Casting

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Casting

• By Jackie Ho

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Casting

• The process of which a material is introduced
  into a mold in liquid state, and is allowed to
  solidify inside the mold, creating a fabricated
  part

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Sand Casting

• Cavity formed by pattern made by wood or metal
• Require a riser since molten metal shrinks as it
  solidify
• Material used in sand casting
• low temperature steel, Al, Mg, and Ni alloy

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• Riser is used to account for the shrinkage of the
  molten metal when it solidifies. The function of
  riser is just to feed molten metal into the void
  where shrinkage occurs.

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Permanent mold casting

• Mold
• Takes weeks to prepare
• is made out of cast iron
• is preheated to 200C before pouring
• expand during the pour
• cavity is bigger than desired dimensions
• Material used in permanent mold casting
• Fe, Al, Mg, Cu based alloys

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Die casting

• Similar to permanent mold casting
• (difference is high pressure is used in this
  type of casting)
• Mold cavity can be very precise
• Very technical and a great deal of skill is
  required to create the die
• Metal used in die casting
• non-Fe, Al, Mg, Zn, Cu based alloys

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Centrifugal casting

• Has a spinning chamber at 300-3000rpm
• Spinning while molten metal is poured in
• Molten metal is thrown to the side where it
  solidifies
• Parts produced have fine grained outer surface
  and impurities in the inner diameter
• Material used in centrifugal casting
• Fe, steel, stainless steel, and alloys of Al, Cu,
  Ni

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Advantages

• Sand casting
• Produce large part
• Can be recycled
• Preparation time for sand mold is fast
• Permanent mold casting
• Fast production rate
• Lower cost production per unit

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Advantages (cont.)

• Die casting
• Good for mass production
• Lifetime production of up to 500,000 castings
• Very fast production rate
• Centrifugal casting
• Very fine-grained outer surface
• Resistance to atmospheric corrosion

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Disadvantages

• Sand Casting
• Limited quantities can be produced
• Metal wasted in the riser
• Permanent mold casting
• Molds take up storage space
• Die casting
• Require a long time to prepare the die
• Centrifugal casting
• Is only good for producing cylindrical parts