What the gas assisted injection molding process actually does
Gas assisted injection molding starts with a short shot: the mould is filled with 60 to 90 percent of its cavity volume, then high-pressure nitrogen is injected through a gas pin into the thickest section of the melt. The gas pushes the remaining resin to the far corners of the cavity and holds pressure from the inside while the part cools. The finished hollow channel part has a solid outer skin and a hollow internal channel, so it keeps structural stiffness while shedding 15 to 40 percent of its weight.
Conventional thick-wall molding would need heavy pack-and-hold to avoid the same sink marks. Nitrogen injection molding applies that pressure from the inside with far less resin and roughly one third of the clamping force, which is why the gas assist process has become the standard route for large, thick-section parts that still need a cosmetic surface.
Why buyers specify gas assist
- Sink mark elimination. Internal gas pressure compensates for volumetric shrinkage, so thick sections stay flat without long pack cycles.
- Material savings. Hollow channels reduce resin consumption on handles, frames and structural housings.
- Lower clamp tonnage. Smaller presses run large parts, cutting energy use and tool wear.
- Shorter cycles. Thin solid skins cool faster, cutting cycle time by 20 to 40 percent on thick-wall parts.
- Better dimensional stability. Lower residual stress means less warpage after ejection.
Where gas assisted injection molding fits
The process suits automotive door handles, instrument panel structures, seat frames, appliance panels and bezels, furniture and chair arms, and medical equipment housings: parts with a structural rib network or thick boss that must stay light and flat. It is not the right choice for fully solid sections, walls under about 3 mm, or heavily glass-filled compounds above roughly 20 percent loading, where gas penetration becomes unpredictable.
What a gas assisted injection molding quotation should include
- Mold flow simulation covering gas channel layout and penetration depth.
- Short shot percentage, gas pressure profile and hold time for your geometry.
- Gas channel cross-section, typically 6 to 12 mm, with smooth transition gradients.
- First-article dimensional report on critical wall thickness.
Compare suppliers on process control, not just unit price. Our custom molding services cover the full sequence from simulation to first article, and the mould and tooling catalogue shows related capability. For parameter background, read injection molding process parameters before your RFQ. Browse the supplier pool in the company directory.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
