The vertical injection molding machine thermocouple for accurate temperature measurement is used as the temperature measuring element, and a millivoltmeter for accurate temperature measurement is added to become a vertical injection molding machine temperature controller, which operates the conduction of the flow between the barrel and the mold, and has the ability to selectively adjust the temperature of each section of the barrel and the mold. The temperatures that must be controlled during the injection molding process of the vertical injection molding machine include the barrel temperature, nozzle temperature and mold temperature. The first two temperatures have an important influence on the plasticization and fluidity of the plastic, while the latter temperature has an important influence on the fluidity and cooling of the plastic.
1. Vertical injection molding machine barrel temperature
The selection of the barrel temperature of the vertical injection molding machine is related to the characteristics of the plastic, especially the fluidity temperature (Tf) or melting point temperature (TM) of the plastic. For amorphous plastics, the high temperature at the end of the barrel should be higher than Tf, while crystalline plastics should be higher than Tm, but the temperature decay of the plastic should be lower than the dissolution temperature (Td) of the polymer. Therefore, the good temperature range of the barrel should be between Tf or Tm - Td. For plastics with narrow Tf or Tm - Td intervals, such as polyvinyl chloride and polyoxymethylene, the barrel temperature should be controlled at a slightly lower level, while for plastics with wide Tf or Tm-Td intervals, such as polyethylene and polypropylene, the barrel temperature can be slightly higher. In addition, the influence of heat resistance, the content and distribution of plastics, fillers and reinforcing agents, handicrafts and injection molds, and injection equipment should also be considered. The barrel distribution is stable, and the barrel gradually rises from the nozzle to the end, so that the raw material temperature rises evenly to achieve the purpose of plasticization symmetry.
2. Vertical injection molding machine nozzle temperature
Since the material temperature will increase with the increase of cutting speed (about 103-102) when the solution is based on the nozzle, the nozzle temperature is slightly lower than the high temperature of the barrel, but if the temperature is too low, the injection working pressure will increase, or the raw material will condense in advance, thus affecting the quality of the handicraft. Since there are many factors that affect the fluidity of the polymer, it is generally adjusted according to the "air injection" or "artwork visual analysis method" before molding to determine the barrel temperature and nozzle temperature of the vertical injection molding machine.
3. Vertical injection molding machine mold temperature
Mold temperature has a considerable impact on the quality of handicrafts, and its selection depends on whether the polymer is crystallized, the specifications and structure of the handicrafts, the provisions of the characteristics, and other injection standards (solution temperature, injection rate and working pressure, molding cycle), etc. For amorphous polymers, mold temperature has an important influence on the viscosity (fluidity) of the solution. If the solution viscosity of the raw material is low, such as Ps, the mold temperature can be slightly lower to increase the output. If the viscosity of the solution is high (such as mPPE, PSF), the higher mold temperature is: mPPE is 120°C~140°C, PSF is 140°C~130°C. For crystalline polymers, the crystals are non-isothermal in the vertical injection molding machine mold. The model temperature of the vertical injection molding machine should be set at the periphery of the temperature (tcm) between Tg and Tm, or slightly lower.
