casting types -1

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CASTING AND ITSTYPES

By WAQAS AHMEDwww.facebook.com/vicky937


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MANUFACTURING Manufacturing is the production of goods for use or sale using

labor and machines, tools, chemical and biological processing, or

formulation. The term may refer to a range of human activity,

from handicraft to high tech, but is most commonly appliedto industrial production, in which raw materials are transformed

into finished goods on a large scale. Such finished goods may be

used for manufacturing other, more complex products, such

as aircraft, household appliances or automobiles,

There are many types of manufacturing process….


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Types of manufacturing process:

1. Casting..

2. Mol ing..

!. Forming..

". Mac#ining..

$. %oining..


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&UT '( AR( G)ING T) *I+CU++,,--


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C A+TING IT+T/0(+,---


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Casting:

“Casting is a manufacturing process by which aliquid material is usually poured into a mold, whichcontains a hollow cavity of the desired shape, andthen allowed to solidify. The solidified part is alsoknown as a casting, which is ejected or broken outof the mold to complete the process”

Casting materials are usually metals or various cold

setting materials that cure after mixing two or morecomponents together; examplesare epo y , concrete, plaster and clay . Casting is most oftenused for making complex shapes that would be otherwisedifficult or uneconomical to make by other methods


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C asting process can e i3i e into t4o asic

categories:5

1. Those for which a new mold must be created forcasting the expandable!mold processes "

2. Those that employ a permanent , reuseable mold thenon!e"pandable!mold processes#


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Types of casting,---

Follo4ing are t#e asic types of casting..:

+an casting

*ie casting

+#ell mol casting

0ermanent mol casting

In3estment casting 6lost 4a casting7

8ost5foam casting

Centrifugal casting


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T#ere is some t#ing else too,---


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0ATT(RN;

“$n casting, a pattern is a replica of the object tobe cast, used to prepare the cavity into whichmolten material will be poured during thecasting process”

#atterns used in sand casting may be made of wood,

metal, plastics or other materials . #atterns are made toexacting standards of construction, so that they can lastfor a reasonable length of time, according to the $ualitygrade of the pattern being built, and so that they willrepeatably provide a dimensionally acceptable casting.


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Types of pattern:5

1.+ingle piece pattern.

2.+plit piece pattern.

!.8oose piece pattern.

".Matc# plate pattern.

$.+4eep pattern.

eleton pattern

?.Follo4 oar pattern.

@.Cope an *rag pattern


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+plit piece pattern:5


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8oose piece pattern:5


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Matc# plate pattern:5


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+4eep pattern:5


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Gate pattern:5


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Cope an *rag pattern:5


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)ne t#ing else..--


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C)R(+

To produce cavities within the casting%such asfor li$uid cooling in engine blocks and cylinderheads%negative forms are used to produce cores


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NOW..!!!

'e s#ell iscuss all types of casting oney one,---


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+AN* CA+TING

Sand casting , also known as sand molded casting , is a metalcasting process characteri&ed by using sand asthe mold material. The term 'sand casting' can also refer to anob(ect produced via the sand casting process. Sand castings are

produced in speciali&ed factories called foundries. )ver *+ ofall metal castings are produced via a sand casting process

Sand casting is relatively cheap and sufficiently refractory even for steelfoundry use. -n addition to the sand, a suitable bonding agent usuallyclay" is mixed or occurs with the sand. The mixture is moistened, typicallywith water, but sometimes with other substances, to develop strength and

plasticity of the clay and to make the aggregate suitable for molding. Thesand is typically contained in a system of frames or mold boxes known asa flask. The mold cavities and gate system are created by compacting thesand around models, or patterns, or carved directly into the sand.


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&asic process

T ere are si steps in t is process:

. #lace a pattern in sand to create a mold.

/. -ncorporate the pattern and sand in a gating system.0. 1emove the pattern.2. 3ill the mold cavity with molten metal.4. 5llow the metal to cool.

