Multi-gating nozzle

Number of injection points. Besides single nozzles, there are also multi-point nozzles, with two to six or more injection points. These are mainly tip nozzles and side gating nozzles, but there are also open and shut-off nozzles. The use of multi-point nozzles enables the cost of a HR system to be reduced by bringing down the number of nozzles and possibly doing away with the manifold. 

Figure 1 Basic variants of injection molds (a) two-plate mold (one cavity) (b) three-plate mold (multi-cavity). Designations a, coupling link b, ejector nxi cl + 2, center rings dl -f- 2, clamping plates e, ejector plate t, ejector pins g, distance plate h, cavity plate i, cavity j, transition plate k, sprue with cone gate 1, runner with 4 sprues m, center bolt n, runner plate o, nozzle rl + 2, insulation plates s, high performance nozzle.

Direct gating to a cold runner in a multi-cavity mould. In this design, the CR is only partially replaced by an HR system. A simple open HR nozzle eliminates the sprue (Figure 1.3e), thus shortening the reqnired mould opening path and making it easier to separate the sprue protrusion from the moulding on the transporter belt. This method is used when the production volume or product shape does not jnstify the use of HR nozzles for each cavity. 

The drawback to a spring-powered drive is indirect control. The gate is opened under pressnre from the melt, which causes an explosive mould filling, and is then closed as a result of a fall in the melt pressure in the channel. If the fall in pressure in the manifold charmels in a multi-cavity mould is not uniform, there may not be simultaneous gate closure. Spring-driven nozzles are rarely used, but their low price makes them an interesting alternative for simpler technical applications. 

The gate channel in the injection mold serves to convey the melt coming from the nozzle of the injection molding machine to the cavity with the lowest possible pressure and heat loss, in shortest possible time and without thermal degradation. In multi-cavity molds, the melt must be supplied to all gates uniformly [1, 2, 7, 12, 19, and 20]. 

S.4 Hot Runner Solutions for Multi-Point Gating through Nozzles and Multi-Nozzles... 

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