What is Gas Assist Injection Molding

Gas-assisted injection moulding is a moulding process where an inert gas is introduced at pressure, pushing the plastic melts into the mould extremities at the end of the polymer injection phase. The process is especially ideal for large handles, equipment covers, doors, bezels, cabinets and skins.

Basic Process

The basic process of Gas Assisted Injection Moulding is unsurprisingly very similar to regular injection moulding. The extruder barrel of an Injection moulding machine melts down raw pelletised plastic material, and then injects this into an injection mould but only up until the mould is about 70% full. Then from a separate entry point, pressurised gas is injected into the mould as the part is cooling. This forces the still molten plastic up against mould walls, where it cools and hardens into your plastic product. The pressure is released from the gas, and then the mould is ejected like a regular injection moulded part.

Advantages

This process forms a hollow, plastic injection moulded part and parts are lighter, greener and cheaper than traditionally injection moulded equivalents. Moulded parts also cool faster in this process because of constant pressurization by the gas. There is also usually less shrinkage as the thicker wall sections are hollowed out by the pressurised gas resulting in no sink mark problems.

Some of the benefits of this process are:

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 the use of smaller plastic injection molding presses

Common Pitfalls

There are many common pitfalls when it comes to Gas Assisted Injection Moulding. Firstly, it is more complex and more expensive to set up than ordinary injection molding. if the tooling price of injection mold shocks you, gas-assisted injection molds will blow you away. Also, by introducing gas into the molding mix, this variable must be precisely tracked, managed and controlled. Without experienced machine operators and technicians, the molding process could go disastrously wrong. The control of the gas also contributes to variable wall thicknesses, especially in tight corners and this is something you generally want to avoid.

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

Molding Materials

As ith structural foam, almost any thermoplastic material can be used in gas assist application including:

Polycarbonate
Polyphenylene Oxide - PPO (Noryl)
Polybutylene terephthalate - PBT (Valox)
Acrylonitrile Butadiene Styrene – ABS
High Impact Polystyrene - HIPS
Polypropylene
High Density Polyethylene - HDPE

Cost Considerations

Along with the potential reduction of part count, additional savings are achieved through the use of the gas assist processes. Since they typically require one-third of the clamping force of conventional injection molding the same part size may be run with a lower tonnage press, not only keeping part costs under control but also introducing less residual stress into the part to further aid dimensional stability. Reduced in-mold pressure subjects the mold to less wear and tear, allowing the use of less expensive aluminum tooling. Parts also weigh considerably less, which results in reduced freight expense and improved material handling efficiencies.

Why Choose Us

As the industry leader in gas assist injection molding, Amazing plastics has extensive molding capabilities to meet the diverse needs of our customers. Please contact us.

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