Die Casting
Casting of metals is a very ancient process. Progress of civilization has been possible because of industrialization, and metal casting is an important part of it. As technology progressed, sand casting, investment casting, lost foam casting, permanent mold casting, centrifugal casting, and die casting processes evolved as well.
Die casting is a foundry process to manufacture accurately dimensioned, sharply defined, smooth or textured surface metal parts of a single metal or an alloy of metals. It is accomplished by injecting liquid metal at a high speed and suitable pressure into reusable steel dies. Of all the casing processes, die casting takes the shortest route between raw material and near net shape, throwing some unique foundry engineering challenges. Sand casting, investment casting, and lost foam casting processes all use gravity to fill the mold, while die casting uses high pressure and velocity to fill the mould. After the mould is filled, it is destroyed to remove the casting. In die casting however, the mould can be reused.
Die casting is believed to have begun sometime during the middle of the 19th century. The earliest examples of die casting mostly used various compositions of tin and lead. This was followed by zinc alloys and then copper and magnesium. While all these metal alloys are still used today, the introduction of aluminium die casting has made it possible to manufacture lightweight parts that are typically required in the aviation industry. Modern science and technology, metallurgical controls and research are making possible still further refinements resulting in new alloys with increased strength and stability.
The Die Casting Process
In the die casting process, a steel mould called the die and shaped as the end object and contains the cavities that form the castings, is made into two halves to permit removal of the castings. This die is capable of producing thousands of parts in rapid succession. The die is then mounted securely in a die casting machine with the individual halves arranged so that one is stationary (cover die) while the other is moveable (ejector die). The casting cycle starts when the two dies are clamped tightly together by the closing mechanism of the machine. Liquid casting alloy is then injected into the die in an extremely short period of time and at very high pressures, where it solidifies rapidly. The die halves are then drawn apart when the machine opens, and the shot which includes the castings is ejected. The dies for the die casting process range from simple to complex and have moveable slides and cores as determined by the configuration of the part. They consist of mechanical features; a metal flow system called runners, gates and vents; and a thermal system because the die also acts as a heat exchanger.
The complete casting process can be classified into five stages – patternmaking, moulding and core making, melting and casting, fettling, and testing and inspection. Quality control of castings is essential in foundries for design process control in order to achieve consistent quality of castings at minimum cost.
The die design is derived from the defined required final condition of the solidification pattern. Earlier, a combination of knowledge and experience was necessary for proper design of a component to be die cast. However, with advances in CAD / CAM and simulation software, most foundries in India strive to be product designer independent.
The major advantages of die casting are:
Limitations of Die castings
Since the casting alloy is injected into the die cavity at a superheated temperature, it behaves like a hydraulic fluid during the very brief period of cavity fill. This forceful pouring of metal results in some air being trapped in the parts, resulting in porosity. It is not therefore easily amenable to heat treatment. The foundry needs to make large initial capital investment, and the process is not suitable for small batch production.
Die Casting in India
Currently, nearly 30-35% of the auto components in a vehicle are made of aluminum alloys, which are mostly developed using high pressure die casting process. As far as India is concerned, the automobile and auto components segment is booming. India is one of the largest manufacturers of two and four wheelers, a sector where die casting is preferred. The demand for high-pressure aluminum die casting parts has increased across numerous industrial applications over the past years, as the process manufactures lightweight parts and provides high flexibility for complex shapes. The success of this segment directly relates to the business opportunities in store for the die casting industry. The rise in technological advancements and innovation is anticipated to propel the adoption of high-strength and lightweight castings, specifically in the auto sector, offering manufacturers new opportunities in adopting aluminum for die casting parts. The introduction of simulation-based castings is one of the key trends that will drive the growth prospects for the global die casting market in the forthcoming years. The simulation-based casting process is used to produce components that are cost-effective, have high-precision, and reliable. This casting process involves various benefits as it ensures easy and accurate fault detection. Simulation-based manufacturing results in reduced wastage and operational costs. Additionally, they can also predict defects and their location easily and more precisely than the conventional method.
