CASTING:Casting is a solidification process in which molten metal flows by gravity or other force into
a mold where it solidifies in the shape of the mold cavity. The term casting is also applied to
the part that is made by this process. It is one of the oldest shaping processes. The principle of
casting seems simple: melt the metal, pour it into a mold, and let it cool and solidify; yet there
are many factors and variables that must be considered in order to accomplish a successful
casting operation.
Solidification Casting Process
Types of Casting:The process casting is classified into two types:Ø Expandable Mold Casting
Ø Permanent Mold Casting
Expandable Mold Casting is further divided into two types:Ø Sand Casting
Ø Other Casting processes (including shell molding, vacuum molding, etc.)
Foundry:A Foundry is a factory equipped for making molds, melting and handling metal in molten
form, performing the casting process, and cleaning the finished casting.
Foundrymen:The workers who perform the casting operations in these factories are called foundrymen.
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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ADVANTAGES AND DISADVANTAGES OF
DIFFERENT CASTING PROCESSES:PRESSURE DIE CASTING:ADVANTAGES
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High speed production can e achieved
as the whole process is completely
automated.
Possible to obtain fairly complex
castings than that feasible by gravity
die casting due to the use of the
moveable cores.
Very small thicknesses can be easily
filled as the liquid metal is injected
under high pressure.
Very good surface finish can be
obtained & most of the pressure die
castings can be directly electroplated
without any further processing.
Closer dimensional tolerances &
better mechanical properties can be
obtained as compared to sand casting.
Very economical for large scale
production.
DISADVANTAGES
Ø Large capital investment is required to
set up a pressure die casting process.
Ø The die casting machines & tooling
costs are very expensive.
Ø Cannot be used for large castings as
the casting machine capacity is
limited.
Ø It is not suitable for all materials
because of the limitations of the die
materials & the alloys used must have
a low melting point.
Ø High porosity is common & heat
treatment is difficult.
APPLICATIONS:Ø
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Automotive parts like wheels, blocks, cylinder heads, etc.
Aerospace castings
Electric motor housings
Kitchen ware such as pressure cooker
Cabinets for the electronics industry
General hardware appliances like pump parts, plumbing parts etc.
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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INVESTMENT CASTING:ADVANTAGES
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Complex shapes which are difficult by
any other method are possible.
Very close tolerances and excellent
surface finish can be obtained.
Ready for use with little or no
machining required.
Almost any metal can be cast.
No flash or parting lines.
Suit for producing complex shapes
where other manufacturing processes
are too costly and time consuming.
DISADVANTAGES
Ø Time consuming as shell molds
cannot be reused.
Ø Expensive as many labor involved in
the preparation of the wax patterns &
shell molds.
Ø The size of the casting is often
limited.
Ø Occasional minute defects.
APPLICATIONS:Ø It is used to cast aluminum alloys, bronzes, stainless steels, and satellite etc.
Ø Glass mold accessory castings, valves and fittings, gears, levers and splines are some
of the popular usages.
LIMITATIONS:It is time consuming process and costly. Exceptional surface finish possible but minute lacuna
can cause rejection of castings as a result scrap rates can be high.
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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SAND CASTING:ADVANTAGES
Ø Low capital investment means that
short production runs are viable.
DISADVANTAGES
Ø Low capital investment means that
short production runs are viable.
Ø Use of sand cores allows fairly
Ø Use of sand cores allows fairly
complex shapes to be cast.
complex shapes to be cast.
Ø Large components can be produced.
Ø Large components can be produced.
Ø Suitable for small batch production
Ø Suitable for small batch production
(small production rates).
(small production rates).
Ø It is a quick process.
Ø It is a quick process.
Ø All kind of metals can be used in
Ø All kind of metals can be used in
sand casting process.
sand casting process.
Ø There is no size limit.
Ø There is no size limit.
APPLICATIONS:Sand casting process is used to make:Ø Engine blocks,
Ø Gear blanks
Ø Crankshafts
Ø Brake drums
Ø Fan blades
Ø Tubes etc.
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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PLASTER MOLD CASTING:ADVANTAGES
DISADVANTAGES
Ø Smooth "As Cast" finish (25 RMS)
Ø More costly than Sand or Permanent
Mold-Casting
Ø Closer dimensional tolerance
than Sand Casting
Ø Limited number of sources
Ø Requires minimum of 0.5 deg. draft
Ø Intricate shapes and fine details
including thinner "As Cast" walls
are possible
Ø Large parts cost less to cast than by
Investment process
APPLICATIONS:It can be used for making quick prototype parts as well as limited production parts.
LIMITATIONS:Ø
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Poor productivity as it has lengthy processing problems.
Close monitoring of the production process.
The problems of poor mold permeability.
Impaired mechanical properties a possibility as a result of slow cooling of the casting.
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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DIE CASTING:ADVANTAGES
Ø Good dimensional tolerances are
possible
Ø Excellent part-part
dimensional consistency
Ø Parts require a minimal post
machining
Ø The process is more economical
and efficient.
Ø It offers a large range of shapes and
components than any other
manufacturing process.
DISADVANTAGES
Ø Economical only in very large
quantities due to high tool cost
Ø Not recommended for
hydrostatic pressure
applications
Ø For Castings where penetrant (die)
or radiographic inspection are not
required.
Ø Difficult to guarantee minimum
mechanical properties
MOLD CASTING:ADVANTAGES
Ø It has better surface finish
Ø It has better dimensional
tolerances.
DISADVANTAGES
Ø The raw materials are relatively
expensive.
Ø The process generates
Ø Machining process is reduced.
noxious fumes which must
Ø Less foundry space required.
be removed.
Ø Semi-skilled operators can
handle the process.
Ø The size and weight range of
castings is limited.
Ø The process can be mechanized.
APPLICATIONS:The applications of mold casting might be:Ø Crankshaft fabrication
CASTING PROCESS ADVANTAGES & DISADVANTAGES
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Ø Steel casting parts
Ø Molded tubing fabrication
Ø Hydraulic control housing fabrication
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