Plastic manufacturing is a domain of production that employs multiple methods of manufacturing. Owing to the high popularity of plastic products, it is important to pay attention to its manufacturing process. Injection molding and extrusion are two of the most popular manufacturing processes employed by plastic manufacturers. It happens to be true that due to slight similarity in the output, these techniques are pitted against each other. This post gives insights about the difference between extrusion & injection molding.
A Brief History of Injection Molding
Injection molding is a manufacturing process where a molten plastic material is injected into a mold to obtain a shaped object. The technique was first invented by Joseph Brahman in the year 1795, however, in 1820, Thomas Burr developed the first hydraulic press. Until 1820, the process remained only patented on paper. In 1894, this process evolved by using copper and brass alloys, and the success leads to the final establishment of an injection molding process in the 1930s. The injection molding is considered to be effective for thermosetting and thermoplastic polymers than for metal alloys. Since then, the process is the most utilized manufacturing process in plastic manufacturing.
A Short Introduction to the Process of Injection Molding
The step-by-step process of injection molding is as follows.
- At first, plastic pellets or granules are filled into a feed section via a hopper.
- These filled plastic granules are compressed inside the feed section. Due to frictional heat, the granules melt, forming a thick liquid called melt.
- From the feed section, the meld goes to an injector. This injector can be of different types. Screw-driven, piston-driven, manual, and hydraulic are some popular types of injectors.
- As the injector is activated, the molten material is injected inside die cavities. The liquid material expands inside the die, while it consumes the shape. The cooling is performed and during this, the material settles and solidifies in the mold.
- Once cooled, the die is opened by die ejectors and a product of the desired shape is obtained.
Injection molding applies to almost all types of plastic product manufacturing. Continuous as well as part manufacturing can be done by using injection molding. Toys, chairs, baskets, casings are some of the products manufactured by this process.
What is Extrusion Molding?
Extrusion molding is a manufacturing process that involves transferring the molten material through a die cavity to form an extruded shape. This process was invented by Thomas Hancock in 1820 but in 1935 it was fully established.
What are the Steps Involved in the Process of Extrusion Molding?
An extrusion molding process proceeds in the following ways
- At first, a powdered plastic or plastic granules are fed into the feeder.
- From the feeder to the die, these granules travel through a screw-thread pattern for even distribution. The feeder is headed by applying the heat jackets on the outer casing. Due to the generated heat, these granules melt into thick, consistent liquid.
- At the end of the feeder, a die is attached, which has a small cavity of the desired shape. The molten material is pushed through the die cavity and extruded from its end.
- As the extruded part cools down, the product is obtained in the desired shape.
Extrusion molding is only applicable for seamless product manufacturing. The continuous products like pipes, tubes, T-sections, are manufactured by using this technique.
Besides the difference in the manufacturing process, injection vs extrusion molding processes can be differentiated based on benefits and functions offered.
Injection molding vs extrusion molding:
- Injection molding is suitable for three-dimensional product manufacturing whereas extrusion molding is only suitable for two-dimensional product manufacturing.
- Injection molding is the oldest plastic manufacturing process whereas extrusion is comparatively new.
- Atypical cross-sections can be achieved by extrusion. However, injection molding may demand intricate dies to achieve the same.
- Injection molding offers strength to products, whereas extruded products are comparatively weaker.
- Injection molding is considered expensive due to costly die requirements. Yet this process is the most utilized due to its efficiency.
Although plastic injection molding and extrusion molding services are widely available, it is important to partner with an experienced company. Veejay Plastic has been providing various types of plastic molding services. They have well-equipped work stations and experienced staff since 1970. They have been dealing with automotive, electronics, aerospace, defense, and packaging industries for a long time.
