What is the Difference between Extrusion and Injection Molding?


If you're in the manufacturing industry, then you've probably heard of extrusion and injection molding. Both are popular methods used to create a wide range of products, from plastic containers to automotive parts. However, despite their similarities, these two processes are quite different from each other. In this article, we will explore the differences between extrusion and injection molding.

Overview of extrusion and injection molding

Extrusion and injection molding are both manufacturing processes used to produce various plastic products. Extrusion involves forcing raw material through a die to create a long, continuous shape, while injection molding involves injecting melted material into a mold to create a specific shape.


Extrusion is a continuous process that involves feeding raw material, such as plastic pellets, into a hopper. The material is then melted and forced through a die using a screw extruder. The die shapes the material into a continuous length, which is cooled and cut to the desired length.

Injection Molding

Injection molding involves melting plastic pellets and injecting the melted material into a mold. The mold is then cooled, and the part is ejected from the mold.

6 Differences between Extrusion and Injection Molding

Extrusion and injection molding are both common plastic manufacturing processes, but they differ in their basic principles and the types of products they produce. Here are 6 of the main differences between extrusion and injection molding:

  1. Principle of operation: Extrusion involves forcing molten plastic through a die to create a continuous shape, such as a tube or sheet. Injection molding involves melting plastic pellets and injecting them into a mold cavity, where they cool and solidify into a specific shape.
  2. Product shape: Extrusion is best suited for creating continuous shapes, such as tubes, pipes, and sheets, although it can also be used to create hollow or semi-hollow profiles. Injection molding is best suited for creating complex, three-dimensional shapes, such as gears, toys, and medical devices.
  3. Tooling: Extrusion dies are typically less complex and less expensive than injection molding tools, which require more detailed molds and higher levels of precision. Injection molding molds are also subject to more wear and tear and may need to be replaced more frequently.
  4. Volume: Extrusion is typically used for the high-volume production of simple shapes, while injection molding is used for the lower-volume production of more complex shapes. However, both processes can be used for both high- and low-volume production, depending on the specific needs of the customer.
  5. Material selection: Extrusion can handle a wide range of materials, including thermoplastics, thermosets, and elastomers. Injection molding is generally limited to thermoplastics, although some specialized processes can handle other materials.


Overall, extrusion and injection molding are both important plastic manufacturing processes while they share some similarities, they are quite different from each other. Understanding the differences between the two processes can help manufacturers choose the best method for their specific application, and offer different advantages and disadvantages depending on the specific application. The choice between these processes will depend on the requirements of the product, the volume of production, and other factors such as cost and lead time.

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