Vertical injection molding machine
temperature control The vertical injection molding machine thermocouple that measures the temperature is used as the temperature measurement element, and the millivoltmeter that measures the temperature becomes the temperature control device of the vertical injection molding machine, which controls the on and off of the current of the barrel and the mold electric heating ring. Selectively adjust the temperature of each section of the barrel and the temperature of the mold. The temperature that needs to be controlled during the injection molding process of the vertical injection molding machine includes the barrel temperature, the nozzle temperature and the mold temperature. The first two temperatures mainly affect the plasticization and flow of plastics, while the latter temperature mainly affects the flow and cooling of plastics. 1. Barrel temperature The selection of barrel temperature of vertical injection molding machine is related to the characteristics of the plastic, especially the flow temperature (Τf) or melting point (Τm) of the plastic. For amorphous plastics, the maximum temperature at the end of the barrel should be higher than Τf, while crystalline plastics should be higher than Τm, but the temperature of the plastic should be lower than the decomposition temperature (Τd) of the polymer. Therefore, the most suitable temperature range for the barrel Should be between Τf or Τm-Τd. For plastics with a narrow range of Τf or Τm-Τd, such as PVC, pom, etc., the barrel temperature should be controlled to a low level. For plastics with a wide range, such as pe, pp, etc., the barrel temperature can be slightly higher. In addition, the thermal stability of plastics, molecular weight and its distribution, fillers and reinforcements, product and mold design, and injection devices should also be considered. Stable distribution of the barrel, generally the hopper rises gradually to the nozzle, so that the temperature of the material rises to the purpose of even plasticizing. 2. The nozzle temperature of the vertical injection molding machine will increase with the increase of the shear rate (about 102-103) when the melt passes through the nozzle. Therefore, the nozzle temperature is slightly lower than the maximum temperature of the barrel. However, if If it is too low, it will increase the injection pressure, or cause premature solidification of the material, which will affect the quality of the product. Because there are many factors that affect the fluidity of polymers, it is generally adjusted through the direct analysis method of air injection or products before molding, so as to determine the best vertical injection molding machine barrel temperature and nozzle temperature. 3. The mold temperature of the vertical injection molding machine has a considerable influence on the quality of the product. Its choice depends on whether the polymer is crystallized, the size and structure of the product, performance requirements, and its injection conditions (melt temperature, injection Speed u200bu200band pressure, molding cycle) etc. For amorphous polymers, the mold temperature mainly affects the melt viscosity (fluidity). If the melt viscosity of the material is low, such as PS, the mold temperature can be low to improve productivity. If the melt viscosity is high, (such as mPPE, PSF), use a higher mold temperature: 110°C ~ 130°C for mPPE, 130°C ~ 150°C for PSF. For crystalline polymers, the crystallization in the mold of the vertical injection molding machine is non-isothermal. The mold temperature of the vertical injection molding machine should be set near or slightly lower than the temperature (Τcm) at which the maximum crystallization rate occurs between Τg and Τm. For example, the Τcm of PP is 65°C, PET is 180°C, and PA-6 is 146°C; the Tg of the three polymers are -20°C, 67°C and 45°C; the mold temperature during injection is 30°C ~ 85°C. ℃, 140℃ ~ 190℃ and 70℃ ~ 120℃, in order to make the material cool and solidify under the condition of maximum crystallization rate. If it causes a supercooled state, the crystallinity is very low, and the rigidity of the product is insufficient, which affects the demolding. However, for polyethylene, even if the degree of supercooling is large, products with high crystallinity can be obtained. Vertical injection molding machine barrel electric heating ring usually includes two-stage, three-stage or four-stage control. The ammeter on the electrical cabinet of the vertical injection molding machine reflects the current of each section of the electric heating coil. The reading of the ammeter is very stable. If the reading of the ammeter is low for a long time during work, there may be a problem with the electric heating coil, or the wire is not contacted well, or the electric heating wire is oxidized and thinned, or a vertical injection molding machine is heated. If the ring burns out, these will increase the resistance value of the parallel resistance of the vertical injection molding machine circuit and cause the current to drop. When the ammeter has a certain reading, you can simply use the vertical injection molding machine plastic strips to wipe the outer wall of the vertical injection molding electromechanical heating ring one by one, and see whether the material is melted or not to judge whether a certain electric heating ring is energized or burned. Recommended reading: (1) Vertical injection molding machine, standard vertical injection molding machine, disc injection molding machine, disc vertical injection molding machine, low pressure injection molding machine. (2) Brand of vertical injection molding machine.
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