The plastic molding industry may be experiencing major shakeups due to the new United States-Mexico-Canada Agreement (USMCA), but shifts in American domestic manufacturing (particularly the automotive sector) mean an increased demand for US blow molding plastic. Companies wanting to produce custom plastic containers or large capacity jars should acquaint themselves with how blow molding works so that they can choose the right fit for their job.

Extrusion Molding

Considered the simplest form of molding, extruded bottle production entails cooling a hot tube of plastic in water within a mold. When the tube is inflated with air, it forms the shape of the mold, creating a finished product. It’s by far the least expensive type of molding, meaning that it is a popular option for making plastic bottles and custom plastic jars.

Injection Molding

In contrast to extrusion molding, injection molding is more labor intensive (and costly), but it can be a good alternative for projects that require more detail, such as an accurate, molded neck. In this method, a polymer is injected into a hot cavity, allowing the manufacturer to create a custom plastic container with a bottle neck, such as with a test tube. Unfortunately, injection molding can only be used on small-scale bottles, and there is no way to control the strength or design of the bottle.

Stretch Molding

Stretch molding is commonly used for plastic soda and water bottles. As with injection molding, the manufacturer starts by injecting a polymer into a heated cavity. After it has cooled, however, the manufacturer reheats the mold to make it malleable. Air can be pumped into this flexible tube, which can stretch to double its original length. Plastic bottles made with this method are also relatively strong. With that said, stretch molding is fairly expensive, and is only profitable for large manufacturing operations.

Despite the mammoth changes taking place in the plastics industry (and plastics technology itself), plastic blow molding is still in high demand. With the glut of services available, always talk to a manufacturer you can trust to find the best method for your products at the best price.