Manufacturing Technology-I

Manufacturing Technology-IMetal Casting ProcessesG.GOPINATHByAP/Mech/RVSTCC

METAL CASTING PROCESSES Sand casting Sand moulds - Type of patterns Pattern materials Pattern allowances Types of Moulding sand Properties Core making Methods of Sandtesting Moulding machines Types of moulding machines - Melting furnaces Working principle of Special casting processes Shell, investment casting Ceramic mould Lost Wax process Pressure die casting Centrifugal casting CO2 process Sand Casting defects Inspection methods

1.ManufacturingManufacturing in its broadest sense is the process of converting raw materials into useful products. IT Includesi) Design of the productii) Selection of raw materials andiii) The sequence of processes through which the product will be manufactured. Casting.Any Product in the engineering industry will be manufactured in the below methods1. By totally deforming the metal to the required shape. (Casting /Forming)1. By joining two metals. (Welding)2. By removing the excess material from the raw stock.(Machining)

Casting.Casting is the process of producing metal parts by pouring molten metal into the mould cavity of the required shape and allowing the metal to solidify. The solidified metal piece is called as "casting". Sand Casting /Sand Moulding.Sand Casting is simply melting the metal and pouring it into a preformed cavity, called mold, allowing (the metal to solidify and then breaking up the mold to remove casting. In sand casting expandable molds are used. So for each casting operation you have to form a new mold.

Types of sand

a) Green-sand - mixture of sand, clay, and water,Binders (Molases, Linseed oil); "Green means mold contains moisture at time of pouring.b) Dry-sand - organic binders rather than clay and mold is baked to improve strengthc) Skin-dried - drying mold cavity surface of a green-sand- mold to a depth of u p t o 25 mm, using torches or heatingd)Core Sande)Baking sandf)Loam Sandg)Parting sand, Etc

PatternsPatterns are the replica or physical models of the final required shape of the casting, made by wood (teak,magony,pine), plastics, Metals, Plaster of paris etc.,Types of patterns.1.Solid pattern2.Split piece pattern3.Three piece pattern4.Loose piece pattern5.Match plate pattern6.Segmental pattern7.Sweep patten8.skeleton Pattern9.shell Pattern.

Pattern Allowance.Allowance are the extra dimensional compensation give to the pattern in order to attain the correct shape and size of the final solidified metal casting.Five types of allowances were taken into consideration for various reasons.

Allowance types refer PDF pg.no 8

Steps in Sand Casting

The cavity in the sand mold is formed by packing sand around a pattern, separating themold into two halves The mold must also contain gating and riser system For internal cavity, a core must be included in mold A new sand mold must be made for each part.1. Pour molten metal into sand mold2. Allow metal to solidify3. Break up the mold to remove casting4. Clean and inspect casting5. Heat treatment of casting is sometimes required toimprove metallurgical properties.

Sand Moulding

Sand Moulding Preparation

Sand Moulding

Sand Moulding

Types of PatternSingle Piece Pattern Split piece pattern

Types of PatternMatch Plate Pattern Cope and Drag pattern

Types of PatternGated Pattern

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Types of PatternLoose Piece Pattern

Types of PatternSweep Pattern

Types of PatternSkeleton PatternSegmental Pattern

Types of PatternShell Pattern

Pattern AllowancesShrinkage Allowances

Pattern AllowancesDraft allowances

Pattern AllowancesDistortion Allowances

Pattern AllowancesMachining Allowances

Pattern AllowancesRapping Allowances or Shake AllowancesNegative AllowanceTo rap the pattern from the sandIt creates some space around the pattern

Moulding SandConstituents of Moulding SandSilica sand grains80-90% Silicon dioxideQuartz rockImparts refractoriness, chemical resistivity, permeability.Clay5-20%Bonding StrengthMoisture2-8%Miscellaneous materials Limestone, magnesia, soda and potash.

Types of Moulding SandGreen Sand 18-30% Silica6-8% waterSoft, light and porous Dry SandGreen sand dried and bakedLarge castingsLoam Sand50% of clay Large Castings

Types of Moulding SandFacing SandFace of mouldSurface of pattern20-30 mmBacking SandBack up facing sandSystem SandNo facing sand Reactivated sandsParting SandAvoids sticking of pattern to mould sand Avoids sticking of cope and dragCore SandSilica and core oil, to prepare core

Properties of Moulding SandPorosity or Permeability (gas holes and pores)FlowabilityCollapsibilityAdhesiveness (should cling or stick to sides of box)Cohesiveness or strength Refractoriness (withstand high temp.)

Moulding Sand Preparation Mixing of sand (Sand ,binders and additives)Sand Tempering (adding moisture)Sand ConditioningMuller MachineRiddles (screening sand)Magnetic SeparatorsAerators(sand grains)

Moulding ToolsShowelRiddleRammerTrowelSlickLifterStrike-off barSprue pin

BellowSwabGate cutterMalletVent RodDraw spikeClampsMoulding boxes

Core A core is a device used in casting process to produce internal cavities and reentrant angles. The core is normally a disposable item that is destroyed to get it out of the piece. They are most commonly used in sand casting.

Core RequirementsStrongPermeableRefractoryLow residual gas formingStableEase collapsable

Core

Core SandSand and BinderSilica, zircon, olivine, carbon, chamotteNot have more than 5% of clay.

Core MakingCore Sand PreparationRoller MillsCore mixersCore MouldingCore Blowing Machines Core Ramming Core BakingCore ovensBatch typeContinuous typeDielectric BakersCore FinishingCore dressingCore coating

Core OvensBatch typeContinuous Type

Types of Core Horizontal CoreVertical CoreBalanced CoreHanging CoreWing CoreRam-up CoreKiss Core

Types of CoreHorizontal Core

Types of coreVertical Core

Types of CoreRam up core