Foundry basics

This pdf includes basics of foundry- introduction, advantages over other manufacturing processes, equipment's(tools), types of moulding sands and properties of moulding sands.

by:
JUKANTI VISHWAS
M.TECH
(Research Scholar)

1. SamskrutiCollege of Engg. & Tech.
Dept. of Mechanical Engineering
J. VISHWAS
ME
UNIT-III
FOUNDRY
SUB: Advanced Workshop Technology

2. CONTENTS
•INTRODUCTION
•ADVANTAGES & LIMITATIONS OF CASTING OVER OTHER
MANUFACTURING PROCESSES
•FOUNDRY EQUIPMENT
•SANDS
•Properties of mouldingsand
•Types of mouldingsand

3. INTRODUCTION
•The foundry industry is probably the oldest branch of engineering, and It is certainly one of the
most important.
•It was practiced by the craftsmen of ancient greekand roman civilizations and even earlier.
•This technique was used for some of the metallic objects in the form of knives, coins, arrows,
household articles and armoury, guns and war materials.
•Copper and bronze were common in ancient times, but now a days all the metals can be cast.
•Some of the items manufactured by foundry.
1.Jewellwery
2.Machine tools
3.Sports
4.Machine frames
5.Power transmission elements.

4. •A foundry is a place where castings are produced.
•Castings are made from patterns which are exact replicas of the article
to be produced.
•The patterns are pressed into sand, and when removed leave their
impression.
•Into this sand impressions or mould, molten metal is poured and
allowed to cool or solidify.
•When it is removed it will be of the same shape as the mould. Only
slightly smaller owing to the contraction of the metal.

5. ADVANTAGES OF CASTING OVER OTHER MANUFACTURING
PROCESSES
1.Casting can produce very complex geometry parts with internal Cavities.
2.It can be used to make small (few hundred grams) to very large size part (thousand of kilograms).
3.Any intricate shape can be Produced.
4.Any Material can be cast ferrous & non-ferrous.
5.It is economical, with very little wastage: the extra metal in each casting is re-mental and re-used.
6.Cast Metal is isotropic. It has the same physical and mechanical properties along and direction.
7.It is a process highly adaptable to the requirements of mass production large number of a given casting can
be produced quickly.
For Examples:Inthe automotive industry there is massive production of cast engine blocks and transmission
cases.
8.Necessary tools required for castings are Cheaper & simple.
9.Certain metals & alloys are produced only by castings.
LIMITATIONS/DISADVANTAGES
1.It gives poor surface finish and mostly requires surface finish operation.
2.Casting defectsinvolves in this process.
3.It gives low fatigue strength compare toforging.
4.It is not economical for mass production.

6. FOUNDRY EQUIPMENT -Hand mouldingtools
The tools are:
1. Shovel 2. Riddle
3. Rammers 4. Trowels
5. Strike-Off Bar 6. Vent Wire
7. Lifter 8. Slick
9. Swab 10. Bellow
11. Gate Cutter 12. Spruepin
13. Draw Screw 14. Mallet
15. Gagger 16. Rapping Plate
17. Clamps 18. Sprit Level
19. strike-off bar 20. mouldingboard and bottom board
21. Mouldingboxes

7. FOUNDRY EQUIPMENT -Hand mouldingtools
1.Shovel:
Ashovelisusedformixingthesandwithotheringredients.Itis
alsousedforhandlingthesandfromoneplacetoanotherinthe
foundaryshop.Itconsistsofasquaremetalpanfittedwitha
woodenhandle
2.Riddle:
Ariddleisusedforcleaningthemouldingsand.Itremovesthe
unwantedmateriallikemetalscrap,ironandothermetalparts,
pebblesetc.,
3.Rammers:
Arammerisawoodormetaltoolusedforrammingorpacking
thesandinthemouldingbox.Ithastwopartspeenandbutt.
Rammersareavailableindifferentdesignsandconstructions.
Thepopularandwidelyusedrammersarepeen-rammer,
bench-rammer,andfloor-rammeretc.,

