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  Various Injection

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  Small Injection

What Is Injection Molding?

Injection molding is a method of producing parts with a heat-melt able plastics material. This is done by the use of an injection molding machine. The shape which is produced is controlled by what is called a "mold." This is a reverse image of the part desired and can be compared to the familiar "Jell-O®" mold. The injection molding machine has two basic parts; the injection unit, which melts the plastic and then injects or moves it into the mold, and the clamping unit, which holds the mold. The unit clamps the mold in a closed position during injection, opens the mold after cooling, and ejects the finished part.

Injection molding is a relatively new method of producing parts. The first injection molding machines were manufactured and made available in the early 1930’s, while other manufacturing methods you may be familiar with date their origins back over 100 years.

What are Plastics?

Plastic is a man-made material which is composed of some of the common elements of nature: carbon, hydrogen, sulfur, nitrogen and chlorine. These basic chemicals are obtained from water, natural gas, oil, coal and even from air and plant life. One definition of plastics is: "a natural or synthetic substance which is pliable or moldable at some stage during its forming or manufacturing." You may also hear the word "polymer" when referring to plastics materials. This simply refers to it as being a group (poly) of small units (mers) joining to form larger units (polymers).

You may also hear the terms "thermo set" and "thermoplastic" used. In this case, thermo set means that the plastic has been chemically changed during heating and molding (set) and cannot be re-melted. Thermoplastics, on the other hand, may be re-melted after molding. Although there are a few thermo set materials which are injection molded, the majority of injections molding materials are thermoplastics.

Plastics materials are further identified as being crystalline or amorphous. The chains which form the plastics are often tightly packed and ordered structures. These are referred to as crystalline polymers. Polymers which have random, unstructured definition are referred to as amorphous. Most crystalline plastics are not 100% crystalline but contain both crystalline and amorphous structure.

Where are Plastics Used?

In today’s world it is hard to find an area where plastics are not used. Plastic is considered one of the basic construction materials much as metal, wood, paper or glass is. From the clothes we wear to the cars we drive, from the dishware we eat from to the chairs we sit on, from our first toys as infants to replacements for worn out body parts, plastics play a large part in our lives, a resource we would have difficulty replacing.

Why Use Plastics?

The first plastics articles were thought of as a cheap, easily broken material, poor substitutes for the original items they were replacing. Not anymore! More and more, plastics are the material of choice for many applications. In automobiles, plastics have been used for some time in the exterior and interior of the vehicle. Now usage is seen even in what is called "under hood applications," an area where parts are exposed to high temperatures, oil, grease and gasoline. Plastics have a long history of use in the aircraft and aerospace industries, and usage has increased with each new design generation. Major steps have been taken in the use of plastics for the food packaging and processing industry, replacing tin cans, glass and cardboard, where cleanliness, recyclability and weight are a concern. Plastic is used in almost all major industries and markets like construction, plumbing, boating and electricity, in addition to consumer goods.

Some of the main reasons plastics are in such wide usage is their ability to withstand both high and low temperatures, and a variety of chemical environments. Another property which gives plastic an advantage in transportation is its low weight to strength ratio. The ability to sterilize and recycle plastic articles into new applications is a major asset. If plastics, for some reason, reach the landfill, they constitute a small percent of the total, falling far behind such items as paper and yard debris. Even at this stage of its life, this discarded plastics material has the advantage over other materials by not degrading into unwanted leach ate and producing pollution. It remains as an inert material.

Provided by the Society of Plastic Engineers

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  Various Injection

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  Various Injection