Plastic Extrusions vs. Injection Molding

At Applied Plastics, we offer a number of services to our customers including custom plastic extrusion, design aid, in-house tooling, warehousing, and inventory management. With our plastic extrusion services, we boast over 22 extrusion lines, making it easy to create extruded tubing and profiles in various sizes, shapes, and degrees of flexibility to meet the needs of nearly any application.

The process of plastic extrusion is very different from injection molding. Although each process has its own unique benefits, they produce different end results. Understanding the differences between these two processes will help you determine which is right for your needs.
 

What is the Difference Between Plastic Extrusion & Injection Molding?

Plastic extrusion and injection molding are two very popular manufacturing methods; however, their differences in output make each process suitable for different needs.
 

Plastic Extrusion

Plastic extrusion involves the process of forcing heated plastic material through a die cavity, producing a continuous product with a fixed cross-sectional profile. This plastic manufacturing method is primarily used to create seamless, continuous products such as T-sections, tubes, and pipes. The process follows these specific steps:

  • Step one. Raw thermoplastic materials, along with the desired additives, are gravity fed from the hopper into the feed throat.
  • Step two. As the material enters the feed throat, it comes in contact with a rotating screw. The screw forces the plastic material forward into a heated barrel, allowing it to gradually melt into a thick, consistent liquid.
  • Step three. When the melted plastic reaches the end of the screw, it travels through a screen pack to remove any contaminants.
  • Step four. The plastic is then forced through a die cavity, which gives the final product its shape or profile. 
  • Step five. After exiting the extruder, the extruded part is allowed to cool.

 

Injection Molding

Injection molding is a plastic manufacturing process that involves injecting molten plastic material into a mold to create the desired shape. It can be used with a wide range of plastic materials to create objects ranging from household products to medical devices, automotive parts, and more. Plastic injection molding follows these steps:

  • Step one. Plastic granules or pellets are fed from a hopper to the feed section.
  • Step two. The plastic is compressed inside the feed section, and frictional heat causes the plastic to melt into a thick liquid.
  • Step three. The melted plastic enters the injector, which then injects it into the mold with enough force to fill every cavity and take on the desired shape.
  • Step four. The product is allowed to cool and solidify inside the mold.
  • Step five. Once cooled, the final part is ejected from the mold.

Although plastic extrusion and injection molding are similar in that they melt plastic to produce specific shapes, they involve different processes and produce different results. For example, injection molding typically produces products that are three-dimensional, while extrusion produces two-dimensional products that can have atypical cross-sections. Additionally, injection molding is often much more expensive, since it requires pricier dies, while plastic extrusion is more cost-effective. 
 

Plastic Extrusions by Applied Plastics

Applied Plastics is an industry leader in custom plastic extrusions. Equipped with 22 extrusion lines, we can create extruded tubing, profiles, and solid rods in a range of sizes, shapes, and colors. With over 40 years of experience, we can develop solutions for any application, no matter how difficult or challenging. To learn more about our capabilities, or to get started on your custom plastic extrusion solution, contact the experts at Applied Plastics today.

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