What is Die Casting?

How Does Die Casting Work?

The die casting process involves several steps, including mould design, metal preparation, injection, casting, and finishing.

Step 1 – Mould Design

The initial step in the die casting process is creating a mould called a die. This mould is usually made from steel or aluminium and is designed to withstand the high temperatures and pressures of the die casting process. 

The mould design begins with developing a CAD design of the required mould. This design is then used to create a mould by CNC machining, which is further used in the casting process.

Step 2 – Metal Preparation

The next step is to prepare the metal for injection. This metal is typically an alloy, such as aluminium, magnesium, or zinc. The metal is melted in a furnace and then poured into a ladle.

Step 3 – Injection Process

Once the metal is in a liquid state, it is injected into the mould under high pressure. The molten metal fills the mould cavity and cools to create the desired shape.

Step 4 – Casting Process

After the metal has cooled and hardened, the mould is opened, and the part is ejected. Ensure that the part has cooled entirely before handling to avoid any potential injuries.

Step 5 – Finishing Process

The final step in the process is to finish the part. Surface finishing plays a vital role in die casting, as it can impact the durability and function of the part. Standard finishing processes include anodizing, powder coating, wet plating, and many more.

Types of Die Casting

Die casting encompasses several distinct processes, each designed to meet specific manufacturing needs based on factors like material type, production speed, and part complexity. The most common die casting methods are hot and cold chamber die casting, but there are additional variations such as vacuum, gravity, high-pressure, and low-pressure die casting. Below is an overview of the key types of die casting, including their suitable materials and typical applications.

Cold chamber die casting is a process in which molten metal is manually ladled into an unheated injection chamber, then injected into the die at high pressure using a hydraulic piston. The cold chamber process is typically used for metals with higher melting points, such as aluminum, magnesium, and copper alloys, as these metals could damage the machinery used in hot chamber die casting.

Hot Chamber Die Casting

In hot chamber die casting, the machine contains a built-in furnace that melts the metal, which is then injected directly from the furnace into the mold. A gooseneck mechanism submerged in the molten metal fills with the material and then injects it into the die under pressure. The hot chamber process is ideal for metals with lower melting points, such as zinc, tin, and lead alloys, because the molten metal is continuously supplied to the machine.

Vacuum Die Casting

Vacuum die casting is a variation of the high-pressure die casting process where the air is evacuated from the die cavity before the molten metal is injected. The vacuum reduces or eliminates trapped gases in the final casting, which leads to improved part density and mechanical properties. The vacuum process also helps reduce porosity, making it an ideal choice for parts subjected to high stress or pressure.

Gravity Die Casting

Gravity die casting, also known as permanent mold casting, involves pouring molten metal into a metal mold (or die) using only the force of gravity. The metal flows into the mold and fills the cavity before cooling and solidifying. No external pressure is applied, and the metal flows into the mold purely by gravity. This process is typically used for simpler parts and offers better mechanical properties than sand casting.

High-Pressure Die Casting

High-pressure die casting is one of the most widely used die casting processes. In this method, molten metal is injected into the die at very high pressure (usually 10-175 MPa) using a piston or plunger. This high pressure ensures that the molten metal fills all areas of the mold, resulting in highly precise and detailed parts with smooth surface finishes. The process is fast, highly automated, and suitable for large production runs

Low-Pressure Die Casting

Low-pressure die casting is a process where molten metal is slowly forced into the mold under low pressure (0.1 to 1 MPa) from a holding furnace located below the die. The metal is pushed into the mold through a riser tube, ensuring a smooth and controlled filling of the cavity. This process minimizes turbulence and gas entrapment, resulting in higher-quality parts with fewer defects. Low-pressure die casting is commonly used for large components like aluminum wheels, engine components, and structural parts, where structural integrity and dimensional accuracy are crucial.

When starting your die casting project, one of the most critical decisions is selecting the right material. The material must be capable of withstanding the high temperatures and pressures inherent in the die casting process, while also meeting the functional and performance requirements of your end-use application. Additionally, it’s crucial to select a material that is compatible with the specific die casting method you plan to use, as different processes may suit particular metals better.

Given the complexity of these factors, working with an experienced die-casting partner can help ensure that you make the best decision based on your project’s unique needs. Among the wide range of materials available, aluminum, magnesium, and zinc alloys are the most commonly used due to their strength, lightweight properties, and versatility.

Below is a comparison of these commonly used die casting materials, along with key characteristics and common applications.

Advantages of Die Casting

When it comes to mass-producing metal parts, die casting is one of the most efficient and cost-effective methods. It’s a process that has been around for centuries, but its popularity has grown in recent years as manufacturers seek ways to reduce production costs.

Here are some of the advantages of die casting:

• Complex shapes: Die casting is a process that can produce complex shapes with tight tolerances
• Versatility: The process is versatile and can be used to cast a variety of metals, including aluminium, zinc, and magnesium
• High production rate: It is a relatively fast process, which can be an advantage when time is of the essence
• Cost-efficient: The process is also relatively inexpensive, making it a cost-effective option for many applications
• Repeatability: It also allows for a high degree of repeatability, meaning that parts can be manufactured to precise specifications.

Applications of Die Casting

Die casting is used in a variety of industries and applications. Some of the most common uses for die casting include:

• Automotive industry: Die casting is used extensively in the automotive industry. It’s often used to create engine blocks, cylinder heads, and transmission cases
• Electrical industry: The electrical industry also relies on die casting for a variety of applications. Die-cast parts are used in the manufacture of electrical components such as switchgear, panel boards, and circuit breakers
• Aerospace Industry: The aerospace industry is a major user of die casting. The manufactured parts are used in the manufacture of aircraft and spacecraft components
• Appliance Industry: The appliance also uses this process to manufacture die-casted parts for many appliances
• Furniture Industry: It is also used in the furniture industry. It’s often used to create furniture hardware such as drawer pulls and knobs

Many other industries use die-casting processes for medical, construction, and toy industries. It is a versatile process that can be used to create various parts and products.