What Is Die Casting
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter, and tin-based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
Advantages of Die Casting
Short Lead Time
A typical casting cycle of a die casting process is very short. In fact, depending on size and material properties, it can be as low as a few seconds only.
Good Mechanical Properties
While not as strong as forged parts, die casting yields excellent mechanical strength. It can yield parts with enhanced durability, hardness, and conductivity as well.
Excellent Precision
Die casting offers tighter tolerances than most other manufacturing techniques. Thus, it is suitable for many delicate applications.
Economical
Die casting is very economical for large batches of production. With time, the cost per part becomes surprisingly low.
Complex Details
You can manufacture complex parts in a very short period with die casting.
Superior Finishing
You can design Die casting parts to have a smooth or textured finishing according to your requirements.
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What Are the Applications of Die Casting
Some examples of die-casting applications are listed below:
Aerospace: A wide range of engines, seating, interior fitting, cockpit control, and other parts are die-cast in aluminum.
Toys: Many toys were formerly manufactured from die-cast zinc alloys such as ZAMAK (formerly MAZAK). This process is still widely used despite plastics taking over much of the sector.
Automotive: Many ICE and EV car parts are made by automotive die casting: major engine/motor components, gearbox/differential housings, vehicle wheels, thermostat housings, suspension parts, interior strength members, and more.
Electronics
Enclosures, heat sinks, hardware.
Military
Vehicle, weapon, and system components.
Furniture
Chair legs, decorative parts, joiners.
Consumer
Product heat-distribution chassis, enclosures, decorative and structural parts.
What Materials Are Used in Die Casting
The materials used in die casting include a wide range of alloys. Some examples include:
Magnesium
Magnesium alloys are widely used for lightweight and high-strength parts. There are limitations in the processing, but magnesium alloys can achieve among the thinnest sections in die casting, because of very low viscosity in the melt.
Zinc
Zinc is very widely die-cast for many lower-strength applications. Zinc and commercial alloys it is a major constituent of are low-cost, easily cast, and sufficiently strong for many components such as enclosures, toys, etc.
Copper
Copper is not widely used in die casting, as it has a tendency towards cracking. It requires a high melt temperature, creating increased thermal shock in the tooling. When it is die-cast, it requires careful handling and a high-pressure process. For more information, see our guide on Copper.
Pewter
Pewter is a soft alloy, mainly tin, with antimony and traces of copper and bismuth. It is used purely for decorative objects and die casts easily in low-pressure equipment.
Aluminum
Aluminum alloys are by far the most important materials in volume die-cast production. They respond best to a hot chamber and high pressure—or more recently vacuum die casting—and provide moderate to high strength and high precision parts. Aluminum alloys are still critically useful in lower-tech processes, too.
Lead
ROHS has resulted in a significant reduction in the use of lead parts. They, however, remain critically important in the manufacture of (ICE) automotive battery parts, particularly terminals. Much development in lead die casting has improved overall automation and process speeds—developments that have fed through to other materials processing.
Tin-Based Alloys
Tin-based alloys impose very low wear and stress on tools due to low viscosity and melting point. While high-tin alloys (other than pewter) are rarely used now, the need does arise and specialists exist to serve in this.
How Does Die Casting Work
The die casting process involves several steps, including mould design, metal preparation, injection, casting, and finishing
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.
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.
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.
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.
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
There are several different types of die casting, each of which has unique benefits. The two most common types of die casting are cold chamber and hot chamber.
Cold chamber die casting
In this type of die casting, the molten metal is injected into the mould cavity using a cold-chamber machine. This machine is typically used to cast metals with high melting points, such as aluminium. The main advantage of cold chamber die casting is that it can be used with various metals and reduces machine corrosion.
Hot chamber die casting
Hot chamber die casting is the most popular method and is relatively faster than cold chamber die casting. A hot-chamber machine is used to perform this process in hot chamber die casting. This machine generally uses metals with a lower melting point, such as zinc.
Both hot chamber and cold chamber die casting offer high accuracy and precision. In addition, both processes are relatively fast and cost-effective.
What are the Most Common Metals Used in Die Casting
The same rule of＂material selection＂applies to every fabrication industry i.e., the quality of the material selected determines how good the final product will be. Just like how you need to ensure that you make the right decision in your plastic material selection for injection molding, so also must you select the right metal material for die casting.
There are different metals from which you can choose for your die casting project. Below are the most common metals used in die casting.
Aluminum Die Casting
Aluminum is one of the favorite metal options used in die casting. It is a light metal suitable for making lightweight parts without compromising strength. It's easy to cast and it provides better finishing options.
Aluminum is an extremely corrosion-resistant metal that contributes to the increased longevity and safety of components. In addition, the toughness and the strength-to-weight ratio are unrivaled.
Zinc Die casting
Like aluminum, zinc is among the favorite metals used in die casting. It's also commonly used for automotive and medical device molding. Because zinc has a low melting point, it requires less energy to produce. Its low melting point also helps to lengthen equipment life, which is why most companies like a medical plastic injection molding company will prefer using it.
Zinc castings are often the greatest option for customizing products for aesthetic reasons. Depending on the application, the material can be plated or painted. It also provides a nice working surface. Zinc enables fabricators to create components with bespoke aesthetic quality.
Magnesium Die casting
Magnesium is very easy to machine. It has a high strength-to-weight ratio and is the lightest die cast alloy available.
