Thursday, May 15, 2014

General Information On Blow Molding

General Information On Blow Molding

By Henry A. Parker


There are many different processes involved with manufacturing. Blow molding is the term used to describe one of those processes in which hollow parts made of plastic are formed. Generally speaking, there are three kinds of this: extrusion, injection and 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.

The first people verified to have used this process are William Kopitke and Enoch Ferngren. The concept of this technique is based on that of glassblowing. Kopitke and Ferngren created a blow-molding machine and in 1938, sold it to Hartford Empire Company. This is what launched the commercial-level of this process.

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 different typologies when it comes to this practice. EBM, or the extrusion process, involves plastic being melted and then extruded into a hollow tube. These processes might be continuous or intermittent. Types of products made from this practice: milk bottles, automotive ducting, shampoo bottles, watering cans, polyethylene hollow products and more.

The injection process, also referred to as IBM, is used in production of plastic goods in bulk and hollow glass. During this procedure, polymer is directly injection molded onto core pins. The pins are rotated to a station for the steps of inflation and cooling. The process is actually the least common of the three types. When it comes to injection stretch, the main techniques: single and two-stage processes.

Advantages and disadvantages come with each of these different processes. Furthermore, they might be utilized for the making of different goods. The practice itself has become more popular and is used in many different industries in operation today.




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