The Role of Mold Temperature Machines in Die Casting Frozen Shelled shrimps,Frozen Bamboo shrimp,Frozen Red shrimp Zhejiang Ocean Family Co., Ltd., , https://www.ocean-family.com
During the die casting process, molten alloy is injected into a mold cavity and solidifies as it loses heat. If the cooling happens too quickly, cold shuts or surface defects can appear in the casting. On the other hand, if the cooling is too slow, it increases the cycle time and reduces overall productivity. Maintaining proper mold temperature is essential for producing high-quality castings. The mold's surface temperature directly affects how the molten metal flows, especially in thin-walled sections with long flow paths.
To ensure the mold cavity is fully filled before the metal solidifies, designers often aim to reduce filling time. In addition, increasing the gate speed can help, though this may cause turbulence. Raising the mold temperature is another effective method. For large-area castings with strict surface requirements, a stable and high mold surface temperature is necessary to minimize cold lines and surface imperfections.
Uneven or incorrect mold temperatures can lead to dimensional instability in the casting, causing warping or deformation during the production process. This can result in defects like hot cracking, sticking, surface depressions, shrinkage cavities, and thermal bubbles. Large temperature differences across the mold can also affect variables such as filling, cooling, and spraying times, making the process less predictable. Moreover, excessive heat can damage the mold, leading to issues like hot cracking in expensive tool steels, which shortens the mold’s lifespan.
Determining the Right Mold Surface Temperature
The ideal mold surface temperature depends on the product design, including its thickness, cross-section, and surface finish requirements, as well as the production cycle. As a general guideline:
- Aluminum alloys: 180–270°C
- Magnesium alloys: 180–300°C
- Zinc alloys: 100–200°C
It's crucial for the mold temperature machine to reach and maintain these specified temperatures. Traditional methods used by technicians include LPG torches, radiant heaters, or plug-in electric heating elements. However, these methods often provide uneven heating and are not always effective. Radiant heaters are more flexible and less damaging to the mold but tend to be less efficient. Plug-in electric heating tubes are better suited for long-term use but have limited application areas.
An alternative approach is using low-speed injection, where the initial injection speed is reduced, allowing the molten metal to preheat the mold. While common, this method can negatively impact mold life and is not recommended for precision molds. During injection, the molten metal rapidly heats the cavity surface, penetrating twice as deep as the mold's internal temperature. This sudden heat influx creates high stress on the cavity surface, increasing the risk of microcracking.
The most effective and reliable heating method for mold temperature machines is using hot oil. Hot oil circulates through channels inside the mold, providing even and controlled heating from the inside out. Unlike water, hot oil can both heat and cool, acting like a heat exchanger. This ensures that the mold temperature remains within an optimal range, even when production is paused, maintaining consistent quality and extending the mold’s service life.