Plastic Extrusion Process: From Start to Finish
Plastic extrusion companies provide a much-needed service. These companies make standard and custom plastic extrusion shapes to meet the demands of multiple industries by using cutting-edge machinery and high-quality material. Although the plastic extrusion process is similar to injection molding, the difference is that extruding is typically continual. What that means is that instead of pulling the finished product out of a die in the case of injection molding, the melted resin gets extruded through a die.
The Extruding Process
Plastic extrusion products are made using raw thermoplastic material, otherwise known as resin. From a top-mounted hopper, this material is gravity fed into the extruder’s barrel. At that point, the operator adds compounds as needed, including UV inhibitors and colorants, into the resin before going into the hopper.
As the resin goes into the feed throat located toward the rear of the barrel, it comes into contact with the screw. This screw rotates, forcing the resin into a heated barrel set at the desired temperature required for melting the type of plastic resin used.
Usually, the heating profile for the barrel uses three or more proportional-integral-derivative controllers to increase its temperature gradually. This gradual heat starts from the rear and moves toward the front, allowing the resin to melt slowly while being pushed through the barrel. Ultimately, this prevents overheating that can cause the polymer to degrade.
The resin then leaves the screw, traveling through a reinforced screen to eliminate contaminants. Most machines have a breaker plate that provides the screen with reinforcement due to extreme pressure during this phase of the process. Once the resin passes through this plate, it enters the die used to create the shape and profile of the finished product.
Top manufacturers use carefully designed dies to ensure an even flow of the resin. Otherwise, there would be stresses at certain points, putting the product at risk of warping when cooled. Next, the product has to cool. In most cases, cooling occurs by pulling the extruded profile through a water bath.
Depending on the circumstances, some manufacturers use a secondary process known as coextrusion. In this case, the manufacturer uses two or more extruders opposed to a single-layer extrusion. The molten plastic feeds from the extruders at different speeds and thicknesses, yet goes into just one extrusion head. That way, the manufacturer can create a finished product that meets custom functional requirements.
RPM Industries manufactures top-of-the-line extruded parts and components. You can get details about our company and services by visiting our website or calling to speak with a representative.