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TOP 6 MOST POPULAR METAL CASTING TECHNOLOGIES

Metal casting technology is a popular technology, playing an important role in industrial and manufacturing industries. Along with advances in science and technology, metal casting technology has also achieved significant developments, creating diverse high-quality products at increasingly competitive costs. In this article, we will learn about the top 6 most popular metal casting technologies today as well as analyze in depth the characteristics and applications of each method.

1. Sand mold casting

1.1. Define:

Sand casting is a casting method that uses molds made from sand, molten metal is poured into the mold. After the metal cools, the mold will be broken to remove the product. Sand casting is used to cast products with weights from a few grams to tons. Sand casting is not only flexible in terms of product size but can also produce very complex or highly detailed castings and can cast almost any metal alloy.

1.2. Advantages and limitations

Advantages	Limitations
Simple production process	Manual process
Low cost molding	The product has poor durability
Low production costs	Low geometric accuracy
Diverse casting materials	Rough surface
The shape is highly complex	Many casting defects
Short production time	Casting quality is unstable

1.3. Sand casting process

Sand casting includes 4 basic steps:

Create sand mold samples
Pour molten metal into the sand mold
Let the metal cool.
Break the sand mold and remove the casting.

1.4. Errors

Shrinkage defect is one of the most serious sand casting defects that reduces casting quality. Here, the shrinkage defect of the casting occurs because the shrinkage process is uneven, leading to shrinkage holes in the molded parts.
Gas porosity is another common sand casting defect, primarily seen in metal casting. Gas porosity is the bubble created in the casting after the cooling step. Air porosity casting problems have three types of bubbles: pinhole, blown hole, and open hole.
Cold Shuts are lines or cracks that form in the middle part of the casting surface at rough edges leading to weak spots.
Misruns are casting defects where the mold cavity is not completely filled with molten metal resulting in unfilled sections or missing parts.

1.5. Application

Sand casting technology has been applied for a long time in the metal casting industry with a variety of casting materials from cast iron, steel, aluminum, and copper.

Sand casting is used for a variety of applications to produce a wide variety of parts including: air compressor pistons, bearings, blowers and impellers, electronics, engine crankshafts, accessories, castings flywheels, fuel and oil tanks, gears, low pressure valves, machinery parts, pump bodies, piston pumps, screws, truck chassis parts, valves….

2. Gravity Casting

2.1 Define

Gravity casting is a method of pouring molten metal into a mold under gravity, without using vacuum, compressed air or centrifugal force. The finished product occurs when the metal crystallizes under gravity.

2.2. Advantages and limitations

Advantage	Limitations
High quality product with smooth surface and high precision with minimal porosity and outstanding mechanical properties	Limited design flexibility
Stable and consistent molding ability	High initial investment costs
Reduce costs	Longer lead time Gravity die casting typically has a longer lead time than other casting methods.
Reduce scrap rate due to high quality products.	Product size is limited.
Applicable to most metals	Gravity die casting is best suited for producing relatively small aluminum castings. This process is not suitable for producing large parts because the weight of the molten metal can cause deformation or cracking of the mold.
	Limited materials

2.3. Gravity casting process:

Mold coating: The mold will be covered with a layer of non-stick material to easily remove the product from the mold

Mold heating: heat the mold to ensure the molten metal is in uniform contact with the mold

Pouring metal into the mold:

After being heated, the mold will be locked tightly. Hot metal is poured into the mold through pouring holes. This process only uses gravity to push the metal into the mold, reducing air gaps and making the product stronger and tighter after completion.

Mold mine

The mold is kept completely closed until the product reaches the desired shape, then the mold is opened to release the product.

gravity-casting

2.4. Gravity casting applications

Gravity casting technology is ideal for the production of diverse complex aluminum castings for automotive parts such as: turbines, brake calipers, couplings, engine cylinder heads, engine blocks and pistons. It is also suitable for many other industries, from lighting components to kitchen appliances.

