GAS ASSIST PLASTIC
INJECTION MOLDING

Less Material. Less Weight. Less Cost. Improved Quality.

EVCO Plastics has employed gas assist molding technology for plastic injection molding in a wide range of applications for over 25 years, providing OEMs with numerous advantages for custom plastic injection molded plastic parts and products. Gas assist injection molded plastics are a great option for companies looking to reduce time and cost without sacrificing quality or design options.

Process

Gas assist molding is a low-pressure plastic injection molding process where pressurized nitrogen gas is injected into the mold, pushing the plastic into the mold extremities, while hollowing out thicker sections in the part.

In the gas assist molding process, the plastic material is melted and injected into the mold cavities via the conventional plastic injection molding process. Plastic material in contact with the mold walls begins to solidify first. As this happens, nitrogen gas is injected into the mold through strategically designed and placed gas channels, providing pressure that pushes the plastic material into the mold extremities. Once the plastic cures, the nitrogen is vented and the gas assist injection molded plastic parts are removed from the mold. Gas assist injection molding process animation.

GasAssistMolding-1

Section view of a part that was molded using gas assist

Advantages

  • Less plastic material needed (material savings)
  • Reduced part weight (in some cases up to 40%)
  • Decreased cycle time
  • Increased part strength and rigidity
  • Reduced warpage and distortion
  • Improved part appearance (eliminates sink marks and surface blemishes)
  • Reinforces ribbed parts
  • Increased design options for complex parts, reducing multiple part assemblies, and metal to plastic conversions
  • Enables use of smaller plastic injection molding presses

In gas assist plastic injection molding, the pressurized gas follows the path of least resistance and displaces the plastic material in the thicker areas of the part, leaving hollow sections for reduced material use and part weight, yet not compromising part appearance or functional performance.

With gas assist molding, localized gas pressure within the mold results in better packing of the plastic which reduces warpage, shrinking, surface blemishes, sink marks and internal stress. Gas assist injection molded plastics generally make for stronger and more aesthetically pleasing parts.

Gas assist molding is used to reinforce ribbed parts and provides more design freedom for complex parts, reducing multiple part assemblies and metal to plastic conversions.

The need for less plastic material and the consistent pressurization within the mold also enable gas assist injection molded plastics to cool faster, reducing cycle times and increasing plastic injection molding machine output – saving time and cost!

In gas assist plastic injection molding, the internal pressure provided by the nitrogen gas enables lowering the outer force needed to hold part shape, so large plastic parts can be produced with less tonnage on smaller plastic injection molding machines.

Applications

Some applications benefiting from gas assist plastic injection molding include:

  • Appliance handles
  • Medical equipment housings
  • Interior and exterior automotive handles
  • Large covers and panels for office equipment
  • Lawn mower handles
  • Steering wheels
  • Basketball backboard frames
  • Long tubular shapes, such as shovel handles
  • Large parts with ribs and bosses

Mold Design

Proper mold design and construction and mold flow analysis are important for successful gas assist injection molding. EVCO Plastics in-house engineering and mold design and building teams are highly experienced. Robotic automation is often employed for increased speed and accuracy.

Plastic Materials

Most thermoplastics materials can be employed in gas assist injection molding, such as ABS (acrylonitrile butadiene styrene), PC (polycarbonate), HIPS (high impact polystyrene), PA (nylon), PBT (polybutylene terephthalate), PET (polyethylene terephthalate), PPE (polyphenylene ether) and PP (polypropylene).

Learn more about how EVCO Plastics provides a competitive advantage with custom plastic injection molding and gas assist plastic injection molding, through early supplier involvement in the engineering and design process, design for manufacturability, project management, material selection support, and via global systems and global locations in the United States, Mexico and China.

When plastics matter to your business, partner with EVCO.
Where innovation takes form.

TECHNOLOGY