Gas assist injection molding

Gas Assist Injection Molding

What is Gas Assist Injection Molding

Gas assist injection molding is a process that utilizes an inert gas (normally nitrogen) to create one or more hollow channels within an injection molded plastic part. At the end of the filling stage, the gas (N2) is injected into the still liquid core of the molding. From there, the gas follows the path of the least resistance and replaces the thick molten sections with gas-filled channels. Next, gas pressure packs the plastic against the mold cavity surface, compensating for volumetric shrinkage until the part solidifies. Finally, the gas is vented to the atmosphere or recycled.

Gas assisted injection molding has been around for well over two decades and many people have had concerns over patent, rights and royalty fees. Within the past few years, some of the original patents have expired. And now, gas assisted injection molding is widely practised. Design engineers and processors alike are discovering that this technology is an attractive option for certain applications and offers many benefits. It is the responsibility of the manufacturer to ascertain that their practice or technology is not covered by current patents.

Gas Assist Injection Molding Process

The main two applications of Gas Assisted injection Molding are to either inject the gas into the component cavity (internal gas injection), or to use the gas on the outside surface, but still within the mould cavity, to consolidate the component (external gas injection).

Gas-assisted injection molding is a specialized injection molding process that allows for the creation of hollow or partially hollow plastic parts with a gas-filled core. This technique is used to improve the structural integrity of parts, reduce material usage, and create complex geometries. The process involves several key steps:

  1. Mold Setup: The first step in gas-assisted injection molding is preparing the mold. Like traditional injection molding, this process involves a two-part mold with a cavity that matches the desired part’s shape. However, gas channels and injection points for the gas must also be integrated into the mold.
  2. Plastic Injection: The process starts with the injection of molten plastic into the mold cavity. The plastic material used in gas-assisted injection molding is typically a thermoplastic, such as polypropylene (PP), polycarbonate (PC), or nylon (PA). The plastic flows into the mold and begins to fill the cavity.
  3. Gas Injection: After the initial injection of plastic, a gas, usually nitrogen, is injected into the center of the plastic material through specially designed gas channels. The gas displaces the molten plastic, creating a hollow or partially hollow core within the part. The gas pressure forces the molten plastic to the mold’s walls, ensuring even distribution.
  4. Packing and Cooling: Following the gas injection, the plastic continues to fill the mold cavity, packing around the gas-filled core. The mold is then allowed to cool. As the plastic cools, it solidifies, encapsulating the gas core and forming a lightweight but structurally sound part.
  5. Gas Decompression: Once the part has fully cooled and solidified, the gas pressure is released, allowing the gas to escape. The gas decompression phase can be gradual to avoid any abrupt changes in pressure that could affect the part’s integrity.
  6. Ejection: Finally, the mold opens, and the gas-assisted injection-molded part is ejected from the mold.

Gas-assisted injection molding is particularly well-suited for applications where the combination of lightweight parts, structural integrity, and complex designs is crucial. It is commonly used in industries such as automotive, consumer products, medical devices, and industrial components. Proper design, material selection, and process optimization are essential for successful gas-assisted injection molding.

Benefits of Internal Gas assisted Injection Moulding

  • Substantial cost reductions resulting from:
    • Reduction in molded plastic weights, and therefore the cost of the material.
    • Reduction in molding time cycles, and therefore the cost of production.
    • Reduced in-mold pressures, and therefore less wear on molds.
  • The use of the gas as a means of transmitting pressure uniformly throughout the molding.
  • Elimination of sink marks.
  • Avoidance of plastic packing from the molding machine.
  • Reduced in-mold pressures by up to 70%, and therefore reduced press lock forces enabling larger moldings on smaller machines.
  • Reduced power consumption.
  • Reduced molded-in stress, and therefore improved dimensional stability with no distortion.