6. 7reak away the sand mold and remove the casting


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*ie casting "ie casting is a metal casting process that is characteri&ed by

forcing molten metal under high pressure into a mold cavity. The moldcavity is created using two hardened tool steel dies which have beenmachined into shape and work similarly to an in(ection mold duringthe process. 8ost die castings are made from non!ferrous metals,specifically &inc, copper, aluminium, magnesium, lead, pewter and tin

based alloys 9epending on the type of metal being cast, a ot# orcold#c am$er mac ine is used.

The casting e$uipment and the metal dies represent large capital costsand this tends to limit the process to high volume production.8anufacture of parts using die casting is relatively simple, involvingonly four main steps, which keeps the incremental cost per item low. -tis especially suited for a large $uantity of small to medium si&edcastings, which is why die casting produces more castings than anyother casting process. 9ie castings are characteri&ed by a verygood surface finish by casting standards" and dimensionalconsistency


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Cast metals:

The main die casting alloys are : %inc, aluminium, magnesium, copper, lead, & tin ;although uncommon, ferous

T e following is a summar' of t e ad(antages of eac allo':

)inc: the easiest metal to cast; high ductility; high impact strength; easily plated; economical forsmall parts; promotes long die life.

*luminium : lightweight; high dimensional stability for complex shapes and thin walls; goodcorrosion resistance; good mechanical properties; high thermal and electrical conductivity; retainsstrength at high temperatures.

Magnesium : the easiest metal to machine; excellent strength!to!weight ratio; lightest alloycommonly die cast.

Copper : high hardness; high corrosion resistance; highest mechanical properties of alloys die cast;excellent wear resistance; excellent dimensional stability; strength approaching that of steel parts.

+ead and tin : high density; extremely close dimensional accuracy; used for special forms ofcorrosion resistance. Such alloys are not used in foodservice applications for public health reasons. Typemetal, an alloy of ead, Tin and 5ntimony with sometimes traces of Copper" is used for casting handset type in letterpress printing and hot foil blocking.


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-uipment:

There are two basic types of die casting machines:

#ot5c#am er mac#ines < col 5c#am er mac#ines .

These are rated by how much clamping force they canapply. Typical ratings are between 2++ and 2,+++ st2, // and 2 ,/// kg"


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0ot#c am$er mac ines:

=ot!chamber machines, also known as gooseneck machines , relyupon a pool of molten metal to feed the die. 5t the beginning of thecycle the piston of the machine is retracted, which allows the moltenmetal to fill the 'gooseneck'. The pneumatic or hydraulic powered

piston then forces this metal out of the gooseneck into the die. Theadvantages of this system include fast cycle times approximately 4cycles a minute" and the convenience of melting the metal in thecasting machine. The disadvantages of this system are that high!melting point metals cannot be utili&ed and aluminium cannot beused because it picks up some of the iron while in the molten pool.

9ue to this, hot!chamber machines are primarily used with &inc, tin,and lead based alloys


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Cold#c am$er mac ines:

These are used when the casting alloy cannot be used in hot!chamber machines; these include aluminium, &inc alloys with a largecomposition of aluminium, magnesium and copper. The process forthese machines start with melting the metal in a separatefurnace. Then a precise amount of molten metal is transported to thecold!chamber machine where it is fed into an unheated shotchamber or in(ection cylinder". This shot is then driven into the die

by a hydraulic or mechanical piston. This biggest disadvantage ofthis system is the slower cycle time due to the need to transfer themolten metal from the furnace to the cold!chamber machine


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9ies:

Two dies are used in die casting; one is called the 'cover die half'and the other the 'e(ector die half'. >here they meet is called the

parting line. The cover die contains the sprue for hot!chambermachines" or shot hole for cold!chamber machines", which allowsthe molten metal to flow into the dies; this feature matches up with

the in(ector no&&le on the hot!chamber machines or the shotchamber in the cold!chamber machines. The e(ector die contains thee(ector pins and usually the runner, which is the path from the sprueor shot hole to the mold cavity. The cover die is secured to thestationary, or front , platen of the casting machine, while the e(ector

die is attached to the movable platen. The mold cavity is cut intotwo cavity inserts , which are separate pieces that can be replacedrelatively easily and bolt into the die halves


