The most detailed injection mold adjustment process. 1of 2
Introduction technology of injection molding machine: injection molding is an engineering technology, which involves the transformation of plastics into useful products that can maintain the part with original performance. The important process conditions of injection molding are the influence of plasticizing flow and cooling temperature, pressure and corresponding various action time.
1.The control of temperature
1）Barrel temperature: The temperature to be controlled during the injection molding process is the barrel temperature, nozzle temperature and mold temperature. The first two temperatures primarily affect the plasticization and flow of the plastic, while the latter temperature primarily affects the flow and cooling of the plastic. Each plastic has a different flow temperature. The same plastic has different flow and decomposition temperatures due to different sources or grades. This is due to the difference in average molecular weight and molecular weight distribution. Plastics are injected in different types. The plasticizing process in the machine is also different, so the temperature of the selected cylinder is also different.
2）Nozzle temperature: The nozzle temperature is usually slightly lower than the maximum temperature of the barrel, as to prevent the "flowing phenomenon" of the melt in the straight-through nozzle. The nozzle temperature should not be too low, otherwise it will cause early condensation of the melt to block the nozzle, or affect the performance of the product due to the injection of the early aggregate into the cavity.
3）Mold temperature: Mold temperature has a great influence on the intrinsic properties and apparent quality of the product. The temperature of the mold depends on the presence or absence of crystallinity of the plastic, the size and structure of the product, performance requirements, and other process conditions (melt temperature, injection speed and injection pressure, molding cycle, etc.)
The pressure during the injection molding process includes plasticizing pressure and injection pressure, and affects the plasticization of plastics and the quality of products directly.
1）Plasticizing pressure: (back pressure) When using a screw type injection machine, the pressure that the top melt of the screw receives when the screw rotates backward is called plasticizing pressure, also known as back pressure. This pressure can be adjusted by a relief valve in the hydraulic system. In the injection, the plasticizing pressure is constant with the rotation speed of the screw. When the plasticizing pressure is increased, the temperature of the melt is increased, but the plasticizing speed is reduced. In addition, increasing the plasticizing pressure often makes the temperature of the melt uniform, the mixing of the colorant uniform, and the discharge of the gas in the melt. In general operation, the determination of plasticizing pressure should be as low as possible to ensure the quality of the product. The specific value varies with the type of plastic used, but usually rarely exceeds 20 kg/cm.
2）Injection pressure: In current production, the injection pressure of almost all injection machines is based on the pressure exerted by the plunger or the top of the screw on the plastic (converted from the oil pressure). The injection pressure plays a role in injection molding by overcoming the flow resistance of the plastic from the barrel to the cavity, giving the melt filling rate and compacting the melt.
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