2.5. Conclusion

die casting is a manufacturing process with many advantages and disadvantages. In general, gravity die casting is a suitable method for businesses that need to produce high-quality metal parts in large quantities and are willing to make initial investments in tooling and equipment. When deciding on a manufacturing process, it is important to consider your specific requirements and constraints. If you require parts with complex shapes or thin walls, other casting methods such as sand casting or flow casting may be more suitable. However, if you need to produce high-quality metal parts in large quantities, gravity die casting may be the ideal method for your project.

3. Centrifugal casting

3.1. Define

Centrifugal casting or rotational casting is a casting technique that uses gravity and pressure to evenly distribute molten metal into a rotating mold, to create products with the desired thickness and shape. Centrifugal casting is commonly used for casting thin-walled cylinders, casting materials such as metal, glass and concrete. Unlike most other casting techniques, centrifugal casting is primarily used to produce rotationally symmetric stock in standard sizes for further machining, rather than parts with a shape to suit the purpose. specific end use.

3.2. Classification of centrifugal casting methods

Vertical Centrifugal Casting

The rotation axis of the mold is in a vertical state

Horizontal centrifugal casting is suitable for cylindrical and circular products.

Horizontal Centrifugal Casting

The long steel mold is rotated at high speed when placed horizontally

This process is especially suitable for long cylindrical parts including straight tube sections, long cylindrical sections with end flanges, or short sections such as rings or flanges where multiple parts can be efficiently machined. fruit from a straight cylinder

Inclined Axis Centrifugal Casting

The rotation axis of the mold has a large angle between the horizontal and vertical

Rarely used

3.3. Advantages and limitations

Advantages	Limitations
Centrifugal casting eliminates defects in the shell of the casting The feeding process is continuous so the product is not porous or pitted Centrifugal castings cure from the outer surface inwards, thereby eliminating shrinkage cavities, air pockets and blow holes.	Limit ratio of length and diameter Vertical centrifugal castings are typically limited to a length (height) to diameter ratio of about 2:1. If this 2:1 ratio is exceeded, the molten metal may not have enough centrifugal force to kept evenly on the mold wall. This affects the calculation of casting weight and machining costs
Controlling substance production Centrifugal force pushes the high density metal against the side walls of the mold while the lower density components move or “float” towards the ID. These lower density items include metal oxides, sulfides , gases and other impurities that would otherwise be introduced into the casting. This phenomenon is called “secondary refining”.	High shaping and molding costs
Centrifugal casting significantly reduces microporosity	It is difficult to ensure the correct diameter of the inner casting hole, the surface of the inner hole is rough, and the machining tolerance is large

3.4. Centrifugal casting process:

Prepare the mold:

The mold is usually made of metal or ceramic, covered with a layer of refractory material. This helps the mold withstand the high temperature of the molten metal.

Rotate the mold

The mold is mounted on a rotating shaft and set to rotate at high speed. Rotation speed is usually between 300 and 3000 rpm.

Metal preparation

As with any casting method, the metal is heated and melted to a liquid state in a separate furnace, maintaining the desired pouring temperature.

Pouring molten metal

Molten metal is poured into a rotating mold. Centrifugal force pushes the molten metal out into the mold wall. This creates a uniform and dense casting.

Solidification of metal

The mold continues to rotate as the molten metal cools and solidifies. Centrifugal force helps remove air bubbles and impurities from the metal. And, the turning process ensures a stable wall thickness, creating sound castings with good mechanical properties.

Cooling and post-machining treatment

After the metal hardens, stop the mold and take the casting out. Additional finishing processes, such as machining or surface treatment are performed if necessary.

centrifugal-casting

4. Lost wax casting (Wax mold casting, thin shell mold casting)

4.1. Define

Lost wax casting, also known as thin shell molding or wax mold casting, is a metal product casting process in which molten metal is poured into a mold created with a wax model (shaped like a products need molding)