8. FOUNDRY EQUIPMENT -Hand mouldingtools
4.Trowels:
Atrowelisusedforfinishingandrepairingamould.Itconsists
ofametal-flatwithdifferentshapesandwoodenhandle.Itis
alsousedforsmoothenthemouldsurfaces,shapingthesquare
corners,finishingthepartingsurfaces.Itisavailableindifferent
shapeslikerectangular,triangular,square,roundetc.,
5.Strike-OffBar:
Astrike-offbarisusedforstrikingofftheexcesssandfromthe
mouldtoprovideasmoothsurface.Itisastraightbarofwood
orsteelandusuallyhaverectangularcross-section
6.VentWire:
Aventwireisusedtoformventsorholesintherammedsand
toprovideeasyescapeofgasesorsteamformedduringpouring
ofmoltenmetal.Itisacircularorrectangularlongneedletool,
pointededgeatoneendandhandleattheotherend

9. FOUNDRY EQUIPMENT -Hand mouldingtools
7.Lifter:
Alifterisusedforpickinguptheunwanteddustanddamaged
partsofthemould.ItisaL-shapedsteeltoolwithlongholding
shankandasmalltoe.Itisavailableinthinsectionsofvarious
widthandlengths,accordingtotheshapeofthemould
8.Slick:
Aslickisusedforrepairandfinishingthemouldsurfaceafter
theremovalofpattern.Itisadoubleendedtoolhavingaspoon
ononeendandaflatontheotherend
9.Swab:
Aswabisusedformoisteningthesandaroundtheedgebefore
thepatterniswithdrawn.Itconsistsofsofthairbrushtohold
wateratoneend,andarubberbuldattheotherend

10. FOUNDRY EQUIPMENT -Hand mouldingtools
10.Bellow:
Abellowisusedtoblowlooseparticlesofsandfromthecavity
andsurfaceofthemould.Sometimes,acompressjetofairis
usedforthispurpose
11.GateCutter:
Agatecutterisusedforcuttingthegateinthemouldwhich
actsasapassageforthehotmetal.ItisU-shapedpieceofthin
sheetmetal
12.Spruepin/Cutter:
Aspruecutterisusedforcreatingarun-throughorsprueforthe
moltenmetalinthecope.Ithastaperedcylindricalshapeand
madefromwood

11. FOUNDRY EQUIPMENT -Hand mouldingtools
13.DrawScrew:
Adrawscrewisusedfordrawnoutthepatternembeddedin
themouldingsand.Itisapointedsteelrod,withaloopatone
end.Woodenmalletisusedforstrikingthedrawscrew,also
calleddrawspike.
14.Mallet:
Amalletisusedtoloosenthepatterninthemouldsothatitcan
beremovedeasily.Itisusedtogetherwithdrawspike
15.Gagger:
Agaggerisusedforreinforcingthemouldingsandinthecope
partofthemouldingbox.Thesearetheironrodsorthickwires
bentatoneorboththeends.Thebottomendofthegagger
mustbekept5to8mmawayfromtheembeddedpattern

12. FOUNDRY EQUIPMENT -Hand mouldingtools
16.Rapping Plate:
A rapping plate is used for lift the large and heavy pattern from
the mould. It is a steel plate and firmly fixed to the top of the
pattern by means of bolts and screw. Rapping plates are
available in many shapes
17.Clamps:
The clamps are used for holding the top and bottom parts of the
mould so that the cope should not rise when the molten metal
is poured into the mould cavity
18. Sprit Level:
A sprit level is used to keep sand bed, mouldingbox and table in
horizontal position. It consists of an air bubble inside a curved
glass tube

13. FOUNDRY EQUIPMENT -Hand mouldingtools
19. Mouldingboard 20. Mouldingbox
AboxtypemouldingboxisshowninFig.4.10(a)isalsoknown
aspermanentflask,theseflasksshouldnotberemovedtillthe
pouringofmoltenmetaliscompleted.Theseboxesare
generallymadeofsteelandusedforsmallandmedium-
sizedcastings.
Amouldingboardisasmooth
woodenboardonwhichtheflaskand
patternsareplacedwhenmouldmaking
isstarted.

