Die casting is a metal forming process featuring the injection of molten metal under high pressure into a reusable steel mould.

This process is capable of producing metal parts with complex geometries, precise dimensions and smooth surfaces.

An overview of the die casting process usually includes the following basic steps:

1. Mould preparation

2. Melting the metal

3. Injection

4. Cooling and demoulding

5. Post-treatment

1. Mould preparation:

First, need to cleane and lubricate the mould to ensure that it releasing smoothly after injection.

The mould usually consists of two halves, called cavities, which are tightly closed together to withstand the high pressures generated when the molten metal is injected.

2. Molten metal:

The metal used is usually melted in a furnace, and common alloys include zinc, aluminium, magnesium, copper, lead and tin.

Depending on the metal used, die casting machines are divided into two types: hot chamber and cold chamber.

Hot chamber die casting machines are suitable for low melting point metals such as zinc and magnesium alloys, while cold chamber die casting machines are suitable for high melting point metals such as aluminium alloys.

3. Injection:

Molten metal is injected into the mould cavity through an injection system.

Injection is carried out under high pressure to ensure that the metal completely fills the mould and to prevent defects such as porosity.

4. Cooling and demoulding:

After the metal is injected into the mould, it needs to be kept under pressure until it is fully cured.

The mould is then opened and the finished part is pushed out.

The cooling time depends on the type of metal used, the thickness of the casting and the complexity of the design.

5. Post-processing:

The finished part may need to be trimmed or deburred to remove excess material.

In addition, surface treatments or other machining may be performed to achieve the desired specifications.

The advantage of die casting is its ability to produce high quality, dimensionally accurate parts quickly for high volume production.

It is widely used in industries such as automotive, consumer electronics and home appliances.

However, moulds are more costly and therefore more suitable for mass production.

Die casting is an efficient and cost-effective method of metal forming that meets the needs of modern manufacturing for complex geometries and high-precision parts.

Mould preparation in the Die Casting Process

In the die casting process, mould preparation is a key step.

It directly affects the quality of the final product and production efficiency.

Mould preparation usually includes the following aspects:

1.Mould design and manufacture

2. Assembly and clamping of mould semi-finished products

3. Mould cleaning and heating

4. Mould lubrication

5. Maintenance and optimisation of the mould

1.Mould design and manufacture:

The design and manufacture of moulds is fundamental to ensure high quality castings.

Moulds must making in high quality tool steel and properly do heat treat to achieve the hardness and durability.

Mould design needs to take into account a variety of factors such as wall thickness, chamfers, parting lines and cooling systems to ensure accuracy and consistency of the castings.

2. Assembly and clamping of mould halves:

The mould consists of two halves: a fixed mould half and a moveable mould half.

In the preparation phase, these two halves will be assembleing correctly and pressurised with a mould press to ensure that they fit tightly together. This step is crucial to ensure that the mould can withstand high pressures and temperatures during the injection process.

3. Mould cleaning and heating:

Before the molten metal is injecting into the mould, engineers need to clean and heat the mould.

This step is to ensure that the mould surface is clean and at the proper temperature to prevent premature solidification of the metal in the mould.

4. Mould Lubrication:

In order to reduce the friction between the metal and the mould and to improve the release performance of the casting.

The internal surface of the mould is spraying with a layer of lubricant or refractory material.

This lubricant not only helps to reduce internal friction, but also helps to maintain the temperature of the mould.

It prevents premature solidification of the metal in the mould and facilitates the removal of the casting from the mould.

5. Mould maintenance and optimisation:

Regular maintenance and optimisation is essential in order to extend the life of the mould and maintain its performance.

This includes cleaning the mould, checking for wear and tear, and repairing and adjusting as necessary.

Through the above steps, the mould preparation stage lays the foundation for the subsequent injection of molten metal, cooling and curing, as well as the removal of castings.

The successful execution of this stage is directly related to the efficiency of the entire die casting process and product quality.

