Five Ways to Improve Aluminum Die Casting Part Quality - 3ERP

Recognized for being incredibly lightweight and durable, aluminum is one of the most popular materials used in the production of functional parts and prototypes. It also offers impeccable corrosion resistance, thermal and electrical conductivity, and also retains dimensional stability even in high temperatures and harsh environments.

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Since this particular metal has such a high melting point, the optimal way to cast aluminum parts is by utilizing the aluminum die casting process. This metal casting process that forces molten metal into a mold cavity under high pressure. Aluminum die casting requires the use of a mold cavity, which is created using two hardened tool steel dies that are machined into a specific shape. With aluminum die casting, a cold-chamber machine is utilized.

Aluminum die casting reduces the amount of steps needed in production and prototyping, ultimately reducing manufacturing costs, while also providing parts with a high quality surface finish and exceptional dimensional consistency. This technique is especially advantageous in small-to-medium sized castings, and is widely used in industries such as automotive, aerospace, medical and more.

However, in order to optimize the part quality in the aluminum die casting process, there are a few critical factors that you should keep in mind. With these tips, you can utilize 3ERP’s professional-grade aluminum die casting services to its fullest potential, while also gaining a better understanding of this extremely popular manufacturing technique.

Understanding All Design Aspects and Geometric Features

Before a designer or engineer can utilize aluminum die casting to its full potential, it’s important that they first understand the design limitations and common geometric features that can be accomplished with this manufacturing technique. Here are some factors that you should keep in mind when designing a part for aluminum die casting.

• Draft – In aluminum die casting, the draft is considered as the amount of slope given to the cores or other parts of the die cavity, which makes it easier to eject the casting from the die. If your die cast is parallel to the opening direction of the die, the draft is a necessary addition to your casting design. If you optimize and implement a proper draft, it will be easier to remove the aluminum die casting from the die, increasing precision and resulting in higher quality surfaces.
• Fillet – The fillet is a curved juncture between two surfaces that can be added to your aluminum die casting to eliminate sharp edges and corners.
• Parting line – The parting line is the point where two different sides of your aluminum die casting mold comes together. The parting line location represents the side of the die that is used as the cover and which is used as the ejector.
• Bosses – When adding bosses to aluminum die casting, these will act as mounting points for parts that will need to be mounted later on. In order to optimize the integrity and strength of bosses, they should have the same wall thickness throughout the casting.
• Ribs – Adding ribs to your aluminum die casting will grant more support to designs that need maximum strength while still maintaining the same wall thickness.
• Holes – If you need to add holes or windows into your aluminum die casting mold, you’ll need to consider the fact that these features will grip to the die steel during the solidification process. To overcome this, designers should integrate generous drafts into hole and window features.

These are just the basics of what you should know when designing for aluminum die casting. If you want to optimize your mold further, you can contact 3ERP’s expert manufacturing team for assistance.

Understanding the Lifespan of Aluminum Die Casting Molds and Tooling

If you decide that aluminum die casting is the right option for your production needs, you should understand the lifespan and maintenance that aluminum die casting molds require. The life of the die is hard to pinpoint because it’s heavily dependant on a number of factors. You’ll want to keep a variety of aspects in mind, including the design of the part, the tool steel used for the die, the mold configuration, heat treatment, the aluminum alloy that is being utilized, the desired part quality and more.

Thankfully, when using 3ERP’s professional manufacturing service for aluminum die casting, our team will help ensure that each of these conditions is met accordingly.

Use Heat Treatment to Extend the Life of Aluminum Die Casting Mold

One of the best ways to extend the life of your aluminum die casting mold is by using heat treatment and die coatings. By applying these techniques, the heat checking will slow down immensely, ultimately extending the life of tooling. Of course, you’ll have to factor in that extra costs of these coatings, and decide whether it’s worth extending the lifespan of the aluminum die casting mold.

When it comes to heat treatment, there are a number of critically important aspects to consider, such as the heat treat furnace used, the number of temperings applied to the die blocks, as well as the quench rate used during the heat treatment processing. At 3ERP, we offer personalized aluminum die casting and heat treatment services that are best-suited for each customer, helping you achieve the perfect balance between affordability and part quality.

