Gas-Assisted Injection Molding
Injection molding is a very popular operation for production of commercial plastic parts with it’s sophisticated control and superior surface details. However, it has limitations, such as long cycle time for parts parts with thick section due to slow cooling. Also packing of thick section can produce sink makrs on the part surface. Large thin parts can have warpage because the residual stress and strain induced during filling and packing. Thus traditional injection molding can ne modified to solve these kinds of problems, also to improve the quality of the part and lower the cost of the production.
Currently, gas-assisted injection molding is in use and being developed worldwide. In the US, the process is knowns as Gas- Assisted Injection Molding (GAIM); it is also called Gas Injection Technique (GIT) in Europe. This process is developed for the hollow plastic parts with separate internal channels. It is unique because it combines the advantage of conventional injection molding and blow molding while differing from both. GAIM offers a cost effective means of producing large, smooth surfaced and regid parts using lower clamping pressure with little or no finishing. By introducing the gas before complete filling, numerous problems such as warpage, sink marks, and high filling pressure are mostly overcome. Moreover, the process gives great benefits in terms of higher stiffness-to-weight ratio tha the solid parts whith the same overall dimensions due to the elimination of material placed inefficiently near the neutral axis of the corss section, thus increasing the freedom of part design.
In comparsion with coventional injection molding, the gas-assisted process is more critical in terms of process control, especially for multi-cavity applications. The quality of the part is determined by both tool and process variable such as degree of under-fill, gas injection condictions, and mold temperature, thus indicating the importance of process control. The process is attracting many molders due to the demand for high auotomated production of gas-assisted injection molded parts. For more details please visit: http://www.plastics-china.com thanks!