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What is vertical injection molding of liquid silicone?

by:FUHONG     2021-07-02
Vertical injection molding machine liquid silicone injection molding, its important content includes the characteristics of the material, the introduction of the molding process, etc. 1. About liquid silica gel Liquid silica gel is a non-toxic, heat-resistant, and highly resilient, flexible thermosetting material. Its rheological behavior is mainly manifested by low viscosity, fast curing, shear thinning, and high thermal expansion coefficient. LSR is a two-liquid rapid vulcanization material with platinum as a catalyst. The injection molding method can be produced in large quantities, rapid vulcanization, and repetitive mechanical production. The product is characterized by good thermal stability, cold resistance, excellent electrical insulation performance, and no toxic substances will be produced during combustion. LSR liquid silicone vertical injection molding machine is widely used in products such as health products, automobiles, baby products, medical products, diving products, kitchen utensils and seals. 2. Liquid silicone rubber (LSR) vertical injection molding machine molding process LSR is a two-component liquid material, divided into A component and B component, the work of the mixer will A component and B component in a precise ratio of 1:1 mixing. And because some products are of colored design, it is equipped with a color pump set and a color metering part. A+B components, additives, colors, etc. enter the plasticizing system after being fully mixed. The plasticizing screw has the functions of homogenization and mixing at the same time. The mixture is injected into the hot mold through the screw, and the silica gel undergoes a curing reaction at a mold temperature of 170-200°C. When using a cold runner system, it is worth noting that the runner should be cold enough. In order to avoid glue leakage, the needle valve is installed on the surface of the mold part. When the glue injection is completed, the needle valve immediately closes the injection nozzle. 3. The feeding system of the liquid silicone (LSR) vertical injection molding machine can choose the following forms: ①Bi-directional pump: can move up and down to feed, can maintain the pressure well, because the A and B pumps are connected and synchronized by hydraulic Pneumatic control, so this type of feeding system is more reliable and accurate. ②One-way pump is a universal type, which can only feed single item. ③Synchronous single-phase pump with check valve. ④The metering cylinder system is mainly used in conjunction with the single-phase pump. 4. Vertical injection molding machine is a key component of liquid silicone rubber injection molding machine. ① The low viscosity of LSR requires consideration of material reflow and glue leakage during processing, so the screw seal is necessary. ②In order to prevent LSR from solidifying, a needle valve nozzle should be used. ③Mixed and metering parts of A and B components 5. Mold design In the mold design, generally there are the following forms: ① Hot runner: waste materials, simple design, low cost, mostly used for large products. ②The cold runner with needle valve can be automated, and the cycle is short. ③ Cold runner without needle valve. Due to the high expansion coefficient of LSR, it will expand when heated, but shrink slightly when cooled, so the parts cannot maintain accurate side margins in the mold, so cold runner processing can be used, and LSR should maintain a low temperature and flow The cold runner adopts a closed system. In the injection cycle, the closed system uses a sealing needle or needle valve in each runner to control the accurate measurement of LSR material. Since silicone rubber has significant thermal expansion characteristics, the shrinkage rate is 2 to 4% (vulcanization temperature is 150 ℃), and silicone rubber has the characteristics of deformation under pressure, so the mold design should pay attention to the following aspects. 5. The design of the liquid silicone vertical injection molding machine mold should pay attention to the following aspects: ①In order to avoid turbulence and jetting, use small injection ports; ②Use needle-shaped or wing-shaped injection ports; ③Use T-shaped guide bolts instead of cylindrical Guide bolt, use injection air gun when demolding, add heat insulation layer/board; ④Do not use anti-rust agent/oil containing polymerization inhibitor, generally toluene, xylene, etc. can be used. In addition, the cured LSR is easy to stick to the metal surface, and the popular demoulding techniques include ejector pin ejection and air ejection. From the above information, it can be seen that the main problems solved by silicone injection molding are its mixing and metering parts, as well as screw sealing and mold design. Mechanical liquid silicone vertical injection molding machine, independent research and development for more than ten years, all-round one-stop liquid silicone injection molding process solution provider. Development of liquid silicone injection mold, imported LSR, made of Korean and Japanese materials, with good quality. Provider of injection molding equipment and insert injection molding technology. Recommended reading: What does PP/PE/PC used in vertical injection molding machine stand for?
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