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Plastic Extrusion Manufacturing vs Injection Molding Manufacturing

Views:17 Publish Time: 2021-12-23 : Louis Lu

Plastic Extrusion Manufacturing vs Injection Molding Manufacturing

Plastic manufacturers mainly use two methods for plastic molding: injection molding manufacturing and plastic extrusion manufacturing. The former method injects molten plastic resin into a mold, lets it settle, and cools it into a specific shape. The latter method pushes the melted plastic through a die to create the desired shape.

Both extruder and injection molding machines can classify plastics and process them into certain shapes. Although the functions of the two methods are similar, the differences still exist.

The injection molding machine produces three-dimensional shapes that cannot remain constant in a parallel line. On the other hand, the extruder creates a continuous linear two-dimensional shape.

This article will mainly discuss injection molding manufacturing and plastic extrusion manufacturing to help you understand the difference between them. Let us take a look!


Introduction to injection molding manufacturing

Injection molding manufacturing is a popular method to mold three-dimensional plastic products. The method is based on molten die casting, consisting of clamping and injection units.

1. Put a collection of plastic resin pellets into a hopper.

2. The hopper sends these pellets into a compression zone, where friction creates heat to melt the plastic.

3. Using a reciprocated screw to push the plastic into the protracted chamber.

4. The melted fluid-like plastic is pressed into the closed mold through the nozzle. Then, the melt can be easily formed into the desired shape.

5. Finally, the ejection cylinder loosens the mold and pushes the part out of the mold onto a conveyor belt.

Introduction to plastic extrusion manufacturing

Unlike plastic injection molding, plastic extrusion manufacturing typically produces 2D shapes rather than 3D. Manufacturers can make additional fabrication, from cutting cross-sections to shaping the pieces into specific product shapes.

1. The raw material enters the hopper first and then is transported to the barrel.

2. When the pellets are moved around the barrel, they are heated at 204 to 276 degrees Celsius.

3. The screw drive motor continuously rotates to move the molten pellets towards the die.

4. Before pressure is applied to force them to the mold, the pellets are conveyed to a feed pipe.

5. The molten material is brought to the cross-section of the mold, where they are cooled.

The difference between injection molding and plastic extrusion manufacturing

lRaw Materials

Both injection molding and plastic extrusion manufacturing use raw materials that are usually in pellet form.

For injection molding, the raw materials include polycarbonate, nylon, acrylic, polyoxymethylene, ABS, and polyethylene. On the other hand, the raw materials used in the plastic extrusion process include clear acrylic, polypropylene, polyurethane, PVC, thermoplastic rubber, and thermoplastic elastomer.


In general, the injection molding process is more expensive. One of the main reasons is that the method can produce plastic with complex shapes and different sizes. On the other hand, plastic extrusion manufacturing can only form a two-dimensional shape.


The injection molding process can produce a variety of products. Some injection molding applications include bottle caps, knife handles, sports equipment, buckles, food packaging, utensils, and vehicle dashboards.

On the other hand, plastic extrusion products are typically found in structural applications like cable housing, hoses, door frames, pipes, and tubes.

lSurface treatment

Generally, injection molding and plastic extrusion manufacturing don't require secondary processes. When the temperature and pressure are right, there is no need for further processing to correct defects in the product.

The surface finish for both injection molding and extrusion manufacturing is relatively smooth. But, the manufacturer can add ingredients to the raw materials that can affect the manufacturing of the two processes.

How Boyu can help you


Since 1998, Boyu has provided businesses worldwide with quality PVC flooring extrusion production lines. With more than 20 years of extrusion experience and advanced extrusion technology.

We have accumulated more than 90 technical patents. The company can provide high-quality, innovative, and efficient extrusion production lines.

Boyu is the right choice to boost the quality of your extruded materials with reliable plastic extruders. Contact us.