You may or may not have heard of blow molding, but there’s no doubt you’ve seen a parts, products, packaging, containers and many other items manufactured using this process. The process has become very common for manufacturing, and almost every industry manufactures products this way for individual components, containers, or shipping. If you’re not sure if your new idea should consider blow molding, we’ll take a look at its history, different types, and recommended applications to better understand if it’s a good fit.
What is Blow Molding?
Blow molding is the process of forming a molten tube (commonly called a parison or preform) of thermoplastic material and placing the molten tube within a mold cavity. The molten tube is inflated with compressed air to take the shape of the cavity, then cooled before removing from the mold. The most common part made with blow molding is a bottle or container, but any hollow thermoplastic part can be blow molded easily.
How Did It Get Started?
Blow molding owes its roots to the process of glassblowing. In the late 1800s there was a method of extruding a celluloid polymer into a tube shape and blow molding a part. The early methods and materials attempting blow molding with plastics were very rough and not capable of mass production. In the late 1930s, the first viable machines and products were developed to produce bottles. The breakthrough that started the revolution of commercial blow molding was the development of low and high density polyethylene that could be utilized to produce consumer packaging. From that point, blow molding became a hit in both Europe and North America.
What Are The Types of Blow Molding?
There are three main types of blow molding:
1. Extrusion (EBM)
The material being used for the extrusion blow molding (EBM) is melted and forced through an extrusion die to form a hollow tube or parison. Two halves of a cooled mold are closed around the hollow tube, then compressed air is injected through a pin or needle to inflate the part to the shape of the mold. When the formed part is cooled, the halves of the mold open to remove the final part. Common examples of parts made by with the EBM process include bottles, industrial containers, automotive products, appliance components, and children’ toys.
2. Injection (IBM)
Injection blow molding (IBM) process injects the polymer material onto a core within a cavity to form a hollow tube (called a preform). The hollow tubes rotate on the core rod to inflate the material before it is cooled in the final shape. This type of molding is normally used to make smaller bottles (usually smaller than 16oz / 500ml in volume) at with high production volume. The process is quickly run in three simple steps: injection, blowing and ejection. All are done in one machine and allow for tight tolerances without extra material wasted. Common examples of the IBM process are pharmaceutical industry bottles, medical industry parts, and cosmetic or other consumer product packages.
3. Injection Stretch (ISBM)
The injection stretch molding method (ISBM) process is comparable to the IBM process with a preform being injection molded. The molded preform is stretched along its length as well as radially before being inflated to form the final part shape. Polyethylene terephthalate (PET) and Polypropylene (PP) are the two most common resins used for ISBM because their physical properties are enhanced by the stretching part of the process. The stretching operation offers improved strength and barrier properties with lighter weights and better wall thickness consistency.
What Are the Best Polymers for Blow Molding?
- Low density Polyethylene (LDPE)
- High Density Polyethylene (HDPE)
- Polypropylene (PP)
- Polycarbonate (PC)
- Polystyrene (PS)
- Polyethylene Terephthalate (PET)
- Polyvinyl Chloride (PVC)
- Acrylonitrile Butadiene Styrene (ABS)
What Industries Use Blow Molding?
Many industries use blow molded parts, and that does include bottles. The key to blow molding is that the part needs one opening to form, which is usually smaller in diameter or size than the overall body dimensions of the part itself. Bottles and smaller containers are the most common products produced, but there are other products using blow molding such as:
- Industrial bulk containers – Think of larger fluid containers like barrels to transport and store water, oil, or anything else liquid.
- Automotive industry – Many of the parts storing fluids use blow molding. Cooling system overflow containers, windshield washer fluid bottles, and even fuel tanks are commonly made with using this process.
- Appliance components – Your major appliances at home include reservoirs that contain fluids and help to wash your clothes and dishes. From big to small, blow molding can quickly created many hard to create shapes.
- Medical supplies and parts – If you’ve been to a health clinic, your dentist, or to visit your family doctor you can quickly start counting how many hollow containers are used. Spray bottles, water bottles, and storage containers line the cabinets.
- Children’s toys – If you have a small child, you could quickly count how many hollow lightweight toys they have. Blocks and squeeze toys are common uses for blow molding, which makes them a great option if you’re producing a new toy option.
- Lawn and garden items – You could almost put lawn and garden into the automotive and bulk container categories as it uses bottles for liquid products for mowers and power equipment for fuel tanks, oil storage and distribution.
Blow molding offers advantages compared to other injection molding processes that you may be researching for your new product. Many industries use one of the three blow molding types to create common every day products, while others use the process to create unique low volume products that may be your competitive focus. Determining if this will be your best choice can be aided by an expert mold maker that also offers resin selection, turn-key assembly options, and program management to see the complete development cycle through with success. If you need expert advice from a partner that can help with your next product idea, call us (425) 339-0288 or email us at firstname.lastname@example.org. We can offer you advice on the best technology to use, the best materials to meet your product demands, and how to navigate through each development stage. At SEA-LECT Plastics, we specialize in military product applications, outdoor adventure gear, musical instruments, supporting the military and marine consumer product industries. Our goal is to make your project efficient and cost-effective to manufacture, assemble, and ship no matter how complicated your concept is.