The cold runner system is used for molding LSR. The advantages of this compound can be maximized, and the production efficiency can be raised to the maximum. To process products in such a way, it is not necessary to remove the glue injection path, so as to avoid increasing the labor intensity of the operation, and sometimes avoid a large waste of materials. In many cases, the structure without glue injection can also shorten the operation time.
The rubber injection nozzle is controlled by a needle valve for positive flow. At present, many manufacturers can provide the injection nozzle with a pneumatic switch as a standard equipment and can set it in various parts of the mold.

Some mold manufacturers have specially developed an open cold runner system, which is so small that it is necessary to set multiple injection points in an extremely limited mold space (thus filling the entire mold cavity). This technology makes it possible to mass produce high-quality silicone rubber products without separating the rubber injection port.

If a cold runner system is used, it is important to form an effective temperature gap between the hot mold cavity and the cold runner. If the runner is too hot, the rubber may be vulcanized before injection. However, if the cooling is too fast, it will absorb too much heat from the gate area of the mold, resulting in incomplete vulcanization.

For products injected with conventional sprues (such as submerged sprues and tapered sprues), it is appropriate to use small diameter glue injection port for feeding (the diameter of the feeding port is usually 0.2mm-0.5mm). LSR compound with low viscosity is like thermoplastic compound, and the balanced runner system is very important. Only in this way, all mold cavities will be filled with compound evenly. By using the simulation software of the design runner system, the development process of the die can be greatly simplified, and its effectiveness is proved by the filling test.

For details of liquid silicone rubber, see:https://www.rtvsilicone.net/product-two-component-addition-silicone-rubber-iota-g30-305-.html