Casting is the process of
producing metal/alloy component
parts of desired shapes by pouring
the molten metal/alloy into a
prepared mold (of that shape) and
then allowing the metal/alloy to
cool and solidify. The solidified
piece of metal/alloy is known as a
CASTING or FOUNDRY”.
EXAMPLES OF CAST PARTS
Crank handle formed by casting; some areas
were machined and assembled after casting
EXAMPLES OF CAST PARTS
Complex part formed by casting
The box containing the mold
The top half of any part of a 2-part mold
The bottom half of any part of a 2-part mold
A shape inserted into the mold to form internal cavities
Hollow mold area in which metal solidifies
Extra cavity to store additional metal to prevent shrinkage
Channels used to deliver metal into the mold cavity
The part of the gating system that receives poured metal
Parting Line / Parting Surface
Separate the cope and drag of a 2-part mold
Taper on a pattern that allows removal from the mold
The process and product of solidifying metal in a mold
CATEGORIES OF METAL CASTING PROCESSES
Expendable mold processes - mold is sacrificed to remove part
TYPES: Sand Casting, Shell mold Casting,, Mold Casting,
Advantage: more complex shapes possible
Disadvantage: production rates often limited by time to make
mold rather than casting itself
Permanent mold processes - mold is made of metal and can be
used to make many castings
TYPES:Die Casting, Permanent Mold Casting, Centrifugal Casting
Advantage: higher production rates
Disadvantage: geometries limited by need to open mold
Wide range of metals, poor
sizes, shapes, low cost tolerance
better accuracy, finish, limited part size
higher production rate
Wide range of metals,
complex shapes, good
complex shapes, high
accuracy, good finish
good finish, low porosity,
high production rate
wide engine blocks, cylinder
low cylinder heads, brake
non-ferrous metals, low prototypes of mechanical
impellers, injection mold
small parts, expensive
simpler gears, gear housings
dimensional costly dies, small parts, precision gears, camera
accuracy, high production non-ferrous metals
bodies, car wheels
Large cylindrical parts, Expensive, limited shapes pipes, boilers, flywheels
IMPORTANT METAL CASTING METHODS
• Sand Casting
• Investment Casting
High Temperature Alloy,
Complex Geometry, Rough
High Temperature Alloy, Complex
Geometry, Moderately Smooth
• Die Casting
High Temperature Alloy,
Moderate Geometry, Smooth
• The most ancient , useful casting process
• Nearly all alloys can be sand casted ,
e.g. steel, nickel, titanium
• Mold can be used only one time
• Parts ranging in size from small to very large
• Production quantities from one to millions
• Sand casting typically has a low production rate.
• Use of a furnace, metal, pattern, and sand mold in this process
Sand Casting process cycle
• Mold-making A sand mold is formed by packing sand into each half of the mold.
• Clamping Binding of the both halves of molds
• Pouring Molten metal ladled and poured into the mold.
• Cooling The solidification and cooling of molten metal for a predetermined
• Removal/Shakeout After predetermined time has passed, breaking the mold
• Trimming Removing the extra parts called flash by cutting from casting
Factors effecting the quality of sand cast :
Strength - Ability of the sand to maintain its shape.
Permeability - Ability to allow venting of trapped gases through the sand
.Permeability is determined by the size and shape of the sand grains.
Thermal stability - Ability to resist damage, such as cracking, from the heat of
the molten metal.
Collapsibility - Ability of the sand to collapse, or more accurately compress, .
Reusability - Ability of the sand to be reused for future sand molds.
• Advantages :
Can produce very large parts.
Many material options.
Low tooling and equipment cost.
Scrap can be recycled.
Short lead time possible.
Poor material strength.
Poor surface finish and tolerance.
Secondary machining often required.
Low production rate.
Aluminum piston for an internal
combustion engine: as-cast and after
High labor cost.
• Applications: Engine blocks and manifolds, machine bases, gears, pulleys
• Investment casting is one of the oldest manufacturing processes
• molten metal is poured into an expendable ceramic mold
• The mold is formed by using a wax pattern
• Using ceramic slurry that hardens into the mold
• Investment casting also called "lost-wax casting"
• Lost -wax processes increases production time and cost
Investment Casting Process Cycle
• Pattern creation (a) Wax pattern
• Mold creation (b) Multiple patterns
assembled to wax sprue
• Immersing -
(c) Shell built
immerse into ceramic slurry
immerse into fine sand
• Wax removal (d) dry ceramic
melt out the wax
fire ceramic (burn wax)
• Pouring (e) Pour molten metal (gravity)
pouring excess metal before solidification
• Casting removal (f) Break ceramic shell
(vibration or water blasting)
Can form complex shapes
Many material options
High strength parts
Excellent surface finish and accuracy
Little need for secondary machining
Time Consuming process
High labor cost
High tooling cost
Long lead time possible
• Applications: Turbine blades, pipe fittings, lock parts, hand tools, jewelry.
• Produces geometrically complex metal parts
• Reusable molds used, called dies.
• A furnace, metal, die casting machine, and die is used
• The metal, typically a non-ferrous alloy such as aluminum or zinc, .
• After the molten metal is injected into the dies,
it rapidly cools and solidifies into the final part, called the casting.
Die casting process cycle
• Clamping -
Preparation, binding and clamping of mold
• Injection Molten metal is transferred to the die
• Cooling Solidification and cooling of molten metal
• Ejection The removing of cast by hydraulic mechanism
• Trimming -.
Cutting the extra metal by sawing
DIE CASTING EQUIPMENT
• Two types of die casting machines are :• Hot chamber die casting machine
• Cold chamber die casting machine
PARTS FORMED BY DIE CASTING
HOT-CHAMBER DIE CASTING
• Used for metal/alloys with low melting temperatures, such as zinc, tin,
• Clamping of the die
• Molten metal poured in a chamber
• Injecting the metal by forcing plunger
• Metal flows through a goose neck
• Low pressure required around 1000 - 5000 psi
• After the solidification , ejection of cast part by hydraulic system .
Hot chamber die casting process
Cold Chamber Die Casting
• Used for alloys with high melting temperatures e.g. aluminum
• Clamping the die
• Horizontally injection..
• High Pressure is required around 2000 - 20000 psi.
• Solidification for predetermined time
• After solidification, the part can be ejected by the clamping unit.