevents the shape from collapsing before the plastic is cooled.
The Advantages
While the shapes made by the custom plastic extrusion can also be made by injection molding or other process, the extrusion process is just as fast and offers limited if any waste.
Once the die is made, it will have a very long life cycle. While an injection mold will last for hundreds of thousands of cycles, they tend to be more costly to replace. By using a die that is lower cost to replace and that has a longer life cycle, there is a cost savings to consider.
In addition, custom plastic extrusion can offer the option to create lengths of material that is not possible with injection molding. Considering the requirements for the part or component and comparing the prices for the two types of production will highlight the cost effectiveness of the extrusion process for many applications.