Magnesium alloys have a number of advantages over other cast metals. Some of those advantages are good fluidity, less sensitivity to hydrogen porosity, and improved castability.
Bronze and Brass Alloys
Bronze and brass are malleable alloys, allowing them to be molded into a variety of shapes and forms, regardless of how complex they are. Because of these metals' dimensional accuracy and flexibility, die casted parts can be made in large quantities.
When compared to other metal casting and forging methods, die casted equipment made with bronze and brass alloys have good dimensional tolerance, material integrity, and surface polish.
Lead Alloys
Lead alloys are specially used for metal parts that need close dimensional accuracy and are highly resistant to corrosion. They are commonly used for fire safety equipment, bearings, and numerous decorative metal objects. Although lead alloys are quite affordable and commonly used, they are not suitable for products that will come in contact with food.
Copper
In general, copper alloys have a high level of corrosion resistance, making them a good choice for long-term cost efficiency. Copper also has the highest mechanical properties of alloy die cast, which makes them applicable in several applications.
Other benefits attributable to this metal are high hardness, outstanding wear resistance, good dimensional stability, and high strength almost like that of steel parts.
Silicon
Silicon is amongst the common metals used in die casting and this is because it provides high strength and serves as an alternative investment for cast steel parts. Its strength makes metal parts very strong and resistant to external factors.
What is Die Casting Used for
Die casting has various material options and design flexibility, which makes it applicable to several industries. Die casting is used for several purposes by many industries. Some of them are
Medical devices
Die casting is usually used to make medical devices as most of them are made from aluminum, which is a metal material. Examples of die casted medical devices are surgical tools, monitors, operating room robots, and gear boxes for hospital beds. They are usually manufactured and assembled in a clean room for medical devices because they need to be contamination-free.
Manufacturing Factory
You can't walk far within the perimeters of a manufacturing plant without finding a few die casted parts. This ranges from air compressors and wall mount bearing housings to industrial pumps, piston connecting rods, and porter cable pump housings.
Outdoor lighting and traffic lights
Lighting enclosures and other parts for traffic lights can be made using aluminum alloys and casting dies. This metal is cheap and lightweight, and it's a good conductor with excellent thermal properties.
Telecommunications
The telecommunication industry as well depends greatly on die cast aluminum parts because of their high conductivity, low weight, and longevity.
While designing a perfect die cast may seem like a daunting task, it is ultimately rewarding when you see your vision come to life in an appealing and functional final product. Here are some of the things you need to keep in mind during the design process:
The die casting process can be used with a variety of metals, including aluminium, and zinc. Each metal has its own unique properties such as fluidity and solidification, which need to be taken into account during the design process The die must be able to withstand the high pressures involved in the process and must be accurately machined to ensure a precise final product.
The production process needs to be taken into account when designing die castings. For example, the design may need to accommodate the use of cores or inserts The part should eject easily from the die without damaging the surface or leaving any flash The part function and intended application must be prioritized when designing die castings. For example, a die casting used in a high-stress environment will need to be designed differently than one that is purely aesthetic.
Die Casting Design Guidelines
As with most manufacturing processes, high-pressure die casting comes with its own set of design rules and constraints. These include parting line considerations, draft angles, and wall thickness limitations.
Parting line
A die casting part is made using two hardened steel dies. The line where the two dies meet is called the parting line, and this line is often visible after casting in the form of flash — a thin extrusion of excess material that has escaped the cavity at the parting line due to insufficient clamping force.
During die casting design, the designer must find a suitable location for the parting line, i.e. decide where the mold will be split in half. Doing so depends on several factors, including:
Material flow: The inlet for metal flow must be located along the parting line to ensure optimal filling of the mold cavity.
Cosmetic features: Cosmetic features should not be located near the parting line, since they may be obstructed by gates and vents.
Post-machining: The parting line area of the casting will likely require the most machining and finishing, so it should be located to provide easy machine tool access.
Small amounts of flash are inevitable, so designers should prepare for the necessity of trimming it after the casting is removed from the mold.
Wall thickness
As with other casting and molding processes, die casting parts are suited to consistent wall thicknesses, as this encourages consistent filling and cooling of the metal castings, reducing the likelihood of uneven shrinkage and warping.
Draft
Metal die casting parts require a small amount of draft — tapered sides of the mold cavity — so the castings can be easily ejected from the dies without damaging them. All surfaces parallel with the die opening direction require draft.
Inner surfaces like untapped holes require a greater draft angle than external walls (which naturally shrink away from the inside of the mold).
Fillets and radii
Fillets are rounded internal corners that increase the load-bearing capacity of die castings. They are also easier to manufacture than sharp internal corners, so should be incorporated into die casting designs as standard. Using an equal radius across fillets is preferable to fillets with varying radii.
Radii are rounded external corners and play a different but equally important function, helping to improve metal flow in the mold cavity.
Ribs
Ribs are small protrusions from the die casting part that serve to increase strength and stiffness without resorting to thicker walls and increased material usage. They also improve metal flow. Note that ribs require their own fillet and radius considerations for maximum strength and flow.
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FAQ
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Zinc is a strong and durable material often used for small die castings. It provides high-quality surface finishing and has a high melting point, making it ideal for high-temperature applications.
Q: Why is die casting so expensive?
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