Selecting the Right Aluminum Alloy

It’s quite obvious that aluminum die casting molds are created with…well…aluminum. However, the aluminum alloy that is selected is a crucial part of this process. Each alloy type offers distinct mechanical advantages and disadvantages, and the right choice will be wholly dependent on what the function of your part will be. To help you get better acquainted with the available materials, here are a few of the most popular alloys used in aluminum die casting:

• Aluminum Alloy A380 – One of the most commonly used alloys for aluminum die casting, offering exceptional fluidity, pressure tightness and resistance to hot cracking.
• K-Alloy – This specialized material is a cold-chamber die cast alloy that is engineered for use in parts that must withstand harsh environments.
• Aluminum Alloy 383 – When your design is more complex, this alloy acts as a great alternative to A380 as it provides better corrosion resistance and is lightweight.
• Aluminum Alloy B390 – Compared to other available materials, this alloy has high hardness and excellent wear resistance.
• Aluminum Alloy A413 – This easily castable alloy is an ideal option for parts that require excellent pressure tightness, such as hydraulic cylinders.
• Aluminum Alloy DCA1 – This alloy is a perfect choice when you need to manufacture parts with high thermal and electrical conductivity, such as heatsinks.

Consult with Manufacturing Experts About Aluminum Die Casting

Last but certainly not least, if you’re interested in implementing aluminum die casting into your product development process, don’t be afraid to consult with the specialists working at a manufacturing and rapid prototyping service. For instance, at 3ERP, we have experts with knowledge on the best practices regarding aluminum die casting, helping to optimize your part design and quality once it’s finally produced.

If you’re in the process of designing an aluminum part or product by die casting, you may feel overwhelmed by the number of factors to take into account at this stage. After all, perfecting the design phase is one of the most crucial steps in successfully and efficiently manufacturing die-cast products.

Luckily, our experts have extensive knowledge of how to design for optimum aluminum die casting production, and this article will give you some insight into what they know. We will cover how to design a product for efficient and effective manufacturing, as well as some of the most common considerations you need to take into account when designing a product to be made through die casting.

Aluminum Casting Design Best Practices: Design for Manufacturing

Design for Manufacturing (DFM) is a term often used in engineering. It refers to the process of optimizing production to make it as simple and cost-effective as possible. DFM focuses heavily on the manufacturing methods and processes used.

One of the main advantages of DFM is that it allows problems with the production method to be detected and solved early on in the design phase. At this stage, issues are much less expensive to resolve than when they are discovered during or after the production run. Applying DFM techniques allows for a reduction in the costs of manufacturing while maintaining a good or better standard of quality.

In order to optimize the production process of aluminum die casts, the following objectives should be targeted:

1. Use the least amount of casting material possible,
2. Ensure that the part or product will easily come out of the die,
3. Minimize the solidification time for a casting,
4. Reduce as much as possible the number of secondary operations, and
5. Ensure that the final product will perform as required.

The best way to meet these optimization objectives is to take into account the design considerations discussed in the following sections during the design phase.

9 Aluminum Die Casting Design Considerations to Keep in Mind

This section gives you an introduction to some of the most common considerations when designing a product to be made using die casting. These tips align with DFM best practices and are recommended by the North American Die Casting Association.

1. Parting line

As you already know from our previous article, the die casting process involves a die that is usually divided into two halves (although it can be divided into more), one of them mobile and the other static, that come together to form the mold where the molten metal will be injected. The parting line of a die-cast component is the interface where the two halves of the die come together.

During the design process, choosing where the parting line will be positioned is one of the first things you have to decide, as it has an effect on other design specifications.

An important aspect of the location of the parting line is that it will also be the place where a common die-casting defect, known as flash, will be located. The flash has to be removed by a secondary process after the cast has solidified, which is why it should be designed to be easily accessible by the trimming machinery.

2. Shrinkage

Shrinkage is a very common and unavoidable phenomenon that happens in most castings, and aluminum is no exception. As the molten metal starts to cool down from melting temperature to room temperature, the cast will shrink towards its center.

Castings commonly shrink between 0.4-0.6% of their volume, which can help the product to be ejected from the external walls of the die. Unfortunately, it can also constrict around any internal protrusions on the mold, making ejection difficult under those circumstances. In these situations, you can make use of a draft to reduce shrinkage and facilitate easier removal of the cast.

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3. Draft

In the context of die casting, a draft is a small taper or inclination that can be seen on the sides of the mold that allow for easy ejection. You might have seen this taper in other kinds of molds, such as baking pans for muffins and bread, where the sides have a slight angle instead of being completely vertical.

This draft has to be included in all cast surfaces that are parallel to the movement of the die, as this will facilitate easier ejection. Failure to include it can cause the cast to be very difficult, if not impossible, to remove without damaging it.

