How to control the temperature of injection molding machine? Precision temperature measurement injection molding machine Thermocouple is used as a temperature measuring element, and the millivoltmeter that accurately measures temperature becomes the temperature control equipment of the injection molding machine; Selectively adjust the temperature of each section of the barrel and the mold temperature.

The temperature that the injection molding machine must control during the injection molding process includes the barrel temperature, nozzle temperature and mold temperature. The first two temperatures seriously affect the plasticization and fluidity of plastics, and the last two temperatures seriously affect the fluidity and cooling of plastics.

1、 Injection molding machine barrel temperature

"The selection of the barrel temperature of the injection molding machine is related to the characteristics of the plastic, and largely depends on the flow temperature (Tf) or melting point (Tm) of the plastic.

For amorphous plastics, the high temperature at the end of the barrel should be higher than Tf, while that of crystalline plastics should be higher than Tm, but the temperature of plastics should be lower than the melting temperature (Td) of polymers. Therefore, the good temperature range of the barrel should be between Ta f or Ta m - Ta d.

For plastics with narrow Tf or Tm Td range, such as PVC, pom, etc., the barrel temperature should be controlled slightly lower; for plastics with wide range, such as pE, APP, etc., the barrel temperature should be controlled slightly lower and the temperature can be slightly higher. In addition, the heat resistance, content and distribution of plastics, fillers and reinforcements, handicrafts, injection molds and injection molding equipment should also be considered. The barrel distribution is stable. Generally, the silo starts and stops the nozzle and gradually rises to make the temperature of raw materials rise evenly, so as to achieve the purpose of plasticization and symmetry.

2、 Injection molding machine nozzle temperature

Due to the different nozzles, the melt temperature will increase with the expansion of the cutting speed (about 103-102), so the nozzle temperature is slightly lower than the high temperature of the barrel, but if it is too low, the injection working pressure will increase, or lead to premature solidification of raw materials, affecting the quality of handicrafts.

Because there are many factors affecting polymer fluidity, it is generally adjusted according to "air injection" or "visual analysis of handicrafts" before molding, so as to facilitate the confirmation of the barrel temperature and nozzle temperature of the injection molding machine.

3、 Injection molding machine mold temperature

Mold temperature has a considerable impact on the quality of handicrafts. Its selection is whether the polymer is crystallized, the specification and structure of the process, and other injection standards (solution temperature, injection rate and working pressure, forming cycle).

For amorphous polymers, mold temperature has a key impact on the viscosity (fluidity) of the solution.

If the melt viscosity of raw materials is low, such as Ps, the mold temperature can be slightly lower to improve the yield. If the melt viscosity is high (such as mPPE, PSF), select a higher mold temperature: mPPE is 120 ℃~140 ℃, and PSF is 140 ℃~130 ℃.

For crystalline polymers, Large injection molding machine The crystals in the mold are non isothermal. The mold temperature of the injection molding machine should be set near or slightly lower than the temperature (Tcm) where a larger crystal velocity occurs between Tg and Tm.

For example, PP is 65 ℃, PET is 190 ℃, and AS-6 is 146 ℃; Tg of several polymers is - 30 ℃, 83 ℃ and 46 ℃ respectively; The mold temperature during injection is 40 ℃~86 ℃, 160 ℃~180 ℃ and 75 ℃~130 ℃ respectively, so that the raw materials can be cooled and dried under the standard of large crystal speed. If it leads to low temperature, the grain size is very low, and the rigidity of the handicraft is not enough, affecting the mold. However, for high-pressure polyethylene, even if the low temperature level is very high, handicrafts with high crystal size can also be obtained.