Gas Assisted Injection Molding – Nitrogen Booster Pressure & Process Guide

Published 2026-10-20 · Jinan Shangling Technology Co., Ltd.

Gas assisted injection molding (GAIM) injects high-pressure nitrogen into the mold cavity during injection molding. The gas holds and packs the melt, creating hollow sections or eliminating sink marks. GAIM reduces part weight and molded-in stress and shortens cycle time, and is widely used for automotive interiors, appliance housings, handles and large flat parts.

1. Selecting the Nitrogen Injection Pressure

Injection pressure is the key GAIM parameter and is set by part geometry and flow length:

1. Thin-wall parts: 5-15 MPa, mainly to eliminate sink marks;
2. Thick-wall / hollow parts: 15-35 MPa, to drive a stable gas channel;
3. Long-flow parts: 60%-80% of the melt injection pressure, matched to the melt flow front.

The gas delay time and holding time must also be tuned: a too-short delay lets gas break through the melt front; a too-long delay means the melt has solidified and no gas channel can form. Trial molding is usually required.

2. Nitrogen Purity

GAIM requires high-purity nitrogen, typically 99.5% or better. Low purity means active components such as oxygen react with the hot melt and cause yellowing or brittleness on the inner wall of the part. Online purity monitoring or an on-site nitrogen generator is recommended.

3. GAIM Nitrogen Supply System & Boosting

A typical GAIM nitrogen supply system: low-pressure nitrogen source (cylinders or generator) → gas booster pump → high-pressure receiver → injection unit (high-pressure gas pin / valve) → mold cavity.

A gas booster pump raises a 0.5-3 MPa low-pressure nitrogen source to the required 5-35 MPa injection pressure with continuous adjustment and high pressure stability. One boosting system can feed several molding machines, which is cheaper and more stable than direct high-pressure cylinder supply.

4. Shangling Solution

Jinan Shangling Technology supplies nitrogen booster pumps and complete GAIM nitrogen supply systems up to 100 MPa, with closed-loop pressure control, auto stop at set point and multi-station timed gas distribution, custom-designed for your machine count and process. For more details, please call 18668913679 or email ljys@163.com.