Within the realm of plastic processing, there are several methods of manufacturing. Two of the most popular processes include extrusion and injection molding. While they produce similar results, they use different equipment and techniques. Whether you are forming plastic pieces for commercial, industrial, or medical use, the manufacturing method you use will vary. Here are the important differences between plastic extrusion and injection molding.
The Key Difference Between Plastic Extrusion and Injection Molding
Both extrusion and injection molding are methods of plastic molding. However, they differ in execution. With extrusion, melted plastic is pushed through a die to create a specific shape. The extrusion method is used for two-dimensional objects.
Unlike plastic extrusion, injection molding can be used to form three-dimensional shapes. With this method, manufacturers inject plastic resin into a mold where it settles and cools into the desired shape.
A Breakdown of the Plastic Extrusion Process
Now that we’ve clarified the key difference between extrusion and injection molding, we can take a more in-depth look at the extrusion process.
First, plastic granules are placed into the feeder, where they are melted into a thick liquid. From the feeder, the meld will be pushed through the die opening and extruded from the end. Once it is cooled, the product will be in the desired shape. From here, manufacturers can cut the plastic piece into different lengths.
The extrusion process is ideal for end products that need a smooth finish, like industrial piping. It can also be used to create complex cross-sections such as tubing found in many medical devices and food processing applications. Products commonly formed using the plastic extrusion method include:
- Pipes
- Tubing
- Straws
- Fence sections
- Window frames
- Plastic sheeting
An Overview of the Injection Molding Process
Injection molding is based on the molten die casting method, which means a thick liquid called melt is injected into a mold to form the desired object.
The injection molding method begins by feeding plastic pellets into a hopper. The granules are then compressed, and the frictional heat melts the plastic. Next, the meld goes into the injector, which directs the liquid into die cavities. From here, the molten material fills the mold, taking the shape of the mold. Once the material is cooled and solidified, the die is opened, and the specific object is obtained.
The injection molding process is reasonably quick and produces a detailed plastic piece that often does not require additional assembly or processing. Because of this quality, injection molding carries a higher cost than plastic extrusion. The injection molding process is often used to make the following plastic items:
- Toys (such as chess pieces)
- Hair products (such as combs)
- Foodservice items (such as plates and cups)
- Chairs
- Baskets and crates
- Automotive components
Equipment for Plastic Extrusion and Injection Molding
Deciding between plastic extrusion vs. injection molding can be a challenging choice for product designers. It’s up to the manufacturer to understand the intricacies of each process to help their clients make informed decisions. It’s important to note that both methods have their advantages and are valuable in the world of plastic manufacturing.
If you’re looking for equipment to support your plastic extrusion or injection molding processes, you can rely on Plastrac for high-quality material blenders and loader systems. We have everything from gravimetric mixers to injection molding accessories to keep your manufacturing company running smoothly. Get in touch with us today for a quote!