External Gas Injection

used for the enhanced surface definitionGas assist molding

Benefits of External Gas Assisted Injection Molding

  • Can eliminate sink marks.
  • Virtually eliminates moulded-in stress and therefore distortion.
  • Improves dimensional stability.
  • Applies pressure more efficiently, and therefore less pressure is required:
    • reducing lock forces or machine size.
    • reducing wear on moulds.
    • reducing power consumption.
  • More design freedom:
    • thicker ribs with reduced wall thicknesses.
    • multi-rib components.
    • flat PP and PE products.

A number of variants of gas use are incorporated into the Internal gas injection process:

  • Full Shot Internal Gas Assisted Moulding
  • Short Shot Internal Gas Assisted Moulding
  • Plastic Expulsion Process PEP
  • Moving Core Gas Assisted Moulding
  • Gas Cool for Internal and External Gas Moulding

Each variant has its uses and benefits.

Gas Assisted Injection Molding Cost?

The cost of gas-assisted injection molding (GAIM) can vary depending on several factors, including the complexity of the part, the choice of materials, tooling requirements, production volumes, and the region in which the manufacturing takes place. Here are the key cost components to consider when evaluating the cost of gas-assisted injection molding:

  1. Tooling Costs: The cost of creating the molds for gas-assisted injection molding can be a significant portion of the overall expenses. This includes the cost of designing and fabricating the molds, which may be more complex and costly than molds for traditional injection molding due to the need for gas channels and injection points. The complexity of the part’s design also impacts tooling costs.
  2. Material Costs: The choice of plastic material can significantly affect the cost. Different thermoplastic materials have varying prices, and the material’s characteristics must match the requirements of the application. Some high-performance materials may be more expensive but necessary for specific applications.
  3. Labor Costs: Labor costs include the expenses associated with skilled operators, quality control, and maintenance of equipment. The labor required for gas-assisted injection molding may be similar to traditional injection molding but could be slightly higher due to the complexity of the process.
  4. Cycle Times: The cycle time for producing parts in gas-assisted injection molding may be longer or shorter than traditional injection molding, depending on factors like part size and design. Longer cycle times can increase labor and energy costs, but shorter cycle times can reduce overall production costs.
  5. Energy Costs: Energy costs are associated with the operation of the injection molding machines and other equipment. Gas-assisted injection molding may consume more energy due to the need for gas injection and potentially extended cooling times. This can impact operational costs.
  6. Maintenance and Repairs: Regular maintenance and potential repairs to the gas-assisted injection molding equipment and molds are ongoing expenses that should be considered.
  7. Gas Costs: The cost of the gas used in the process (typically nitrogen) must be factored in, including the expense of gas storage and supply systems.
  8. Waste Handling: Managing the waste gas created during the process requires specific systems. Proper venting and gas handling must be in place to ensure worker safety and environmental compliance.
  9. Post-Processing Costs: While gas-assisted injection molding can reduce the need for post-processing and finishing work due to improved aesthetics, some parts may still require additional treatments, such as painting, plating, or assembly, which can add to the overall cost.
  10. Production Volume: The economies of scale come into play with production volume. Larger production runs can help spread out fixed costs, making gas-assisted injection molding more cost-effective per part. Smaller runs may have a higher per-part cost.
  11. Geographical Location: The cost of production can vary based on the location of the manufacturing facility, labor costs, and regional material availability.
  12. Quality Control and Testing: Ensuring the quality of gas-assisted injection-molded parts may involve quality control and testing procedures, which have associated costs.

It’s essential to work closely with experienced professionals and manufacturers to get accurate cost estimates for your specific gas-assisted injection molding project. They can help you assess the design, material selection, tooling, and other factors to determine the overall cost and make informed decisions regarding the process’s economic feasibility for your specific application.

