Gas Assisted Injection Molding

1. Applications of Gas Injection Molding (GIM) Technology

Gas assisted injection molding, often simply referred to as gas assist molding, is a highly mature technology that has been applied in the plastic processing industry for many years. This advanced manufacturing process, much like injection blow molding, has transformed how complex plastic components are produced. One of the most important application areas of this technology is in the production of thick-walled plastic parts, such as automotive handles and similar products. Plate-type parts or other plastic components with locally thickened sections are also significant application areas for gas assisted injection molding.

Gas assisted injection molding involves introducing high-pressure inert gas into the thick-walled sections of the molded part, creating hollow sections within the injection molded component, and pushing the melt to complete the filling process. This achieves uniform gas pressure holding or uses gas to directly achieve local high-pressure holding of the part, eliminating sink marks in the product. Unlike some traditional methods, including certain injection blow molding techniques, this process offers unique advantages in handling complex geometries.

Traditional injection molding processes cannot combine thick and thin walls in a single molding operation. Furthermore, conventional methods often result in products with high residual stress, which can lead to warping and deformation, as well as surface sink marks. Similar to how injection blow molding revolutionized certain manufacturing sectors, gas assist technology has overcome these limitations by hollowing out the interior of thick-walled sections, successfully producing products that combine thick and thin walls. Additionally, the products exhibit excellent surface quality, superior overall quality, and low internal stress.

The versatility of gas assisted injection molding has made it a preferred choice in various industries, complementing processes like injection blow molding where different manufacturing requirements exist. From automotive components to consumer electronics, medical devices to household appliances, GIM technology continues to expand its applications due to its ability to produce high-quality parts with complex geometries.

1. Composition of Gas Assisted Injection Molds

Gas assisted injection molds are not significantly different from traditional injection molds, with the primary additions being gas inlet components (known as gas pins) and the inclusion of gas channel designs. These specialized features distinguish them from both standard injection molds and those used in injection blow molding processes.

The term "gas channel" can be simply understood as the passage for gas, i.e., the path that gas follows after entering the mold. Some channels are part of the product itself, while others are specially designed material positions to guide gas flow. This strategic design element is crucial to the gas assist process and differs from the air channels found in injection blow molding tools, which serve different functional purposes.

If the gas channels are completely aligned with the material flow direction, this is most conducive to gas penetration, resulting in the highest hollowing rate. Therefore, during mold design, every effort is made to align the gas channels with the material flow direction. This design consideration is similar to how material flow is optimized in injection blow molding molds, though the specific implementation differs significantly.

The gas pins used in these molds are precision components that control the introduction of gas into the molten plastic. These pins must withstand high pressures and temperatures, much like critical components in injection blow molding machinery that handle similar operational stresses. The placement and design of these pins are critical factors in determining the quality of the final product.

Unlike some injection blow molding molds that focus on creating uniform hollow shapes, gas assisted molds must balance the needs of both material flow and gas distribution. This dual requirement makes mold design for gas assist processes particularly challenging, requiring expertise in both traditional injection molding and gas dynamics within molten polymers.