14. Types of mouldingsand
backingsand,coresand,drysand,facingsand,greensand,loam
sand,partingsand,systemsand
Backingsandorfloorsandisusedtobackupthefacingsandandisusedto
fillthewholevolumeofthemoldingflask.Backingsandissometimescalled
blacksandbecauseofold,repeatedlyusedmoldingsandisblackincolordue
toadditionofcoaldustandburningoncomingincontactwiththemolten
metal.
Coresandisusedformakingcoresanditissometimesalsoknownasoilsand.
Coresandishighlyrichsilicasandmixedwithoilbinderssuchascoreoil
whichcomposedoflinseedoil,resin,lightmineraloilandotherbindmaterials.
Pitchorfloursandwatermayalsobeusedinlargecoresforthesakeof
economy.

15. Types of mouldingsand
Drysand
Greensandthathasbeendriedorbakedinsuitableovenafterthemakingmoldandcoresiscalleddry
sand.Itpossessesmorestrength,rigidityandthermalstability.Drysandismainlyusedforlarger
castings.Moldpreparedinthissandareknownasdrysandmolds.
Facingsandformsthefaceofthemould.Itisnexttothesurfaceofthepatternanditcomesintocontact
withmoltenmetalwhenthemouldispoured.Initialcoatingaroundthepatternandhenceformoldsurface
isgivenbyfacingsand.Facingsandhavehighstrengthrefractoriness.Facingsandismadeofsilicasand
andclay,withouttheuseofalreadyusedsand.Differentformsofcarbonareusedinfacingsandto
preventthemetalburningintothesand.Afacingsandmixtureforgreensandofcastironmayconsistof
25%freshandspeciallypreparedand5%seacoal.Theyaresometimesmixedwith6-15timesasmuch
finemoldingsandtomakefacings.
Greensandisalsoknownastemperedornaturalsandwhichisajustpreparedmixtureofsilicasand
with18to30%clay,havingmoisturecontentfrom6to8%.Theclayandwaterfurnishthebondforgreen
sand.Itisfine,soft,light,andporous.Greensandisdamp,whensqueezedinthehandanditretainsthe
shapeandtheimpressiontogivetoitunderpressure.Moldspreparedbythissandarenotrequiring
backingandhenceareknownasgreensandmolds.Greensandiseasilyavailableanditpossesseslow
cost.Greensandiscommonlyemployedforproductionofferrousandnon-ferrouscastings.

16. Types of mouldingsand
Loamsandismixtureofsandandclaywithwatertoathinplasticpaste.Loamsandpossesses
highclayasmuchas30-50%and18%ofwater.Patternsarenotusedforloammoldingand
shapeisgiventomoldbysweeps.Loamsandisparticularlyemployedforloammoldingused
forlargegreyironcastings.
Partingsandwithoutbinderandmoistureisusedtokeepthegreensandnottosticktothe
patternandalsotoallowthesandtothepartingsurfacethecopeanddragtoseparatewithout
clinging.Partingsandiscleanclay-freesilicasandwhichservesthesamepurposeasparting
dust.
Systemsand
Inmechanizedfoundrieswheremachinemoldingisemployed.Systemsandisusedtofillthe
wholemoldingflask.Inmechanicalsandpreparationandhandlingunits,facingsandisnot
used.Theusedsandiscleanedandre-activatedbytheadditionofwaterandspecialadditives.
Thisisknownassystemsand.Sincethewholemoldismadeofthissystemsand,theproperties
suchasstrength,permeabilityandrefractorinessofthemoldingsandmustbehigherthanthose
ofbackingsand.