How the metal melting during the die casting process

During die casting, the melting of metal is happening in two main ways:

Hot chamber die casting and cold chamber die casting.

1. Hot chamber die casting:

This method is suitable for low melting point metals such as zinc, tin and lead alloys.

In hot chamber die casting, the molten metal is heated to a molten state and held in a molten pool inside the casting machine.

When die casting is running, a hydraulic or pneumatic piston pushes the molten metal from the molten pool into the mould cavity.

Since the molten metal is in direct contact with the machine, production will carry out quickly and efficiently.

2. Cold chamber die casting:

This method is suitable for high melting point metals such as aluminium, magnesium and copper alloys.

In cold chamber die casting, the metal is first heated to a molten state in a separate furnace.

The molten metal is then fed into the injection chamber of the die casting machine via a pouring system.

During this process, the metal does not come into contact with the machine, thus reducing the risk of erosion and corrosion.

This process is to produce castings of complex shapes because of its faster cooling rate and the possibility of cooling while maintaining high pressures.

In both methods, the melting of the metal is done in specially designed furnaces.

These furnaces can be induction furnaces, electric arc furnaces, or other types of furnaces, depending on the type of metal .

For example, aluminium alloys are often using induction furnaces, as these furnaces provide uniform heating and reduce oxidation.

In addition, in some modern die casting processes, electromagnetic induction heating technology may to melt the metal.

This technique offers the advantages of fast heat-up, ease of control and high melting efficiency, while reducing fume emissions.

Whichever method it is, the metal is injected into the mould when it reaches the appropriate melting temperature and is rapidly cooled and solidified under high pressure to form the desired casting shape.

This process requires precise control of temperature, pressure and time to ensure the quality and accuracy of the final product.

How the die casting process in cooling and de-moulded

Cooled and de-moulded are two key steps in the die casting process.

They are done through the flow of coolant and cooling by spraying the release agent.

This is work in conjunction with a pick-up machine.

1.Cooling process

*Cooling method:

Die casting moulds are usually cooled by oil cooling.

Set cooling water channel in the mould, through the cooling oil to take away the heat absorbed by the mould, so as to achieve the effect of cooling.

Indirect cooling is also a commonly method, which can avoid the contamination of the workpiece.

That is, the cooling oil does not directly contact the workpiece, but is recycling through the cooling channels inside the mould.

* Cooling control:

The cooling time needs adjusting according to the size of the die casting.

Wall thickness and other factors to ensure that the metal liquid can solidify completely.

In high-efficiency production and large thick-walled castings in die casting, often need to be forced cooling to maintain the thermal balance of the mould.

In order to improve production efficiency and casting quality.

* The role of the mould release agent:

In the die casting process, in order to prevent the high temperature metal liquid from sticking to the mould, mould release agent usually spraying to the mould surface .

The water in the release agent evaporates quickly at high temperatures, forming a protective film that prevents the liquid metal from adhering to the mould.

The release agent not only helps cooling, but also reduces the thermal shock to the mould and prolongs the life of the mould.

2. Mould release process

* Mould release method:

When the die casting is finish, the die casting is ejected from the mould using special ejector equipment.

Mould release can be carried out by ejecting, pushing out, rotating, etc., depending on the structure of the product and the design of the mould.

*Cautions:

Care should be taken during the demoulding process avoding damage or deformation to the die casting.

After demoulding, trimming and surface treatment of the die casting will to improve the quality and performance of the product.

* Post-treatment:

After demoulding, the die castings may processing by removing remnants, trimming, deburring and other processing treatments.

According to the requirements of the product, surface treatment such as painting and plating also carring out to improve the corrosion resistance and aesthetics of the product.

Die casting process of cooling and mould release is to ensure product quality and production efficiency is an important link.

Through reasonable cooling design and demoulding technology, can effectively improve the quality of die casting, and prolong the service life of mould.