Injection point
Cold runner system is used when molding LSR. It can maximize the advantages of this compound and can maximize production efficiency. By processing products in such a way, it is not necessary to remove the injection channel, thereby avoiding increasing labor intensity of the operation, and sometimes avoiding a large amount of waste of materials. In many cases, the glueless structure also reduces operating time.
The rubber injection nozzle is controlled by a needle valve for forward flow control. At present, many manufacturers can provide injection nozzles with gas control switches as standard equipment and can be set in various parts in the mold. Some mold makers have developed an open cold runner system, which is so small in volume that it is necessary to set multiple injection points in the extremely limited mold space (thus filling the entire cavity). This technology makes it possible to produce high-quality silicone rubber products in large quantities without the need to separate the injection nozzle.
If a cold runner system is used, it is important to create an effective temperature gap between the hot mold cavity and the cold runner. If the runner is too hot, the compound may begin to vulcanize before injection. However, if it is cooled too quickly, it will absorb too much heat from the gate area of the mold, resulting in incomplete vulcanization.
For products injected with conventional injection runners (such as submerged runners and conical runners), it is suitable to use a small-diameter injection port feeding (the feeding port diameter is usually 0.2mm-0.5mm) for pouring. Low-viscosity LSR compounds are just like thermoplastic compounds. Balanced runner system is very important. Only in this way, all mold cavities will be filled evenly with the compound. The simulation software for designing the runner system can greatly simplify the development process of the mold and prove its effectiveness through the filling test.