17. Properties of mouldingsand
Thebasicpropertiesrequiredinmoldingsandandcore
sandareadhesiveness,cohesiveness,collapsibility,flowability,drystrength,green
strength,permeability,refractorinessdescribedasunder.
Adhesivenessisapropertyofmoldingsandtogetthestickoradheretoforeignmaterial
suchstickingofmoldingsandwiththeinnerwallofmoldingbox.
Cohesivenessispropertyofmoldingsandbyvirtuewhichthesandgrainparticlesinteract
andattracteachotherwithinthemoldingsand.Thus,thebindingcapabilityofthemolding
sandgetsenhancedtoincreasethegreen,dryandhotstrengthpropertyofmoldingandcore
sand.
Collapsibility
Afterthemoltenmetalinthemouldgetssolidified,thesandmouldmustbecollapsibleso
thatfreecontractionofthemetaloccursandthiswouldnaturallyavoidthetearingor
crackingofthecontractingmetal.Inabsenceofcollapsibilitypropertythecontractionofthe
metalishinderedbythemoldandthusresultsintearsandcracksinthecasting.This
propertyishighlyrequiredincores.

18. Properties of mouldingsand
Drystrength
Assoonasthemoltenmetalispouredintothemould,themoistureinthesandlayeradjacent
tothehotmetalgetsevaporatedandthisdrysandlayermusthavesufficientstrengthtoits
shapeinordertoavoiderosionofmouldwallduringtheflowofmoltenmetal.Thedry
strengthalsopreventstheenlargementofmouldcavitycausebythemetallostaticpressure
oftheliquidmetal.
Flowabilityorplasticityistheabilityofthesandtogetcompactedandbehavelikeafluid.It
willflowuniformlytoallportionsofpatternwhenrammedanddistributetheramming
pressureevenlyallaroundinalldirections.Generallysandparticlesresistmovingaround
cornersorprojections.Ingeneral,flowabilityincreaseswithdecreaseingreenstrengthand
viceversa.Flowabilityincreaseswithdecreaseingrainsizeofsand.Theflowabilityalsovaries
withmoistureandclaycontentinsand.
Greenstrength
Thegreensandafterwaterhasbeenmixedintoit,musthavesufficientstrengthand
toughnesstopermitthemakingandhandlingofthemould.Forthis,thesandgrainsmustbe
adhesive,i.e.theymustbecapableofattachingthemselvestoanotherbodyand.therefore,
andsandgrainshavinghighadhesivenesswillclingtothesidesofthemoldingbox.

19. Properties of mouldingsand
Permeabilityisalsotermedasporosityofthemoldingsandinordertoallowtheescapeofanyair,gases
ormoisturepresentorgeneratedinthemouldwhenthemoltenmetalispouredintoit.Allthesegaseous
generatedduringpouringandsolidificationprocessmustescapeotherwisethecastingbecomesdefective.
Permeabilityisafunctionofgrainsize,grainshape,andmoistureandclaycontentsinthemoldingsand.
Theextentoframmingofthesanddirectlyaffectsthepermeabilityofthemould.Permeabilityofmold
canbefurtherincreasedbyventingusingventrods.
Refractorinessisdefinedastheabilityofmoldingsandtowithstandhightemperatureswithoutbreaking
downorfusingthusfacilitatingtogetsoundcasting.Itisahighlyimportantcharacteristicofmolding
sands.Refractorinesscanonlybeincreasedtoalimitedextent.Moldingsandwithpoorrefractoriness
mayburnontothecastingsurfaceandnosmoothcastingsurfacecanbeobtained.Thedegreeof
refractorinessdependsontheSiO
2i.e.quartzcontent,andtheshapeandgrainsizeoftheparticle.The
highertheSiO
2contentandtherougherthegrainvolumetriccompositionthehigheristherefractoriness
ofthemoldingsandandcoresand.Refractorinessismeasuredbythesinterpointofthesandratherthan
itsmeltingpoint.
Miscellaneouspropertiesofmoldingsand
Inadditiontoaboverequirements,themoldingsandshouldnotsticktothecastingandshouldnot
chemicallyreactwiththemetal.Moldingsandneedbeeconomicallycheapandeasilyavailableinnature.
Itneedbereusableforeconomicreasons.Itscoefficientsofthermalexpansionneedbesufficientlylow.

20. ThankYou