Guide To Blow Molding For Beginners

Everyday hollow plastic items such as shampoo bottles, watering cans, storage drums, and milk cartons have a specific production method in common-blow molding. This flexible method enables the formation of hollow, thin-walled plastic containers by adding thermoplastic to a mold and shaping it as needed by blowing flattened air inside. The commonly utilized plastics in the blow molding process are polypropylene, polyethylene, polyvinyl chloride, and terephthalate. Blow molding is a production method employed for creating hollow plastic objects through the inflation of a heated plastic tube unless it makes a mold filled and creates the desired shape.

Uses of blow molding

This production method is employed to join and create hollow plastic parts commonly utilized in industrial and packing applications like tubs, drums, and plastic ducting. The flattened air component makes the blow molding production process differ from the standard injection molding. The usual injection molding process is more often used to produce solid objects. The blow molding method, step by step, begin by turning melted and softened plastic into a pipe-like structure employing extruding machinery before a hole is created in one end for the flattened air to go through. This hot plastic pipe is known as a parison. Then, the insertion of the parison is done into the mold and compressed into a place to let the flattened air push the plastic out and form the hollowed-out, final shape.

After the plastic part has hardened, its ejected from the mold and left for cooling. The three major types of blow molding are extrusion blow molding, injection blow molding, and stretch molding. Extrusion blow molding employs a parison inserted inside the molding machinery and shaped by the melting of the plastic for fitting the mold and then hollowed out by flattened air. This method is employed in about three fourth of all blow molding uses. It produces watering cans, automotive ducting, shampoo bottles, and milk bottles. The significant benefits of this blow molding method are its fast-manufacturing rates, low cost, and the capability to produce complicated geometrics. Some disadvantages of the extrusion blow molding process include the mere manufacturing of hollow components and the low strength of the material produced. When used to manufacture wide neck bottles, spin trimming is needed. Injection blow molding employs a preformed plastic shape rather than a parison, which is backed by a metal core pin and hollowed out by flattened air. It is a process where the material is injected and melted into an exactly dimensioned die till it solidifies and cools to the desired shape of the product.

In stretch molding, the formation of the parison is like the injection blow molding, but the difference between the injection molding and stretch molding is that after getting sent to the blow mold, it is stretched and heated downward with the help of the core before inflation. The stretching method permits using increased strength inside the material. Stretch molding is very beneficial for low quantities and for allowing the mold to be shaped in non-round and rectangular shapes. Still, the stretch molding process restricts the designs of bottles. It is utilized to manufacture parts subjected to internal pressures or with highly durable demands like soda bottles. The blow molding’s future is the machinery’s innovation. The challenge to the blow molding technology is providing an attractive, economical, and technological solution for manufacturing products that consider environmental concerns of disposing products.

What can be manufactured with the blow molding process?

A massive benefit of the plastic blow molding process is that an extensive range of products can be made with it. From jars, shampoo bottles, and plastic food flasks to industrial tubs, drums, and automotive ducting, plastic blow-molded goods can be seen across all commercial and domestic life sections. As well as inside the drink and food packing sector, blow molding components are commonly used to develop products for the automobile industry; for example, automobile liquid storage containers, fuel tanks, and parts of the cooling system.

The medical industry depends on the blow molding process for storage flasks ,spraying water bottles for medications and sanitizing products. In contrast, several household items also incorporate blow molding materials, including reservoirs in dishwashers and washing machines. Finally, several toys of children such as balls, dolls, and plastic blocks have come into existence due to plastic blow molding. Blow molding also makes huge industrial items like drums, plastic tubs barrels, and storage tanks to transport liquids. And there is a huge market demand growing for PP bottle-making machine suppliers and exporters as dozens and dozens of blow molding companies are competing to get an edge over others. The phases of the blow molding method are given below:

1 Preparation

In a usual manner, the blow molding process begins with bringing raw plastic to the equipment, but there are preparation stages for all plastic products producers make. Plastic processing can be done in its natural state or blended with a wide variety of additives and colors. Producers’ modernized material handling systems – consisting of surge bins, grinders, blenders, and other parts- are utilized to manage, mix, and move around the blow molding machinery of producers. Automated material handling devices and material blenders give continuous batches of material more efficiently than a person could. These batches encompass exact precise mixes of color, regrind, additives (reclaimed plastic), additives, and virgin material. Mixed, managed, and moved according to the project’s conditions, the plastic material is readied to start the blow molding procedure. The material management system loads it inside a hopper on the blow molding equipment’s top and does its feeding into an extruder.

2 Extrusion

A screw inside the barrel on an extruder unceasingly turns, pushing down the plastic to the barrel’s length. With mechanical friction, the transformation of the plastic is done from the solidified pellet condition to the molten state that permits it to be turned into shapes. Heaters on the head and barrel maintain a continuous temperature, producing material consistency as the movement of the plastic takes place down the barrel. Then, the consistently heated molten plastic is pushed over an extrusion head and die tooling that establishes a parison.

3 Establishing  A Parison

The parison is a plastic hollow tube that will turn into the completed bottle, shape, or container. The die tooling and extrusion head determine the quantity and shape of parisons that will be manufactured. One extrusion head may be utilized for huge or heavy parts, letting just a single part be produced during the machine’s every cycle. Smaller components manufactured on the same machinery might use extrusion heads capable of creating numerous parisons. This lets numerous components be manufactured through every machine cycle.

4 Mold It

Then, the extruded parison is compressed into mildew and cut. Following that, a blow pin enters the parison’s top to seal the tube, and then the flattened air pushes the plastic out for matching the mold. Usually, molds are composed of aluminum or other metals that can be cooled down to facilitate the finished component’s speedy establishment. After cooling down the plastic and hardening it, the mold does open, and its part is ejected.

5 Plastic Recycling

Manufacturers remove excessive flash or plastic from the mold either through a machine or manually. The flash is then sent with the help of a grinder, where it is cut into tiny pieces and then moved to a surge bin. The reintroduction of regrind or recycled material can be done to the production process by employing a material handling technology to ensure no waste.