What is the Difference Between Extrusion Blow Molding and Injection Molding?

MMAdminApril 7, 2019 ,

When designing a mold for a product, there are so many different processes from which a company may choose, usually depending on the best fit for your needs. Today, extrusion blow molding and injection molding are the most popular ways to create cost-effective and high-quality plastic parts. So, what is the difference and which process will better fit your molding needs?

What is Extrusion Blow Molding?

Blow molding is a specialized type of plastic processing used to create hollow plastic parts. The extrusion form of blow molding is a manufacturing process whereby plastic is melted and extruded into a mold. This process is specific to producing a high volume of hollow, one-piece objects. Therefore, if you are looking to make a lot of bottles, this process is a great one!

Within the extrusion blow molding process, the plastic is melted and then extruded into the parison. The parison is sealed into the mold and then air is blown into the mold thereby shaping it into the desired plastic product. Once the plastic has cooled, the mold is opened, and the part is removed.

Some advantages of extrusion blow molding include:

  • Quick and cost effective for high-volume outputs
  • Versatile for many applications and industries
  • Precise design replication

Some examples of parts and products that are developed through extrusion blow molding include water bottles, lotion and other small bottles, automotive parts, coolers, milk jugs or any other type of hollow object.

What is Injection Molding?

On the other hand, injection molding is a manufacturing process used to create solid plastic parts. This process typically requires a lot of upfront engineering and design to develop detailed tooling or molds. Injection molds are usually made of aluminum or stainless steel and once formed, the molds are injected with liquid polymers at a very high temperature and at an extreme pressure. Once this happens, then the molds are cooled down and then can be removed as a complete plastic part.

Some advantages of injection molding include:

  • Detailed tooling that allows for multi-cavity mold options
  • Efficient and precise for large volumes (mainly of small parts)
  • Low scrap rates due to the efficient use of the materials
  • Ability to change color or material easily

Injection molding is ideal for high volume orders and mass production of the same part. With this molding process, the mold is the key to building a perfect, precision part. The cost of precision typically makes an injection mold more expensive than a blow mold.

Having an understanding of the difference between these two manufacturing processes and knowing which method is best for your product production is crucial for all aspects of your prototyping, planning, manufacturing, and costing.

At Monroe Mold, we specialize in extrusion blow molds with special expertise in polyethylene applications. From product development and design, to complete in-field mold startup, we are your one-stop mold manufacturer. For more information on our molding solutions, please contact us today at (734)-241-6898.