Pressure die casting is a type of die casting that involves using a metal mold that’s usually made from premium, heat-resistant steel grades, into which a non-ferrous metal like aluminum or zinc is injected. Basically, the mold cavity, or die, is machined into whichever shape is needed, and the molten metal is forced into it under pressure and high velocity.
The two main types of pressure die casting are low- (LPDC) and high-pressure (HPDC) die casting. LPDC requires the metal to be injected into the mold at low pressures, between around 2–15 psi, and takes a more controlled and gentle approach which takes longer because the inert gas pressure gently forces the alloy upwards into the mold. HPDC involves injecting the alloy into the mold at higher pressures, around 1,500–25,400 psi, is faster than LPDC, usually taking between 10 and 100 milliseconds to inject the alloy into the die through a high-speed ram. It’s better suited to extra high-volume production and parts that need to have very tight tolerances.
Apart from these, die casting in general can also be classified based on the type of chamber: hot or cold. Hot chamber die casting is where the metal is heated inside the casting machine. Many Juize customers prefer this method when working with tin, magnesium, lead alloys, and other lower-melting-point metals. In cold chamber die casting, the metal is pre-heated in a furnace before being transferred into the casting machine. Our customers find that this method works perfectly with brass, copper, aluminum, and other metals with high melting points.
The pressure die casting process begins with an engineered closed steel die cavity, into which the molten metal is forcefully injected under pressure. This die is made out of two main parts, one moving, and one stationary, which are secured to the die casting machine’s platens. The machine itself has an injection mechanism on one end that uses both hydraulics and pressurized gas to propel a piston forward, and, on the other end, a clamping mechanism that uses hydraulics and mechanical toggles. The design ensures the machine can survive intense pressure during injection, and the die remains firmly closed as the metal part hardens. Impressively, this process can convert molten metal into a solid, near-net-shape part within just a few seconds. You can see all the different parts involved in the below diagram.
Non-ferrous metals are usually used for HPDC because they just fit the bill. Aluminum (particularly 380, 390, 412, 443, and 518) is a common go-to because it’s dimensionally stable, corrosion-resistant, electrically conductive, and able to withstand high temperatures. Compared to aluminum, zine alloys (like Zamak 2, Zamak 3, and Zamak 5) they have a lower melting point, but they’re strong and ductile, and can be used with both hot and cold chamber die casting systems.
Magnesium is another option as it’s the lightest structural metal, highly machinable, and suitable for hot chamber die casting thanks to its lower melting point. Ideal for high strength-to-weight ratio applications, many Juize customers prefer using magnesium (like AE42, AM60, AS41B, and AZ91D) for certain automotive and aerospace components. In addition to the aforementioned industries, these materials are also used in the pressure die casting process to make things like consumer electronics, and other decorative items that require intricate shapes or thin walls.
A few of the process’s downsides are its high initial cost and material limitations (it can only work with non-ferrous metals). There tend to be size limitations for cast parts, and it can be prone to porosity issues, cold shuts (where two fronts of molten metal meet but don’t fuse properly, creating a weak spot), and misruns which lead to incomplete castings or parts that are not fully formed. You may experience flash—excess thin layers of metal that escape and need trimming. This can be minimized, though, by clamping the mold halves tighter. Finally, it can create blisters—a type of gas porosity that looks like raised bubbles on the surface. If you try to minimize any trapped air further, you may be able to avoid this.