Die casting is a foundry process to manufacture accurately dimensioned, sharply defined, smooth or textured surface metal parts of a single metal or an alloy of metals. It is accomplished by injecting liquid metal at a high speed and suitable pressure into reusable steel dies. Of all the casing processes, die casting takes the shortest route between raw material and near net shape, throwing some unique foundry engineering challenges. Sand casting, investment casting, and lost foam casting processes all use gravity to fill the mold, while die casting uses high pressure and velocity to fill the mould. After the mould is filled, it is destroyed to remove the casting. In die casting however, the mould can be reused.
Die casting is believed to have begun sometime during the middle of the 19th century. The earliest examples of die casting mostly used various compositions of tin and lead. This was followed by zinc alloys and then copper and magnesium. While all these metal alloys are still used today, the introduction of aluminium die casting has made it possible to manufacture lightweight parts that are typically required in the aviation industry. Modern science and technology, metallurgical controls and research are making possible still further refinements resulting in new alloys with increased strength and stability.
The Die Casting Process
In the die casting process, a steel mould called the die and shaped as the end object and contains the cavities that form the castings, is made into two halves to permit removal of the castings. This die is capable of producing thousands of parts in rapid succession. The die is then mounted securely in a die casting machine with the individual halves arranged so that one is stationary (cover die) while the other is moveable (ejector die). The casting cycle starts when the two dies are clamped tightly together by the closing mechanism of the machine. Liquid casting alloy is then injected into the die in an extremely short period of time and at very high pressures, where it solidifies rapidly. The die halves are then drawn apart when the machine opens, and the shot which includes the castings is ejected. The dies for the die casting process range from simple to complex and have moveable slides and cores as determined by the configuration of the part. They consist of mechanical features; a metal flow system called runners, gates and vents; and a thermal system because the die also acts as a heat exchanger.
The complete casting process can be classified into five stages – patternmaking, moulding and core making, melting and casting, fettling, and testing and inspection. Quality control of castings is essential in foundries for design process control in order to achieve consistent quality of castings at minimum cost.
The die design is derived from the defined required final condition of the solidification pattern. Earlier, a combination of knowledge and experience was necessary for proper design of a component to be die cast. However, with advances in CAD / CAM and simulation software, most foundries in India strive to be product designer independent.
The major advantages of die casting are:
- Die cast parts are net shape or near-net, that is, they are cast to their finished size, requiring no or minimal machining operations.
- A variety of metal and metal alloys can be cast, from aluminum to zinc.
- Very large and very small castings can be made from automotive engine blocks and transmissions to miniature gears and pinions.
- Smoother surfaces than most forms of casting such as sand or permanent mould.
- Holes can be cored and made to tap drill sizes.
- External threads on parts can be included in the cast.
- Intricate shapes can be produced both on the inside and outside of the casting, automotive transmission valve are an example.
Limitations of Die castings
Since the casting alloy is injected into the die cavity at a superheated temperature, it behaves like a hydraulic fluid during the very brief period of cavity fill. This forceful pouring of metal results in some air being trapped in the parts, resulting in porosity. It is not therefore easily amenable to heat treatment. The foundry needs to make large initial capital investment, and the process is not suitable for small batch production.
Die Casting in India
Currently, nearly 30-35% of the auto components in a vehicle are made of aluminum alloys, which are mostly developed using high pressure die casting process. As far as India is concerned, the automobile and auto components segment is booming. India is one of the largest manufacturers of two and four wheelers, a sector where die casting is preferred. The demand for high-pressure aluminum die casting parts has increased across numerous industrial applications over the past years, as the process manufactures lightweight parts and provides high flexibility for complex shapes. The success of this segment directly relates to the business opportunities in store for the die casting industry. The rise in technological advancements and innovation is anticipated to propel the adoption of high-strength and lightweight castings, specifically in the auto sector, offering manufacturers new opportunities in adopting aluminum for die casting parts. The introduction of simulation-based castings is one of the key trends that will drive the growth prospects for the global die casting market in the forthcoming years. The simulation-based casting process is used to produce components that are cost-effective, have high-precision, and reliable. This casting process involves various benefits as it ensures easy and accurate fault detection. Simulation-based manufacturing results in reduced wastage and operational costs. Additionally, they can also predict defects and their location easily and more precisely than the conventional method.
Key players in the market have already started focusing on capturing growing market share in the region by using advanced die casting software. Indian foundries, especially in developed states like Maharashtra, are leading in automation, leading to better quality control of castings.