Knowing how various processes that you’re paying for work is important to many clients, and plastic injection molding is a great example. It’s often quite helpful to know the basics on how plastic injection molding works if you’re ordering such products, and this process can be broken down fairly simply.

At EnviroTech Custom Injection Molders, we’re here to offer a wide range of plastic injection molded products, including industrial molding for numerous purposes and processes like thick wall molding, near net shape molding and more. Here is a basic explanation on how the process of plastic injection molding works, from the basic components involved to the key metrics and parameters that are considered within it.

Plastic Fed Into Feed Hopper

The plastic injection molding process begins with the selection of plastic granules or powder. This is a vital part of the process – selecting the ideal material is critical to the success of the final product.

From here, the plastic will be fed into what’s known as the feed hopper. This refers to the opening at the top of the injection molding machine where raw plastic material is poured in.

Heating Via Screw

Another key component in the process is the screw, which will be located within a heated barrel. Here, it will mix and melt the plastic material as it turns.

This turning creates friction, which in turn melts the plastic and prepares it for the next step in the process.

Injection Into Mold

Once heated and melted, the screw will then push the plastic through a nozzle into a mold. The mold is where the molten plastic takes its final shape according to your desired specifications.

The molding machine will have two halves – an injection side and a clamping side. Once injected, these two halves come together to solidify and cool the plastic within seconds.


After cooling, the final product is ejected from the mold. It’s important to note that this process can happen very quickly, allowing for high volume production of identical parts.

Final Inspection And Shipping

Once ejected, the part goes through a final inspection process to ensure quality control. It will then be packaged and shipped to the client.

Important Metrics and Parameters

Within the plastic injection molding process, there are several key metrics and parameters that will be monitored to ensure an ideal product:

  • Mold temperature: As you may have expected, one of the single most important factors in plastic injection molding is the temperature of the mold. This will vary based on the type of plastic being used.
  • Injection pressure: Vital for everything from material flow to filling the mold, injection pressure must be closely monitored and controlled.
  • Cooling time: While the speed of plastic injection molding is a major selling point, proper cooling time is still essential for ensuring an ideal final product. This will vary based on several factors, including part size and complexity.
  • Nozzle pressure: The nozzle pressure is the force that pushes the molten plastic into the mold. This must be carefully monitored to avoid any defects in the final product.
  • Recovery rate: This refers to how quickly the material will be prepped for the next cycle of the process, such as the cooling time mentioned above.
  • Wall thickness: Finally, another key parameter is the wall thickness of the product. This will vary based on your desired specifications and the complexity of the mold design.
  • Shrinkage rate: Depending on the type of plastic being used, there will be a specific shrinkage rate that must be accounted for in the design process to ensure an accurate final product.
  • Clamping force: This refers to the amount of force required to keep the mold closed during the injection process. It must be carefully calculated to avoid any defects or inconsistencies in the final product.
  • Screw speed: The speed at which the screw turns will affect the melting and mixing process, which in turn can impact the final product. Proper screw speed is crucial for consistency.

By understanding these key components and metrics, clients can ensure that their products are being produced with precision and accuracy. At EnviroTech Custom Injection Molders, we pride ourselves on our expertise in plastic injection molding and our ability to deliver high-quality products for a wide range of applications. Contact us today to learn more about how we can help bring your project to life. We’re standing by to take your call and help you design and produce the very best plastic products!