Plastic extrusion process 

How it works?

Advantage / Disadvantage

Plastic profile extrusion is a molding method in which plastic resin is continuously melted, pushed through a die with the desired cross-section (a “profile”), and then pulled through a water bath until fully cooled. The formed plastic can then be fabricated and either cut into multiple parts or wound as a single part.

There are four zones through which the material moves through:

• Extruding zone, in which resin is melted, additives such as talc, foaming agents, glass, or color may be 

added, and the material is forced through the extruder die assembly. 

• Sizing zone, in which a pull vacuum is used to prevent collapse and control warpage as the plastic 

hardens. This step is only used in profiles with one or more hollows.

• Cooling zone, in which the plastic is ran through cool water tanks until it hardens completely.

• Processing zone, in which the extrusion is measured for quality and processed in-line with the application 

of adhesion promoters, tape, slip coating, and/or ink-jet printing. This step is optional.

• Cutting zone, in which the extrusion is cut to desired lengths or spooled.

Compared to other forming and molding processes, extrusion has a number of advantages and disadvantages:

ADVANTAGES

•High production rates

•Low cost tooling

•Short tooling lead times

•Many types of raw materials

•Lowest cost conversion processes for plastics

•Can combine multiple durometers in a single extrusion

DISADVANTAGES

•Only provides a uniform cross sectional shape

•Surface area is not class A for all materials

•Tolerances are greater than injection mold

Secondary operations required to add a third