A lot of different practices are involved when it comes to manufacturing goods. Blow molding is one of the many and is designed to make hollow parts from plastic. In general, the three types: injection, extrusion, injection stretch.
This practice begins with melting plastic. This is then formed into a preform or parison. The former is used for injection and injection stretch procedures. Parison refers to plastic in a tube shape that includes a hole at the end for compressed air to pass through. This is clamped to the mold and the air is blown inside. Pressure from said air is strong enough to push plastic to fit the mold. After it has cooled and hardened, the mold opens and is ejected.
Two men are considered the first to have employed this practice: Enoch Ferngren and William Kopitke. These two also built a device for this practice and sold it to Hartford Empire Company in the year 1938. The concept of the process itself is based on that of glassblowing. The selling of the machine led to the commercial use of this practice.
Limitations of variety and number in the products meant that this process did not become popularized until later. Once variety and production rates grew, the number of the goods increased as well. In the United States soft-drink industry, the plastic bottles that were made in 1977 was zero. The number increased to ten billion by 1999. In the modern day, even more products are being blown, a number that is expected to increase as time goes.
There are multiple typologies with this practice. Extrusion process, also known as EBM, involves the plastic being melted and later extruded in a tube that is hollowed out. The process might be intermittent or continuous. The kinds of products typically made with this approach: watering cans, automotive ducting, milk bottles, polyethylene hollow products, shampoo bottles and more.
IBM, or the injection process, is used for producing hollow glass and plastic goods in large quantities. With this, the polymer is injection molded on core pins, which are then rotated onto a station for inflation and cooling. This is the process that is used the least in different types. There are two main techniques associated with injection stretch practice: two stage and single.
There are disadvantages and advantages associated with the three different types of molding. Likewise, these are employed for the manufacturing of different parts. The practice, as a whole, has become more common and is employed in numerous industries of today.
