If you want to design an aluminum part or component, then it is important to consider the type of manufacturing process that you will need in producing it. There are different ways of forming aluminum, and one of the most common options to consider is aluminum die casting. For most industrial, automotive, and telecommunications products, aluminum die casting is the preferred method. Most often, it is also used for hydraulic, electrical, and lighting components.

If you need more information about the aluminum die casting process and need some help in deciding if it is the appropriate method for your application, then you are in the right place.

An Explanation of Aluminum Die Casting

Aluminum die casting refers to the metal-forming process that allows for the production of complex aluminum parts. Molds of aluminum alloy are heated in extremely high temperatures until they are completely molten. The liquid form of aluminum will be embedded into the mold (the cavity of a steel die) under high pressure. The die is composed of two halves, and once the molten aluminum has turned into a solid, they are separated from each other, exposing the cast aluminum part.

The produced aluminum product is accurately created with a smooth surface and often needs a small amount or no machining processes. Provided that steel dies are utilized, the process can be repeated several times with the use of the same mold before it gets damaged. This means that aluminum die casting is the perfect process for the high-volume production of aluminum parts.

Important Things You Need to Know About Aluminum Die Casting

The Benefits of Aluminum Die Casting

Die casting aluminum provides a lot of benefits compared to other metal-forming processes, making it the appropriate choice when generating aluminum parts.

One of the most evident is its capability to generate very complicated shapes that can neither be created effectively by machining nor extrusion. One of the best examples of this is the creation of complicated automotive parts including engine blocks and transmissions. Other methods cannot consistently accomplish the tight tolerances and complicatedness needed for these products. Additional benefits include its capacity to produce both small and large parts, as well as its capability to produce smooth or textured surfaces.

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Major Concerns Of Part Design

There are a few factors that need to be considered when it comes to designing the part that needs to be cast.

First, the mold should be designed in such a way that it can be separated and permits the solidified aluminum part to be removed effortlessly. The line that indicates where the two halves of the mold will be separated is also known as the parting line. It is important to consider this, especially during the early stages of die design.

Another important factor to consider is the location of injection points. You can customize your die in such a way that there are numerous injection points, especially when the molten metal has the tendency to solidify prior to reaching every gap in the die. This can be very helpful when there are craters in the design. This means that you can fill them with aluminum and can take off the part when the mold is separated.

It is also important to consider the denseness of the part’s walls. Typically, there are no guidelines when it comes to the minimum wall thickness due to the latest technology developments, however, it is always favorable to have a constant thickness.

What Makes It Different from Permanent and Green Sand Mold Casting?

Two of the common alternatives to aluminum die casting are permanent and green sand mold. Green sand process is less expensive compared to the other processes since it uses wet sand in making the mold for the cast. The molten metal will be poured into a sand cast mold.

In contrast to die casting where the molten aluminum is injected, with permanent mold castings, it will be gravity poured into the mold. Permanent mold castings can likely generate stronger casts. However, die casting provides better-finished surfaces and better tolerances compared to the other two methods, and there is usually no need for consecutive surface treatment.

Options for Finishing and Machining

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Oftentimes, die-cast aluminum parts only need minimal machining, but there are various options for surface finishing. Parts that are made from die casting have an excellent surface finish based on casting standards. However, it is still possible that there are imperfections such as metal seams that appear on the location where both mold halves meet. If there are rough surfaces or any other imperfections on the part, then this can easily be addressed by sandblasting, sanding, or orbital sanding.

Most often, to improve fatigue resistance on die-cast aluminum, the cold working method of shot peening is used. Another alternative is to apply a decorative or a protective coating on the finished part, for instance, a powder coat. Nevertheless, there are also other types of modifications that can be used on the parts after casting including drill tapping.

The Most Popular Aluminum Die Casting Alloys

Some of the most popularly used aluminum alloys for die casting include A380, 383, A413, A360, B390, and CC401. When it comes to selecting the right alloy, the main consideration is your intended application.

For instance, when A360 is molten, it provides superior corrosion resistance, excellent fluidity, and pressure tightness, while B390 provides extreme hardness and extraordinary wear resistance while offering the least ductility of all cast alloys. That is why it is used for several applications, including automotive engine blocks. On the other hand, Alloy A380 is the ideal jack-of-all-trades, providing an excellent combination of product and casting properties. It is also the most used alloy for casting different varieties of products.

What is a Mold?

A die casting mold is composed of two halves which form a cavity. Usually, this is created from heat-resistant, high-quality steel grades. The liquid melt will be poured into the cavity, then pressed appropriately during the casting process. The halves are placed on a movable and fixed machine plate. While the casting process is done, extreme pressure will be used on the mold halves; this is the reason why the mold includes latches.

Additionally, there are specific parts of the mold that are heated or cooled so that the casting can be solidified as needed. Producing the molds can be time-consuming as well as very expensive. However, plenty of castings that can be generated by using just one of these molds. Another benefit of a reusable casting mold is that the molten liquid can cool down quickly.

Procedures and Functionality

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When it comes to die casting, there are two various ways of producing the components, either through the cold chamber or hot chamber die casting. In both processes, a release agent will be sprayed on the mold before the casting process will start. This can guarantee that the successive cast part can be easily removed from the mold.

Nevertheless, the melted liquid will not be directly poured into the mold cavity, but rather, it will be poured into the casting chamber that is found in the die casting machine. Then, a piston will be used in pressing the alloy into the mold via one or more channels. These two processes differ based on the structure of the casting chamber.

Hot Chamber Die Casting Process

One of the distinctive features of a die casting machine for a hot chamber is that the casting chamber is consistently connected with the liquid alloy. The melt will go through a valve then into the casting chamber, where high speed will be used in pressing it into the closed die casting mold with the use of a piston. This process is commonly used for alloys that have low melting points including tin, lead, or zinc.

Cold Chamber Die Casting Process

A die casting machine for a cold chamber is designed in such a way that the casting set is placed outside the melt. To manufacture a component, the alloy is poured into the casting chamber. Afterward, it will be pressed into the die casting mold via its channels. This method is more appropriate for materials having a higher melting point including copper and aluminum.

For both processes, once the alloy has already been pressed into the mold, then the component will be solidified using extreme pressure. As a result, the latches of the mold will be opened. The portion with a gate will be taken out from the mold through automatic ejector pins and could be processed further when needed. To put it simply, the casting process can be separated into various steps, and the process will only take hundredths or thousandths of a second:

  • Filling the alloy into the casting mold.
  • Processing the component under high pressure.
  • Separating the mold and taking out the component.

Conclusion

Ultimately, the process that you choose when metal forming will likely depend on the intention of your aluminum part, your budget, as well as the number of parts that you want to produce. Die casting could be a costly method, however, it is well worth it if you have a highly complicated design, and you need a large volume of parts.

SEI Castings offer custom castings, enclosures, and many more. For more information about our products, you may email us at sales@seimw.com.