After the alloy solution is pressed into the mold cavity, it solidifies and forms due to the loss of heat. If the heat transfer rate is too fast, the casting may have the defect of cold lines. On the contrary, if the heat transfer rate is too slow, the molding cycle of the casting will be increased and the productivity will be reduced. The control of the mold surface temperature is very important for the production of high-quality die castings. The temperature of the mold will affect the flow of the metal solution on the surface of the mold cavity. Especially for thin-walled parts with long flow paths. In order to make the metal solution fill the mold cavity before solidification, in addition to choosing a design that shortens the filling time, the gate speed can also be increased (but it is easy to produce turbulence) to increase the mold temperature. In addition, castings with large areas and extremely high surface requirements also require higher and more stable mold surface temperatures to reduce cold lines and surface defects.
 
Uneven or inappropriate mold temperature will also lead to unstable casting dimensions, deformation of ejected castings during production, and defects such as thermal pressure, mold sticking, surface depression, internal shrinkage and hot bubbles. When the mold temperature varies greatly, it will have different degrees of impact on variables in the production cycle, such as filling time, cooling time and spraying time. The appropriate mold surface temperature distribution should be determined according to the shape of the product, such as thickness, cross-sectional thickness variation, top surface requirements, and production cycle. The approximate surface temperature of alloy molds is: aluminum alloy 180-270℃; magnesium alloy 180-300℃; zinc alloy 100-200℃.
 
To achieve the required mold temperature, die-casting factory technicians often use LPG guns, followed by radiation heaters, or plug-in electric heating tubes, but the effect is not ideal and the mold temperature cannot be uniform. However, the use of radiation heaters is more flexible and less harmful to the mold, but the efficiency is lower; plug-in electric heating tubes are only suitable for long-term heating positions and have a more limited application range.
 
In addition, using the low-speed injection method - that is, reducing the primary injection speed and directly heating the mold with metal solution is also a very common method, but this method has an adverse effect on the life of the mold and is not suitable for expensive precision molds. Since the injection is in the instantaneous stage, the temperature of the solution will penetrate the surface of the mold cavity, and the penetration depth is about twice the thickness of the casting. During the period of intense high heat intrusion, the high temperature state of the mold cavity surface will cause high stress on the mold cavity surface, and the chance of micro-phenomenon will double.
 
The most ideal heating method is hot oil heating. Hot oil passes through the pipes in the mold continuously to heat the mold from the inside, so that the mold reaches a state suitable for production. Since thermal oil can not only heat, but also cool like water, it functions like a heat exchanger and can keep the mold temperature within a certain range. Even when production is interrupted, the mold temperature can be properly maintained.
 
The mold temperature controller uses a heat-conducting medium with high thermal conductivity to remove excess heat from the mold in a very short time. After setting the thermal balance temperature, the mold temperature controller can automatically control its temperature within a very small error and maintain a constant value.  If you want to know more about the application of mold temperature controllers in the die-casting industry, please consult Hengde Company. We will have a professional team to serve you 24 hours a day.

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