In the injection molding of liquid silicone rubber, a method called edge free and runner free molding has become popular. This is a molding method that does not produce useless solidified materials and does not require secondary processing. It is a molding method that does not have injection ports, flow channels (even if there are, solidification does not occur), and does not produce waste adhesive edges. In order to implement this molding method, the construction of the model and the smoothness of the parting surface, as well as the measurement and discharge accuracy of the injection machine, must meet the requirements. Even in terms of materials, they must be materials that are difficult to generate waste rubber edges. After the rubber material enters the mold cavity and fills the mold cavity, due to excessive rubber material or thermal expansion of silicone rubber, the rubber material flows into the parting surface and becomes waste rubber edges after solidification. If the parting surface is designed to be narrower, it will be difficult to generate waste adhesive edges. However, at the same time, it is also difficult to remove air, which becomes the reason for the presence of bubbles in the finished product.

The curing characteristics of waste free adhesive edge forming materials. Compared with the materials used before, the curing curve of this material shows a rapid turning point (with a short time from the beginning to the end of curing). By selecting the appropriate injection conditions for this type of material, before the material fills the mold cavity, curing has not yet begun and the material has good fluidity. However, when the material fills the mold cavity, curing immediately ends, and even if there is residual pressure, the material will not flow onto the parting surface, preventing waste adhesive from forming edges

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