| 摘要 |
A gas control unit (12) for a gas-assisted injection molding system (10), wherein a quantity of gas is introduced into a mold cavity (22) in combination with a quantity of plastic material during the molding process. The gas control unit (12) operates on the basis of regulating the mass of gas within the system, as opposed to the final hold pressure. Because the mass of the gas is constant within the gas control unit (12) throughout an injection cycle, a preferred initial-to-final (hold) pressure ratio can be determined through mathematical computations for a particular modling system. As a result, once the required mass of gas has been isolated from a suitable source, releasing the gas to the mold cavity (22) results in a predictable pressure. This capability permits the gas control unit (12) to determine whether the gas has fully expanded and, therefore, whether the gas has properly filled the mold cavity (22) so as to produce a properly molded article (21). |
