Die Castings

What is Die-casting?

The process of die-casting begins with a liquid aluminium or zinc alloy, or magnesium being injected into a mould called a die. This is process is under high pressure, ensuring that the material takes the shape of the interior of the die. This creates a strong and uniform product.

The majority of applications can be satisfied using aluminium alloy which forms the basis for a variety of products used within the lighting, medical,  automotive, defence, marine, structural and architectural, electronics, consumer appliance, and complex machinery industries.

Aluminium alloys are a combination of aluminium and varying compositions of silicon, copper, zinc, or magnesium. The ratio of each of these other materials presents different properties depending on what product is required and how durable or flexible the product needs to be.

ADC12 is one of the more popular aluminium alloys with the main alloying elements of silicon, copper, and magnesium. With these alloying elements, ADC12 has several advantages; relatively lightweight, increased flowability, stability in complex shapes, corrosion resistance, high thermal conductivity, and increase wear resistance.

What is the Die-casting Process?

The process generally follows these three steps:

1 – Designing and Producing the Die

A die is created from steel alloy and is designed to ensure the correct injection of the moulten material and removal of the finished product. Each die consists of two, or more, parts that are brought together during the casting process and then separated once the material has cooled sufficiently for the product to be released.

More complex shapes will require a die with many parts to create specific shapes, holes, etc. One part of the die will include a sprue hole where the aluminium is injected to fill the three-dimensional cavity inside.

Dies can be reused many thousands of times (hits), although the specific number of times will depend on the product design, the type of alloy used, and the required level of quality of the part being produced. Dies can have a number of cavities to produce more than one of the same item or perhaps left and right-handed options.

Once the die tool is installed into the die-casting machine, its sections are lubricated, using a water-in-oil emulsion, and clamped together to prepare for filling.

2 – Injecting the Material

The moulten material is injected into the die under high pressure; between 1,500 and 25,400 psi. This ensures the material quickly moves around and adheres to all the details of the die, as this step of the process only takes a few seconds.

3 – Cooling the Material

After being cast, the die stays closed as the material cools. Cooling allows the material to solidify as a single solid component. After cooling, the die is separated to reveal a product of the exact profile of the die.

The Advantages of Aluminium Die-casting

Many of the positive characteristics of aluminium die casting come from the properties of aluminium itself. Die-casting takes advantage of aluminium’s many assets to easily manufacture useful products with high longevity. Such benefits include:

Aesthetic Design: Die-casting lends itself to component designs that cannot be reproduced using other forms of production. Complex shapes, produced quickly, make die-cast products very cost-effective and the perfect solution for aesthetic and architectural applications.

Customisation: The high-pressure process easily moulds aluminium into complex and detailed forms. Using aluminium also allows for variations in the wall thickness of parts, so, within reason, products can be created as thin or as thick as required.

Weight and Strength: Aluminium is an incredibly strong metal, even at low temperatures. It is also lightweight, making it the perfect material for durability and ease of use. This is especially true of products with thin walls because aluminium can withstand pressure even within a lightweight frame. Additionally, die-casting often eliminates the need for a part to be assembled using fasteners or fixings. With a product cast as one piece, its strength comes from the alloy and is not limited by potentially weak joints.

Higher productivity: Aluminium is easy to work with, making it faster to manufacture parts from aluminium rather than other metal alloys. The pressure and speed with which the aluminium is injected into the die quickens the overall process and requires less machining than other casting processes.

Resistance to Corrosion: Aluminium atoms have a high affinity for oxygen. As soon as aluminium, or its alloys, come into contact with the atmosphere, the aluminium atoms bond to oxygen, forming a protective outer layer of aluminium oxide. When aluminium oxide contacts water, its chemical structure changes so it is unable to react with the water, and therefore does not rust. Aluminium’s corrosion-resistant capabilities are important to consider for die-cast products that may be used in environments where other metals would be prone to rust, such as Automotive, Marine, and Defence equipment.

Cost-efficiency: The ease with which aluminium can be worked, and quickly die-cast into a variety of complex forms, means that a higher number of products can be produced in a shorter time frame which leads to cost-effective production.

Thermal and Electrical Conductivity: Heat and electrical current easily flow through aluminium. For this reason, aluminium can be used to produce a variety of electrical products, such as automotive and commercial lighting heat sinks and fixtures.

Dimensional Stability: Die-cast aluminium products reliably maintain their shape and structure from the end of the die-casting process and throughout the product’s application.

The Disadvantages of Aluminium Die-casting

The main disadvantage to die-casting is the initial high capital cost. Both the equipment required and the die tools are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process, a large production volume is usually required.