Blow Molding: How It Works

Before going into detail as to how blow molding works, it helps to understand what it is. This manufacturing process is actually comprised of two parts. First is a parison, which is the starting tube made from molten plastic. The second part is the inflation of the tube, which is what molds the part or component into the desired shape.

This particular type of molding is used to make hollow plastic containers. Some examples include jars; containers; and bottles for milk, sports drinks, shampoo and conditioner, and so on. In other words, the containers that hold products used by millions of people around the world on a daily basis are created using this molding process.

This process offers many advantages. The blow molding method works well for creating complex shapes, production times are fast, and the empty plastic containers are recyclable.

There are three specific types of blow molding machines, as outlined below:

  • Extrusion Blow Molding (EBM) – This method is used for extremely high production. Depending on the customer’s need, EBM can work in conjunction with other manufacturing processes, such as filling and labeling. With this method, plastic is melted and then extruded into a parison. Next, the parison is inserted into a metal mold that has been cooled, followed by air being blown into the parison to inflate it into the desired shape.
  • Injection Blow Molding (IBM) – For this method, the parison is made using a separate operation. This type of molding starts with molten plastic, which is injected into a preform mold that has been heated. The plastic then seeps around a hollow core rod. After all of the plastic is injected, it then transfers to a second station in the machine that blows the container. The third station is where the core rod is stripped away and the parts exit the machine. IBM is the method used for manufacturing single-serve and small plastic products, like medicine bottles.
  • Stretch Blow Molding (SBM) – This process is used to make parts that have a biaxial molecular alignment. With SBM, the parison is mechanically elongated in the mold and then significantly expanded using a blowing process. Compared to the other two methods, SBM requires a cooler temperature, thereby making the process somewhat challenging to control. However, not only is there less wasted material, the finished product is stronger.

Pet All Manufacturing Inc. provides machinery for all three molding methods. For more information please contact us: 905-305-1797.

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