Advantages of the GAIM Process
Gas injection provides a solution to a number of problems that occur in conventional injection molding.
1. Reducing stress and warpage
With gas, the pressure is equal everywhere throughout the continuous network of hollow channels. When designed properly, these provide an internal runner system within the part, enabling the applied pressure, and therefore the internal stress gradients, to be reduced markedly. This reduces a part’s tendency to warp.
2. Elimination of sink marks
Sink marks resulting from ribs ot bosses on the back side of a part have long been a problem. These surface marks result from the volume contraction of the melt during cooling. Sink mark can be minimized or eliminated if a hollow gas channel can be directed between the front surface of the part and the back side detail. With a channel as the base of a rib, material shrinka are away from the inside surface of the channel as the molded part cools because the material is the hottest at the center. Therefore, no sink mark occours on the outside surface as the part shrinks during cooling.
3. Smooth surface
Unlike structural foam, gas injection permits lighter weight and saves material in a structurally rigid part. With gas holding, a good surface quality can be achieved.
4. Reduced clamp tonnage
In conventional injection, the highest pressure occurs during the packing phase. The maximum injection pressure is significantly lower in GAIM and a controlled gas pressure through a network hollow channels is used to fill out the mold. This means that clamp tonnage requirements can be reduced by as much as 90%.
5. Elimination of external runners
One of the best features of gas injection is that flow runners can be bulit right into the part. Frequently, all external runners can be eliminated, even on a larger and complex part. These benefits include the reduced tooling costs, the lower quantities of regrind from runners, and the improvement of temperature control over the plastic melt. Ofter the internal runners can be improve the flow pattern in the mold and eliminate or control knit-line locations resulting from multiple injection gates. In addition to serving as flow channels, the ribs and thick sections can provide structural rigidity when required.
6. Permitting different wall thickness
A constant wall thickness is maintained in the plastic parts, With gas injection, this design rule is flexible. Different wall thickness are possible if has channels are designed into the part at the transition point. This permits uniform material flow in the mold and avoids the high stress and warpage that normally results from this sort of geometry.
7. Cycle time Reduction
Compared with structural foam, gas-injection parts do not have the same inherent insulating characteristics, so that cycle time are faster-reportedly even faster than would be conventional injection of the same part with no hollow sections.
8. Resin saving
Gas asssit plays a direct role in part-weight saving in the conventional of current tools. The main factor is reducing weight is that the part cavity is never completely filled. Another major contributor to resin saving is scrap reduction. With proper tool design, gas assisted allows scrap-free startups amd production runs.
Write by David at 2nd, Oct. More details about plastic injection molding please visit our site: http://www.plastics-china.com
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