Designing an aluminum component or product can be overwhelming, considering the various factors involved in the process. One of the crucial aspects of creating die-cast products efficiently and successfully is perfecting the design. Fortunately, this article offers insights into designing optimal aluminum die casting products. We’ll provide tips on designing components for effective manufacturing and discuss important considerations for designing products intended for die casting.

Best Practices for Designing for Manufacturing

Design for Manufacturing (DFM) is a term commonly used in engineering circles. Essentially, it involves optimizing production to ensure that the product is manufactured in a simple and cost-effective manner. DFM focuses primarily on manufacturing processes and methods. One of the key benefits of DFM is the ability to detect and resolve production issues during the design phase.

Addressing issues at this stage is more cost-effective than identifying them during or after manufacturing. Implementing DFM techniques enables cost reduction while maintaining product quality. To optimize the manufacturing of aluminum die casts, several key objectives should be emphasized:

1. Minimize casting material usage whenever possible.
2. Ensure easy removal of the product or component from the die.
3. Reduce solidification time for casting production.
4. Minimize the need for secondary operations.
5. Ensure the final product functions as required.

To achieve these optimization goals, certain factors must be considered during the design stage.

Shrinkage

Shrinkage is a common issue in castings, albeit unavoidable. As the molten metal cools, the cast product tends to shrink towards the center. While shrinkage assists in removing the product from the die, it can also impede ejection due to restrictions caused by interior bulges on the mold. Drafts are used to mitigate shrinkage and aid in easy cast removal during such circumstances.

Draft

In die casting, draft refers to the slight taper or inclination on the sides of the mold, facilitating easy cast removal. This taper is akin to what you might observe in baking pans, where the sides have a slight angle rather than being completely vertical.

Drafts must be applied to all cast surfaces to ensure easier ejection. Failure to include draft can make cast removal difficult and may result in damage. Draft is typically expressed in degrees or millimeters, and its amount may vary throughout the design.

For example, exterior drafts are usually smaller as the cast shrinks away from them, whereas interior drafts are larger since the metal shrinks around them.

Parting Line

The die casting process involves a die typically divided into two halves: one static and the other movable. When combined, they form a mold into which molten metal is poured. The parting line denotes the interface where these two halves meet.

During the design phase, determining the parting line’s location is crucial as it significantly affects other design specifications. When selecting the parting line’s position, consideration must be given to the location of a common die-casting defect, known as flash.

After the cast has hardened, the flash is removed during secondary processing. Thus, it should be situated where trimming machinery can easily access it.

Wall Thickness

Wall thickness must be carefully considered to minimize material waste, ensure efficient production, and achieve product success. Excessively thin walls can impede the smooth flow of molten metal, leading to premature solidification before the mold is completely filled.

Thin walls may also be prone to warping under post-mold machining pressure. Conversely, overly thick walls result in excessive waste casting material and longer solidification times.

Uniform wall thickness promotes smooth molten metal flow, efficient solidification, optimal strength, and minimized casting defects. If variations in wall thickness are necessary, transitions should be gradual rather than abrupt.

Fillets and Radii

Fillets and radii are curved connections between surfaces, with fillets on the inside edges and radii on the outside edges. These curved edges are crucial in die casting design, facilitating smooth molten metal flow inside the mold.

Sharp corners in the die can disrupt metal flow and weaken the cast product. Radii also eliminates the need for cutting sharp edges and corners in secondary processes.

Bosses

Bosses are protruding features on cast components used as mounting points or standoffs. Including bosses in cast design can eliminate the need for boring operations as secondary processes.

Uneven wall thickness resulting from extensive changes can cause sinking and uneven shrinkage, compromising part appearance and integrity. Bosses should be designed with even wall thickness relative to the part.

Creating a hole in the middle of the boss ensures uniform wall thickness. Additionally, adding fillets where the boss connects to the rest of the cast promotes smooth molten metal flow. Accurate draft angles for bosses and ribs enhance strength.

Ribs

Ribs can help in adding more strength to the product without the need to use too much metal. It comes in the form of small bridges of material that are usually added between walls.

Additionally, they can also help the metal reach all the corners of the die by creating more flow pathways. In some aluminum parts, the boss will be used as a mounting, while the ribs will be linked to the outer wall, providing more structural strength to the boss.

The best practice is to add ribs to the design in odd numbers or make sure that they offset from one another to help in preventing any stress affecting ribs that are placed adjacent to each other.

Undercuts

Also known as recessed surfaces, undercuts cannot be accessed using a straight tool. The essence of undercuts can prevent cast product from ejecting after hardening since the die will grip the cast. Consequently, it can also prevent die separation.

This is the reason why it is important that the design should be done carefully. In case the design requires an undercut, then make sure that the parting line is placed around the undercuts. Another solution would be to use dies that are made up of several parts compared to having just the cavity and core or you could also use semi-permanent molds.

However, it is important to keep in mind that these methods could likely increase the complexity and cost of the die. Furthermore, it is impossible to use semi-permanent molds, which requires the use of sand cores, in high-pressure die casting processes.

SEI manufactures custom aluminum die cast products. If you need assistance with your aluminum die casting project, then you may contact us at sales@seimw.com.