A Guide To Plastic Injection Molding Machines - FOW Mould (2022)

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Plastic injection molding is basically the process of making plastic parts by injecting molten plastic into metal. Its history is traced to 1872. In an attempt to replace ivory billiard balls with plastic balls, American inventor John Wesley Hyatt developed the first plastic injection molding machine.

As much as his goods didn’t fulfill the market’s requirements, his machine did. The plastic injection mold making industry has progressed significantly since the machine’s birth, from producing small and basic plastic parts like buttons to producing complex medical equipment today.

How A Plastic Injection Molding Machine Works

A Guide To Plastic Injection Molding Machines - FOW Mould (1)

Plastic injection molding is basically a four-step process: Melting down the material, Injecting the molten substance using a mold, Allowing the molten substance to cool and solidify, and lastly but not least Taking the hardened material out of the mold. The Plastic injection molding machine works in the following way.

  • Plastic pellets are put into a barrel from a hopper to start the plastic injection molding process. There is an internal auger in the barrel. Simply described, an auger is a revolving screw-like device that feeds material.
  • The barrel and screw are heated by heat bands on the outside, melting the plastic into a molten state.
  • When the machine's cycle begins, the mold closes and the auger, like a large plunger in a syringe, plunges forward under high pressure.
  • The internal auger injects molten plastic into the cavity, which is an empty section of the mold, in less than a few seconds. The plastic forms into the shape of the cavity in less than 60 seconds on average.
  • The mold will then open when the plastic part has solidified, and the part is ejected. The procedure might resume once the plastic injection molding machine ejects the solidified plastic item.

Main components of injection molding machine

A Guide To Plastic Injection Molding Machines - FOW Mould (2)

We cannot explain the injection molding process without mentioning the injection molding machine. Understanding the injection molding machine will help you to understand the process better and easier. The injection molding machine has several components which include:

  • The Injection Unit: This component of the injection molding machine is responsible for heating and injecting resins into the plastic injection mold. A hopper, barrel, ram injector, reciprocating crew, screws, and nozzle are among the components of the device. The material is fed to a barrel through a hopper, which is a huge container with an open bottom.

    The injection molding material is forced forward via a heated area by the barrel, which is equipped with a ram injector. Injection molding materials are propelled forward using reciprocating screws. The resins are then forced to travel towards the plastic injection mold through the slots in the screw. The resins and molten metal are melted in the heating channel.

  • The Clamping Unit. Molds are normally made in two sections, which are clamped together. The injection molds are fastened together just before the injection procedure. Each half must be secured to the platen, which resembles a huge plate.

    The molds are opened with a clamping motor after the injected molten resins have cooled to the desired temperature. The solid plastic object was forced out of the open chamber by an ejection system with an ejection bar in the back half of the mold.

  • The Mold Base. The mold core and the mold cavity are the two major components of a mold. These two components are attached to the platens of a mold base to form a pair. The support plate, sprue bushing, and locating ring on the front part of the molded baseline the mold base with the nozzle.
  • An ejection system and a support plate are located on the back part of the mold base. As previously stated, the ejection system includes an ejection bar. It aids in the removal of solidified plastic injection molds from the mold cavity, as the name implies.
  • The Mold Channels: Mold channels are the channels via which plastic resins flow into mold cavities. To make a single component, these channels are incorporated into the mold design. The molten plastic enters through the sprue and then continues into the runners.

    The runners guide the plastic resin through a gate, allowing the molten resin to fall into the hollow. Cooling channels are occasionally made to let water travel along the mold walls and speed up the cooling process of molten plastic.

  • Mold Design. In addition to the mold base and mold channels that are discussed above, there are a number of other designs that should be considered while building a mold. Complex geometries and features must be included in the plastic injection mold design for instance the undercuts.

    Some devices can also be introduced along the parting direction into the injection mold. The injection moulding design includes the draft angle that is applied to the mold walls.

  • Mold Tooling. Let's take a deeper look at injection mold tooling. Molds manufactured of steel or aluminum are used in custom tooling. Each metal has its own set of benefits and is employed in different ways, of course, based on the sort of plastic part needed. The two primary components of the part cavity are the mold core and mold cavity. When the mold is closed, the area between these two forms the part cavity, which is then injected with molten plastic resin.
  • Specifications Of Machines. A plastic injection molding machine has different specifications. Injection molders are typically characterized by the clamp force tonnage that they provide. The pressure used to inject the molten resins also plays a big role. High tonnage is required for materials that require a high injection pressure. The shot capacity, clamp stroke, mold thickness, and platen size are all critical variables that must be considered when purchasing a plastic injection molding machine.

