Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
Gas-assisted molding (GAM or GAIM) is an injection molding technology that injects inert high-pressure nitrogen when the plastic is filled into the cavity appropriately (75%~99.9%), and uses the gas to push the molten plastic to continue to fill the cavity, and uses gas pressure maintenance instead of traditional plastic pressure maintenance.
The key to gas-assisted molding lies in metering management and gas injection. First, high-pressure nitrogen is directly pressed into the molten plastic in the mold cavity through the gas-assisted controller, and then the gas is used to expand the inside of the plastic part to form a hollow structure.
At this stage, a certain amount of plasticized plastic is filled into the mold cavity to ensure that the gas will not damage the surface of the product during inflation and produce the desired effect.
At different time points during or after the injection period, gas is injected into the mold cavity, and its pressure must be higher than the injection pressure in order to make the product hollow.
When the interior of the product is filled with gas, the pressure exerted by the gas on the hollow part is the holding pressure, which helps to significantly reduce the shrinkage and deformation rate of the product.
As the cooling cycle ends, the gas pressure in the mold drops to atmospheric pressure, and then the product is pushed out of the mold cavity.
Gas-assisted molding has many advantages, including but not limited to:
1. Reduce the residual stress of the product and prevent the product from deforming.
2. Solve the problem of shrinkage marks on the surface of the product, which is suitable for products with large thickness changes.
3. Shorten the product production molding cycle and improve production efficiency.
4. Save plastic raw materials to the greatest extent, with a maximum saving rate of 30%.
5. Reduce the clamping force of the injection molding machine, reduce machine wear and extend the life of the machine.
6. Reduce the pressure in the mold cavity, thereby reducing mold loss and extending the life of the mold.
7. For certain types of plastic products, it is allowed to use lightweight materials such as aluminum alloy to make molds.
8. Simplify complex product designs.
The process of gas-assisted molding can be divided into two modes:
1. Nozzle air intake mode
- Mold closing
- Shooting seat moving forward
- Molten plastic filling
- Gas injection
- Pre-plastic metering (gas pressure holding)
- Shooting seat moving backward (exhaust pressure relief)
- Cooling and shaping
- Mold opening
- Ejection of parts
2. Air needle air intake mode
- Mold closing
- Molten plastic filling
- Gas injection
- Pre-plastic metering (gas pressure holding)
- Cooling and shaping (exhaust pressure relief)
- Mold opening
- Ejection of parts
The following conditions are required to realize gas-assisted molding:
1. Injection molding machine
2. High-pressure nitrogen source (such as high-pressure nitrogen generator)
3. Pipeline system for conveying gas
4. Effective flow device for controlling nitrogen pressure (such as nitrogen pressure controller)
5. Molding mold used for gas-assisted process (gas-assisted mold)
- The drying temperature of the raw materials should be consistent with traditional molding
- The plasticizing temperature of the barrel should be slightly higher than that of traditional injection molding
- The mold temperature is strictly controlled and the cooling water path layout should be uniform
- The injection pressure is equivalent to that of traditional injection molding
- The injection speed usually adopts high-speed filling
- The injection pressure holding function of the injection machine can be turned off
- The maximum pressure of the high-pressure nitrogen generator should not exceed 35MPa
- The parameter settings of the nitrogen pressure controller should include gas pressure, gas pressure holding time, pressure increase and decrease rate, and start delay
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