The role of die casting mold heating and cooling system
The heating and cooling system for die-casting molds is a key component for ensuring a stable die-casting process and improving the quality of die-cast parts and production efficiency. Its role runs through all stages of the die-casting cycle, significantly impacting molten metal filling, solidification, and mold life. The primary function of the heating system is to preheat the mold to an appropriate temperature (usually 150-300°C, adjusted according to the type of alloy) at the beginning of production to prevent the molten metal from rapidly cooling after entering the low-temperature mold, which can lead to defects such as insufficient filling or the formation of cold shuts and insufficient pouring. For large molds or molds with complex cavities, uniform preheating can reduce temperature gradients within the mold, prevent cracks caused by thermal stress, and extend the life of the mold. For example, when die-casting aluminum alloys, excessively low mold temperatures (below 150°C) can cause the fluidity of the molten metal to drop sharply, making underfilling a common problem when filling complex cavities . The heating system ensures that the mold quickly reaches the operating temperature at the beginning of production, ensuring smooth die-casting.
The core function of the cooling system is to accelerate the solidification rate of the die-casting through forced cooling after the molten metal fills the cavity, shortening the molding cycle and improving production efficiency. At the same time, reasonable cooling can control the solidification sequence of the die-casting, so that the die-casting solidifies from the area away from the gate toward the gate, facilitating shrinkage compensation and reducing internal defects such as shrinkage cavities and shrinkage. For example, when die-casting an automobile transmission housing, by installing reinforced cooling water channels in the thicker wall bearing seat area, the solidification rate in this area can be accelerated, reducing the overall solidification time from 60 seconds to 45 seconds, increasing production efficiency by 25%, and reducing internal pores and shrinkage. The cooling system also stabilizes the temperature of the mold during continuous production, avoiding thermal deformation, surface oxidation, and increased wear caused by the continuous increase in mold temperature (over 350°C), and ensuring the stability of the dimensional accuracy of the die-casting.
The synergistic effect of the heating and cooling systems can optimize the temperature field distribution of the mold and reduce the internal stress and deformation of the die-casting. During the die-casting process, the uniformity of the mold temperature directly affects the uniformity of the die-casting’s shrinkage. Excessive temperature differences (over 50°C) can lead to inconsistent shrinkage in different parts of the die-casting, resulting in defects such as warping and cracking. The heating system can compensate for the heat dissipation differences in different parts of the mold through zoned heating, while the cooling system achieves overall mold temperature balance by precisely controlling the cooling intensity of each area. For example, for die-castings with slender ribs, the ribs dissipate heat quickly and are prone to low temperatures. Local heating (such as installing heating rods in the mold area corresponding to the ribs) combined with weak cooling can ensure that the temperature in this area is consistent with that of other parts, reducing rib deformation and cracking.
The heating and cooling systems significantly impact the mold’s service life. Proper temperature control can reduce thermal fatigue damage. Repeated heating and cooling cycles generate alternating thermal stresses on the mold surface. When these stresses exceed the material’s fatigue limit, thermal cracks (turtle cracks) appear, leading to mold failure. The heating system reduces the mold’s heating rate, minimizing thermal shock. The cooling system controls the cooling rate to prevent a sharp drop in mold surface temperature and reduce thermal stress. For example, H13 steel molds, without cooling or with uneven cooling, typically develop noticeable thermal cracks after producing 50,000 to 100,000 pieces. However, molds equipped with a proper cooling system can extend their service life to 200,000 to 300,000 pieces. Furthermore, the cooling system reduces oxidation and corrosion on the mold surface, maintaining the cavity surface roughness and ensuring the surface quality of die-cast parts.
The flexibility and controllability of the heating and cooling system can adapt to the needs of different die-casting processes and die-casting parts, improving the versatility of the mold. By adopting a zoned heating and cooling design, the temperature of each zone can be flexibly adjusted to meet the process requirements of die-casting parts with different structures or different batches in the same mold. For example, in a multi-cavity mold, the cooling intensity of each cavity can be independently controlled to compensate for filling and solidification differences caused by differences in the pouring system, ensuring the consistency of the quality of the die-casting parts in each cavity. For new products that require process testing, the adjustability of the heating and cooling system allows engineers to quickly adjust mold temperature parameters, optimize the die-casting process, and shorten the trial mold cycle. With the development of intelligent die-casting technology, the heating and cooling system can be combined with temperature sensors and PLC control systems to achieve real-time temperature monitoring and automatic adjustment, further improving the stability and intelligence level of the die-casting process.