Types of plastic injection molding machines

A Guide To Plastic Injection Molding Machines - FOW Mould (3)

Basically, molding machines are classified according to the kind of drive systems they employ. They include hydraulic, electrical, and electrical injection molding machines.

Hydraulic Injection Molding Machine

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Until 1983, when the first all-electric injection molding machine was introduced, the hydraulic technique was the only alternative accessible to molders. During the injection molding process, pressure-creating substances known as hydraulic oils are used to create pressure. This oil is pumped through a hydraulic motor, which rotates the screw.

The creation of leak-free systems for the molding process is one of the most important aspects of hydraulic injection. Hydraulic oil may frequently spill into the plastic, causing imperfections. To protect the engine, it was necessary to carefully study seal design. Hydraulic injection molding machines have been popular due to their inexpensive cost and ease of maintenance.

Electrical Injection Molding Machine

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The first electronic hydraulic machine was introduced in Japan in the 1980s. It has been utilized as a replacement for the larger hydraulic machine ever since. High-speed service motors are used in electrical injection molding. It is simple to operate and more modern than the traditional hydraulic ones.

Based on the injection molding cost, a lot of factories prefer this type of machine. This is because of the comfort and speed of production provided by this equipment, it is extremely cost-effective. At the same time, an electric hydraulic machine requires less maintenance and has a digital control option. This allows you to customize the amount of energy and pressure required.

Hybrid Injection Molding Machine

A Guide To Plastic Injection Molding Machines - FOW Mould (6)

Hydraulic injection molding and electrical injection molding are combined in this molding technology. It was created with both molding advantages and has proven to be superior to the previous two varieties. This molding method is very flexible and has the same selling quality as the previous two types of molding machines.

A hybrid injection molding machine is preferred by many injection molding companies because it can save energy like an electrical system while maintaining the hydraulic unit’s accuracy. It may switch between the DC pump motors and the hydraulic pump, allowing each to function just when it is required. There are no quality compromises as a result of this.

How To Choose The Right Injection Molding Machine

A Guide To Plastic Injection Molding Machines - FOW Mould (7)

Injection molds, products, materials, shape, output, and other aspects are usually crucial when looking for the right injection molding machine. So, before making a decision, consider the following aspects.

  • The dimensions of the molds for example length, height, and width
  • The molds' weight
  • The design structure within the molds
  • The types and numbers of plastics that are there
  • Other forming specifications, such as the injection mold machine quality level, manufacturing speed, etc

While the aforementioned are the most important aspects to consider when choosing a plastic injection molding machine, there may be more factors to consider based on the project and the product’s uniqueness. Always ask for recommendations from injection molding manufacturers when you visit a company

Furthermore, purchasing an industrial machine with only a little knowledge may turn your money into a negative investment.

Where to get plastic injection molding service

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Plastic injection molding is a cost-effective solution that can help companies improve their operations and optimize their existing components. However, before a lot of industries benefit from plastic molding, they must first identify a reputable provider that can match their requirements. There are a number of factors that should be considered when looking for a plastic injection molding service.

The injection molding materials used, understanding injection molding machine specifications, avoiding defects, considering the type of process suitable for a particular part, mold design and tooling, and plastic part decoration are some of those things to keep in mind when making your choice. When looking for a plastic injection molding factory, be sure to look at the following factors:

  • Reliability
  • Company dependability
  • The experience of the team of designers in the factory
  • Availability of Technology and machinery
  • The Volume and capacity of production
  • The Services offered
  • The Use of the product
  • The quality control processes

Researching plastic injection molding firms in your area is no longer sufficient. In order to avoid frequent difficulties such as late deliveries, poor quality, and capacity limits, you must know exactly what to look for in a provider. Immould injection molding company is the best China injection mold manufacturer. With 40 years plus experience in the field, we provide solutions for all plastic injection molding services globally. Our mold engineers and technicians are experts at creating unique components that meet exact client requirements.


Injection molding is an excellent method for large-scale completed production. It’s also handy for finished prototypes that are being tested by consumers or even mold suppliers. So understanding everything about it is very crucial for businesses that need to invest in high-quality products for their clients. For more information contact us.

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