Difference Between Injection Molding and Extrusion Molding

Both the terms injection and extrusion molding are the processes used for manufacturing of different types of 3D or 2D products. Both the processes have their advantages based on their manufacturing.

The process of injection molding is a type of manufacturing process which includes squeezing the liquid plastic into a mold which further becomes hard. This process is a bit complicated as well.

On the other hand, the process of extrusion molding is a type of process in which molten plastic or any other material is pushed through a 2D die opening and as a result linear shapes are produced.

Let us discuss the difference between the two methods of molding in detail.

Injection Molding vs Extrusion Molding

The main difference between the two terms, injection molding and extrusion molding are based on the benefits and functions which are offered by the two. The process of their manufacturing is also a very important reason for their differentiation. Injection molding is majorly suited for the manufacture of 3D products and it is quite expensive as well. On the other hand, the process of extrusion molding is preferable for manufacturing 2D products.

Injection Molding vs Extrusion Molding

In injection molding, the process of manufacturing products is based on the molten die casting method. It helps in the production of 3D products.

This process was fully established in the year 1930. As compared to any other process of molding, injection molding is a bit complicated method to perform.

The process of extrusion molding is a type of manufacturing process which involves transferring the molten material through a die cavity to form an extruded shape.

This process is known to be invented by Thomas Hancock in the year 1820. This process is only applicable got seamless product manufacturing. With the help of this technique pipes, tubes etc. can be manufactured easily.

Comparison Table Between Injection Molding and Extrusion Molding

Parameters of Comparison  Injection Molding Extrusion Molding 
Specification This process enables manufacturers to use multiple types of plastic resin which also includes recycled materialsThe process of extrusion allows for additional fabrication and alterations to the product
Suited for  It helps in the production of 3D products  It is preferrable for producing 2D products  
Advantage The most important advantage of plastic injection is that it allows easy creation of three-dimensional plastic products and the process works relatively quickly and captures the complexities of the mold as well.The benefit of extrusion molding process is that the dies create very smooth finishes that are ideal for many products like pipes, straws and other commonly used products.
Can manufacture  It is suitable for manufacturing products like plastic bottle caps, syringes etc.  This process is suitable for the production of door frames, seals, pipes etc.
Cost Due to the requirement of costly dye, the process of injection molding is a bit expensive method This process of molding is not very expensive as compared to injection molding

What is Injection Molding?

The process of injection molding is a process that is always preferred for small containers or products.

This process is performed by injecting and then re-heating the material which is further stretched for greater strength and then the product is blown into molds.

The steps involved in injection molding starts with the collection of the resin pellets which will manufacture place in the hopper.

The pellets are fed by the hopper with the help of a compression zone in which friction is created which in return creates heat so that plastic could be melted.

Further, the plastic in a molten state will pass through a small nozzle into a mold like structure. Now the plastic will fill the mold and take the shape as well.

When it gets cooled and becomes hard, the 3D shape will be taken by the plastic.

What is Extrusion Molding?

The process of extrusion molding is used for making parts of a continuous length and uniform cross-section.

The plastic products produced by this process have high melting viscosity, this allows the extrudate to retain the shape which has been imparted to it by the dye while the extrudate is in the stage of quenching.

The shape of the obtained cross-section varies and it can also be manufactured according to your needs such as rectangle, L or T shape, solid round shapes etc.

The process of extrusion molding has an edge overdrawing as it uses a type of stress which is compressive and it also allows large deformation. This process also produces comparatively weaker products.

The most suitable material for extrusion molding is thermoplastic. Materials that have very high strength and stiffness in the molten form are also considered very convenient.

The process of extrusion molding is suitable for manufacturing 2D products and a very new process as well.

Main Differences Between Injection molding and Extrusion Molding

  1. The process of injection molding is suitable for manufacturing 3D products on the other hand extrusion molding is suitable for manufacturing 2D products.
  2. The process of injection molding is a very old process of plastic manufacturing whereas extrusion molding is a new process.
  3. If we use injection molding then it ensures strength to the products and extrusion molding produces comparatively weaker products.
  4. The process of injection molding is quite expensive as it requires costly dye. On the other hand, extrusion molding isn’t that expensive.
  5. Injection molding is a bit complicated method as compared to extrusion molding.

Conclusion

Both the methods have their purposes and advantages and each of these methods is important for the manufacturing of plastic products. These methods of extrusion help in the production of 3D as well as 2D products.

But the only difference here is that injection molding cannot achieve atypical cross-section which can be produced by extrusion manufacturing

References

  1. https://www.sciencedirect.com/science/article/pii/S093964119900034X
  2. https://www.sciencedirect.com/science/article/pii/S0022354915300745
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