Gas Assisted Injection Molding
Gas assisted injection molding is ideal for manufacturing thick-walled plastic parts. The plastic is melted and injected into the mold cavity through the traditional injection molding process. When 80-90% of the total molded volume is reached, nitrogen is injected into the mold to remove the uncured plastic parts. The plastic is pushed into the end of the mold to eliminate sink marks and surface imperfections.
  • Detailed DFM analysis
  • Mold making and prototyping
  • ISO 9001:2015, IATF 16949:2015 certificated
  • 24/7 engineering support
  • Tolerance within +/- 0.0004 in (0.01mm)
  • Material selection assistance
How does Gas Assisted Injection Molding Work?
1. Inject Filling
Molten plastic is injected into the mold and flows evenly within the cavity until the entire cavity is filled, but this only completes 80-90% of the filling.
2. Inject Nitrogen
Molten plastic is injected into the mold and flows evenly within the cavity until the entire cavity is filled, but this only completes 80-90% of the filling.
3. Holding, Cooling
The injected nitrogen exerts evenly distributed pressure on the mold wall from the inside to the outside of the previously filled plastic in the gas channel, reducing shrinkage and warpage. At the same time, fill a small amount of raw materials and wait for the parts to cool down.
4. Gas Releasing & Stripping
After the parts are cooled and solidified, the gas is released, then the mold is opened, and the injector system discharges the parts, completing the entire production cycle.
Benefits of Gas Assisted Injection Molding
Gas Assisted Injection Molding (GAIM) offers a viable option for thick-wall plasitc parts manufacturability and allows designers greater imagination when creating injection molded parts.
Increased Strength & Rigidity
The nitrogen pushes the uncooled portion of the plastic out of the mold, making the part hollow, which greatly increases its strength, toughness and durability.
Increased design flexibility
The ability to produce thicker plastic parts combined with good appearance using this process allows a variety of structures to be designed into your parts
Reduced Cost
Nitrogen pushes excess plastic out of the mold, saving material, reducing weight, Reducing molding cycle, increasing efficiency and saving costs.
Improved Appearance
Gas assist eliminates defects such as warping, flow marks and shrinkage caused by excessive wall thickness, improving the appearance of the part.
Gas Assisted Injection Molding Materials
At Attractive Plastics, in addition to providing a variety of conventional gas assisted injection molding materials, we also offer a variety of additive plastics to meet special requirements.
  • Regular Plastic Materials
  • Additives & Fibers Plastics
Gas Assisted Molding Plastics
Both amorphous and semi-crystalline plastics can be used in gas-assisted injection molding. Amorphous materials have low difficulty in injection molding but have average performance. Semi-crystalline materials have high difficulty in injection molding but have good product performance. The actual choice also needs to be weighed based on product requirements and process conditions.
Gas-assisted Molding Amorphous Plastics: ABS, PS, PP, PC
Gas-assisted Molding Semi-crystalline Plastics: PET, Nylon, Nylon+glass fiber, PBT, PE, PPO
More Details>>
Additives & Fibers Plastics
In the process of developing thick-walled plastic parts and components, in order to improve the performance of plastics, various additives are added to gas-assisted molded plastics to improve the overall performance of plastic parts and meet special requirements.
Examples of common additives include:
  • UV absorbers
  • Flame retardants
  • Plasticizers
  • Carbon fibers
  • Antistatic additives
  • Glass fibers
More Details>>
Gas Assisted Injection Molding Design Tips/Considerations
Design tips/considerations
Gas channel locations
Gas channel location, gas inlet, gas outlet layout, and material flow are critical to the success of the process
Simple gas channels
The gas channel should be as simple as possible, straight without turning, to avoid the problem of sharp corner stress.
Avoid sharp corners
When the airway passes through a sharp corner, it is prone to rupture when turning. Sharp corners should be avoided during design, and rounded corner transitions should be designed as much as possible.
Wall thickness
The size of the gas channel can be designed according to the thickness of the part. The product wall must be able to withstand the high pressure of gas without breaking. The recommended minimum thickness is 3 ~ 4mm.
Gas Venting and Recovery
Before opening the mold, the gas inside the part should be exhausted. Designing retractable mold pin vents is a better solution. If nitrogen is to be recovered, a filtration device should be used.
Define airflow paths. Avoid branching airflow channels
Branch gas channels are not conducive to the forward flow of gas, and small differences in conditions between the two branches will lead to differences in air flow resistance, resulting in different distributions of the same gas expected in the gas channels.
Avoid closed loop gas channels
In mold desgin stage, avoid designing closed-loop gas channels. Once the gases meet, part of the plastic in the channel cannot be pushed out of the mold, which increases the risk of shrinkage and increases the cooling time and cycle time.
The gas channel should extend to the area where the melt last filled.
Extending the gas channel to the thickest area can better discharge the plastic in the thick area, which is beneficial to molding products with better appearance.
Applications of Gas Assisted Molding
Gas assisted molding is a specialized injection molding process that injects an inert gas into the polymer melt to create hollow interior cavities in molded parts. This allows for weight reduction, cost savings, and the ability to create complex geometries not possible with standard injection molding. Common applications include automotive parts, consumer products, medical devices, and industrial components.
  • Automotive – Interior and exterior automotive handles, Steering wheels
  • Electrical – Appliance handles
  • Medical – Medical equipment housings
  • Consumer – Lawn mower handles, Children balance handlebars
  • Office – Covers and panels for office equipment
Gallery of Gas Assisted Injection Molding Parts
Dive into Attractive Plastics' extensive gallery that showcases some of our completed thick wall plasitc parts and take confidence that we can create your gas assisted molding plastic project according to your strict specifications.
Superior Custom Gas Assisted Molding Manufacturer
As a manufacturer specializing in gas-assisted molding. Our team leverages state-of-the-art equipment and technology to create complex thick plastic parts with exceptional surface finishes. We understand the intricacies of gas-assisted molding and how to optimize the process for maximum efficiency and quality.
Our proficiency in gas-assisted injection molding extends to a wide range of applications, including automotive components, consumer electronics, and medical devices. We pride ourselves on our ability to handle even the most challenging designs and materials, delivering innovative solutions that meet our customers' unique needs. By staying at the forefront of this specialized manufacturing process, we continue to set the standard for excellence in gas-assisted molding.
Reviews from Our Customers
A customer’s words have a more substantial persuasion than a company’s claims. We have served hundreds of satisfied customers and here are some reviews they give us.
Their gas assist modling expertise resolved our component's tricky warpage issue. Precise gas vent location and volume optimization resulted in remarkably flat parts passing all dimensional controls. It will be of great help to the overall advancement of the project, and there will be more cooperation in the future.
David Moon
Vice President
Our designers work closely with their engineers to develop gas injection molded components for a complex medical equipment. Although the development cycle is long, they are still very patient. These experiences have taught me that Attractive Plastics is very professional and trustworthy gas-assisted molding manufacturer.
Carl Harris
Pruchasing Manager
Success prototyping a complex gas-assisted overmold eliminated a multistep assembly. Their expertise streamlined manufacturing for significant cost savings. Currently in mass production, and all are qualified. Highly recommended. They are a professional and reliable injection molding service supplier.
Tony Jones
Consistent dimensional accuracy across millions of parts can be achieved through strict process control. Their extensive industry knowledge and experience ensure the long-term production of our injection molded plastic parts. Obviously, attractive plastics did it. We are satisfied and highly recommend them
Ben Holder
Their injection molding expertise resolved a short shot defect in an extremely narrow ribbed section of our equipment control panel. They control the process and adjust the mold to reduce defects to acceptable levels for us. They have very good control over the process and molds.
Anne Zaremba
Our Gas Assisted Molding Service for Various Industries
Our custom gas assisted injection molding process is suitable for solve the various demands of industries, including the automotive, medical, electronic & electrical and consumer goods fields etc.
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Gas Assisted Injection Molding FAQs

