Mold sprue bushing

The molding compound flowing from the nozzle enters the mold and is distributed into the cavities. This is the task of the sprue- and numer system (see Figure 4-1). It consists of several sections, that may differ in design, subject to requirement. As the melt leaves the nozzle, it passes through the sprue bush and into the runner, which connects to the gates of the cavities. 

Moving the injection unit up against the mold s sprue-bush, as well as moving it away again (sprue-break or complete retraction)... 

The plasticating unit moves up to the mold s sprue bush. The nozzle is opened, and the material located in the screw s ante-chamber is injected into the mold by the forward movement of the screw. 

At the start of the injection process, the molten, homogenized material is poised in the injection chamber. The nozzle is closed, so that no material can escape. As soon as the plasticating unit has been moved against the mold s sprue bush, the nozzle can be opened to allow the melt free passage into the mold. 

That part of the injection molding tool, against which the nozzle pushes during the injection process to inject the melt. The bore of the sprue bush is cone-shaped and with many single impression molds connects directly into the cavity... 

Injection nozzle n. A short, thick-walled, hardened-steel tube that conducts the molten plastic emerging from an injection cylinder into the mold. It usually terminates in a hemispherical tip that closely mates a recess in the mold called a sprue bushing and is enclosed by band heaters that are controlled by a temperature sensor. 

Nozzle na-z9l [dimin. of nose] (1683) n. In injection or transfer molding, the orifice-containing fitment at the delivery end of the injection cylinder or transfer chamber that contacts the mold s sprue bushing and conducts the softened resin into the mold. The nozzle is shaped to form a seal... 

Sprue bushing (British sprue bush) n. A hardened steel insert in an injection mold that contains the tapered sprue passage and has a suitable seat, usually hemispherical, making a seal with the nozzle of the injection cylinder. 

Once the interlocks are satisfied, the mold closes. Then the injection unit occasionally moves slightly forward to coimter a motion called sprue breakaway. With cold runner systems, the injection rmit is moved slightly away from the sprue bushing to facilitate sprue removal and/or prevent nozzle freeze-off. Thus, injection unit must be moved forward to provide intimate contact between the nozzle and sprue bushing during injection. Sprue breakaway is not used with hot runner systems. 

As an alternative, the screw and barrel (plunger, barrel, and stuffing mechanism) are horizontal, feeding into the horizontally positioned closed mold through a sprue bushing at the parting line of the closed mold (Fig. 6.21). 

Mineral-insulated cable heaters are often coiled and used on hot sprue bush-ing/runnerless molding nozzles. The coil heaters are capable of high operating temperatures, up to 815°C. 

The support plate backs up the B plate in the mold, and melt is delivered from the nozzle to the sprue bushing. The locating ring aligns the mold with the nozzle, whereas the leader pins and bushing align the two sides of the mold. In the ejection system, the sprue puller and ejector pins, are attached to the ejector plate, which is, in turn, connected to the machine s ejection plates by the ejector rod. When the mold is opened, the sprue puller draws the part to the B side of the mold, whereas the... 

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