Gas Injection Moulding Process: A Guide for Plastic Manufacturers

Gas Injection Moulding Process: A Guide for Plastic Manufacturers

Gas Injection Molding (GIM) is an advanced plastic processing technology. Gas Injection Molding (GIM) is an advanced plastic processing technology that injects gas into molten plastic. to form parts with complex shapes and excellent properties. This technology has widespread applications in many industries, including automotive, medical, electronics, and consumer products.

The working principle of GIM is quite simple. First, plastic pellets are heated to their melting point and then injected into a closed mold. During this process, one or more gases, such as nitrogen or carbon dioxide, are injected. These gases become trapped inside the plastic as it cools and solidifies, creating a part with a microporous structure. This microporous structure improves the strength, wear and impact resistance of the part while also reducing its weight.

GIM has many advantages. First, it can produce parts with complex shapes and internal structures that traditional injection molding technology cannot achieve. Second, because the gas is locked inside the part, the dimensional stability and repeatability of GIM parts are very good. Additionally, GIM can reduce the weight of a part, thereby improving its fuel efficiency and durability.

However, GIM also has some disadvantages. First of all, its equipment cost is high and it requires specialized gas injection machines and molds. Secondly, the production cycle of GIM is longer because the plastic pellets need to be heated first and then injected into the mold. In addition, GIM also requires high operator skills, requiring precise control of gas pressure and injection time.

GIM has a wide range of applications. For example, automakers can use GIM to produce lightweight yet strong parts such as body panels and seat supports. Medical device manufacturers can use GIM to produce parts with complex shapes and internal structures, such as artificial joints and dental equipment. Electronic product manufacturers can use GIM to produce parts with good insulation properties and wear resistance, such as mobile phone cases and computer keyboards.

What is Gas Injection Moulding?

Gas injection moulding (GIM) is a low pressure process that requires the injection of pressurized nitrogen gas into the interior of a mold. The gas flows through strategically placed gas channels to displace the material in the thick areas of the part by forming hollow sections. GIM is typically used to manufacture handles for cars and white goods, automotive panels and similar parts with thicker cross-sections.

How Does Gas Injection Moulding Work?

The basic concept of the GIM process is quite similar to the regular injection moulding process. In GIM, the plastic material is injected into the mold cavities like the regular injection moulding process but only up to 70%~80% of the mold volume. The melted plastic in contact with the mold walls begins to solidify, then nitrogen gas is injected into the mold through strategically designed and placed gas inlets, providing pressure that pushes the plastic into the mold extremities. The path of the bubble is controlled by taking the path of least resistance through the hottest, least viscous plastic, which keeps it centered from the colder walls of the mold. Finally, the molded part is ejected like the regular injection moulding process.

Advantages of Gas Injection Moulding

This process forms hollow parts that are cheaper than traditionally injection molded equivalents. Molded parts also cool faster in this process. There is also usually less shrinkage as the thicker wall sections are hollow. Some of the benefits of this process are:

  • Thicker parts
  • Low clamp force
  • Lightweight products
  • Reduced part deformation (warpage)
  • Minimal residual stresses
  • No sink marks
  • Greener

Disadvantages of Gas Injection Moulding

This molding technique is very difficult to apply to multi-cavity molds, especially if the cavity sizes are dissimilar. Clear or transparent plastic materials are an inappropriate option for this technique as the cosmetic-appearance can deteriorate. Some of the drawbacks of this process are:

  • Higher initial investment for gas equipment
  • Higher maintenance costs for gas equipment
  • Higher complexity of mold design and gas channel placement
  • Higher risk of gas leakage and contamination

Applications and Examples of Gas Injection Moulding

Gas injection molding, also known as gas-assisted injection molding, is a specialized injection molding technique that offers numerous advantages and finds diverse applications across various industries. The process involves injecting a controlled volume of nitrogen or other inert gas into the mold cavity after the initial injection of plastic material. This gas forms a hollow channel or pocket within the part, creating unique design features and improving part quality.

One of the primary applications of gas injection molding is in the automotive industry. Gas-assisted injection molding is used to manufacture automotive components such as instrument panels, door panels, and interior trims. By incorporating gas channels into these parts, manufacturers can reduce material usage, achieve consistent wall thickness, and produce lightweight yet structurally rigid components. Gas-assisted injection molding also helps in eliminating sink marks and reducing warpage, resulting in high-quality and aesthetically pleasing automotive parts.

In the consumer goods industry, gas injection molding is widely used to produce furniture components, electronic housings, and appliance parts. For instance, gas channels can be strategically placed in furniture legs and supports to increase strength while reducing material consumption. In electronic housings, gas-assisted injection molding helps prevent cosmetic defects such as warpage and surface sink marks, ensuring precision fit and finish. Additionally, the technique allows for the creation of hollow spaces in appliance parts, making them lightweight and cost-efficient.

Another significant application of gas-assisted injection molding is in the production of industrial and agricultural equipment. Components such as tool handles, machine housings, and agricultural equipment parts benefit from the improved structural integrity and weight reduction achieved through gas channels. The technique enables manufacturers to create sturdy yet lightweight parts that can withstand heavy-duty usage and demanding environments.

Gas injection molding also plays a vital role in the manufacturing of medical devices and equipment. For instance, gas channels are used in the production of medical instrument handles to improve grip and ergonomic design. Additionally, gas-assisted injection molding ensures uniform wall thickness in medical equipment housings, minimizing the risk of defects and improving the overall performance and reliability of these critical devices.

Overall, gas injection molding finds applications in a wide range of industries, including automotive, consumer goods, industrial equipment, and medical devices. The technique enables manufacturers to create complex and innovative designs, reduce material usage, improve part quality, and achieve cost-effective production. Whether it’s enhancing automotive interiors, optimizing consumer products, improving industrial equipment, or manufacturing reliable medical devices, gas-assisted injection molding continues to be a versatile and valuable process in modern manufacturing.


Gas injection moulding (GIM) is a low pressure process that uses pressurized nitrogen gas to create hollow sections in thick plastic parts. GIM offers many advantages such as lower cost, faster cooling, less shrinkage, less warpage, less stress, and no sink marks. However, GIM also has some disadvantages such as higher initial investment, higher maintenance costs, higher complexity of mold design and gas channel placement, and higher risk of gas leakage and contamination. GIM is suitable for producing thick parts with complex shapes and high surface quality in various industries.