Metal castin new

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Casting Process


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CASTINGPATTERNMAKING:

In pattern making, a physical model ofcasting, i.e. a pattern is used to make the

mold. The mold is made by packing

some readily formed aggregated

materials, like molding sand, around the

pattern. After the pattern is withdrawn, its

imprint leaves the mold cavity that is

ultimately filled with metal to become the

casting.

n case, the castings is required to behollow, such as in the case of pipe

fittings, additional patterns, known as

cores, are used to develop these cavities.
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COREMAKING& MOLDING:

In core making, cores are formed,

(usually of sand) that are placed

into a mold cavity to form the

interior surface of the casting.

Thus the annul space between themold-cavity surface and the core

is what finally becomes the

casting.

Molding is a process that consistsof different operations essential to

develop a mold for receiving

molten metal
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ALLOYMELTINGANDPOURING:

Melting is a process of preparing

the molten material for casting. It

is generally done in a specifically

designated part of foundry, and

the molten metal is transported tothe pouring area wherein the

molds are filled
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CASTINGCLEANING:

The casting is separated from the mold

and transported to the cleaningdepartment.

Burned-on sand and scale are removed.

Excess metal is removed (Fins, wires,

parting line fins, and gates).

Subsequently the casting can be

upgraded using welding or other such as

procedures.

Final testing and inspection to check for

any defects

Advantages:Improves the surface appearance and finish of casting

Improves overall quality and functionality by removing impurities, such as

sand, scale and excess metal

Finally the sand from the mold is separated and processed through a

reclamation system for further use.
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INDUSTRIALPROCESSDESCRIPTION

The metal casting process has been divided intothe following five major operations:

Obtaining the Casting Geometry:The process is referred as the study of thegeometry of parts and plans, so as to improve

the life and quality of casting.

Advantages of Good Casting GeometryReduces defects, post casting operations, andrejected castings

Significantly reduce energy and environmentalimpacts

Saves energy

Improves overall quality and life of casting
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A key part of designing a mold involves the use ofcores. Cores are preformed masses of bondedsand or some other material that are used to makethe internal passageways of a casting. Castings

may require a single core, a complex assembly ofcores or no cores at all. Like castings, cores aremade in a mold, called a coldbox.

Typically cores are made of sand and may becombined with other materials that bind the sand

together. Metal cores are used in permanent moldand diecasting processes. The type of cores usedin each metalcasting process will also be part ofyour decision making process.


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TYPES OF MOLDING PROCESS

1 Expendable Mold1.1 Permanent Pattern

1.1.1 Sand Casting

1.1.2 Plaster

Molding

1.2 ExpendablePattern

1.2.1 Lost Foam

1.2.2 Lost Wax

(investmentcasting)

1 Permanent Mold1.1 Die

1.1.1 Hot Chamber

1.1.2 Cold Chamber

1.1.3Thixotropic

Mold prepertation =) metal heating =) pouring =) cooling =) processing


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SAND CASTING


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The set of channels through which a molten metal flows

to the mold cavity is called gating system.

Typical gating system consists of a pouring cupand a

spruereceiving the poured melt, runner

a channelthrough which the melt is supplied to the gates through

which the molten metal enters the mold cavity.


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INVESTMENT CASTING


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EXPANDABLEMOLDPERMANENTPATTERN

SHELL MOLDING

Shell moulding is a process for producing simple or complex near

net shape castings, maintaining tight tolerances and a high degree

of dimensional stability. Shell moulding is a method for making high

quality castings. These qualities of precision can be obtained in a

wider range of alloys and with greater flexibility in design than die-

casting and at a lower cost than investment casting.

INVESTMENT CASTING


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Shell molding

Advantages

Better surface finish

Better dimensional tolerances.

Reduced Machining. Less foundry space required.

Semi skilled operators can handle the process.

The process can be mechanized.

Disadvantages

The raw materials are relatively expensive.

The process generates noxious fumes which must be removed.

The size and weight range of castings is limited.


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LOST FOAM CASTING

INVESTMENT CASTING

Lost foam casting(LFC) is a type of investment casting

process that usesfoam patternsas a mold. The method

takes advantage of the properties of foam to simply and

inexpensively create castings that would be difficult to

achieve using other casting techniques.
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LOST FOAM CASTING

Lost foam casting(LFC) is a type of investment casting

process that usesfoam patternsas a mold. The method

takes advantage of the properties of foam to simply and

inexpensively create castings that would be difficult to

achieve using other casting techniques.
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Lost foam casting


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Lost foam, is similar to Investment or Lost wax, in

that the medium, or pattern device, is Expendable,

they melt or evaporate away, leaving the cast part.

They both have advantages, for the type of function

they were designed. One Process's advantage,

could be the other Process's weak area.

These points are brought up in the text portion of

Education Section.


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PERMANENT MOLD

DIE CASTINGLiquid metal injected into reusable steel mold, or die,

very quickly with high pressures .

Die casting is a process in which the molten metal is

injected into the mold cavity at an increased pressureThe mold used in the die casting process is called a die.


