Types of casting process | definition , drawing

Types of casting process 

Casting is a manufacturing process in which molten material, such as metal or plastic, is poured into a mold and allowed to cool and solidify into the desired shape. There are several types of casting processes, including:

1. Sand Casting.

2. Investment Casting.

3. Die Casting.

4. Permanent Mold Casting.

5. Centrifugal Casting.

6. Continuous Casting.

1. Sand Casting: 

This is the most common type of casting process, which involves making a mold by packing sand around a pattern made of wood or metal. The mold is then filled with molten metal or other materials, and after the metal cools and solidifies, the sand is removed from the casting. 

Process of sand casting:

The construction of a sand casting involves several steps, including:

Pattern making: The first step is to create a pattern of the part to be cast. The pattern is typically made from wood, metal, or plastic and is an exact replica of the final product. The pattern is used to create the sand mold.

Mold preparation: Next, the mold is prepared by placing the pattern in a flask and filling the flask with a mixture of sand and a binder, which helps hold the sand together. The mold is then compacted to ensure that the sand is tightly packed around the pattern.

Pattern removal: Once the mold has been created, the pattern is removed from the mold, leaving a cavity in the shape of the part to be cast.

Pouring: Molten metal is then poured into the mold cavity through a gating system, which is a network of channels and runners that direct the flow of metal into the mold.

Cooling and solidification: The molten metal is allowed to cool and solidify in the mold cavity, taking on the shape of the cavity.

Shakeout: Once the metal has solidified, the sand mold is broken apart to remove the casting. This process is called shakeout, and it involves using mechanical methods such as vibration or impact to break the sand mold and remove the casting.

Finishing: The final step in the sand casting process is to finish the casting by removing any excess material, smoothing any rough surfaces, and adding any necessary features or details to the casting. This may involve additional machining or surface treatments, depending on the requirements of the final product

Application of sand Casting: 

Sand casting is a popular metal casting technique used to produce a wide variety of metal parts and components. Some common applications of sand casting include:

Automotive parts: Sand casting is commonly used to manufacture automotive parts such as engine blocks, transmission cases, brake components, and suspension parts.

Aerospace parts: Sand casting is used to manufacture a variety of aerospace components such as turbine blades, compressor casings, and structural components.

Industrial machinery parts: Sand casting is used to produce a range of industrial machinery parts such as pumps, valves, gears, and bearings.

Art and decorative pieces: Sand casting can also be used to create artistic and decorative pieces such as statues, sculptures, and ornamental railings.

Architectural components: Sand casting is used to produce architectural components such as columns, balusters, and other decorative elements.

Marine components: Sand casting is used to produce marine components such as propellers, rudders, and ship fittings.

Military components: Sand casting is used to produce military components such as weapon parts, tanks, and ammunition.

Advantage and disadvantage of sand Casting

Advantages of Sand Casting:

Versatility: Sand casting is a versatile method that can be used to create complex shapes and components of different sizes and geometries.

Low cost: Sand casting is a cost-effective method, as the molds used are made of sand, which is inexpensive and readily available.

Reproducibility: Sand casting allows for the production of multiple copies of the same component with consistent quality.

Flexibility: The molds used in sand casting can be easily modified or repaired, allowing for flexibility in the manufacturing process.

Large components: Sand casting is ideal for producing large components that would be difficult or impossible to produce using other methods.

Disadvantages of Sand Casting:

Surface finish: The surface finish of components produced using sand casting may not be as smooth or refined as those produced using other methods.

Tolerances: Sand casting may not be suitable for producing components with tight tolerances or precision requirements.

Porosity: Sand casting can result in components with porosity, which can affect their strength and durability.

Process limitations: Certain materials may not be suitable for sand casting due to their melting point or chemical properties.

Time-consuming: Sand casting can be a time-consuming process, as the molds need to be prepared and cooled before the component can be produced.

2. Investment Casting: 

This process is also known as the lost wax casting process. A pattern is made of wax or a similar material, which is then coated in ceramic and fired in a furnace. The ceramic mold is then filled with molten metal, and after the metal cools and solidifies, the ceramic shell is broken off to reveal the final casting.

Here are the basic steps involved in the investment casting process:

Pattern Creation: A pattern of the final part is created using wax, plastic or other materials that can be easily melted or burned out. The pattern is an exact replica of the final part and includes all the features such as holes, slots, and surface details.

Mold Making: The pattern is then coated with a ceramic slurry, which is made up of multiple layers of ceramic material. After each layer is applied, it is allowed to dry and harden. The finished mold is then heated to remove the wax or plastic pattern, leaving behind a cavity that is an exact replica of the pattern.

Pouring: The mold is placed in a furnace and heated to a high temperature to remove any remaining moisture and strengthen the mold. The mold is then filled with molten metal through a sprue, which is a channel that allows the metal to flow into the mold.

