Plastic injection molds are designed as hollow metal blocks which come with cavities. Plastic injection molds are utilized for giving shape for molten plastics, and this is done through the process of injection. There will be many holes inside these molds, and they help in realizing the temperature control via oil, heaters, or even water.

The sprue which is present in the mold allows melted plastic for flowing in. This will next enter the cavities via gates and runners. After it gets cooled, the mold gets opened. Later the molded parts should get ejected through a push on ejector plate by ejector rod which is part of the injection molding machine.

Some of the parts of the injection molding machine are guide pins, runner, gate, sprue, locating ring, mold cavity, the ejector, the shot, ejector plate, and clamping plate. The guide pins are installed on the one half of the plastic injection mold. Then two halves are aligned through entering the holes which are on the other half. The function of this guide pins is to locate the core, and the cavity inserts in the proper position.

injection molding products

injection molding products, *picture from

The runner in this injection mold machine is used to connect sprue bush to the molding cavities. It is the passageway for the flow of material. The section shape here is usually trapezoid or round. Gate is the narrowest position in the runner, and through this, the flow material can enter the molding cavity. There are a lot of different types in the gate. The sprue is nothing but the tapered hole which is present at the center of plastic injection mold to which the flow material travels from the nozzle. Locating ring present in the plastic injection mold is used to locate the mold on the fixed pattern. This makes sure that the injection nozzle can line up with sprue bush.

Mold cavity present in the injection mold machine is the space which is mold shaped for producing the actual molding product. The ejector is used to push molding parts and runner out of that mold. The shot in the injection mold machine is the total amount of the material which goes into cavities, and this also includes the material going to molding parts and runner. Ejector plate here is utilized for holding the ejector in the proper position. The clamping plate is also present in the injection mold machine, and this is used to clamp the mold to the platen injection machines.

Why plastic injection mold?

There are many reasons to choose plastic injection molds. Some of them are

High precision

Since plastic injection mold follows a highly accurate approach, it is utilized for producing highly diversified plastic parts of almost all types. Even though there are some design restrictions, all types of injection molds usually ensure molded products with high precision. This is the reason it can deliver a final product with a precision 0.005 in tolerance.

High efficiency

Today, plastic injection molding has become one of the most commonly used and preferred technologies mainly for long production periods. This is because plastic injection molding is really fast. Even though the production speed always depends on the complexity of the structure of the mold, usually the interval between the cycle times is just 15 to 30 seconds.

Labor cost

The injection molding equipment usually demands very less human supervision. This is because these molding machines usually work through automatic tools which are self –gating. This also realizes highly streamlined operation as well as continuous production.


Today one most gives high attention to sustainability as well. So, it becomes very important for product developers to choose the process which helps in waste elimination and environmental protection. Plastic injection molding is considered a highly effective process along with this; it is also highly resourceful. This is because, in the case of plastic injection molding, only the required amount of plastic is used for producing the final product. Along with this, even if there are some excessive materials, they can be recycled and used further.

Highly flexible

The best thing is plastic injection molding is highly accurate, and along with this, it is highly flexible as well. To understand this, it is possible to change the material type in this case. Other than this, it is also easy to change the color once the mold is made. When the requirement is to change the product shape, it can be achieved through adding or removing some steel to it.

Cheap and light

When we consider the density, compared to metal, the density of plastic is much lower. The best thing about this plastic injection molding is, it is one- time process, and there is no need for secondary machining. This is the reason it is much cheaper compared to metal.

These are the main reasons behind choosing the plastic injection molding today. Along with providing high accuracy, highest flexibility they are available for a lower price. Most of the enterprises choose this plastic injection molding for these reasons, and along with this, they are lighter as well.