Liquid silicone molding characteristics

RELEASE TIME:2018-05-11 14:38:22AUTHOR:Zhongshan Jvtech Technology Co., Ltd.

With the liquid silicone in the medical products, baby products, automobile manufacturing, food industry, electronic products, diving supplies, kitchen utensils and seals, etc. have been widely used and become irreplaceable materials. Traditional hot-pressing and molding processes (plastic products and solid-state silicones) can no longer meet the needs of the market. The liquid silicone injection process has developed rapidly in recent years, but information or experience sharing on the liquid silicone mold process or injection molding on the Internet has been analyzed. Less and less, most of the content comes from books or related materials. The lack of details, experience, and depth will bring you a series of technical questions about this industry.

Molding characteristics

Liquid silicone is usually composed of A/B glue, hardness is usually divided into 3,5,10,20-80 degrees (the lower the hardness is, the better the fluidity is, the material is basically the same as rice soup). The work of the mixer will be A component and The B component is thoroughly mixed in a precise 1:1 ratio. (It can be cured only after A glue and B glue are mixed), and then it is fully mixed through the Static Mixer and injected into the injection tube before injection molding. The liquid silicone is injected into the hot runner mold to produce silicone products, which can achieve a molding, no waste, and can be automated.

Because some products are colored designs, they are equipped with color pump sets and color measurement parts. A+B components, additives, colors, etc., are mixed well into the plasticizing system. The plasticizing screw has the function of homogenization and mixing at the same time. The mixture is injected into the hot mold through the screw, and the curing reaction occurs at the mold temperature of 170-200°C. When using a cold runner system, it is worth noting that the runner is cold enough. In order to avoid leakage, the needle valve is installed on the surface of the mold part. When the injection is completed, the needle valve immediately closes the nozzle.

Injection molding machine gun barrel has circulating cooling water (about 25 degrees Celsius), mold temperature is usually set at 120-180 degrees (depending on the thickness of the product glue position), when the material injected into the mold cavity after curing through the mold temperature (mold and injection molding There must be a heat shield between the machines.) Problems in product injection in silicone injection are mainly caused by trapped air and batch fronts. These two problems are mainly solved by vacuuming the molds. Therefore, the design and manufacture of silicone injection molds are particularly important. . Of course, injection molding machines also need peripheral equipment such as vacuum pumps and barometers.

Through the above information, we can see that the main problem solved by silicone injection molding is its mixing and metering part, as well as the screw seal and mold design.