Casting has been a part of human lives for thousands of years. We only knew a single die casting process until the invention of gravity die casting or the low-pressure die casting process. Everyone started referring to the traditional one as high-pressure die casting (HPDC) with some minor tweaks.
In this article, we discuss high-pressure die casting, its applications, and the advantages it has on offer.
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Definition of high-pressure die casting
HPDC or high-pressure die casting is a process wherein a metal die with a cavity (in the negative shape of the part to be created) is filled with a molten liquid and is sealed. It then follows up by exposing the liquid to high pressure (exceeding 1000 bar) till it solidifies.
How is it different from low-pressure die casting
In low-pressure die casting, the machine operator is responsible for not levying any additional pressure to the molten alloy. In contrast, in HPDC, the alloy is subjected to high pressure resulting in higher dimensional accuracy and thinner walls. HPDC is also faster and can achieve better thickness than its counterpart.
In HPDC, there are two ways to inject the molten alloy into the mold –
In this process, the chamber is in constant contact with the hot metal, and the liquid alloy passes through the valve into the die. Learn more about the process in our article on hot chamber die casting.
In this process, the chamber is kept outside the melt to prevent constant contact with the hot liquid. It uses channels to transfer the same into the dies. Understand the entire process by reading our article on cold chamber die casting.
Application of HPDC
In the current day, HPDC is useful in creating magnesium automotive structural components. It is also ideal for producing a diverse range of products such as engine mounts, cross-car beams, and more. Because of its flexible approach, it finds usage from the easiest to the most complex areas.
The actual HPDC process depends on the output it is trying to create. Nevertheless, it consists of the following elements –
1. Mold preparation
In the first step, the machine operator applies a lubricant to the inner walls of the mold. It creates a film over the walls, helping in easier removal of the cast and better heat management. Then the mold is completely sealed from three sides using clamps and gates.
2. Injecting liquid metal
The molten alloy is injected into the mold at high speed, depending on the type of chamber used. The pressure may range between 1,500 to 25,000 PSI (pounds per square inch). The pressure levels are kept intact until the solidification is complete.
3. Ejecting the cavity
The mold uses ejector pins to eject the cast from the mold post solidification. The operator must be careful about not removing before the metal solidifies completely.
4. Shakeout and polishing
Post ejection, the operator separates the cast and the mold from any scrap. Not everything that he uses is a part of the final product. So he must be careful in removing them all before reusing the mold.
The cast is also checked for finishing. In most cases, it is smooth and doesn’t require additional processes. But if the operator is not happy with its finish, it is sent for polishing to achieve the desired output.
Here are all the advantages of following HPDC for your casting endeavors –
- The output usually has high dimensional accuracy with a smooth surface. It may require drilling in some instances
- HPDC is a cost-efficient process if you are looking to manufacture a lot of homogeneous products
- It is ideal for components requiring thin walls
- It is a fast process and can achieve higher production rates compared to other die casting processes
Even though the upfront costs involved with high-pressure precision die casting are high, it becomes cost-efficient in the long run. But it would help if you remembered these machines have a fixed production run, and you need to replace them once it is achieved. Also, minor factors such as lubricant quantity, composition, and others can impact the final output.
HPDC is a commonly used process useful in many industries. They have been using it to produce a plethora of solid metal products with good dimensional accuracy and accurate composition.
The article is a part of our comprehensive guide on “Die casting: Process, Equipment, Uses, and More”