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The ejector die half%


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The cover die half%


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Process:

The following are t he four steps i n traditional diecasting , also known as high-pressure diecasting ,

these a re a lso t he b asis f or a ny of the d ie ca stingvariations

1. Die p reparation,

2. F illing,3. Ejection,4. Shakeout


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*d(antages and disad(antages:

*d(antages of die casting:

?xcellent dimensional accuracy dependent on casting material, but typically +. mmfor the first /.4 cm +.++4 inch for the first inch" and +.+/ mm for each additionalcentimeter +.++/ inch for each additional inch".Smooth cast surfaces 1a @/.4 micrometres or +.+2@+. + thou ".

1educes or eliminates secondary machining operations.

1apid production rates.Casting of low fluidity metals.

The main disad(antage to die casting is the very high capital cost. 7oth thecasting e$uipment re$uired and the dies and related components are very costly,as compared to most other casting processes. Therefore to make die casting an

economic process a large production volume is needed. )ther disadvantages arethat the process is limited to high!fluidity metals, and casting weights must be between 0+ grams o&" and + kg /+ lb". -n the standard die casting processthe final casting will have a small amount of porosity. This prevents any heattreating or welding, because the heat causes the gas in the pores to expand,which causes micro!cracks inside the part and exfoliation of the surfac e


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Shell molding

Shell molding , also known as shell-mold casting, is an expendable mold casting form the mold . As compared to sand casting

a higher p roductivity ra te, and lower l abor r equirements. It is u sed forsmall to m edium parts t hat r equire h igh precision. Shell mold casting is a

metal casting process si milar t o sa nd casting, in that molten metal ispoured into an expendable m old. However, in shell mold casting, the m old isa thin-walled shell created from applying a sand-resin mixture a round apattern. The p attern, a m etal piece i n the sh ape of the d esired p art, isreused to f orm multiple sh ell molds. A reusable p attern allows for h igherproduction rates, while t he d isposable m olds en able com plex g eometries t obe cast . Shell mold casting req uires t he u se of a metal pattern, oven, sand-resin mixture, dump box, and m olten metal.Shell mold casting a llows t he u se of both ferrous an d non-ferrous m etals,most commonly using cast iron, carbon steel, alloy steel, stainlesssteel, aluminum alloys, & copper al loys . Typical parts a re sm all-to-medium in size an d requ ire h igh accuracy, such as gear housings,cylinder h eads, connecting rods, & lever arm s


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0rocess:

T e process of creating a s ell mold consists of si steps:

3ine silica sand that is covered in a thin 0@6 " t ermosetting p enolic resin andli-uid catal'st is dumped, blown, or shot onto a hot pattern. The pattern is usuallymade from cast iron and is heated to /0+ to 0 4 AC 24+ to 6++ A3". The sand isallowed to sit on the pattern for a few minutes to allow the sand to partially cure.The pattern and sand are then inverted so the excess sand drops free of the pattern,

leaving (ust the 'shell'. 9epending on the time and temperature of the pattern thethickness of the shell is + to /+ mm +.2 to +.B in".The pattern and shell together are placed in an oven to finish curing the sand. Theshell now has a tensile strength of 04+ to 24+ psi /.2 to 0. 8#a".The hardened shell is then stripped from the pattern.Two or more shells are then combined, via clamping or gluing using a thermoset

adhesive, to form a mold. This finished mold can then be used immediately orstored almost indefinitely.3or casting the shell mold is placed inside a flask and surrounded with shot, sand,or gravel to reinforce the shell.The machine that is used for this process is called a s#ell mol ing mac#ine . -t heats the

pattern, applies the sand mixture, and bakes the shell.


