The injection molding process was invented in 1872. Since then, the injection molding business and the plastic industry has ballooned into a multi billion dollar business venture. In fact, thirty two percent of plastics by weight are processed through injection molding. Injection molding has greatly helped in making the US economy boom because through it, cheap and durable consumer and industrial items essential to almost all industries is made possible.
Components of the injection molding machine
The injection molding machine converts granular or pelleted raw plastic into final molded parts through the use of a melt, inject, pack and cool cycle for thermoplastics.
A basic injection molding machine is typically composed of the following: injection system, hydraulic system, mold system, clamping system and control system. The clamping tonnage and shot size are both used in identifying the dimensions of the injection molding machine for thermoplastics, which is the main factor in the whole process. Other consideration include rate of injection, pressure, design of screw, thickness of the mold and distance between tie bars.
Functions of the machine
The injection molding machine can be classified into three categories, namely: general purpose machines, precision/tight-tolerance machines and high-speed thin-wall machines. All three types require auxiliary equipment to function. These support equipment includes dryers (resin), material handling equipment, granulators, mold temperature controllers and chillers, part-handling equipment and part-removal robots.
There are a lot of companies specializing in quality injection molding, but they are not all the same. The best ones fast, flexible and customer driven both for large and small quantities. These companies usually have state-of-the-art facility with full scale thermoplastic and thermoset capabilities, computer-aided manufacturing, skilled machine operators and quality assurance team.

Plastics are synthetically produced non-metallic compounds. It can be molded into various forms and hardened for commercial use. Plastic molding products can be seen everywhere. Examples are jars, protective caps, plastic tubes, grips, toys, bottles, cases, accessories, kitchen utensils and a lot more.
Even the keyboard and the mouse that you use are made through plastic molding. Even the plastic parts of the chair that you are sitting on are created this way.
The basic idea in plastic molding is inserting molten liquid plastic into a ready shaped mold, for example the mold of a bottle. It will be then allowed to cool, then the mold will be removed to reveal the plastic bottle.
Plastic molding can also custom-mold a wide variety of plastic products including: garden pots, cabinets, office trays and boxes, barriers, barricades and traffic signage and displays for product and marketing promotions.
If you are planning to go into plastic molding business, you should first know the different processes. Choose from a plastic molding process that fits your budget, your expertise, and your resources. Here are basic definitions of various methods of plastic molding.
The Plastic Molding Processes:
1. Injection Molding
In Injection Molding, melted plastic is forced into a mold cavity. Once cooled, the mold can be removed. This plastic molding process is commonly used in mass-production or prototyping of a product. Injection molding machines were made in the 1930��s. These can be used to mass produce toys, kitchen utensils, bottle caps, and cell phone stands to name a few.
2. Blow Molding
Blow molding is like injection molding except that hot liquid plastic pours out of a barrel vertically in a molten tube. The mold closes on it and forces it outward to conform to the inside shape of the mold. When it is cooled, the hollow part is formed. Examples of blow molding products are bottles, tubes and containers.
Equipments needed in setting-up a blow molding business are relatively higher than injection molding.
3. Compression Molding

In this type of plastic molding, a slug of hard plastic is pressed between two heated mold halves. Compression molding usually uses vertical presses instead of the horizontal presses used for injection and blow molding. The parts formed are then air-cooled. Prices of equipments used for compression molding are moderate.
4. Film Insert Molding
This plastic molding technique imbeds an image beneath the surface of a molded part. A material like film or fabric is inserted into a mold. Plastic is then injected.
5. Gas Assist Molding
Also called gas injection molding is used to create plastic parts with hollow interiors. Partial shot of plastic is then followed by high-pressure gas to fill the mold cavity with plastic.
6. Rotational Molding
Hollow molds packed with powdered plastic are secured to pipe-like spokes that extend from a central hub. The molds rotate on separate axes at once. The hub swings the whole mold to a closed furnace room causing the powder to melt and stick to the insides of the tools. As the molds turn slowly, the tools move into a cooling room. Here, sprayed water causes the plastic to harden into a hollow part. In this type of plastic molding, tooling costs are low and piece prices are high. Cycle time takes about 40-45 minutes.
7. Structural Foam Molding
Structural foam molding is a process of plastic molding usually used for parts that require thicker walls than standard injection molding. Inserting a small amount of nitrogen or chemical blow agent into the plastic material makes the walls thicker. Foaming happens as the melted plastic material enters the mold cavity. A thin plastic skin forms and solidifies in the mold wall. This type of plastic molding can be used with any thermoplastic that can be injection molded.
8. Thermoforming
In this plastic molding process, sheets of pre-extruded rigid plastics are horizontally heated and sucked down into hollow one-piece tools. When the hot plastic solidifies, its shape conforms to that of the mold.
Tooling costs are usually low and piece prices vary on the machinery.
Plastic molding is a very technical process. It needs experts in this type of manufacturing business for it to be competitive in the market. Therefore, a very scientific and systematic study should be first made before going into this endeavor.