4.2. Advantages and limitations

Advantage	Limitations
Application of any material and flexibility in terms of production capacity . Materials are not limited , not limited , such as aluminum , magnesium alloy , titanium alloy , copper alloy , copper alloy , etc. All types of steel , heat - resistant alloys such as cobalt and nickel , and applied materials .	Castings created by this casting method are not very durable and are at risk of natural damage, such as breaking and breaking if subjected to strong impacts.
Able to cast complex parts , have thin walls, high surface quality , and high precision. By 90%, there is a significant reduction in the amount of mechanical work, many finished parts can be used immediately. Lost wax casting is possible to obtain products ranging in weight from a few grams to several kilograms .	Mold and machinery costs are more expensive than other casting methods, requiring high initial investment costs.
Products created by the flow casting method have very high precision and surface gloss: + There is no mold parting surface, so there are no mold deviations and defects caused by mold assembly, + There is no sample drawing process, so errors due to sample drawing are reduced + Hot liquid metal is poured into the mold, reducing thermal stress, so the casting is less likely to crack or warp.	The product may be pitted and contain air during the molding process.
Short machining time and labor saving, no need for many large machining processes and parts , saving materials Whether .

4.4. Lost wax casting process

The lost wax casting process can vary depending on the industry and application, but it generally includes the following steps:

Wax modeling stage
Steps to create the mold shell: dotting paste and sanding zirconium powder
Drying and wax release process
Casting stage
Processing stage after casting

See more details about lost wax casting process

5. High Pressure Die Casting

5.1. Define

High pressure die casting (HPDC) is an effective way to produce to produce different CD products. The process of stamping metal and printing metal at high speed and high pressure into the cavity. The mold has a fixed half and a moving half, both of which are attached to the pressure plates of the die casting machine

5.2. Classifcation

Hot chamber pressure casting:

Hot chamber die casting is a highly applicable manufacturing technique for metals with low melting temperatures such as magnesium, lead and zinc.

Hot chamber die casting requires a mold with a cavity filled with molten metal. Once the metal cools and solidifies, the mold opens and ejects the final part, completing a processing cycle. This cycle then continues

Cold chamber pressure casting;

Cold chamber die casting is the preferred manufacturing process for metals that maintain high melting points. Typically, these metals include aluminum alloys, zinc alloys, brass, and copper

With cold chamber die casting, the metal is first heated to a molten state in a separate furnace. The molten metal is then transferred to the casting machine and fed into the machine room. The machine uses a pressurized piston to force molten metal into the mold cavity. This separation of processes directly distinguishes cold chamber molding from hot chamber molding.

5.3. Advantages and limitations

Advantage	Limitation
produce large, light alloy parts in high volumes with high speed and efficiency	The product may form pores. Although careful process design and control can minimize this problem, it cannot be completely eliminated
The product has an outstanding surface finish, excellent uniformity and optimal mechanical properties	Limited heat treatment High pressure molding limits the ability to fully heat treat molded parts due to uneven heat between the porosity zones.
High efficiency, cost saving Due to its dimensional accuracy and smooth surface, high pressure casting minimizes post-casting machining.	High investment cost: High pressure casting has significant initial costs, especially setup and tooling costs. These costs may be limited for small-scale manufacturing or prototyping. However, these costs are often offset over time in high-volume production due to lower unit costs .
Ability to mold many complex shapes

5.4. High pressure die casting process

Mold manufacturing: A hardened steel mold is machined to create a cavity in the shape of the final product, along with a runner system to spray the molten metal.
Mold setup: The mold is mounted on a molding machine (DCM) and preheated. The larger the production run, the more economical it becomes as some setup processes can take time.
Melting the metal : The alloy used for this part is melted in an electric or gas-powered furnace until it becomes a liquid.
Metal injection : The molten alloy is then injected into the mold at high pressure. This high pressure ensures complete cavity filling and precise mold replication.
Metal Cooling: The molten metal cools rapidly and solidifies into the shape of the die with additional pressure to compensate for shrinkage.
Mold ejection: The two halves of the mold are separated and the finished part is ejected using a pin or ejector plate. Further refinement may be necessary.
Recycling: Excess material is trimmed and recycled for the next production cycle.