Solidification: The molten metal cools and solidifies in the mold, taking the shape of the cavity created by the pattern. Once the metal has solidified, the mold is broken open, and the metal part is removed.

Finishing: The metal part is then finished by removing any remaining ceramic material, cutting off the sprue and any other excess material, and polishing the surface to achieve the desired surface finish.

The investment casting process is commonly used to produce parts for the aerospace, automotive, and medical industries, where high precision and complex shapes are required.

Application of investment Casting:

 Here are some common applications of investment casting:

Aerospace: Investment casting is commonly used in the aerospace industry to produce components such as turbine blades, engine parts, and other critical components where precision and high performance are required.

Automotive: Investment casting is used in the automotive industry to manufacture various components such as engine parts, transmission components, and suspension parts.

Medical: Investment casting is used in the medical industry to produce components such as orthopedic implants, surgical instruments, and dental components.

Jewelry: Investment casting is used in the jewelry industry to produce complex and intricate designs in gold, silver, and other precious metals.

Industrial machinery: Investment casting is used in the production of industrial machinery components, such as gears, pumps, and valves.

Energy: Investment casting is used in the energy industry to produce parts for turbines, generators, and other components used in power plants.

Military and defense: Investment casting is used in the military and defense industries to produce components such as weapon parts, armor, and other critical components.

Advantages and disadvantages of investment Casting process:

Advantages:

Design flexibility: Investment casting offers great design flexibility and can produce complex shapes with high accuracy and repeatability.

High-quality parts: The investment casting process produces parts with excellent surface finish, dimensional accuracy, and tight tolerances.

Versatility: Investment casting can be used to create parts in a wide range of metals, including aluminum, stainless steel, titanium, and copper alloys.

Low wastage: Investment casting is a low wastage process since the material used to create the mold can be reused multiple times.

Cost-effective for small production runs: Investment casting is a cost-effective option for small production runs since the cost of tooling and setup is relatively low.

Disadvantages:

Time-consuming: Investment casting can be a time-consuming process, particularly for larger parts. The process typically involves multiple steps and can take several weeks to complete.

Costly for large production runs: The cost of tooling and setup can be expensive for large production runs, making investment casting less cost-effective than other manufacturing methods such as die casting.

Limited to smaller parts: Investment casting is generally limited to smaller parts due to the size limitations of the molds.

Limited to certain metals: Some metals are difficult to cast using the investment casting process, such as high-strength steels and some non-ferrous metals.

Limited by mold materials: The mold materials used in investment casting are limited to ceramics and other high-temperature materials, which can limit the types of parts that can be produced.

3. Die Casting: 

This is a process where molten metal is injected into a mold cavity under high pressure. The mold is typically made of steel and is designed to produce complex shapes with high accuracy and repeatability.

The die casting process involves the following steps:

Mold preparation: A mold, also known as a die, is created based on the design of the part to be produced. The mold is typically made from steel and consists of two parts that are held together by a clamp. The mold is then coated with a lubricant to facilitate the flow of the molten metal.

Melting the metal: The metal to be used for casting is melted in a furnace to a temperature of around 600-700°C. The type of metal used depends on the requirements of the part being produced.

Injection: Once the metal has melted, it is injected into the mold under high pressure using a hydraulic press. The pressure applied to the molten metal is typically around 10,000 psi.

Cooling: After the mold is filled with molten metal, it is cooled using a cooling system. This allows the metal to solidify and take on the shape of the mold.

Ejection: Once the metal has cooled and solidified, the two halves of the mold are opened, and the part is ejected. The excess metal, known as flash, is trimmed away using a trimming press.

Finishing: The final step involves cleaning, polishing, and finishing the part to achieve the desired surface finish and dimensions.

Die casting can produce parts with complex shapes and tight tolerances. The process is widely used in the production of automotive parts, electronic components, and household appliances.

Types of die Casting:

1. Hot chamber die Casting.

2. Cold chamber die Casting.

3. Vacuum Die Casting.

4. Squeeze Casting.

5. Semi-Solid Die Casting.

1. Hot Chamber Die Casting: In this process, the metal is melted in a furnace and then transported to the die casting machine via a gooseneck. This technique is suitable for metals with low melting points such as zinc, magnesium, and copper.

2. Cold Chamber Die Casting: In this process, the molten metal is poured into a cold chamber from an external furnace, which is then transported to the die casting machine via a ladle. This technique is used for metals with high melting points such as aluminum and brass.

3. Vacuum Die Casting: In this process, a vacuum is applied to the die cavity to remove any air or gas present. The molten metal is then injected into the cavity, producing a high-quality, void-free casting.

4. Squeeze Casting: In this process, the molten metal is poured into the die and then compressed using a hydraulic press. This technique produces high-quality, dense castings with improved mechanical properties.

5. Semi-Solid Die Casting: In this process, the metal is partially melted to create a slurry with a semi-solid consistency. This slurry is then injected into the die casting machine and solidified into a final product. This technique is suitable for producing complex shapes with high precision and strength.