About injection molding
In injection molding, plastic granules are heated and "injected" under pressure into metal molds, where the molten plastic hardens into a designated shape. The mold then opens and the newly formed part is removed and inspected, ready for shipment or secondary manufacturing operations. Injection molding is an extremely versatile and popular form of molding. Other processes include extrusion, thermoforming, and blow molding.
 
About insert molding
 Injection molding becomes insert molding when a specifically designed insert (typically of metal) is nested in the mold before the molten plastic is injected. The plastic hardens around the insert and the resulting part is a combination of plastic and insert. A simple example would be certain scissors in which metal blades are inserted into the mold, and plastic handles are molded around the blades.
 
Ahout injection molding machine
 Broken down to its most fundamental components, an injection molding machine, or press, is comprised of three functional units: 1) injection (which melts and transmits the plastic granules), 2) mold (the custom designed portion which produces a specialized product,) and 3) clamping (which provides the controlled pressure to open and close the mold.) The following diagram, Figure 1, illustrates a simplified injection molding machine.

About mold
 In injection molding, a mold is a specially designed metal tool consisting usually of a "mold base" and one or more "cavities." The cavities are contoured to the exact specifications of the desired product, and it is into these cavities that the molten plastic is forced and hardens. The cavities are situated in the mold base. A carefully engineered mold base will not only safely anchor and house the more delicate cavities, but also provide for the quick and efficient production of a high quality part. Considerations for the design of a mold base include 1) the proper transmission of molten plastic along a system of channels (called "runners,") 2) the precise cooling and/or secondary heating necessary for a given part, and 3) the separating and ejecting of the part from the mold (and any runner) after it is complete. The following diagram, Figure 2, illustrates a simplified mold base.

Plastic injection moulding is a process of manufacturing parts from thermoplastic as well as thermosetting plastic materials. This process is used for manufacturing smaller parts and even car body panels.

The plastic molding industry has seen a rising trend over the past few years. The industry manufactures products for a large variety of industries including automotive, packaging, aerospace, medical as well as construction industry. Plastic moulding is used for manufacturing small things like bottle caps, milk cartons, pocket combs and many other things that are made of used in everyday life. It is one of the most commonly used processes of manufacturing parts.

The advantages of plastic moulding include the following:

The process has a high rate of production.
This process can make use of a wide range of materials and is not restricted to using a particular raw material.
Once parts are made, there are very few instances when finishing of these parts is required. This saves a lot of money which is otherwise spent on finishing of goods.
The cost of labor in this industry is less because the process is not a difficult one.
There is very less wastage in the process of plastic moulding.
It is a cost effective process that enables the industry to make more profits.
A few disadvantages of this process are listed below:

The equipment and machinery used is very expensive.
The process has to ensure the parts being manufactured are moldable. This often results in the process becoming a little expensive.
A plastic moulding machine has a material hopper, a plunger and heating unit. The heating unit is also known as presses. These hold the molds in which different components that are being manufactured are shaped. Molds are the tools that are used for producing the plastic components or parts. These are also known as dies. The molds are generally made of steel, aluminum or an alloy of beryllium and copper. The material used for making the mold depends upon the cost that the industry is ready to put in for the molds. There are different types of molding processes that can be used depending upon the part being manufactured.

The use of compressors, presses, heaters, knives and other equipment may often require protection from hazards in the plastic molding industry. Those working in the industry need to protect themselves from such hazards. They therefore need to use safety equipment like guards and wear clothing that is heat resistant and can also protect the workers from getting injuries. In addition, the plastic molding machinery must be properly taken care of and maintained by lubricating the various parts whenever necessary to remove jams. This ensures that the machine starts properly without requiring any of the workers to face any hazard.