Advantages of gas assisted injection molding

Gas-assisted injection molding (GAIM) offers several advantages that make it a preferred choice for specific manufacturing applications. Here are the key reasons why gas-assisted injection molding is used:

  1. Weight Reduction: One of the primary reasons to use gas-assisted injection molding is to reduce the weight of the final plastic part. By introducing a gas core, the part becomes inherently lighter while maintaining its structural integrity. This is particularly valuable in industries where weight reduction is critical, such as automotive and aerospace. Lighter components can contribute to improved fuel efficiency, reduced emissions, and better performance.
  2. Enhanced Structural Integrity: Gas-assisted injection molding provides internal support to the part through the gas core. This internal structure improves the part’s strength and rigidity, reducing the risk of deformation, warping, and other structural issues. Parts created with this method can better withstand load-bearing and stress requirements.
  3. Improved Aesthetics: Gas-assisted injection molding results in smoother and blemish-free surfaces on the finished parts. The reduced need for post-processing or finishing work makes it an excellent choice for applications where aesthetics are crucial. Parts can often be used as-is without additional treatments.
  4. Cost Savings: While the initial tooling and setup costs for gas-assisted injection molding can be higher, the long-term cost savings are significant. The process reduces material usage, decreases cycle times, and minimizes the need for secondary operations, resulting in cost-efficiency over the product’s lifecycle.
  5. Complex Geometries: Gas-assisted injection molding allows for the creation of intricate and complex part geometries. The gas core displaces the molten plastic, enabling the creation of thin walls, hollow sections, and intricate shapes that would be challenging or impossible to achieve with traditional injection molding.
  6. Material Savings: The reduced material requirements in gas-assisted injection molding not only lower production costs but also contribute to sustainability efforts by minimizing material waste. This aligns with environmental goals and reduces the environmental footprint.
  7. Versatility: Gas-assisted injection molding can be used with a wide range of thermoplastic materials. This flexibility allows manufacturers to select materials that meet specific requirements for each application, from impact resistance to flame retardancy.
  8. Improved Process Control: The gas-assisted injection molding process offers better control over the distribution of the plastic material within the part, resulting in uniform wall thickness and reduced likelihood of defects.
  9. Fast Cycle Times: In some cases, gas-assisted injection molding can lead to faster cycle times compared to traditional injection molding. The reduced cooling requirements and the ability to create thinner walls contribute to quicker production.
  10. Reduced Tooling Costs: The lightweight nature of gas-assisted parts often allows for the use of smaller, less expensive molds, reducing tooling costs, especially for large and complex parts.

While gas-assisted injection molding offers numerous benefits, it’s essential to carefully consider the specific requirements of a project to determine whether this process is the right choice. It excels in applications where a combination of weight reduction, structural integrity, complex designs, and cost-efficiency is essential.

Disadvantages of gas assisted injection molding

Gas Assist Injection Molding is a versatile and innovative manufacturing process that offers numerous advantages, as discussed in the previous article. However, like any manufacturing technique, it has its disadvantages and limitations. Here are some of the key disadvantages of Gas Assist Injection Molding:

  1. Higher Initial Costs: Setting up Gas Assist Injection Molding requires specialized equipment, molds, and gas injection systems. The initial investment can be higher compared to traditional injection molding, making it less accessible for some businesses.
  2. Complex Design Requirements: Designing for Gas Assist Injection Molding can be more challenging compared to conventional injection molding. It requires expertise in creating molds with gas channels and determining the proper locations for gas injection. Designing complex geometries and hollow parts can also be intricate.
  3. Tooling Complexity: The molds used in Gas Assist Injection Molding are more complex than those used in traditional injection molding. The need for gas injection ports, venting, and other features can increase tooling costs and complexity.
  4. Material Selection: Not all plastic materials are suitable for Gas Assist Injection Molding. The choice of material is critical to the success of the process. Some materials may not respond well to the gas-assisted technique or may have limited options in terms of color or finish.
  5. Limited Applications: Gas Assist Injection Molding is not suitable for all types of parts. It is most effective when used for components with complex geometries, thick sections, and the need for weight reduction. Simple, small, or flat parts may not benefit from the process.
  6. Longer Cycle Times: While Gas Assist Injection Molding can result in faster cycle times compared to conventional injection molding, it is generally slower than other rapid manufacturing techniques like compression molding. Longer cycle times can impact production efficiency.
  7. Waste Gas Handling: Managing the waste gas created during the process requires specific systems. Proper venting and gas handling must be in place to ensure worker safety and environmental compliance.
  8. Energy Consumption: Gas Assist Injection Molding may consume more energy due to the need for gas injection and the extended cooling times required for some parts. This can affect both operational costs and environmental considerations.
  9. Maintenance and Repairs: Gas Assist Injection Molding equipment and molds require regular maintenance. Any issues with the gas injection system, molds, or other components can lead to production interruptions and additional costs.
  10. Limited Supplier Base: Finding suppliers and manufacturers experienced in Gas Assist Injection Molding can be challenging in some regions. This limitation can affect the availability of the process for certain projects.

