To control the temperature of injection molding during the processing of injection molds, it is necessary to start from three aspects: barrel temperature, nozzle temperature, and mold temperature. The following are specific control methods:

Material barrel temperature control

Temperature gradient setting: The temperature distribution of the entire material barrel should maintain a certain gradient, gradually increasing from the end near the hopper towards the nozzle. One end of the hopper mainly heats the plastic, and the temperature of the first half of the compression section is slightly lower than the melting point of the plastic, while the temperature of the second half is higher than the melting point of the plastic.

Adjust according to the characteristics of plastics: Different plastics have different flow temperatures and thermal decomposition temperatures, and the temperature of the material barrel should be maintained within an appropriate range above the viscous flow temperature and below the thermal decomposition temperature of the plastic. For thermosensitive plastics or plastics with low relative molecular weight and wide distribution, the barrel temperature should be selected at a lower value, that is, only slightly higher than the viscous flow temperature, to avoid thermal degradation.

Consider the type of injection machine and the structure of the parts: the temperature of the barrel is related to the type of injection machine and the structural characteristics of the parts and molds. For example, when injecting the same plastic, the temperature of the screw type barrel can be 10-20 ℃ lower than that of the plunger type. Thin walled parts or products with complex shapes and embedded parts, due to difficult flow or easy cooling, should use higher barrel temperatures; On the contrary, for thick walled parts, simple parts, and non embedded parts, lower barrel temperatures can be used.

Control residence time: In order to prevent the molding material from overheating and degrading in the barrel, in addition to strictly controlling the maximum temperature of the barrel, it is also necessary to control the residence time of the material or melt in the barrel, which is particularly important for thermosensitive plastics. Usually, after the temperature of the barrel is increased, the residence time of the material or melt in the barrel should be appropriately shortened.

To determine whether the material temperature is qualified, the air injection method can be used for observation, or the quality of the parts can be directly observed. When injecting into the air, if the material flow is uniform, smooth, without bubbles, and has a uniform color, it indicates that the material temperature is appropriate; If the material flow is rough, has silver threads or discoloration, it indicates that the material temperature is not qualified.

Nozzle temperature control

Temperature range setting: The nozzle temperature is usually slightly lower than the maximum temperature of the barrel, roughly the same as the temperature at the middle end of the barrel, to prevent molten material from drooling in the straight through nozzle. But the temperature cannot be too low, otherwise it will cause premature solidification of the melt, resulting in either clogging of the nozzle holes or the introduction of cold material into the mold cavity, ultimately leading to molding defects.

Mold temperature control

Using temperature control devices: Mold temperature control devices (such as water temperature machines, oil temperature machines, chillers, mold heating rods, etc.) are key tools for achieving mold temperature control. These devices can accurately maintain the mold temperature within the set range. Adopting automatic temperature control equipment (such as ENGEL's e-tem temperature control equipment) to achieve energy-saving operation by automatically adjusting the pump speed and maintaining a constant mold temperature.

Reasonably arrange heating and cooling channels: ensure uniform temperature distribution of the mold and avoid excessive local temperature differences. Install temperature sensors in the mold, monitor the mold temperature in real time, and adjust it through feedback through the control system. Using efficient cooling media (such as water or oil) and a reasonable layout of cooling channels to improve cooling efficiency. Collaborate with temperature control devices using digital solutions such as ENGEL's iQ flow control to automatically adjust pump power and flow rate, ensuring temperature stability and energy efficiency.

Considering the characteristics of plastics: Different plastic materials have different melting temperatures and thermal deformation temperatures, and the mold temperature needs to be adjusted according to the material properties. For example, PC/ABS material has high heat resistance and good dimensional stability, and its mold temperature needs to be precisely controlled to ensure product quality. For high viscosity plastics such as polycarbonate, higher mold temperatures are generally used to improve their flowability and filling ability, and to increase tissue density. For plastics with low viscosity, such as polyethylene, polypropylene, polyvinyl chloride, etc., lower mold temperatures can be used. For thick walled parts, the mold temperature is low, which can easily generate vacuum bubbles and internal stresses. Generally, a higher mold temperature is used.

Mold insulation treatment: Insulation treatment is carried out on the surface of the mold or skeleton board to reduce heat loss. For hot runner molds, reduce the heat exchange between the hot runner section and the cooled injection molded parts to minimize energy loss.

Dynamic control: A combination of high-temperature steam heating and cooling water cooling is used to achieve dynamic control of mold temperature. This technology can maintain high temperature of the mold during the filling and holding stages, thereby obtaining high-quality products.

Following the principle of temperature control: different rubber materials require different mold temperatures; Molds with different surface qualities and structures require different mold temperatures, which requires targeted design of temperature control systems; The temperature of the front mold is higher than that of the rear mold, usually with a temperature difference of about 2-3 ℃; The temperature of the front mold with spark pattern requirements is higher than that of the front mold with general smooth surface requirements. When the front mold needs hot water or hot oil, the temperature difference is generally around 40 ℃; When the actual mold temperature cannot reach the required mold temperature, the mold should be heated up. Therefore, when designing the mold, full consideration should be given to whether the heat brought into the mold by the rubber material can meet the mold temperature requirements; The heat brought into the mold by the rubber material is not only consumed through thermal radiation and conduction, but the vast majority of the heat needs to be carried out of the mold by the circulating heat transfer medium.