What is Die Casting? – its Diagram & How it Works

In today’s world, die casting has made creating smaller items with complex shapes possible using various methods. After a variety of casting processes out there, die casting tends to stand out as it offers lots of benefits in the manufacturing world.

Die casting is a metal casting process that involves the introduction of motel non-ferrous alloys into dies under high pressure at high speed to rapidly create molded products.  These kinds of casting are known for high dimensional accuracy and can produce thin-walled items with complex shapes in mass.

Most 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. Well, in this reading, we’ll explore what die casting is, its applications, parts, diagram, and how it works.

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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. it is typically used when a high volume of production and when quality, a consistent part is needed.

It is known as one of the quickest and most economical casting processes. And can produce a hundred of thousands of casting of the same item using one mold, offering equal quality to the items. 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 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 casting are used to produce finished products like locks and gear, hooks, door handles, pumps, power tool housing, and other engineering castings. Other examples of die casting products are engine fans, compressor valve and camera housings.

In electrical item, die casting are used to products like the interior enclosure of computers, secure housing and electronic parts. Zinc is commonly used for electrical equipment due to zinc’s electrical conductivity and superior EMIand ESD shielding.

Aluminum die castings have excellent durability, recyclability and are lightweight. With the high increase of electric vehicles, aluminum are highly used for producing casting of these properties.

Diagram and Parts of Die Casting

Diagram of die casting

Types of Die Casting

The various types of die casting process 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 known as gooseneck casting. In the hot chamber, the casting chamber is constantly in contact with a liquid alloy and molten metal passes through a valve into the casting chamber. 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 to quickly transfer molten metal into a mold cavity.

Cold chamber die casting

In these types of die casting, immersion of the injection mechanism in the molten bath is eliminated. Molten metal is automatically or manually pour into an injection system in a cold chamber. It is carryout by filling a casting chamber with alloy and pressing it to pass through channels to the die-casting mold.

Unlike hot chamber, cold chamber dies casting is suitable for metals with a higher melting point,s 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, low-pressure die casting is not suitable for an item with a tin wall, because the minimum wall thickness that can be obtained is 30mm. it is a slower process.

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. After solidification of the metal, the die is unlocked, opened, and the casting ejected.

Vacuum  process

This process is a new process that offers good strength and minimal porosity to the casting. It is similar to low-pressure die casting, except for the arrangement of die-casting mold and molten metal bath. The vacuum here is a cylinder chamber, which helps in forcing molten metal into a mold cavity. these types of casting are carryout on items having post-casting heat treatment uses.

Squeeze die casting

Squeeze die casting is established as a working solution for casting metals and alloys with low fluidity. It is carryout by filling molten metal in an open die. The die is squeezed closed, forcing metal into a mold cavity. these types of die-casting are often used for strengthening fiber and are mostly related to molten aluminum. It produces a good dense product.

Semi-solid die casting

This process is also known as thermoforming. It offers maximum density and minimum porosity just as of the squeeze process. Materials are cut into smaller slags before heating. After heating to a phase transition between solid and liquid, it is forced into a mold cavity. Nonferrous metals are often used e.g. magnesium alloy and aluminum alloy.

How Does Die Casting Works?

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 pressurized 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: The metal object solidifies and needs to be ejected. 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
  • One of its greatest advantages is that one mold can be repeatedly used for the same production.
  • 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

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
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