3 Material for automatic molding without glue edge/runner
In the injection molding of liquid silicone rubber, a method called edgeless, runnerless molding has become popular. This is a molding method that does not produce useless cured products and does not require secondary processing, that is, a molding method that does not have a sprue or runner (even if there is no curing), and does not generate waste rubber edges. In order to implement this molding method, the structure of the model and the smoothness of the parting surface, the metering and discharge accuracy of the injection machine must meet the requirements, and even in terms of materials, it must be a material that is difficult to generate waste rubber edges, and the glue entering the mold cavity must meet the requirements. After filling the mold cavity, due to the excessive amount of rubber or the thermal expansion of silicone rubber, the rubber flows into the parting surface and becomes a waste rubber edge after curing. If the parting surface is designed to be narrower, it will be difficult to generate the waste rubber edge, but at the same time, the air will not be easily discharged, so it becomes the reason for the air bubbles in the finished product.

Cure characteristics of molding materials for the waste-free edge. Compared with the previously used materials, the curing curve of this material is in a state of sharp inflection (very short time from the beginning of curing to the end of curing). By selecting the proper injection conditions for this type of material, curing has not yet started before the material fills the cavity, and the material has good fluidity, and when the material fills the cavity, curing ends immediately, even if there is residual pressure, the material will not Flow onto the parting surface to prevent the formation of scrap edges.

The above has introduced the latest developments of liquid silicone rubber and the new materials suitable for it. In order to make these automatic molding and composite molding with plastic in a short time, high efficiency and precision can be improved. When choosing the right material, there is no doubt that the injection molding machine and the model are the key.