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A 3antages an isa 3antages:

)ne of the greatest ad(antages of this process is that it can becompletely automated for mass production. The high productivity,low labor costs, good surface finishes, and precision of the processcan more than pay for itself if it reduces machining costs

. There are also few problems due to gases, because of the absenceof moisture in the shell, and the little gas that is still present easilyescapes through the thin shell. >hen the metal is poured some of theresin binder burns out on the surface of the shell, which makesshaking out easy .


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0rocess:

T ere are four main t'pes of permanent mold casting:

1. gra3ity

2. slus#

!. lo45pressure

". 3acuum.


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ra(it' process:

The gravity process begins by preheating the mold to 4+!/++ AC 0++!2++ A3" to ease the flow and reduce thermaldamage to the casting. The mold cavity is then coated witha refractory material or a mold wash, which prevents the castingfrom sticking to the mold and prolongs the mold life. 5ny sandor metal cores are then installed and the mold is clampedshut. 8olten metal is then poured into the mold. Soon aftersolidification the mold is opened and the casting removed toreduce chances of hot tears. The process is then started all overagain, but preheating is not re$uired because the heat from the

previous casting is ade$uate and the refractory coating shouldlast several castings. 7ecause this process is usually carried outon large production run workpieces automated e$uipment isused to coat the mold, pour the metal, and remove the casting


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Slus :

&lush casting is a variant of permanent molding castingto create a hollow casting or hollow cast . -n the processthe material is poured into the mold and allowed to cooluntil a shell of material forms in the mold. The

remaining li$uid is then poured out to leave a hollowshell. The resulting casting has good surface detail butthe wall thickness can vary. The process is usually usedto cast ornamental products, such

as candlesticks, lamp bases, and statuary, from low!melting!point materials. 5 similar techni$ue is used tomake hollow chocolate figuresfor aster and C ristmas


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8o45pressure:

ow!pressure permanent mold '(() " casting uses agas at low pressure, usually between 0 and 4 psig /+ to++ k#ag" to push the molten metal into the mold cavity.The pressure is applied to the top of the pool of li$uid,

which forces the molten metal up a refractory pouringtube and finally into the bottom of the mold. The pouringtube extends to the bottom of the ladle so that thematerial being pushed into the mold is exceptionally

clean. o risers are re$uired because the applied pressure forces molten metal in to compensate forshrinkage. Dields are usually greater than 3 4 becausethere is no riser and any metal in the pouring tube (ustfalls back into the ladle for reuse


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5acuum:

Eacuum permanent mold casting retains all of theadvantages of ##8 casting, plus the dissolved gases inthe molten metal are minimi&ed and molten metalcleanliness is even better. The process can handle thin!walled profiles and gives an excellent surface finish.8echanical properties are usually + to 4 better thangravity permanent mold castings. The process is limitedin weight to +./ to 4 kg


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A 3antages an isa 3antages :

The main advantages are the reusa le mol goosurface finis# goo imensional accuracy

There are three main disadvantages%1. high tooling cost ,2. limite to lo45melting5point metals!. s#ort mol life


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'e s#ell iscuss all processes one yone,---


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0ro uce a master pattern:

5n artist or mould!maker creates an original pattern

from wa , cla', wood, plastic, steel, or anot er material9.!!!


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Moul ma>ing:

5 mould, known as the master die , is made of the master pattern. The master pattern may be made from a low!melting!point metal, steel, or wood. -f a steel pattern wascreated then a low!melting!point metal may be castdirectly from the master pattern. 1ubber moulds can also

be cast directly from the master pattern. The first stepmay also be skipped if the master die is machined

directly into steel.


