injection point
A cold runner system is used when molding LSR. The advantages of this compound can be maximized and production efficiency can be maximized. By processing products in this way, there is no need to remove the glue injection channel, thereby avoiding increasing the labor intensity of the operation and sometimes avoiding a large amount of waste of materials. In many cases, the no-jet construction also reduces operating time.
The rubber injection nozzle is controlled by a needle valve for forward flow. Currently, many manufacturers can provide injection nozzles with air-controlled switches as standard equipment, and can be installed in various parts of the mold. Some moldmakers have specially developed an open cold runner system that is so small that multiple injection points must be set up 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 having to separate the glue injection port.
If a cold runner system is used, it is important to create an effective temperature separation between the hot mold cavity and the cold runner. If the runner is too hot, the compound may begin to vulcanize before injection. But if it is cooled too quickly, it will absorb too much heat from the gate area of the mold and will not fully vulcanize.
For products injected with conventional pouring channels (such as submersible runner and tapered runner), it is suitable to use a small diameter injection port for feeding (the diameter of the feeding port is usually 0.2mm-0.5mm) for pouring. Low-viscosity LSR rubber is just like thermoplastic rubber. It is very important to balance the runner system. Only in this way can all mold cavities be evenly filled with rubber. The use of simulation software for designing runner systems can greatly simplify the mold development process and prove its effectiveness through mold filling tests.