VESTIGE NOZZLE ASSEMBLY FOR INJECTION MOLDING

摘要

A hot tip nozzle assembly (50) for injection molding plastic components comprises a nozzle housing (58) defining a hot runner passage (84) and a nozzle tip section (60) which is received in the hot runner passage. The nozzle tip section (60) defines a hot runner tip passage (94) in flow communication with the hot runner passage (84). The nozzle tip section slides (60) freely within the hot runner passage (84) during injection molding. A stop is provided on the nozzle tip section (92) to limit downward movement relative to the cavity gate and automatically position the nozzle tip (90) relative to the injection gate (128) of the mold. In addition, axial thermal expansion of the nozzle housing (58) is not imparted to the nozzle tip section (60). The nozzle tip section (60) also has a restricted length that can axially thermally expand. Accordingly, the position of the nozzle tip (90) is only minutely affected by even larger temperature changes in the nozzle assembly. This controlled thermal expansion together with the sliding movement of the nozzle tip section (92) relative to the nozzle housing (58) maintains the nozzle tip (90) at a substantially constant position during the injection molding operation and minimizes vestige formation in the molded components.