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0ro uce t#e 4a patterns: 5lthough called a wa" pattern , pattern materials also include plasticand fro&en mercury. >ax patterns may be produced in one of twoways. -n one process the wax is poured into the mold and swished

around until an even coating, usually about 0 mm +. / in" thick,covers the inner surface of the mould. This is repeated until thedesired thickness is reached. 5nother method is filling the entiremould with molten wax, and let it cool, until a desired thickness hasset on the surface of the mould. 5fter this the rest of the wax is

poured out again, the mould is turned upside down and the waxlayer is left to cool and harden. >ith this method it is more difficultto control the overall thickness of the wax layer


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In3estment:

The ceramic mould, known as the investment , is produced by threerepeating steps: coating, stuccoing, and hardening. The first stepinvolves dipping the cluster into a slurry of fine refractory materialand then letting any excess drain off, so a uniform surface is

produced. This fine material is used first to give a smooth surfacefinish and reproduce fine details. -n the second step, the clusteris stuccoed with a coarse ceramic particle, by dipping it intoa fluidised bed, placing it in a rainfall!sander, or by applying by

hand. 3inally, the coating is allowed to harden. These steps arerepeated until the investment is the re$uired thickness, which isusually 4 to 4 mm


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*e 4a :

The investment is then allowed to completely dry, which can take 6to 2B hours. 9rying can be enhanced by applying a vacuum orminimi&ing the environmental humidity. -t is then turned upside!

down and placed in a furnace or autoclave to melt out andGorvapori&e the wax. 8ost shell failures occur at this point because thewaxes used have a thermal expansion coefficient that is much greaterthan the investment material surrounding it, so as the wax is heated itexpands and induces great stresses. -n order to minimi&e thesestresses the wax is heated as rapidly as possible so that the surface ofthe wax can melt into the surface of the investment or run out of themold, which makes room for the rest of the wax to expand. -n certainsituations holes may be drilled into the mold beforehand to helpreduce these stresses. 5ny wax that runs out of the mold is usuallyrecovered and reused.


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&urnout pre#eating:

The mold is then sub(ected to a burnout , which heats the mold between 3 / ;C & 1/< ;C to remove any moisture and residualwax, and to sinter the mold. Sometimes this heating is also used asthe preheat, but other times the mold is allowed to cool so that it can

be tested. -f any cracks are found they can be repaired with ceramicslurry or special cements. The mold is preheated to allow the metalto stay li$uid longer to fill any details and to increase dimensionalaccuracy, because the mold and casting cool together


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0ouring:

The investment mold is then placed cup!upwards into a tub filledwith sand. The metal may be gravity poured, but if there are thinsections in the mold it may be filled by applying positive air

pressure, vacuum cast, tilt cast, pressure assisted pouring,or centrifugal cast


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T#e in3estment s#ell for casting a tur oc#arger rotor:


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A 3ie4 of t#e interior in3estment s#o4s t#e smoot#surface finis# an #ig# le3el of etail:


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A 3antages of In3estment casting:

* very smooth surface is obtained with no parting line.

+imensional accuracy is good.

Certain unmachinable parts can be cast to preplanned shape.


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*isa 3antages of In3estment casting:

This process is e"pensive, is usually limited to smallcasting, and presents some difficulties where cores areinvolved.

9oles cannot be smaller than 1B1< in. .-mm# and should be no deeper than about . times the diameter.

$nvestment castings require very long production!cycle

times versus other casting processes.

This process is practically infeasible for high!volumemanufacturing, due to its high cost and long cycle times.


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8ost5foam casting

+ost#foam casting +=C " is a type of evaporative! pattern casting process that is similar to investmentcasting except foam is used for the pattern insteadof wax.This process takes advantage of the low boiling point offoam to simplify the investment casting process byremoving the need to melt the wax out of the mold


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0rocess:

3irst, a pattern is made from pol'st'rene foam , which can be done many different ways. 3or smallvolume runs the pattern can be hand cut or machined from a solid block of foam; if the geometry issimple enough it can even be cut using a hot!wire foam cutter . -f the volume is large, then the

pattern can be mass!produced by a process similar to in>ection molding . #re!expanded beads of polystyrene are in(ected into a preheated aluminum mold at low pressure. Steam is then applied tothe polystyrene which causes it to expand more to fill the die. The final pattern is approximatelyH*.4 air and /.4 polystyrene. #re!made pouring basins, runners, and risers can be ot glued tothe pattern to finish it.

