Mar 26/19

Here Is Everything You Need to Know About Blow Molding

Blow molding can be found around you and you don’t even know it. That soda that your drinking has a plastic bottle, which was blow-molded.

In the United States, The plastics industry is the 3rd largest manufacturing industry. Plastics make our lives easier and help us produce things more cost-effectively.

But what exactly is it? And how does it work? Read on to find out!

What is it?

This process can be used to manufacture plastic products. The process involves heating a plastic tube (known as a preform or parison) to its melting point and then putting that into the cavity of a mold.

They then use compressed air to inflate the molten plastic like a balloon so that it takes the shape of the mold but is hollow inside. The amount of plastic used and the air pressure determines how thick the final product is.

The History

Blow molding has its roots in glass blowing, where a craftsman would heat the glass to its melting point and then blow through a tube to inflate the glass. This process has been around since as far back as the 1800s. A patent from the time shows the process being used with celluloid polymer. These early methods were not suited for mass production.

In the 1930s, they developed commercial machines to manufacture blow-molded bottles and made mass production possible. The materials available were too brittle and took too long to produce to effectively utilize the process to make large quantities.

Blow molding exploded into industrial prevalence with the creation of low and high-density polyethylene. This revolutionized many industries including the soft drink bottling industry and the automotive industry.

What Can You Make?

You can make just about any hollow plastic container with blow molding, but the process isn’t limited solely to bottles. Here are some commonly blow-molded products:

  • Construction Barrels and Barriers
  • Stadium Seating
  • Coolers
  • Fan Housing
  • Toys and Sporting Goods
  • Watering Cans

Blow molding is also widely used in the automotive industry and makes the design and mass production of auto parts simple and cost-effective. Here are some commonly blow-molded automotive parts:

  • Automotive Ductwork
  • Liquid Reservoirs
  • Mud Guards
  • Consoles
  • Seating
  • Storage Systems
  • Electrical Covers
  • Fenders
  • Paneling

To sum up, blow molding has a wide variety of uses and is a great way to produce a large number of parts inexpensively.

The Process

There are a few different types of blow molding. Their differences lie mostly in how they form the parison, the size of the parison, and how the parison moves between the molds. The main types of blow molding are:

  • Extrusion Blow Molding (EBM)
  • Injection Blow Systems (IBS)
  • Injection Stretch Blow Molding (ISBM)

Modern blow molding is a largely automated process, allowing for the production of thousands of parts in a short time period. The process includes the following steps:

  • Plastic pellets are fed into the machine via a hopper or screw depending on the machine.
  • Plastic melts and then gets shaped into a parison, which looks like a tube with a hole at one end.
  • Clamped in place inside the mold.
  • Compressed air inflates the parison.
  • The heated plastic balloons to fill the space of the mold.
  • After the plastic cools, the machine opens the mold and removes the part, sending it on to any applicable finishing, if any.

Furthermore, with IBS and ISBM, a preform replaces the parison. Tubes with a single hole made ahead of time, know as a preform, are manufactured through injection molding. A single perform design might be used for several different designs of blow-molded products and is another way to streamline production in some cases.

Blow Molding Materials

Plastics that are suited for this process include:

  • PVC
  • PET
  • Nylon
  • ABS
  • EVA
  • TPE
  • Low and High-Density Polyethylene
  • Polypropylene
  • Co-polyester
  • COP and COC
  • Polystyrene

The wide variety of materials available for use in blow molding means that you can use the process to develop parts to fit your exact needs.


There are many advantages to the blow molding process over other forms of plastic product manufacturing. Blow molding is a cost-effective alternative to injection molding, with both production and machinery being cheaper typically.

Blow molding works well for products that are one single piece. It can produce objects that do not require assembly or the connecting of halves. Therefore, particularly effective for containers that require exterior threading.

Blow molding also reduces flash. Flash is the little burs or plastic bleed around seems of products. This excess plastic from the production process requires extra finishing work to sand off or remove it before a part can be shipped. Blow molding techniques create a little-to-no flash, resulting in quicker turn around times for blow-molded products.

Your Product’s About to Blow Up!

Choosing blow molding to bring your product to life is a great solution for mass-producing simple, effective designs without spending too much money. We have a talented team of trained professionals who can take your product from idea to reality. In short, we’ll work with you throughout the design and production processes to ensure that the end result is a product you can be proud of.

So, contact us today so we can assist you in getting your product out of your head and out into the world!