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Numerous products are made from blow molding. Any consumer item that has a three-dimensional shape and is hollow, such as tanks and CD cases, is manufactured using the blow molding process. Blow molded products are capable of holding a variety of substances such as herbicides, pesticides, cosmetics, and automotive oil. The plastic utilized for these processes are all thermoplastic resins. They include acetal, polysulfone, polyamide, polystyrene, butadiene styrene, Barex, polyvinyl chrloride (PVC), and high and low density polycarbonate.

Plastic blow molding can be categorized into three types: injection blow molding, extrusion blow molding, and stretch blow molding. All of these processes consist of two steps, which vary the most in the early stages. The ultimate shape of the blow molded plastic depends on the shape of the mold cavity. While blow molded products come in an assortment of standard shapes and sizes, there are some products that can be made using custom blow molding, and are thus used for special applications.

The blow molding process is implemented in order to form a smooth, airtight, uniform product that does not need to be assembled together. The first step in the blow molding process involves melting the plastic, and then using injection molding to form it into a preform, or parison. A parison is a piece of plastic shaped like a tube with a hole on one end which allows compressed air to pass through. The preform, which is soft and moldable, is pushed by a metal ram and expanded to the designated height of the product.

Air pressure is introduced to the inside of the parison via a blow pin. The air pressure causes the parison to expand like a balloon and fully take the shape of the mold cavity. The final product can be cooled either by running cold water through the mold, by conduction, or by evaporating inconsistent fluids within the container. The blow molding process merely takes a few seconds; thus, blow molding machines are capable of producing up to 20,000 containers in an hour. There are three methods in which blow molded plastic can be produced: extrusion, injection, and stretch blow molding. Read More…

Leading Manufacturers

Western Case, Inc.

Riverside, CA | 951-214-6380

Custom-Pak, Inc.

Clinton, IA | 563-242-1801

Iceberg Molding

Sturgis, MI | 269-651-9488

Manufacturers Custom Products

Woodridge, IL | 630-988-5055

Western Industries, Inc.

Winfield, KS | 620-221-9464

Gemini Group, Inc.

Auburn Hills, MI | 248-435-7271

The first method, extrusion blow molding, is the simplest of the three. It allows for a wide range of sizes, shapes, handleware, and openings for containers. In creating the containers, the process utilizes two mirror molds, which results in a seam running down the middle of the product. The second process, injection blow molding, hybridizes the processes of blow molding and injection molding. In this process, the plastic preform is injection-molded before being blown into a mold. This process involves is not suitable for manufacturing any kind of handleware, but is permissible for small containers.

The process of stretch blow molding has two different methods: injection stretch blow molding (ISBM), and reheat and blow molding (RHB). These processes are often used to manufacture bottles for beverages such as water and juice. The ISBM process involves injection molding a preform, and then moving it to the next station to be blow-molded. ISBM is a costly process, and is used to manufacture liquor bottles, water bottles, and peanut butter jars.

RHB involves purchasing a preform from another vendor who has already injection-molded the material. The preform is reheated to prepare it for the blow-molding process. RHB is much more cost-effective than ISBM, because it eliminates the need for injection molding equipment and provides access to various pre-made preforms.

The blow molding process has many advantages compared to other methods of plastic manufacturing. Blow molding is less costly than injection molding, and is suitable for fabricating plastic parts that are hollow. Blow molding also has a faster cycle time compared to other processes such as rotational molding.

There are many situations where a single blow molded plastic part can take the place of a group of parts. One problem that could arise is that the plastic could have an uneven thickness, leaks, or holes. Even walls are more easily created with the rotational molding process, but plastic blow molding is recommended for high-volume production.

Blow Molding Informational Video