ext, the foam cluster is coated with ceramic investment, also known as the refractor' coating, viadipping, brushing, spraying or flow coating. This coating creates a barrier between the smooth foamsurface and the coarse sand surface. Secondly it controls permea$ilit', which allows the gas created

by the vapori&ed foam pattern to escape through the coating and into the sand. Controlling permeability is a crucial step to avoid sand erosion. 3inally, it forms a barrier so that molten metaldoes not penetrate or cause sand erosion during pouring. 5fter the coating dries, the cluster is placedinto a flask and backed up with un#$onded sand . The sand is then compacted using a vibration

table. )nce compacted, the mold is ready to be poured . 5utomatic pouring is commonly used in3C, as the pouring process is significantly more critical than in conventional foundr' practice.There is no bake!out phase, as for lost!wax. The melt is poured directly into the foam!filled mould,

burning out the foam as it pours. 5s the foam is of low density, the waste gas produced by this isrelatively small and can escape through mould permeability, as for the usual out gassing control


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0rocess:

-n centrifugal casting, a permanent mold is rotated continuouslyabout its axis at high speeds 0++ to 0+++ rpm" as the molten metalis poured. The molten metal is centrifugally thrown towards theinside mold wall, where it solidifies after cooling. The casting isusually a fine!grained casting with a very fine!grained outerdiameter, owing to chilling against the mould surface. -mpuritiesand inclusions are thrown to the surface of the inside diameter,which can be machined away.

Casting machines may be eit#er #ori ontal or 3ertical5a is. =ori&ontal axis machines are preferred for long, thin cylinders,vertical machines for rings.


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Features of centrifugal casting:

Castings can be made in almost any lengt , t ic8ness & diameter .

9ifferent wall t ic8nesses can be produced from the same si&e mold.

?liminates the need for cores .

1esistant to atmosp eric corrosion , a typical situation with pipes.

Mec anical properties of centrifugal castings are excellent

)nly c'lindrical s apes can be produced with this process.


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Materials:

Typical materials that can be cast with this processare iron steel stainless steels glass an alloysof aluminum copper nic>el.

Two materials can be cast together by introducing a secondmaterial during the process.

Applications:

Typical parts made by this process are pipes oilers pressure3essels fly4#eels cylin er liners an ot#er parts t#at are a i5symmetric . -t is notably used to cast cylin er liners and slee3e3al3es for piston engines, parts which could not be reliablymanufactured otherwise .


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'9/ CA+TING,..-----


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A 3antages of Casting:

1. )n &asis of +i e of ) Dect to e Manufacture :Si&e of cast ob(ects vary over large range. 5n ob(ect from gmto 2//tonn, anything can be cast.

2. )n &asis of Comple ity:

Casting can be effectively used for complex shaped ob(ects. -tcan work where general machining processes can not be used,as in complicated inner and outer shapes of ob(ect.

!. 'eig#t +a3ing:

Component made with casting process is lighter than thecomponent made with other machining processes.

". Control )3er T#e 0rocess:

Casting provides versatility. >ide range of properties can beattained by ad(usting percentage of alloying elements.


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$. Accuracy:

Casting can be made with hair like precision provided proper molding and casting techni$ue is employed.


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*isa 3antages of Casting:

Though casting is cheapest for M*SS #roduction, it becomes non economical in case of ?O@ production.

Sand casting leaves rough surface which needsmachining in most of cases. -t adds up the cost in

production.

-n sand casting, poor dimensional accuracy is achieved.

Cast products are superior for compressive loads but theyare very poor in tensile or shock loads. They are brittle".


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FINA88/ T9ATE+ A88 ,------


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casting types -1

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