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When you're in the process of designing an aluminum part, it is essential to consider which manufacturing process you'll use to produce it. There are various methods for forming aluminum, and aluminum die casting is one of the most common options for designers to consider.
Aluminum die casting is the method of choice for many automotive, industrial, and telecommunications products. It's also often used to produce electrical, hydraulic, and lighting components.
If you would like to know more about the aluminum die casting process and would like some help deciding if it is the right choice for your application, you're in the right place.
Table of Contents
What is Aluminum Die Casting? The Process Explained
1. The Top Considerations During Part Design
2. The Advantages of Aluminum Die Casting
3. Options for Machining and Finishing
4. How it Compares to Green Sand and Permanent Mold Casting
5. The Most Common Aluminum Die Casting Alloys
Aluminum die casting is a metal-forming process that allows for the creation of complex aluminum parts. Ingots of aluminum alloy are heated to very high temperatures until they are entirely molten.
The liquid aluminum is injected under high pressure into the cavity of a steel die, also known as a mold — you can see an example of a mold for automotive parts above. The die is made up of two halves, and after the molten aluminum has solidified, they are separated to reveal the cast aluminum part.
The resulting aluminum product is precisely formed with a smooth surface and often requires minimal or no machining processes. Given that steel dies are used, the process can be repeated many times using the same mold before it deteriorates, making aluminum die casting ideal for the high-volume production of aluminum parts.
A few considerations have to be taken into account when designing the part to be cast.
Firstly, the mold must be designed to separate and allow the solidified aluminum part to come out. The line that marks where the two halves of the mold come apart is referred to as a parting line, and you have to consider it in the early stages of die design.
Another important consideration is the location of injection points. The die can be designed with several injection points in cases when the molten metal would otherwise solidify before reaching every crevice in the die. This can also help if cavities are included in the design; you can surround them with aluminum and still have the part come off when the mold is separated.
You must also consider the thickness of the part's walls. There are usually no guidelines for a minimum wall thickness, thanks to recent technology developments, but having walls with consistent thickness is often preferred.
Die casting aluminum offers several advantages over other metal-forming processes that might make it the appropriate choice to create your aluminum parts.
One of the most noteworthy is the ability to produce very complex shapes that neither extrusion nor machining can effectively create. A perfect example of this is the production of complex automotive parts, like transmissions and engine blocks. Other processes cannot consistently achieve the complexity and tight tolerances required for these products.
Additional advantages include the ability to have textured or smooth surfaces and the capacity to accommodate both large and small parts.
Die cast aluminum parts often require minimal machining, and several options are available for surface finishing. Die casting has a very good surface finish by casting standards but can still have imperfections, like metal seams where the mold halves meet. A rough surface or other imperfections inadequate for the part can be addressed by sanding, sandblasting, or orbital sanding.
The cold working process of shot peening is often used on die cast aluminum to improve fatigue resistance. Alternatively, a protective or decorative coating can be applied to the finished part, such as a powder coat. Other types of modifications can also be applied to the parts after casting, such as drill tapping.
Green sand and permanent mold are two common alternative casting processes to aluminum die casting. Green sand processes use wet sand to create the mold for the cast, making it less expensive than the other two processes. Above, you can see an operator pouring molten metal into a sand cast mold.
Unlike die casting, which uses injection, permanent mold castings require the molten aluminum to be gravity poured into the mold. Permanent mold castings can also potentially produce stronger casts.
Nevertheless, die casting offers better tolerances and better-finished surfaces than the other two methods, often eliminating the need for subsequent surface treatment.
A few of the most commonly used aluminum alloys for die casting are A380, 383, B390, A413, A360, and CC401. The primary consideration when choosing an appropriate alloy is your intended application.
For example, A360 offers excellent corrosion resistance, pressure tightness, and very good fluidity when molten. B390 offers outstanding wear resistance and high hardness while having the lowest ductility of all cast alloys, which is why it is used for applications such as automotive engine blocks. Alloy A380 is the perfect jack-of-all-trades, offering a good combination of casting and product properties, and is the most commonly specified alloy for casting a wide variety of products.
At the end of the day, the metal-forming process you choose will depend on your budget, the purpose of your aluminum part, and how many parts you want to manufacture. Die casting can be an expensive method, but it's worth it if your design has high complexity and you require a high volume of parts. Goalsure are happy to answer any questions you have about the die casting process and how it works for you.
Every die casting project is different, and we treat your order with due care and individuality. Contact us now to get a free suggestion for your next custom aluminum molds project.