While Gas Assist Injection Molding has its disadvantages, it remains a valuable manufacturing method for specific applications where its advantages outweigh the drawbacks. Businesses should carefully evaluate their needs, budget, and design requirements to determine if Gas Assist Injection Molding is the right choice for their projects.

Applications of gas assisted injection moulding parts

Most injection molded parts can benefit from the use of gas-assisted moulding. Applications from consumer goods to automotive parts benefit from the process. The typical are: Toys, auto parts & anything with thick areas.

External Gas Assisted Moulding Applications:

  • Flat panels for office equipment.
  • Computer enclosures.
  • Furniture, i.e. tabletops.
  • Automotive panels.
  • Domestic appliances – e.g. fridges.

At Sincere Tech, we are dedicated to maintaining our position as a leading gas-assisted injection moulding company by embracing industry advancements and anticipating future trends. We actively explore innovative materials and composites that offer improved performance and sustainability. Through ongoing investments in research and development, we deliver cutting-edge solutions that address the evolving needs of our customers. As one of the best injection mold suppliers in China, we pride ourselves on our commitment to excellence.

In line with our commitment to sustainability, we prioritize environmentally friendly practices. We proactively seek sustainable alternatives, such as biodegradable polymers, and implement recycling initiatives to minimize the environmental impact of our manufacturing processes. By choosing our custom injection molding services, you can align your brand with sustainable manufacturing practices and contribute to a greener future.

Quality is of the utmost importance to us, and we maintain stringent quality control measures throughout the entire manufacturing process. Our state-of-the-art facilities and skilled technicians ensure that each product undergoes rigorous inspection and testing, guaranteeing exceptional performance, reliability, and customer satisfaction.

When you partner with Sincere Tech as your preferred China mold maker, you can expect the highest level of professionalism, expertise, and innovation. We are dedicated to helping you bring your ideas to life, delivering superior products that excel in performance, durability, and cost-effectiveness.

Our expanded capabilities include:

  1. Rapid Prototyping: We offer rapid prototyping services to quickly transform your concepts into tangible prototypes, allowing for iterative design improvements and accelerated product development.
  2. Gas assisted injection molding: Our advanced tooling capabilities and rich experience enable us to create high-quality gas assist molds with high quality gas assisted injection molding parts, ensuring consistency and precision in your gas injection-molded products.
  3. Overmolding: We specialize in overmolding, which allows for the combination of multiple materials or components, resulting in enhanced functionality, aesthetics, and durability.
  4. Insert Molding: Our expertise in insert molding enables us to securely encapsulate inserts within the molded parts, facilitating efficient assembly and enhancing product performance.
  5. Two-Shot Molding: With two-shot molding, we can produce complex, multi-material components in a single operation, reducing assembly requirements and enhancing design possibilities.
  6. Value-Added Services: In addition to injection molding, we offer a range of value-added services, including product assembly, packaging, and logistics support, streamlining your supply chain and reducing costs.

Partner with Sincere Tech Mould suppliers for your custom injection molding needs, and benefit from our comprehensive capabilities, unwavering commitment to quality and sustainability, and our drive to exceed your expectations at every step of the process. Together, let’s bring your innovative ideas to life.

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