Mold gate valve

A resin injection gun was developed to interface with the injection gate valves, with an anti-dripping system. Molds are opened automatically when the sensors measure a preset degree of polymerization, reducing cycle times. Five hydraulic hoists on the five parallel molding fines... 

Another gate valve is the spear system in which the probe, using electronic controls, alternately melts and freezes the gate as required by the cycle. Both techniques, and other similar ones, are particularly suitable for use in runnerless molding. 

The mold is designed for optimum material flow and gating. It is also designed for gas (or water, if used) injection and venting. The mold must also have shut-offs for the gas (and water), and another shut-off valve for the overflow. 

To mold micron-scale precision parts with shot weights of only 0.0022 g, electrical operating IMMs are being used. Those who desire precise shot size (dosing) can buy electric injection machines with servomotors capable of very accurate screw positioning. With hydraulic IMMs, molders can install a valve gate that shuts when the correct amount of plastic has been injected into the mold. 

Cascade injection molding can be used for parts with long flow paths, if the mold is equipped with more than one gate. As shown in Figure 2, the melt is injected over the first valve and the second valve is opened when... 

No back flow should be allowed. That means the resin should flow from the injector s outlet to the mold inlets (gates), but not in the opposite direction. This is especially important when multiple injection gates are used with constant flow rate injection boundary conditions. If the resin pressure inside the mold exceeds the instantaneous injection pressure at any of the gates, an injector with a one-way flow feature does not allow the resin to flow backward by closing the valve at the exit of the injector. 

Valve gating nozzles used in sprueless molding also belong in the general category of shutoff nozzles, as do the nozzles which are used for impact molding. 

Gating nozzles, hot-runners and insulated runner molds, nozzle manifolds, and valve gating nozzles are used for obtaining sprueless moldings. Elimination of the sprue and runner system reduces costs through scrap and labor savings. 

The most sophisticated type of gate is valvegating. It is used in both hot and cold runner molding. The principle of valve-gating is that the opening and closing of the gate is controlled by mechanical means such as hydraulic or pneumatic... 

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