6 Major Types of Casting. Part-2

Hello everyone,

This is part 2 of the casting series.

What are the types of casting? There are major 6 types of casting that are widely used.

1. Sand Casting
2. Investment casting
3. Die Casting
4. Centrifugal Casting
5. Gravity Die Casting
6. Vacuum Die Casting

Sand Casting

• Process:

1. Place a pattern in sand to create a mold.
2. Incorporate the pattern and sand in a gating system. Remove the pattern.
3. Fill the mold cavity with molten metal.
4. Allow the metal to cool.
5. Break away the sand mold and remove the casting.

• Advantages:

1. Simple production process
2. Low-cost process
3. Wider material choice
4. Complicated parts can be casted

• Disadvantages:

1. Low strength
2. Low dimensional accuracy
3. Surface roughness is not good
4. Interchangeability is difficult to achieve

Investment casting

• Process

1. Produce a master pattern
2. Create a mold
3. Produce wax patterns
4. Apply Investment Material

• Coating
• Stuccoing
• Hardening

5. Dewax

6. Burnout preheating

7. Pouring

8. Divesting (Casting Removal)

9. Finishing

• Advantages:

1. Excellent surface finish
2. High dimensional accuracy
3. Extremely intricate parts are castable
4. No flash or parting lines

• Disadvantages:

1. It can be difficult to cast objects requiring cores
2. This process is expensive, is usually limited to small casting
3. Holes cannot be smaller than 1/16 in. (1.6?mm) and should be no deeper than about 1.5 times the diameter
4. Investment castings require longer production cycles compared to other casting processes
5. There are many process factors to affect the quality of the mould and casting, so the quality management system is challenging

Die Casting

Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mould cavity.

The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.

Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter, and tin-based alloys.

• Advantages:

1. The metal liquid does subject to high pressure and fast flow rate during die-casting
2. Good product quality, stable size, and good interchangeability
3. The production efficiency is high, and the die-casting mold is used many times
4. It is suitable for mass production with good economic benefits.

• Disadvantages:

1. The process is limited to high-fluidity metals.
2. Die casting involves a large number of parts
3. In the standard die casting process the final casting will have a small amount of porosity.

Centrifugal Casting

• Process:

1. The permanent mold is rotated continuously
2. Molten metal is poured into the mold
3. Because of the centrifugal force, molten metal spread throughout the mold.
4. Rapid cooling at the surface of the mold
5. Machining (Finishing)

• Advantages:

1. No wastage of molten metal
2. No need of models while producing hollow casting
3. Casting has high density and low defect
4. It is convenient to manufacture barrel and sleeve composite metal castings.

• Disadvantages:

1. Used for only hollow pipes casting
2. Diameter of inner hole is not accurate
3. The surface roughness is poor of the inner hole

Gravity die casting

• Process:

1. It's permanent mold casting, where molten metal is poured into the mold from the vessel
2. The mold cavity fills with no force other than gravity.
3. The filling is controlled by tilting the die.
4. Rapid solidification.
5. Finishing

• Advantages:

1. Mechanical properties 15% higher than sand casting
2. Higher dimensional accuracy and lower surface roughness
3. Good quality stability than sand casting.

• Disadvantages:

1. The certain measures should take to evacuate the exhaust gas
2. Cracks can easily accure when metal gets solify
3. Metal moulds take long time to manufacture and higher cost

Vacuum die casting

• Process:

1. It's an advanced die casting process, where the exhaust gas is removed by vacuum.
2. When the molten metal is poured with high pressure the exhaust should go out fast from the mold cavity
3. So there is a vacuum pump to remove the gas quickly from the mold cavity.
4. This process eliminates the pores inside die casting.

• Advantages:

1. Eliminates pores in the die casting
2. It is possible to cast larger casting with smaller machine
3. It improve filling condition, so thinner parts can be casted

• Disadvantages:

1. The mould sealing structure is complicated
2. If this process is not properly, then effects will not be very good.

This bring me to the end of this part 2 of the casting series.

Thank you for reading.

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