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Low Pressure Die Casting (LPDC)  involves filling a die-cast mold with molten metal under low pressure. It is highly accurate due to the constant filling of the die cavity during the shrinking phase (solidification). This means it compensates for the reduction in volume. Other attributes include reduction in oxide formation and porosity and superior consistency of molten metal from top to bottom.

The LPDC process begins by heating the metal alloy to its liquid state in a crucible. The molten metal is then transferred to a riser system, which acts as a reservoir, maintaining a constant head of metal. Unlike other casting methods, low pressure—typically ranging from 0.01 to 0.08 MPa—is gradually applied to the molten metal, forcing it to flow slowly and evenly through sprues and runners into the intricately designed dies. This slow and controlled filling process minimizes turbulence and gas entrapment, leading to fewer defects and improved cast quality.

The dies, which are precision-engineered to the finest tolerances, are clamped together under high pressure, ensuring tight sealing and dimensional stability during the casting cycle. Once the metal has solidified, the dies are opened, and the castings are ejected or extracted, ready for further processing, such as trimming, machining, or finishing.

Advantages of Low-Pressure Die Casting

This method allows precise control of the filling process. Injecting the molten metal in this way reduces oxide formation and reduces porosity, ensuring superior consistency from top to bottom. As such, low pressure casting results in exceptional density and strength values as well as excellent dimensional accuracy. While this method is greatly suited to simpler, symmetrical forms, more complex geometries can be achieved with the use of sand cores within the molds. With the advantage of uncomplicated machinery and technology, the low pressure die casting process lends itself well to automation.

How Does Low Pressure Die Casting Work?

Low-pressure die casting uses small pressure, typically around 20-100 kPa (2.9-14.5 psi), instead of gravity to fill a die. Unlike the traditional die casting process, it has a unique setup and uses several pieces of equipment. Below is an illustration of the setup and pieces of equipment that are needed.

1.The process begins with a melting furnace which melts the metal alloys and brings them to the casting temperature

2.The molten metal will then go to a holding furnace below the mold, which functions as a container while maintaining the liquid at the casting temperature.

3.Low pressure forces the molten metal through a riser tube into the mold. The liquid metal moves under constant pressure until the molten metal solidifies in the die cavity.

4.On solidification, the pressure is released, and the remaining molten metal goes back through the riser tube to the holding furnace for recycling. Finally, the casting will be easily removed once the mold is cooled.