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1.Heat is transferred to the atmosphere and mould frame through thermal radiation. The heat absorbed by the heat conducting fluid is taken away by the mold temperature machine. The thermal balance of the die can be described as: P=Pm-Ps. The P is the heat that is taken away from the mold, Pm is the heat introduced by the plastic, and the Ps is the heat emitted from the mold to the atmosphere.
2.Preparatory condition temperature control system for effective control of mold temperature consists of mold, mold temperature machine and heat conducting fluid. In order to ensure that heat can be added to the mold or removed, all parts of the system must meet the following conditions: first, in the mold, the surface area of the cooling channel must be large enough, the diameter of the channel to match the pump capacity (pump pressure). The temperature distribution in the cavity has a great influence on the deformation and internal pressure of the parts. A reasonable cooling channel can reduce internal pressure and improve the quality of injection molded parts. It can also shorten cycle time and reduce product cost. Secondly, the mold temperature machine must be able to make the temperature of the heat conducting fluid constant in the range of 1 ~3 ~C, according to the quality requirements of the injection molded parts. Thirdly, the heat conducting fluid must have good heat conduction ability, and most importantly, it must be able to import or export a large amount of heat in a short time. From a thermodynamic point of view, water is obviously better than oil.
3.The working principle of the mould temperature machine consists of water tank, heating and cooling system, power transmission system, liquid level control system, temperature sensor, injection port and other components. Usually, the pump in the power transmission system makes the hot fluid reach the mold from the water tank with the built-in heater and cooler, and then return to the water tank from the mold; the temperature sensor measures the temperature of the hot fluid and transmits the data to the controller of the control section; the controller adjusts the temperature of the hot fluid, thereby indirectly adjusting the temperature of the mold. . If the mold temperature exceeds the set value of the controller in the production of the mold temperature machine, the controller will open the solenoid valve to connect the inlet pipe until the temperature of the hot fluid, that is, the mold temperature returns to the set value. If the mold temperature is below the set point, the controller will turn on the heater.
4.the type of mold temperature machine is based on the use of heat transfer fluid (water or heat transfer oil) to be divided. The maximum outlet temperature is usually 95 degrees. The oil delivery mold temperature machine is used for working temperatures above 150 degrees Celsius. Usually, the mold temperature machine with open water tank heating is suitable for water or oil temperature machine. The maximum outlet temperature is 90 ~150 ~C. The main characteristics of this mold temperature machine are simple design and economical price. On the basis of this machine, a high-temperature water heater is developed, which allows the outlet temperature to be 160 degrees Celsius or higher. Because the heat conductivity of water is much better than that of oil at the same temperature when the temperature is higher than 90 degrees Celsius, the machine has outstanding high-temperature working ability. In addition, there is a mandatory flow of mold temperature machine, for safety reasons, this mold temperature machine designed to operate at temperatures above 150 degrees Celsius, the use of heat conductive oil. In order to prevent the oil from overheating in the heater of the mould heater, the machine uses a forced flow pump system, and the heater consists of a certain number of tubes stacked together, with finned heating elements in the tubes for conduction.
5.Controlling the temperature in the mold is uneven and also related to the time point in the injection cycle. The temperature of the cavity rises to the highest level after injection, when the hot melt touches the cold wall of the cavity and the temperature drops to the lowest level when the part is removed. The function of the mold temperature machine is to keep the temperature constant between theta 2min and theta 2max, that is to say, to prevent the temperature difference (?) theta w) from fluctuating in the production process or the gap. The following control methods are suitable for controlling mold temperature: controlling fluid temperature is the most common method, and the control accuracy can meet most of the requirements. Using this control method, it is shown that the temperature of the controller is not consistent with the mold temperature; the mold temperature fluctuates considerably and the thermal factors affecting the mold are not directly measured and compensated for, including the change of injection cycle, injection speed, melting temperature and room temperature. Next is the direct control of mold temperature. This method is to install a temperature sensor in the mold, which will be used only when the mold temperature control accuracy is relatively high. The main characteristics of mold temperature control include: the temperature set by the controller is consistent with the mold temperature; the thermal factors affecting the mold can be directly measured and compensated. Usually, the mold temperature stability is better than that by controlling the fluid temperature. Besides, the mold temperature control has a good repeatability in the production process control. The third is joint control. Combined control is the synthesis of the above methods, which can control the temperature of fluid and mold simultaneously. In the joint control, the position of temperature sensor in the mold is extremely important. When the temperature sensor is placed, the shape, structure and the position of cooling channel must be considered. In addition, temperature sensors should be placed in a decisive position for the quality of injection molded parts. There are many ways to connect one or more mold temperature machines to the controller of injection molding machine. It is better to use digital interface, such as RS485, in terms of operability, reliability and anti-interference. Between control unit and injection molding machine, information can be transmitted through software. The mold temperature machine can also be automatically controlled.
6.The configuration of the mould temperature machine and the configuration of the mould temperature machine should be judged comprehensively according to the material processed, the weight of the mould, the required preheating time and the productivity kg/h. When using heat conduction oil, the operator must comply with such safety regulations: do not place the mold heater near the heat source stove; use tapered leak-proof and heat-resistant flexible or hard pipes for joints; regularly check the temperature control loop mold heater, joints and.