What is gas assisted molding?

Gas assisted molding is an injection molding process that utilizes the injection of pressurized gas into the mold cavity to create hollow interior cavities within plastic parts. This specialized process enables the production of lightweight, rigid, and dimensionally stable injection molded parts with thick walls and hollow sections. Gas assisted injection molding requires specialized equipment like gas injection needles and is commonly used to manufacture automotive, medical, and consumer product parts with weight reduction, sink elimination, and material savings benefits compared to solid plastic parts.

What are the advantages of gas-assisted molding?

The advantages of gas-assisted injection molding are as follows

  • Thinner, lighter parts with less material usage
  • Improved strength and structural integrity
  • Better surface finish quality
  • Reduced clamping force requirements
  • Shorter cycle times due to faster cooling
  • Lower molded-in stresses and less warpage
  • Allows greater design freedom
  • Reduce shrinkage

What is the process of gas-assisted injection molding?

Gas-assisted injection molding is a specialized injection molding process that involves injecting pressurized gas into the molten plastic in the mold cavity to create hollow interior channels or cavities within the part. The typical process consists of these key steps:

  1. Plastic resin is injected into the mold cavity under high pressure to partially fill the cavity (about filling 80%).
  2. Once the plastic has partially solidified, an inert gas like nitrogen is injected through the sprue or a dedicated gas injection channel.
  3. The gas follows the path of least resistance and creates hollow sections within the part, conforming to interior contours.
  4. The expanding gas packs the plastic against the interior mold surfaces, eliminating sink marks and controlling part dimensions.
  5. The part is allowed to completely cool and solidify before the mold opens and the part is ejected.
  6. The residual gas is vented out automatically or in a separate degassing process.

The hollow sections formed by the gas reduce the weight of the part and lower material costs. The gas pressure also minimizes part warpage and shrinkage. This allows the production of large,hollow plastic components with premium surface finish and dimensional accuracy.

What are the materials for gas-assisted injection molding?

The gas assisted injection molding material must allow proper gas penetration and distribution in the mold. The melt viscosity, gas solubility, and rate of crystallization are important factors. Amorphous thermoplastics have molecules that resist gas diffusion and are best suited for gas-assisted molding.

The most common materials used for gas-assisted injection molding are:

Polyethylene (PE) – Popular for large parts like automotive bumpers and industrial containers due to its low cost, chemical resistance, and ease of molding.

Polypropylene (PP) – Used for consumer products, appliances, medical devices. Offers high strength, stiffness, and heat resistance.

Acrylonitrile butadiene styrene (ABS) – Provides good stiffness, dimensional stability, and ability to be plated or painted. Used for automotive, electronics, and appliance housings.

Polycarbonate (PC) – Chosen when high strength and heat resistance are needed. Used for medical components, electronic enclosures.

Nylon – Offers a good balance of strength, durability, and chemical resistance. Used for automotive and industrial parts.

PPO – Polyphenylene Oxide: Amorphous plastic with excellent dimensional stability and heat resistance. Common in automotive, electronic housings.

PET – Polyethylene Terephthalate: Extensively used for packaging containers owing to its clarity, strength and barrier properties. Amorphous structure suits gas assist.

PMMA – Polymethyl Methacrylate (Acrylic): Amorphous plastic valued for optical clarity and weather resistance. Used for medical devices, LCD screens.

What is the lead time for gas assisted tooling?

Depending on the complexity and size of your gas-assisted plastic parts, we will make an overall assessment and respond to you with a reasonable production time, which usually takes 4 to 6 weeks to complete.

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