In today’s world, die casting has made creating smaller items with complex shapes possible using various methods. After various casting processes out there, die casting tends to stand out as it offers many benefits in the manufacturing world.
Die casting is a metal casting process that involves the introduction of molten non-ferrous alloys into dies under high pressure at high speed to rapidly create molded products.
These kinds of castings are known for high dimensional accuracy and can produce thin-walled items with complex shapes in mass.
Most of the time, items produced with die casting require less machining after molding, which is why these items can be found in automobiles, motorcycles, home appliances, industrial equipment, etc. In this reading, we’ll explore what die casting is, its applications, parts, diagrams, and how it works.
Let’s Get Started!
Related: What is Sand Casting, its Applications & How it Works?
What is Die Casting?
Die casting is an automated casting process that forces liquid metal under high pressure (150 to 1200 bar) into a mold cavity at a high filling speed.
This type of casting offers uniform quality to the component produced. People typically use it when they need a high volume of production and a consistent part.
It is known as one of the quickest and most economical casting processes. It is capable of producing hundreds of thousands of identical castings from a single mold, ensuring the items are of equal quality.
As earlier mentioned, the die-casting process is suitable for multiple and mass production of components. It is better and faster than sand casting due to the demolition of the mold when bringing out the casting.
Applications of Die Casting
The applications of die casting are most suitable for casting medium-sized parts with complex details. The technique is often performed on nonferrous metals like magnesium, aluminum, etc.
Die casting is one of the largest casting methods that is used to manufacture consumer, commercial, and industrial products like automobiles, toys, parts of the sink faucet, connector housing, gears, etc.
Furthermore, die castings are used to produce finished products like locks and gears, hooks, door handles, pumps, power tool housings, and other engineering castings. Other examples of die casting products are engine fans, compressor valves, and camera housings.
In electrical items, die castings are used in products like the interior enclosures of computers, secure housing and electronic parts. Zinc is commonly used for electrical equipment due to its electrical conductivity and superior EMI and ESD shielding.
Aluminum die castings have excellent durability and recyclability and are lightweight. With the high increase of electric vehicles, aluminum is highly used for producing castings of these properties.
Related: What is Investment Casting? Diagram, & How it Works
Diagram and Parts of Die Casting
Types of Die Casting
The various types of die-casting processes are hot chamber, cold chamber, low pressure, high pressure, vacuum, squeeze, and semi-solid.
Hot chamber die casting:
The hot chamber is the most popular type of die casting. It is also referred to as gooseneck casting. In the hot chamber, the casting chamber is constantly in contact with a liquid alloy, allowing molten metal to pass through a valve into it. Piston also plays an important role.
It helps to press the molten metal in the chamber at high speed. Hot chamber types of die casting are suitable for casting metals with low melting points and fluidity, e.g. copper, magnesium, zinc, tin, lead, etc.
One of the greatest advantages is that direct immersion helps quickly transfer molten metal into a mold cavity.
Cold chamber die casting
This type of die casting eliminates the injection mechanism’s immersion in the molten bath. Molten metal is automatically or manually poured into an injection system in a cold chamber.
It is carried out by filling a casting chamber with alloy and pressing it to pass through channels to the die-casting mold.
Unlike hot chamber, cold chamber die casting is suitable for metals with a higher melting point, for example, aluminum and copper. This is because of the corrosive nature of the metals, making them not suitable for immersion in hot chamber die casting.
Low-pressure dies casting
Low pressure uses metals or alloys with low melting points. It has the possibility of casting components from 2 to 150kg, offering high strength and complex geometry. It also improves dimensional accuracy and material utilization.
However, because low-pressure die casting can only achieve a minimum wall thickness of 30mm, it is not suitable for items with thin walls. It’s a slower process.
Related: What is Centrifugal Casting? Its Diagram & How it Works
High-pressure die casting
It is a process in which molten metal is forced under pressure into a locked metal die cavity, where it is held by a powerful press until the metal solidifies. Once the metal solidifies, we unlock the die, open it, and eject the casting.
Vacuum process
This is a new process that offers good strength and minimal porosity in the casting. It is similar to low-pressure die casting, except for the arrangement of the die-casting mold and molten metal bath.
The vacuum here is a cylinder chamber, which helps in forcing molten metal into a mold cavity. Items requiring post-casting heat treatment undergo these types of casting.
Squeeze die casting
Squeeze die casting is established as a working solution for casting metals and alloys with low fluidity. Molten metal fills an open die during its execution. The die is squeezed closed, forcing metal into a mold cavity.
Often used for strengthening fiber, these types of die-casting primarily involve molten aluminum. It produces a good, dense product.
Semi-solid die casting
This process is also known as thermoforming. The squeeze process results in maximum density and minimum porosity. Before heating, we cut the materials into smaller slags.
Once the material reaches a phase transition between solid and liquid, a mold cavity forces it in. Nonferrous metals are often used, e.g., magnesium alloy and aluminum alloy.
Related: What is Evaporative Pattern Casting (EPC)? Diagram & How it Works
How Does Die Casting Work?
Die casting is a process that involves the injection of molten metal into a mold cavity, which is connected to a casting chamber.
The mold cavity is filled with liquid alloys and pressed under high pressure to solidify the casting. This process is applicable to both hot and cold chamber types of die casting.
High-pressure die casting involves injecting molten metal into a three-dimensional mold, which takes the shape of the casting.
The metal is heated to extreme temperatures until it changes to a molten state, which is then forced into the mold’s cavity to take its shape when cooled. The four steps in the die-casting working process include
1. Preparing the Mold: A special lubricant is applied to the inner walls of the mold to control its temperature, allowing easy removal of the casting once it’s cooled.
2. Injection: The molten metal is injected into the mold at high pressure, with the mold bust closed tightly to prevent rejection. The pressure ranges from 1,500 to 25,000 PSI (Pounds per Square Inch) depending on the use case.
3. Cavity Ejection: As the metal object solidifies, it requires ejection. Most die-casting molds feature an ejector pin that automatically releases the cavity.
4. Shakeout: The final step of die-casting involves separating scrap and waste metal from the mold, as high-pressure types produce excessive amounts of scrap metal. Some molten metal may stick to the mold, requiring removal for reuse.
Advantages
Below are the benefits of die casting:
- It offers accurate dimension and a good surface finish, helping to eliminate post finishing
- It can be fully automated
- The ability to repeatedly use one mold for the same production is one of its greatest advantages.
- It offers a fast production rate
- Casting has long service life and close tolerance
- It is economical
- It is used for casting a wide range of complex application
- Good processing properties
- Offers high electrical conductivity
- It has high corrosion resistance
- High strength and hardness
- High thermal conductivity
- Good EMF/RFI isolation
Related: What is Sand Casting Sand, its Properties & Types?
Disadvantages
Below are the limitations of die casting:
- High die cast
- Gasses entrapped in the form of porosity
- Metals and alloys with a high melting point cannot be applicable
- Too long lead time
- Smaller production runs may reduce the cost-effectiveness