Keep in mind that the amount of draft, expressed in either millimeters or degrees, will vary considerably throughout most designs. For example, outside walls require only a relatively small draft as the cast shrinks away from them, but inside walls and holes require a larger draft as the metal shrinks and grips around them.

4. Wall Thickness

In order to ensure rapid production, reduce material waste, and create a successful product, wall thickness has to be carefully considered.

A wall design that is too thin could prevent an adequate flow of the molten metal, making the metal solidify before the mold is completely filled. Thin walls can also be susceptible to warping when post-mold machining forces are applied. Excessively thick walls, on the other hand, not only waste casting material, but they increase solidification times, potentially eliminating the fast production cycle advantage of high-pressure die casting.

Wall thickness should also be as uniform as possible. This allows the molten metal to flow easily, which is essential for having an effective solidification process that ensures optimal cast strength and reduces the possibility of cast defects. If variations in thickness are necessary, gradual transitions should be used instead of sudden changes.

5. Fillets and Radii

Fillets and radii are curved junctures between two surfaces that would otherwise create a sharp edge. The following image shows an example of a part that incorporates each of these features. The key difference is that fillets exist on the internal edges of the part while Radii are found on the external edges.

These rounded edges are extremely important in die casting design, as having them allows the metal to flow easily when injected. Sharp corners in the die create turbulence in the metal flow, which can reduce the strength of the cast component. Radii can also eliminate the need for trimming sharp corners and edges through a secondary operation.

6. Bosses

Bosses are protruding features of cast products that are normally used as standoffs or mounting points. This video displays a good visual for what a boss is by showing a boss being added to a doorknob. Including bosses in your design can prevent the need for time-consuming boring operations as a secondary process.

Since major changes in wall thickness can cause uneven shrinkage and sinking that negatively impact a part’s appearance and even its integrity, bosses must be designed to maintain a uniform wall thickness relative to the surrounding part. A common method for maintaining a uniform wall thickness is to add a hole to the center of the boss.

You should also consider adding ample fillets at the location where the boss connects to the rest of the cast, to allow for proper metal flow. A proper draft angle must also be considered for bosses, as well as ribs to increase its strength.

7. Ribs

Ribs are small bridges of material that can be added between walls to increase their strength without adding too much metal. They also help molten metal to reach every part of the die by increasing the available flow pathways.

The image below shows a cast aluminum product that includes a boss which will be used for mounting, and three ribs connected to an outer wall, which increases the structural soundness of the boss.

In accordance with best practices, ribs are usually added to a design in odd numbers or are otherwise offset from one another in order to prevent stresses impacting ribs that are adjacent to each other.

The image above shows an example of a design with an even number of ribs, going against best practices.

8. Undercuts

Undercuts are known in manufacturing as recessed surfaces that cannot be accessed with a straight tool. The nature of undercuts can prevent die separation and cast ejection after solidification as the die will be essentially “gripping” the cast product, which is why careful design is important.

The following image shows a component with and without an undercut. You can see that the figure on the right has a depressed surface where the small and big cylinders connect which would make it impossible to eject from the die.

If an undercut is essential to your design, you can design your parting line around the undercuts. Another method is to use dies that are made up of more parts than just the core and cavity, like in the following animation, or by using semi-permanent molds.

These methods, however, increase the cost and complexity of the die considerably. Additionally, semi-permanent milds, which include the use of sand cores, cannot be used in high-pressure die casting processes.

9. Holes and Windows

Accounting for the holes and windows needed in a final die cast part during the design phase can significantly reduce the amount of post-molding machining required. Eliminating or minimizing drilling, milling, and other machining activities wherever possible by thoughtful mold design can drastically improve manufacturing times.

Holes and windows have the added benefit that they generally do not introduce too many new challenges when incorporated into a design. However, you should still take into account that they will make the molten metal flow more complex, which could lead to turbulence and potential casting flaws associated with turbulence. Adding fillets and radii to any edges on holes and windows can help mitigate this issue.

It is also important to remember that holes and windows in the cast can grip the die during ejection, meaning you have to incorporate drafts around them during the design phase.

Conclusion

As you have now seen, designing for aluminum die casting presents many challenges. This article gives you an idea of some of the most important aspects that have to be considered during the design stage, though it’s possible that you may encounter even more obstacles impacting your specific project.

In this article, we’ve briefly touched on secondary, or post-molding, operations as an aspect of die casting design, particularly since minimizing them is a good way to optimize the manufacturing process. To get a better understanding of what they entail, what applications they are relevant for, and more view our article on secondary operations for die cast parts.

Are you interested in learning more about Die Casting Services? Contact us today to secure an expert consultation!