A pressure die casting machine, as the name implies, is used to perform cast die casting that is essentially a metal casing process which forces molten metal into a mold cavity under high pressure. The mold cavity is created with multiple hardened tool steel dies which have been machined into shape. It works very similarly to an injection mold during the process. Most die castings are made of non-ferrous metals, including aluminum, copper, zinc, magnesium, lead, pewter and tin-based alloys. Depending on the application, you have a choice between high pressure die casting machine and low pressure die casting machine. In this article, we’ll talk about how they are different from one another.
When using a high pressure die casting machine, molten metal is injected into the mold at high speed and high pressure. Horizontal high pressure die casting machines can make sure the die closes entirely. Based on the metal being used, the injection unit that fills the mold can either be hot chamber or cold chamber:
● Hot Chamber High Pressure Die Casting Machines: The hot chamber system involves the use of metals such as magnesium, zinc and lead. During the hot chamber die casting process, the metal is held within the high pressure die casting machine itself, then pulled into the chamber and forced into the mold by the injection piston. As the piston pumps, it forces metal along the nozzle and into the die.
● Cold Chamber High Pressure Die Casting Machines: In the cold chamber process, the metal is first melted in one furnace and transferred to the other (i.e., the holding furnace). It is then injected into the mold as it gets poured into a shot sleeve. Metals that are used with a cold chamber high pressure die casting machine typically include aluminum, copper and magnesium.
High pressure die casting machines are suited for production of a broad range of automotive castings, including gearbox casings, engine blocks, oil sumps, engine mounts, and structural parts like cross-car beams. They are also used in many other sectors, such as the manufacturing of lighting components or the relatively more complex and demanding applications like aerospace engine parts.
Contrary to the above, low pressure die casting machines are used to perform low pressure die casting (LPDC), a common process used in foundries today wherein the die is slowly filled with molten metal, reducing turbulence. Low pressure die casting machines are widely used in automotive applications including wheels, suspension, steering and engine parts. Other applications in which a low pressure die casting machine is used include pipe benders and bell housings. Low pressure die casting machines are able to achieve castings with superb metallurgical quality.
In order to choose the right machine to meet your component requirement, you need to understand the distinct capabilities and restrictions between a high pressure die casting process and low pressure die casting process.
In terms of light metal castings, high pressure die casting is the more commonly adopted process, which accounts for about 50% of total usage. On the other hand, low pressure casting accounts for around 20% of light metal casting.
Low pressure die casting is typically used for metals with low melting points and enables the production of components up to 330 lbs. The primary advantage is its ability to form complex geometries and high strength, while being able to maximize material usage.
Low pressure die casting process is ideal for thin-walled parts with the required thickness below 3 millimeters. It also has slower component production compared to high pressure die casting process. The size of casting is also affected by machine size.
Conversely, a high pressure die casting process is commonly used to work with softer metals like zinc and aluminum. The molten metals are forced into mold under higher pressure and speed. This enables a much quicker component production than low pressure die casting.
High pressure die casting is also able to offer smoother surfaces for finishing options. How you go about finishing the surface will depend on the quality of finish on the dies. You can also apply additional coatings directly with these high-quality finishes.
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