Liquid silicone rubber injection point
When molding LSR, a cold runner system is used. It can maximize the advantages of this adhesive material and improve production efficiency to the maximum extent. By processing products in this way, there is no need to remove the injection channel, thus avoiding increased labor intensity and sometimes avoiding significant material waste. In many cases, the non injection channel structure can also shorten the operation time.
The injection nozzle of the rubber material is controlled by a needle valve for forward flow. Currently, many manufacturers can provide injection nozzles with pneumatic switches as standard equipment and set them in various parts of the mold. Some mold manufacturers have specifically developed an open cold runner system, which is so small that multiple injection points need to be set up in the extremely limited mold space (thus filling the entire mold cavity). This technology enables the mass production of high-quality silicone rubber products without the need to separate the injection ports. If a cold runner system is used, it is important to establish an effective temperature gap between the hot mold cavity and the cold runner. If the flow channel is too hot, the rubber material may start vulcanization before injection. But if cooled too quickly, it will absorb too much heat from the sprue area of the mold, resulting in incomplete vulcanization.
For products injected with conventional sprues (such as submerged sprues and conical sprues), it is suitable to use small-diameter injection ports for feeding (usually with a diameter of 0.2mm-0.5mm) for pouring. Low viscosity LSR adhesive, like thermoplastic adhesive, requires a balanced flow channel system to ensure that all mold cavities are uniformly filled with the adhesive. By using simulation software for designing flow channel systems, the development process of molds can be greatly simplified, and its effectiveness can be demonstrated through filling tests.