| 摘要 |
An apparatus and method for injection molding includes a first melt passage for the flow of a first material, and a second melt passage in communication with the first melt passage for the flow of a second material. The apparatus and method for injection molding also includes a valve pin that passes through the second melt passage. The valve pin has a first portion allowing the flow of the second material, but not the first material, through the second melt passage, and a second portion restricting the flow of the first material and the second material through the second melt passage. The valve pin may also be used to restrict material flow from a melt channel into a cavity. In addition, a back-flow control valve may be combined with a melt passage of the apparatus and method for injection molding. The back-flow control valve has a first portion for permitting flow of material through the melt passage, and a second portion for restricting flow of material through the melt passage.
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