Frequently Asked Questions (FAQs)
Pressure casting (referred to as die casting) is a casting method in which liquid or semi-liquid metal or alloy is poured into the pressure chamber of the die casting machine to fill the cavity under high pressure and high speed, and the casting is formed and crystallized under high pressure.
Because the liquid metal is subjected to a very high specific pressure, the flow rate is very high, and the filling time is very short. High pressure and high speed are the two main characteristics of the liquid metal filling forming process in die casting and the most fundamental difference between die casting and other casting methods.
For example, the injection ratio is in the range of several to dozens of mpa, even as high as 500MPa; The filling speed is 0.5-120m /s, the filling time is very short, generally 0.01-0.2s, the shortest is only a few seconds dry.
Die-casting metal materials’ main die-casting alloy materials are tin, lead, zinc, aluminium, magnesium, copper and so on. Zinc and aluminium alloys are the most widely used, followed by magnesium and copper alloy. The electronic industry mainly uses zinc, aluminium, and magnesium alloy.
In 1838, die-casting machines were invented to make moulds for movable type printing. The first patent related to dying casting was issued in 1849 for small, manual machine-producing type printing presses.
In 1885 Otto Mergenthaler invented the Linotype machine, which die-cast an entire line of text into a single type, and brought unprecedented innovation to printing. After the large-scale industrialization of the printing industry, the traditional hand-pressed type was replaced by die casting.
Around 1900, the introduction of typography into the market further improved the automation technology of the printing industry, so sometimes you can see more than a dozen die-casting machines in the newspaper office. As consumer products continue to grow, Otto’s invention has found more and more applications. Parts can be manufactured in large quantities using die casting. In 1966, General Dynamics invented the precision and tight die casting process called double punch die casting.
Learn more about die casting history, you can check on wikipedia information.
High pressure dies casting technology can produce very large light alloy parts quickly.
These devices provide light alloy parts with high accuracy, superior surface finish, excellent uniformity, and optimal mechanical properties.
The high-pressure die-casting process can also produce components with thin walls and “co-cast” parts with different plug-ins, such as screws and liners, which later become integral parts of the product.
- High production efficiency. Due to the fast filling speed, short filling time, rapid solidification of the metal industry, and die-casting operation cycle speed. Among all kinds of casting processes, die casting has the highest productivity and is suitable for mass production.
- Easy-to-use inserts. The positioning mechanism is easy to install on the die casting die, easy to insert the insert and meets the local special performance requirements of the die casting.
- The die casting has good process characteristics and dense organization, which has high strength and hardness and good wear and corrosion resistance.
In the future, the die-casting industry will be full of technological innovation, product innovation and competition between brands. Still, in the end, all products will have high technology, parameters, life, and corrosion resistance. To survive and develop in the new era, die-casting enterprises will give up the production of single varieties and specifications of die-casting products to develop the model of multi-varieties and multi-specifications of products to meet the needs of more and more complete sets of manufacturing project users. So at that time, when the user needs a certain set of die-casting mold products, they only need to select one of the die-casting companies to complete the supply of all molds
Die casting technology uses a machine, mold, alloy and three other elements, the pressure, speed and time of the unified process. Pressure is the main feature of the die-casting process for hot metal working to distinguish other casting methods. Pressure casting is a kind of special casting method with less cutting and no cutting, which develops rapidly in modern metalworking technology. It is filling the casting mold with molten metal under high pressure and high speed and forming the casting by crystallization and solidification under high pressure.
The pressure chamber is immersed in the liquid metal of the heat preservation melting crucible. The injection part is not directly connected to the machine base but mounted on the crucible. The advantages of hot chamber die casting are a simple production process and high efficiency, Less metal consumption, stable process. But in the pressure chamber, the injection punch is immersed in liquid metal for a long time, which affects the service life. And easy to increase the iron content of the alloy.
The cold chamber die casting machine refers to the injection chamber, and injection punches are not immersed in molten metal, but a quantitative amount of molten metal is poured into the injection chamber; the vertical chamber cold chamber die casting machine is positioned vertically, apparently following the hot die casting machine. The Czech engineer Josef Polak invented the typical and mature vertical cold chamber, the die-casting machine, in 1927.
The thickness of the aluminium alloy die-casting wall is called wall thickness, a key element of practical significance in the die-casting process. The effective wall thickness of casting parts depends on the casting parts’ actual structure and the aluminium alloy’s characteristics. It has a close relationship with the main parameters of the die casting process. To achieve various regulations, thick walls and symmetrical wall thickness are appropriate.
- Aluminum die-casting commercial wall is unsuitable for too-thin, large-scale too-thin walls, easy-to-appear undercasting, cold separation and other defects.
- The choice of aluminum die-casting commercial wall thickness: under normal conditions, the wall thickness is not suitable for more than 4.5mm. The wall thickness of small and medium-sized casting parts is suitable for 1-3mm of zinc alloy material, 1.5-4mm of aluminium and magnesium alloy, and 2-4mm of copper alloy.
- The thickness of aluminium die-casting products should be symmetrical, which is beneficial to the additional condensation after the aluminium alloy liquid “filling”. It can prevent forging ground stress, shrinkage, cracks and other shortcomings.
- For a part of the thick-walled tube on aluminium die-casting products, reinforcement plates or cast inserts can be selected to enhance the physical properties and improve the process performance.
- It is not suitable to lift the wall’s thickness to improve the bearing capacity of aluminium die-casting products. When the thickness of the casting exceeds the required minimum, the impact toughness will decrease. The casting wall is too thick and easy to causes shrinkage and porosity. It will give the aluminium die-casting production process to the initial set length, large shrinkage, core pulling, difficult mould and other adverse conditions.
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