Advantage and disadvantage of die Casting:

Advantages:

High accuracy and precision: Die casting allows for the production of complex shapes with high levels of accuracy and precision. This makes it ideal for the production of intricate parts that require tight tolerances.

High production rate: Die casting is a fast process that can produce large quantities of parts in a short amount of time. This makes it ideal for mass production.

High strength: The parts produced by die casting are usually very strong and can withstand high stress and pressure.

Good surface finish: The parts produced by die casting have a smooth surface finish that requires little or no additional processing.

Disadvantages:

High cost of equipment: The equipment used for die casting is expensive and requires a significant initial investment.

Limited material selection: Die casting is typically used with non-ferrous metals such as aluminum, magnesium, and zinc. This limits the range of materials that can be used for production.

Porosity: The high pressure used during die casting can sometimes result in porosity, which can weaken the parts produced.

Size limitations: Die casting is typically used for small to medium-sized parts, which limits its use for larger parts.

4. Permanent Mold Casting: 

In this process, a reusable mold is made of metal, typically cast iron or steel. Molten metal is then poured into the mold, and after the metal cools and solidifies, the casting is removed from the mold.

Process of permanent Mold Casting:

Here are the steps involved in permanent mold casting:

Design the mold: The first step in permanent mold casting is to design the mold according to the desired shape of the final product. The mold can be made from various materials such as aluminum, steel, graphite, and ceramic.

Preparing the mold: Before casting, the mold needs to be cleaned and coated with a release agent to prevent the molten metal from sticking to the mold. The mold is also preheated to ensure that it is at the appropriate temperature for casting.

Melting and pouring the metal: The metal is melted in a furnace and then poured into the mold through a sprue, which is a channel that allows the metal to flow into the mold cavity. The metal is poured under gravity, so this process is also called gravity die casting.

Cooling and solidification: Once the metal is poured into the mold, it starts to cool and solidify. The mold is typically cooled with water or air to speed up the solidification process. The cooling rate is controlled to ensure that the metal solidifies uniformly and without defects.

Removing the casting: After the metal has solidified, the mold is opened and the casting is removed. The casting may require some finishing operations such as sandblasting, trimming, or machining to remove any excess material or rough edges.

Reusing the mold: The mold can be reused to produce additional castings, which makes permanent mold casting a cost-effective and efficient process. 

5. Centrifugal Casting: 

This process involves pouring molten metal into a spinning mold, which creates a centrifugal force that distributes the metal evenly around the mold cavity. This is often used to produce cylindrical or symmetrical parts.

Process of centrifugal Casting:

Here is the general process of centrifugal casting:

Preparation of the mold: The mold is typically made of metal and is usually cylindrical or conical in shape. The mold is mounted on a rotating spindle and is preheated to a specific temperature to prevent thermal shock during casting.

Preparation of the metal: The metal to be cast is melted in a furnace and brought to a specific temperature and chemistry suitable for the intended part.

Pouring of the metal: The molten metal is poured into the spinning mold through a sprue at the top. The centrifugal force generated by the rotation of the mold distributes the molten metal evenly along the mold cavity walls.

Cooling of the part: As the molten metal is poured into the mold, the centrifugal force helps to distribute the metal evenly along the mold cavity walls. The metal solidifies as it cools, forming a solid cylindrical part.

Removal of the part: Once the part has cooled and solidified, the mold is stopped and the part is removed. The part is then cleaned, finished, and inspected for quality.

6. Continuous Casting: 

This is a process where molten metal is continuously poured into a mold and allowed to solidify as it moves through the mold. This is often used to produce long metal rods or sheets.

These are some of the most common casting processes, and each has its own advantages and disadvantages depending on the type of material being cast and the desired shape and properties of the final product.

Process of continuous Casting: 

The process of continuous casting typically involves the following steps:

Melting: The first step in continuous casting is melting the metal. The metal is typically melted in a furnace or an electric arc furnace.

Refining: After melting, the metal is refined to remove impurities such as sulfur and phosphorus. This is typically done using various methods such as fluxing, degassing, and filtration.

Casting: Once the metal has been refined, it is poured into a tundish, which acts as a reservoir. From the tundish, the molten metal flows through a series of channels or tubes, called the "mold oscillation system," and into the mold.

Solidification: As the molten metal cools, it solidifies and takes on the shape of the mold. The mold is typically made of copper or steel and is water-cooled to help the metal solidify quickly.

Withdrawal: As the metal continues to solidify, it is pulled out of the mold using a withdrawal system. The withdrawal speed is carefully controlled to ensure that the metal solidifies uniformly and with the desired properties.

Cutting: Once the metal has been withdrawn from the mold, it is cut to the desired length using a cutting torch or saw.

Finishing: Finally, the product is finished by heat treatment, straightening, and/or other secondary operations.