Rubber injection molding commissioning method?

Apr 28, 2022

1、 Liquid injection molding of silicone rubber
The liquid silicone rubber injection molding method, which started in the 1970s, is becoming more and more popular. Nowadays, as a molding method of silicone rubber, it has been recognized. Firstly, the commonly used LIMS method is explained. If LIMS (liquid silicone rubber injection molding) is explained in one sentence, it is a method to pump the addition cured liquid silicone rubber into the injection molding machine and cure it in the model. From the difference between the process flow and curing reaction of the two methods, LIMS has several advantages:
① It can improve product quality: no reaction by-products are generated and no impurities are mixed.
② Can improve production efficiency: through rapid curing to seek to shorten the molding cycle.
③ Labor saving: the processes of material conveying, metering, mixing and injection can be realized continuously and automatically to reduce power consumption.
④ Suitable for composite molding: due to the good fluidity of the material, low molding pressure and wide curing temperature range, composite molding can be carried out in addition to the molding of embedded parts.
2、 Materials for automatic forming without glue edge / Runner
In recent years, in the injection molding of liquid silicone rubber, a method called no glue edge and no runner molding has become popular. This is a molding method that does not produce useless solidified products and does not need secondary processing, that is, it is a molding method without injection port, flow channel (even if there is no solidification), and no waste rubber edge. In order to implement this molding method, the structure of the model and the smoothness of the parting surface, the measurement and discharge accuracy of the injection machine must meet the requirements, and even in terms of materials, it must be difficult to generate waste rubber edges. After the rubber entering the mold cavity fills the mold cavity, due to excessive 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 narrow, it is difficult to generate the waste rubber edge, but at the same time, the air is not easy to be discharged, so it becomes the reason why the finished product contains bubbles.
Compared with the previously used materials, the curing curve of the material turns rapidly (the time from the beginning of curing to the end of curing is very short). By selecting the appropriate injection conditions of this kind of material, that is, before the material fills the mold cavity, the curing has not started, and the material fluidity is very good. When the material fills the mold cavity, the curing ends immediately. Even if there is residual pressure, the material will not flow to the parting surface to prevent the formation of waste glue edge.
As for the fully automatic molding process, people have studied it from the aspects of injection machine, mold, material and so on. It can not only save manpower in process operation, but also reduce the material cost because it will not produce useless solidified products. From the perspective of taking into account environmental protection, this method has also attracted much attention. For the injection molding of the micro oil seal, it is required to be used within 10s.

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