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In a cold chamberprocess, the molten metal is ladled intothe cold chamber for each shot. There is less time exposure ofthe melt to the plunger walls or the plunger. This is particularlyuseful for metals such as Aluminum, and Copper (and itsalloys) that alloy easily with Iron at the higher temperatures.

PERMANENT MOLDDIE CASTING

COLD CHAMBER


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In a hot chamberprocess the pressure chamber is connected to

the die cavity is immersed permanently in the molten metal. The inlet

port of the pressurizing cylinder is uncovered as the plunger moves

to the open (unpressurized) position. This allows a new charge of

molten metal to fill the cavity and thus can fill the cavity faster thanthe cold chamber process. The hot chamber process is used for

metals of low melting point and high fluidity such as tin, zinc, and

lead that tend not to alloy easily with steel at their melt temperatures.

PERMANENT MOLDDIE CASTING

HOT CHAMBER


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Manifacturing techniques


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TERMSOFCASTNG

Riser: A column of metal placed in the mold to feed

the casting as it shrinks and solidifies. Also known

as a "feed head."

Riser:A column of metal placed in the mold to feed the casting as it shrinks andsolidifies. Also known as a "feed head."

Runner: The channel through which the molten metal is carried from the sprue to the

gate.

Cores:A separated part of the mold, made of sand and generally baked, which is usedto create openings and various shaped cavities in the casting.

Gate:A channel through which the molten metal enters the casting cavity.

Sand:A sand which binds strongly without losing its permeability to air or gases.


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TERMSOFCASTNG

Binders: Materials used to hold molding sand together.

Parting Line: Joint where mold separates to permit removal of the pattern. The axe

which shows how and where to open the mold

Centrifugal Casting: Process of filling molds by pouring metal into a mold which isspinning or revolving about an axis. Cast iron pipe can be created using this method.

Chaplet:A metal support used to hold a core in place in a mold. Not used when

a core print will serve.

Draft: Slight taper given to a pattern to allow drawing from the sand.

Pouring: Filling the mold with molten metal.

Shrinkage: The decrease in volume when molten metal solidifies.


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SELECTINGTHERIGHTMETALCASTING

PROCESS

For any Metal Casting Process, selection of right alloy, size,shape, thickness, tolerance, texture, and weight, is very vital.

Special requirements such as, magnetism, corrosion, stressdistribution also influence the choice of the Metal CastingProcess.

Views of the Tooling Designer; Foundry / Machine House needs,

customer's exact product requirements, and secondaryoperations like painting, must be taken care of before selectingthe appropriate Metal Casting Process.

Tool cost.

Economics of machining versus process costs.

Adequate protection / packaging, shipping constraints,

regulations of the final components, weights and shelf life ofprotective coatings also play their part in the Metal Castingprocess.


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Advantages Disadvantages Recommended

Application

Least Expensive in

small quantities (less

than 100)

Ferrous and non -

ferrous metals may be

cast

Possible to cast very

large parts.

Least expensive

tooling

Dimensional

accuracy inferior to

other processes,

requires largertolerances

Castings usually

exceed calculated

weight

Surface finish of

ferrous castings

usually exceeds 125

RMS

Use when

strength/weight

ratio permits

Tolerances,

surface finish and

low machining cost

does not warrant a

more expensive

process

SANDCASTING


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PERMANENTANDSEMI-PERMANENTMOLD

CASTING


Application

Less expensive

than Investment or

Die Castings

Dimensional

Tolerances closer

than Sand Castings

Castings are dense

and pressure tight

Only non-ferrous

metals may be cast

by this process

Less competitive

with Sand Cast

process when three

or more sand cores

are required

Higher tooling cost

than Sand Cast

Use when

process

recommended for

parts subjected tohydrostatic

pressure

Ideal for parts

having low

profile, no coresand quantities in

excess of 300


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PLASTERCAST


Application

Smooth "As Cast"

finish (25 RMS)

Closer dimensionaltolerance than Sand

Cast

Intricate

shapes and fine

details including

thinner "As Cast"

walls are possible

Large parts

cost less to cast than

by Investment

process

More costly than

Sand or Permanent

Mold-Casting

Limited number of

sources

Requires minimum

of 1 deg. draft

Use when parts

require smooth "As

Cast" surface finish

and closertolerances than

possible with Sand

or Permanent Mold

Processes


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INVESTMENTCAST


Application

Close dimensional

tolerance

Complex shape, finedetail, intricate core

sections and thin walls

are possible

Ferrous and non-

ferrous metals may becast

As-Cast" finish (64 -

125 RMS)

Costs are higher than

Sand, Permanent

Mold or Plaster

process Castings

Use when

Complexity

precludes use of

Sand or PermanentMold Castings

The process cost is

justified through

savings in

machining orbrazing

Weight savings

justifies increased

cost


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DIECASTING


Application

Good dimensional

tolerances are

possible

Excellent part-part

dimensional

consistency

Parts require a

minimal postmachining

Economical only in very

large quantities due to

high tool cost

Not recommended forhydrostatic pressure

applications

For Castings where

penetrant (die) or

radiographic inspectionare not required.

Difficult to guarantee

minimum mechanical

properties

Use when quantity of

parts justifies the high

tooling cost

Parts are not

structural and are

subjected to

hydrostatic pressure

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Metal castin new