Blow Molding Machines
Blow molding machines are used to produce hollow plastic products like bottles and containers. The process is similar to glassblowing but it’s more efficient and industrialized.
Plastic pellets are fed through an extruder and into an accumulator or extrusion die that creates a tube shape called a parison. The inflated product is then clamped in place and pressurized air blows through it.
Extrusion Process
In extrusion, a standard raw material called a billet or ingot is used as the starting point for the process. This is then melted and pushed through a die that has a specialized shape with a fixed cross sectional profile, forming continuous objects of a particular length. The process is normally performed at very high volume manufacturing rates, due to its ability to produce long, continuous products with a fixed cross sectional profile in a very short amount of time.
Plastics are fed into the extruder barrel, where they are melted by mechanical energy generated by rotating screws and by heaters arranged along the barrel. The melt is conveyed through a feed section, a transition section, and a metering section of the screw. Air should be removed from the pellets before they reach this section of the barrel, as conveying it forward will contribute to gel formation during melting.
The resulting molten plastic is then forced through a heated die that has a specialized shape with an exact and accurate cross sectional profile, giving the final product its recognizable form. It is then pulled through a cooling bath and, if applicable, through additional downstream equipment that may include flavoring, coloring and additive machines.
The cooled and hardened plastic is then cut to the desired length, which is often determined by the finished size of the product that will be manufactured. This enables the production of products with complex shapes that could not be formed using a simpler, less expensive injection molding process. The finished piece is then ready for any finishing and packaging operations that are needed.
Molding Process
Blow molding is a plastic manufacturing process that uses air pressure to mold hollow products like bottles and containers. Its roots go back to glass blowing, and it was the first process to produce a variety of shapes. It was also the first to create plastic bottles for consumer and industrial products.
In the first step of this process, molten plastic is formed into a tube-like shape called a parison. This is usually made of a low-density or high-density polyethylene, polypropylene, or polyethylene terephthalate.
The parison is then clamped into a hollow mold and the air is blown into it. The inflated blow molding machine plastic conforms to the mold’s shape and cools. The mold then opens and the product is ejected. Water channels inside the mold assist cooling.
This is the most commonly used blow molding process and is suitable for a variety of products. Its key advantages include reduced flash (excess polymer bleed around the seams of the products) and fast production speeds. It is heavily reliant on petroleum, but it can make more complex designs than other processes such as injection blow molding.
Injection-stretch blow molding is a variation of this process and is suitable for large products, such as PET bottles, with good optical and barrier properties. It is particularly useful for materials with low melt strength or viscosity, and it allows larger parisons to be molded without sagging.
Thermoplastic Materials
There are many different thermoplastics that can be used in the plastic blow molding process. Each type of material offers its own unique advantages and properties, but a few of the most common are HDPE (High-density polyethylene), PVC (Polyvinyl chloride), and ABS (Acrylonitrile Butadiene Styrene). These materials are cost-effective and durable, and they can easily tolerate the stress of constant use.
Blow molding is a fast, efficient, and economical method for producing large or small series of parts. It can also be used to make prototypes for testing and marketing purposes. Its versatility allows it to be used for a wide range of applications, from medical and automotive to consumer electronics and food.
When it comes to blow molding, the most important factor is selecting the right raw materials. The raw materials can have a huge impact on the final product’s durability and quality. It’s important to choose a supplier that uses high-quality, reliable equipment and works with top-notch manufacturers.
One of the best providers is Proto Labs, which uses a rotating wheel to perform all of the steps involved in the process. Several molds are located on the periphery of the wheel, which is separated into different sections for clamping, cutting, inflating, cooling, and ejecting. This means that each mold can be used repeatedly and allows for high production volumes.
Applications
Blow molding is an ideal process for high-volume blow molding machine factory production of hollow plastic products such as bottles and containers. It can be used to produce a wide range of shapes and sizes from a number of different raw materials including low and high-density polyethylene as well as acrylonitrile butadiene styrene (ABS).
Raw plastic pellets are fed into the machine via a hopper or screw depending on the type of blow molding machine. Once the plastic has been superheated and melted, it’s formed into a tube called a parison. The parison looks like a test tube and is transferred to the mold and inflated with forced air. The air pressure determines how thick the walls of the final product will be.
Extrusion blow molding can be continuous or intermittent, with each new parison being blown from the metal mold when it is cooled. This allows for a higher rate of production than injection blow molding while also providing greater control of wall thickness.
Injection blow molding is the other main type of blow molding. The process starts with a preform made from injection molding, which is then transferred to the blow molding machine for stretching and inflation. Injection blow molding provides more control over the dimensional stability of the final product and is generally more expensive than other types of blow molding.
