Different types of metal casting in Manufacturing

What is metal Casting Process?

Casting is a manufacturing process that involves pouring molten material into casting mold and then allowing the material to solidify. The Solidified material takes the shape of casting mold and is known as Casting.

this image shows various types of casting processes to manufacture metal parts.
Casting Parts Example

The metal casting process is extensively used to manufacture complex or large parts that are very difficult or non-economical to manufacture with other manufacturing techniques. 

For example, To manufacture heavy equipment such as ships, propellers, crankshaft, engine blocks, etc. casting process is cost-effective.

Advantages of Metal Casting Process

The metal casting process has the following advantages compared to other manufacturing methods.

  • Manufacturing complex shapes is possible.
  • Large size components casting is possible.
  • Low cost.
  • A wide variety of metal casting material grades are available.
Disadvantages of Metal Casting Process

Along with so many advantages, different types of casting process has the following limitations as well.

  • Wide tolerance range for most of the casting processes.
  • Post casting operations such as machining are required to finish the parts.

Types of Casting

Various types of metal casting methods are available to manufacture complex metal parts. Each technique has its advantages and limitations. You can select the best metal casting process according to design and manufacturing requirements. Following types of casting techniques are available to manufacture metal parts.

  1. Sand Casting
  2. Investment Casting
  3. Die Casting
  4. Centrifugal Mold Casting
  5. Low-Pressure Casting
  6. Gravity Die Casting
  7. Vacuum Die Casting

1. Sand Casting

The Sand Casting Process utilizes synthetic or natural bonded sand as the mold material. Sometimes clay is also used along with sand. To cast high melting point materials such as steels, 98% pure silica sand is recommended. Whereas, for lower melting point metals (such as cast iron or Aluminum), 94 to 98% pure silica sand will also work.

A large number of the metal casting parts are sand-casted parts. For example, engine blocks are manufactured using sand casting.

Sand Casting Process

The sand casting process majorly involves the following four steps.

  1. Pattern Making
  2. Mold making
  3. Melting and pouring
  4. Cleaning.
This image shows the process of sand casting
Sand Casting Process
Step-1: Pattern Making

Pattern (replica of the part) manufacturing is the first step during the casting operation.

Step-2: Mold Making

Mold Making involves packing sand around the pattern in cope and Drag. The cop and drag meeting line is known as the parting line of the part. Gate, sprue, runner, riser, and vents are part of the mold. After the sand packing, the pattern is removed from the mold.

Step-3: Melting and Pouring

After the mold is ready, the next step is pouring the molten metal inside the mold from the gate. After filling the metal, it is allowed to solidify. 

Step-4: Cleaning

Cleaning of casting involves:

  • Trimming of the gate, runner, riser, vents, etc.
  • Removal of sand from the casting. 
Advantages of Sand Casting

Following are the advantages of using sand casting for manufacturing metal parts.

  • Low Mold Cost.
  • Low Manufacturing cost for small volumes.
  • Sand casting for large size parts is possible.
  • Ferrous and non-ferrous materials can be sand cast.
Limitations of Sand Casting

Following are the limitations of the sand casting process to manufacture metal parts.

  • Low accuracy.
  • Rough surface finish.
  • High cleaning and machining cost.

2. Investment Casting

Investment Casting is used to manufacture precision metal parts with details, without parting line, and involves following steps.

Step-1

Create a disposable pattern infusible material such as wax.

Step-2

Pattern material is covered with several layers of refractory material to generate a thick shell around the pattern.

Step-3

Mold is heated to remove the wax pattern after the shell is hard.

Step-4

During the casting process, molten metal is fills inside the hardened shell. After solidification, metal takes the shape of the wax pattern. The next step is the removal of the refractory shell.

Advantages of Investment Casting

Following are the advantages of manufacturing metal parts by using investment casting.

  • High dimensional tolerance.
  • Good surface finish.
  • The parting line is not visible.
  • Can cast ferrous and non-ferrous materials.
  • The casting of thin-wall parts with details is possible.
  • Reduced machining cost.
Disadvantages of Investment Casting

The investment metal casting process has the following disadvantages.

  • Holes smaller than 1.6 mm are difficult to manufacture in investment casting
  • High Cost.
  • Investment casting patterns are not reusable. 

3. Die Casting

This type of Casting utilizes reusable metal dies. It has application to cast non-ferrous metals such as copper, magnesium, aluminum, tin, zinc, etc.

The Metal Die Casting process involves the injection of high-pressure liquid material into the metal casting die. After liquid material solidifies, the part is removed from the die.

Die Casting process involves injection of high pressure liquid material into metal casting die.
Die Casting Process
Advantages of Die Casting

Following are the advantages of the metal die casting process to manufacture metal parts.

  • Good part tolerances are achievable.
  • Reduced post-processing such as machining operations.
  • Consistency in manufactured part dimensions.
  • Good surface finish.
  • Shorter cycle time.
Limitations of Die Casting

Following are the limitations of using the die casting process to manufacture metal parts.

  • High Tooling cost and lead time.
  • Economically feasible for high production rates only.
  • Removal of parts from mold is a challenge.
  • Not all metal alloys can be die-cast.

4. Vacuum Die Casting

The vacuum die-casting process is similar to the die casting process. But in this void and air bubbles are removed from parts by utilizing a vacuum pump to remove gases from a die casting part.

Advantages of Vacuum Die Casting

Vacuum die casting has the following advantages while used to manufacture metal parts.

  • Excellent surface finish.
  • High dimensional accuracy parts.
  • Reduced voids and air bubbles in die casting parts.
Disadvantages of Vacuum Die Casting
  • High Cost Compared to die casting.

5. Low Pressure Die Casting

In the low-pressure die casting process, casting mold is filled with molten metal at relatively low pressure (approximately 0.7 bar). This low pressure continues until metal solidifies. After solidification, the operator removes the cast metal part from the die.

this image shows various components of low pressure metal die casting process.
Low Pressure Die Casting
Advantages of Low Pressure Die Casting
  • Complex geometries are possible to manufacture.
  • High dimensional accuracy.
  • Automation is possible.
Disadvantages of Low Pressure Die Casting
  • Large cycle time.
  • Maximum possible wall thickness is 3mm.

6. Centrifugal Casting

In centrifugal types of casting, the machine poured the molten material into a rotating mold. Due to centrifugal forces inside the mold, molten material takes the shape of the cylinder. This type of casting process has application in manufacturing round or revolve-shaped parts.

This image shows centrifugal types of casting process.
Centrifugal Casting
Advantages of Centrifugal Casting
  • Minimum wastage of material because runner and gate system is not required.
Limitations of Centrifugal Casting
  • Can manufacture only round shape symmetric parts.
  • Variation in the inner diameter of the centrifugal casting parts.

To sum up, Metal Casting is a widely used manufacturing process to shape metal parts. The selection of the type of metal casting process depends on production volume and part design requirements.

We will keep updating this article on various types of casting. You can give your suggestion and ask questions on types of casting in the comment box. We suggest you read this article on various types of drilling machine operations.

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