Casting A4

							Casting
Die Casting
     Metal injected into mould under high pressure.
     Good surface finish and good dimensional accuracy.
     Materials used predominantly Aluminium, Zinc and Copper alloys.
     Pure Aluminium is rarely cast due to high shrinkage, and susceptibility to hot
      cracking. It is alloyed with Silicon, which increases melt fluidity, reduces machine-
      ability.
    Copper is another alloying element, which increases hardness, reduces ductility, and
      reduces corrosion resistance.
    A high cost, due to expensive die cast moulds.
    Manufacture process: Hot and Cold Chamber process, cold chamber for high
      melting point alloys such as copper and aluminium. Hot chamber process for metals
      with a low melting point.
Advantages:
    Can produce large parts
    Can form complex shapes
    High strength parts
    Very good surface finish and accuracy
    High production rate
    Low labour cost
    Scrap can be recycled
Disadvantages
    Trimming is required
    High tooling and equipment cost
    Limited die life
    Long lead time

Pressure Casting
     Pressure is usually required because of viscosity related flow limitations.
     This process, similar to injection moulding, is a variant of porous mould casting in
      which the ceramic suspension is injected into the mould under high pressure.
    The moulds may be fabricated from plastic, plaster or ceramics.
    The higher the applied pressure, the shorter the casting time.
    Material used, Aluminium alloy.
    Producing methods High Pressure Casting and Low Pressure Casting.
Advantages
    Complicated shapes can be made
Disadvantages
    Expensive die and machine
Gravity Die Casting
      This is a low-tech process is well suited for the batch production of simple forms
       without undercuts.
      This process is where the liquid metal is poured into metallic moulds without
       application of any external pressure.
    The liquid metal enters the cavity by gravity.
    Manufacturing Process: Mazak, an alloy of zinc and aluminium, is first melted in a
      crucible furnace. Molten metal is then poured by ladle into a open steel mould where
      it is allowed to cool and solidify. The mould is then turned upside down and tapped
      with a hammer to release the finished casting.
Advantages
    Minimal Finishing required
    Accurately dimensioned
    sharply defined
    smooth or textured-surface metal parts
    The process is suitable for mass production
Disadvantages
    Limitation of geometry / size.
    Beyond a particular shape and size the process becomes uneconomical.
    Difficult to attach gates and risers.



Sand Casting
     Produced by forming a mould from a sand mixture and pouring molten liquid metal
      into the cavity in the mould. The mould is then cooled until the metal has solidified.
      In the last stage the casting is separated from the mould
    Green sand is a mixture of silica sand, clay, moisture and other additives.This must
      be mixed carefully as if too much water is added - when molten aluminium is poured
      into the mould an explosion can result.
    The air set method uses dry sand bonded to materials other than clay, using a fast
      curing adhesive.
    Metals used typically iron, steel, bronze, brass, aluminium, magnesium alloys or
      various pot metal alloys, which often include lead, tin, and zinc.
Process of Manufacture
    Place a pattern in sand to create a mould.
    Incorporate a gating system.
    Remove the pattern.
    Fill the mould cavity with molten metal.
    Allow the metal to cool.
    Break away the sand mould and remove the casting.
Industrial Casting
   Brass, Bronze, Aluminium, Stainless steel, and Nickel-boron alloys.
Major Casting Processes:
   Sand Casting
   Shell Moulding
   Investment Casting
   Lost Foam Casting
   Die Casting
   Pressure Die Casting
   Gravity Die Casting
   Centrifugal Casting