1. The heat balance control of injection molding machine and the heat conduction of mold are the key to the production of injection molding parts. Inside the mold, the heat brought by plastics (such as thermoplastics) is transferred to the material and the steel of the mold through thermal radiation, and to the heat-conducting fluid through convection. In addition, heat is transferred to the atmosphere and mold base through thermal radiation. The heat absorbed by the heat conduction fluid is taken away by the mold temperature machine. The heat balance of the mold can be described as P=Pm-Ps. Where P is the heat taken away by the mold temperature machine; Pm is the heat introduced by plastic; Ps is the heat emitted by the mold to the atmosphere.
2. The temperature control system is composed of three parts: mold, Dongguan mold temperature machine and heat conduction fluid. In order to ensure that heat can be added to or removed from the mold, all parts of the system must meet the following conditions: first, inside the mold, the surface area of the cooling channel must be large enough, and the diameter of the flow channel must match the capacity of the pump (pump pressure). The temperature distribution in the cavity has a great influence on the deformation and internal pressure of the part. Reasonable setting of cooling channel can reduce internal pressure and improve the quality of injection molding parts. It can also shorten cycle time and reduce product costs. Secondly, Dongguan mold temperature machine must be able to keep the temperature of heat transfer fluid constant within the range of 1 ℃ - 2 ℃, which is determined according to the quality requirements of injection molding parts. The third is that the heat-conducting fluid must have good thermal conductivity. The most important thing is that it can introduce or export a large amount of heat in a short time. From the perspective of thermodynamics, water is obviously better than oil.
3. Working principle of Dongguan mold temperature machine: composed of water tank, heating and cooling system, power transmission system, liquid level control system, temperature sensor, injection port and other components. Generally, the pump in the power transmission system makes the hot fluid reach the mold from the water tank with 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 part; The controller regulates the temperature of the hot fluid, thus indirectly regulating the temperature of the mold. If the mold temperature machine is in production and the mold temperature exceeds the set value of the controller, the controller will open the solenoid valve and connect the water inlet pipe until the temperature of the hot liquid, that is, the mold temperature returns to the set value. If the mold temperature is lower than the set value, the controller will turn on the heater.
4. The types of Dongguan mold heaters are divided according to the heat transfer fluid (water or heat transfer oil) used. Generally, the maximum outlet temperature of the water mold heater is 120 ℃. The oil mould temperature machine is used for occasions with working temperature ≥ 150 ℃. Generally, the mold temperature machine with open water tank heating is suitable for water temperature machine or oil temperature machine, and the maximum outlet temperature is 90 ℃ to 150 ℃. The main characteristics of this mold temperature machine are simple design and economic price. On the basis of this machine, a high temperature water temperature machine has been developed. Its allowable outlet temperature is 180 ℃ or higher. Since the thermal conductivity of water is much better than that of oil at the same temperature when the temperature is higher than 90 ℃, this machine has outstanding high temperature working capacity. In addition, there is also a forced flow mold temperature machine. For safety reasons, the design operating temperature of this mold temperature machine is more than 150 ℃, using heat transfer oil. In order to prevent the oil in the heater of the mold heater from overheating, the machine uses a forced flow pumping system, and the heater is composed of a certain number of stacked tubes, in which there are heating elements with fins for guiding.
5. The uneven temperature in the mold is also related to the time point in the injection cycle. After injection, the temperature of the mold cavity rises to the highest, when the hot melt touches the cold wall of the mold cavity, and the temperature drops to the lowest after the parts are removed. The function of the mold temperature machine is to keep the temperature constant at θ 2 min and θ 2 max, that is to prevent temperature difference △ θ W fluctuates up and down in the production process or gap. The following control methods are applicable to the control of mold temperature: control of fluid temperature is the most common method, and the control accuracy can meet the requirements of most cases. Using this control method, the temperature displayed on the controller is not consistent with the mold temperature; The temperature fluctuation of the mold is quite large, and the thermal factors affecting the mold are not directly measured and compensated. These factors include the change of injection cycle, injection speed, melting temperature and room temperature. The second is the direct control of mold temperature. This method is to install a temperature sensor inside the mold, which can only be used when the mold temperature control accuracy is relatively high. The main features 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. Generally, the stability of mold temperature is better than that of fluid temperature control. In addition, the mold temperature control has good repeatability in the production process control. The third is joint control. Joint control is a combination of the above methods, which can simultaneously control the temperature of fluid and mold. In the joint control, the position of the temperature sensor in the mold is extremely important. When placing the temperature sensor, the shape, structure and the position of the cooling channel must be considered. In addition, the temperature sensor should be placed at a place that plays a decisive role in the quality of the injection molding part. There are many ways to connect one or more mold temperature machines to the controller of the injection molding machine. It is better to use digital interface, such as RS485, in consideration of operability, reliability and anti-interference. Information can be transferred between the control unit and the injection molding machine through software. The mold temperature machine can also be controlled automatically.
6. Configuration and use of Dongguan mold temperature machine: The configuration of Dongguan mold temperature machine shall be comprehensively determined according to the processed materials, mold weight, required preheating time and productivity kg/h. When using heat transfer oil, the operator must comply with the following safety regulations: Do not place the oil mold heater near the heat source furnace; The connector shall be a taper leak-proof hose or hard pipe with temperature and pressure resistance; Regularly check the temperature control circuit, connector and mold for leakage and normal function; Regularly replace the heat transfer oil; Synthetic oil should be selected, with good thermal stability and low coking tendency. In the use of oil-type mold temperature machine, the selection of appropriate heat transfer fluid is extremely critical. The water mold temperature machine uses water as the heat transfer fluid, which is economical, clean and easy to use. Once the temperature control circuit, such as the hose coupling, leaks, the water flowing out can be directly discharged to the sewer. However, there are also disadvantages of using water as heat conduction fluid: the boiling point of water is low; Depending on the composition of the water, corrosion and scaling may occur, resulting in increased pressure loss and reduced heat exchange efficiency between the mold and the fluid. When using water as heat transfer fluid, the following precautions should be taken into consideration: pre-treatment of temperature control circuit with anti-corrosion agent; Use filter before water inlet; Clean the water mould temperature machine and mould regularly with rust remover. There is no water defect when using heat transfer oil. Oil has a high boiling point. They can be used at temperatures higher than 350 ℃ or even higher. However, the heat transfer coefficient of heat transfer oil is only 1/3 of that of water. Therefore, oil mold heaters are less widely used in injection molding than water mold heaters
Dongguan mold temperature oil-type mold temperature machine water-type mold temperature machine hotline: 13602318867 0769-83660871 Email: xiongdajun@163.com