Views: 3 Author: Site Editor Publish Time: 2022-04-19 Origin: Site
The plastic injection molding machine adopts the thermocouple of the plastic injection molding machine for accurate temperature measurement as the temperature measuring element. It adds a millivolt meter for accurate temperature measurement to become the temperature control mechanism of the plastic injection molding machine, operating between the barrel and the mold: Conductivity of the turn flow and the ability to selectively adjust the temperature of each section of the barrel and mold.
The temperature that the plastic injection molding machine must control during the injection molding process includes the barrel temperature, the nozzle temperature, and the mold temperature. The first two temperatures have an important influence on the plasticization and fluidity of plastics. In contrast, the latter temperature has a more critical influence on the fluidity and coldness of plastics.
The choice of barrel temperature of the plastic injection molding machine is related to the characteristics of plastic, especially the fluidity temperature TF or melting point temperature of the plastic. For amorphous plastics, the high temperature at the end of the barrel should be higher than Tf, while for crystalline plastics, it should be higher than Tm. Still, the temperature decay of the plastic should be lower than the polymer's dissolution temperature (Td).
Therefore, a suitable temperature range for the barrel should be between Tf or Tm - Td. For plastics with a narrow Tf or Tm-Td interval, such as PVC and POM, the barrel temperature should be controlled slightly. While for plastics with wider Tf or Tm-Td intervals, such as polyethylene and polypropylene, the barrel temperature can be slightly higher.
In addition, heat resistance, content, and distribution of plastics, fillers, reinforcements, handicrafts, injection molds, and injection equipment should also be considered. The distribution of the barrel is stable, and the barrel gradually rises from the beginning to the end of the nozzle so that the temperature of the raw material rises evenly and achieves the purpose of plasticizing symmetry.
Because when the solution is based on the nozzle, the temperature of the material will increase with the increase of the cutting speed (about 103-102), the nozzle temperature will be slightly lower than the high temperature of the barrel if the temperature is too low, the working pressure of injection will increase. Large or the raw materials will be thickened in advance, which will easily affect the quality of handicrafts. Many factors affect the fluidity of the polymer. Generally, it will be adjusted according to the "air injection" or "art visual analysis method" before molding to determine the plastic injection molding machine's barrel temperature and nozzle temperature.
The mold temperature has a considerable impact on the quality of the handicraft. The choice generally depends on whether the polymer is crystallized, the specification and structure of the handicraft, the specification of the characteristics, and other injection criteria (solution temperature, injection rate, working pressure, molding cycle time) )Wait.
For amorphous polymers, mold temperature significantly affects the viscosity (flowability) of the solution. If the solution viscosity of the raw material is low, such as Ps, the mold temperature can be slightly lower to improve the output. If the viscosity of the solution is high (e.g., PPE, PSF), the higher mold temperature is 120°C~140°C for PPE and 140°C~130°C for PSF. The crystals are non-isothermal in a plastic injection molding machine for crystalline polymers. The mode temperature of the plastic injection molding machine should be set at the periphery of the temperature (TCM) between Tg and Tm or slightly lower.