The thermal uniformity of the mold heating tube is a key factor in ensuring the forming quality of the mold. Its realization requires comprehensive consideration from multiple aspects such as design and selection, material application, installation process and control system.
During the design and selection stage, it is crucial to rationally plan the layout of the heating tubes. Three-dimensional thermal field simulation analysis was conducted based on the shape and size of the mold to determine the arrangement and spacing of the heating tubes. For large molds, a circular and matrix interlaced distribution is adopted to avoid local heat concentration or insufficiency. For instance, in injection molds, heating tubes are evenly arranged around the cavity to ensure that the molten plastic is heated consistently during the filling process. At the same time, choosing the appropriate type of heating tube, such as finned heating tubes, can effectively enhance heat exchange efficiency and promote uniform heat diffusion by increasing the heat dissipation area.
Material properties have a significant influence on thermal uniformity. The pipe material of the heating tube should have good thermal conductivity, such as stainless steel 304 material, which has a stable thermal conductivity coefficient and is corrosion-resistant, ensuring rapid heat conduction. The uniformity of resistivity of the heating wire material should not be ignored either. Nickel-chromium alloy heating wires, due to their stable resistivity and resistance to high-temperature oxidation, have become the preferred choice for ensuring thermal uniformity. In addition, the thermal conductivity of the filling material is equally crucial. Using high-purity magnesium oxide powder for filling, its excellent insulation and thermal conductivity can evenly transfer heat to the surface of the pipe, reducing the accumulation of internal heat.
The installation process determines the actual usage effect of the heating tube. Install strictly in accordance with the design requirements to ensure that the heating tube is in close contact with the mold. The gap is filled with interference fit or thermal grease to reduce the contact thermal resistance. For instance, when installing heating tubes in die-casting molds, the installation holes are finely processed to ensure that the heating tubes fit the hole walls to over 95%. At the same time, the wiring method of the heating tubes should be reasonably arranged to avoid uneven power distribution of each heating tube due to differences in line resistance, which may affect thermal uniformity.
The control system is the core guarantee for achieving thermal uniformity. The intelligent temperature control system is adopted, and the mold temperature is monitored in real time through multi-point temperature sensors. If thermocouple sensors are installed at the key parts of the mold and the temperature data is fed back to the temperature controller, the temperature controller will automatically adjust the power of the heating tube according to the preset temperature curve. The PID control algorithm is applied to achieve temperature regulation, keeping the temperature fluctuation range within ±2℃. In addition, some advanced systems also have self-learning capabilities, which can automatically optimize the temperature control strategy based on the usage of the mold, further enhancing thermal uniformity.
Regular maintenance is also an important measure to maintain thermal uniformity. Check whether there is scale on the surface of the heating tube and clean the impurities that affect heat conduction in time. Test the accuracy of the temperature control system and calibrate the temperature sensor; Evaluate the power attenuation of the heating tubes and replace those that are aging or have declined in performance in a timely manner. Through strict control and continuous maintenance throughout the entire process, the thermal uniformity of the mold heating tubes can be effectively guaranteed, improving the quality of mold processing and production efficiency.