high-pressure-casting

5.5. Application

Various industries that use high pressure die casting include: automotive, aerospace, and medical, with the automotive industry being the largest user. The automotive industry uses high pressure die casting for: chassis, body, transmission, engine, interior and wheels. The aerospace industry uses high-pressure die casting for airframes and engine parts. The medical industry uses this technique for surgical equipment including: forceps, scissors and clamps as well as X-ray equipment and even heat sinks for some implants

6. Low pressure die casting

6.1. Define

Low pressure die casting (LP casting) is a metal casting process that injects molten metal into a mold under relatively low pressure (

6.2. Advantages and limitations

Advantage	Limitations
High precision due to maintaining low pressure during solidification	Takes longer to fill a given mold shape than other molding processes, such as high-pressure die casting
Minimizes impurities from oxidation or retained slag	The possibility of erosion occurs in aluminum castings. Erosion mainly occurs from the interaction between molten metal and the metal components of the device.
Insert the molten metal into the mold without disturbance. Avoiding stirring and splashing of liquid metal helps avoid oxide formation, which in turn leads to lower levels of unwanted impurities in the final casting process.	Minimum wall thickness of approximately 3 mm is required
Produce castings with minimal porosity using low pressure	Energy consumption compares favorably with that of other casting techniques.
The regulated flow and solidification of the metal enhance the mechanical properties of the casting.	High initial investment costs. The cost includes the purchase of a low-pressure molding machine, mold preparation, and additional auxiliary equipment.
Controlled mold filling results in fewer casting errors and therefore less material rejected as scrap	Systems that control cast metal temperature and pressure to fill molds require highly skilled operators with appropriate training.
Can produce many types of non-ferrous alloys, such as: magnesium, aluminum and zinc

6.3. Low pressure die casting process

Melt the metal alloy in the furnace and bring it to casting temperature

The heating process continues until the appropriate temperature for molding is reached. Different alloys have distinct melting points, so Determining this casting temperature is an important step in ensuring that the alloy is fully melted and ready for casting and the integrity of the final product.

Transfer the molten metal to the holding furnace below the mold

When the liquid metal reaches the appropriate temperature, it is transferred to a furnace located below the mold. This holding furnace helps maintain the molten metal at the required temperature and ensures a continuous supply of raw materials for the casting process.

Force the molten metal through the riser tube into the mold by applying low pressure

The molten metal is then forced through a refractory tube or duct using low pressure. The applied pressure is usually significantly lower than other casting methods, typically less than 0.8 bar. Low pressure is controlled in low pressure molding and the slowness of the process facilitates a smooth and controlled flow up through the riser and into the mold cavity through the mold base. This pressure is usually maintained throughout the solidification phase to ensure complete mold filling.

The metal solidifies under constant pressure in the mold cavity

The molten metal begins to cool as it enters the mold, but it only begins to solidify when it drops to liquid temperature. Solidification takes place under constant pressure, ensuring full mold filling as the metal cools and contracts. This controlled solidification reduces the formation of defects and ensures uniform structure in the molded part.

Release the pressure and recycle the remaining molten metal

After the metal solidifies in the mold cavity, the pressure is released. Any remaining molten metal is then typically collected and recycled for future use, minimizing material waste.

Take the casting out

The mold now contains the solidified molding component, which is allowed to cool. Cooling helps complete the solidification process and enhances the overall integrity of the molded part. Once cooled enough, the mold is opened and the finished casting is removed.

low-pressure-casting

6.4. Application of low pressure die casting

Low pressure die casting is primarily used to produce complex, high-quality parts, including: aluminum alloy engine blocks and suspension parts for automobiles, cylinder heads, aluminum wheels, heat dissipation for electronic components, pump housings, impellers and even golf club heads. Low pressure die casting is suitable wherever complex geometries and intricate designs need to be produced.

The above article has provided information about the top 6 most popular casting technologies today: main characteristics, advantages, limitations, casting process and applications of each casting technology. Hopefully this article has brought you useful insights to choose the most suitable casting method for your product.

If you want to learn more information about casting technology, please immediately contact Vietnam Industrial Services and Solutions Joint Stock Company (VISC). Visit our website to update, explore leading industrial products and solutions and receive the most favorable quotes.