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MOLD AND MOLD MAKING
PREPARED BYDobariya gautam mansukhbhai
MOLD AND MOLD
MAKING
About mold
DEFINATIONPreparing molding sand is packed rigidly around the pattern is withdrawn , a cavity corresponding to
shape of the pattern remains in the sand and is known as mold cavity.
MOLDING SANDS• SOURCES
• 1.River beds
• 2.Sea ,lakes ,desert
• TYPES• 1.Natural sand
• 2.Synthetic sand
• 3.Loam sand
• INGREDIENTS
• 1.Refractory sand grains
• 2.Binders
• 3.Water
• 4.Additives
TYPES OF SANDS USED IN MOLDS
• 1.Green sand
• 2.Dry sand
• 3.Loam sand
• 4.Synthetic sand
• 5.Core sand
• 6.Parting sand
• 7.Facing sand
• 8.Backing sand
• 9.Sharp sand
• 10.System sand
• 11.Heap sand
• 12.Oil & molasses
sand
• GREEN SAND
• It containing 5% water and 15-30% clay.• Prefer for small, medium, size casting.
• DRY SAND
• Green sand mold when dried results in a dry sand mold.• Dry mold possess• 1.grater strength. • 2. Thermal stability.
• FACING SAND• Fresh and specially prepared molding sand.• Facing sand comes in direct contact with the
molten metal being poured and therefore it should possess much improved properties as compared to ordinary sand.
• It reduce mold material cost.
• BACKIG SAND• It is sand which backs up the facing sand• It does not come in contact with the pattern.• It has black colour known as BLACK SAND.
• SHARP SAND• It need not have necessarily sharp grains.• A sharp sand is one which is substantially free of
bond.
• SYSTEM SAND• It is one which is used in a mechanical sand
preparation and handling system.
Nd is • HEAP SAND
• It is the sand put on the floor as a heap when it is prepared for use.
• OIL & MOLASSES SAND
• Sand using oil binders or molasses binders are known as oil & molasses sand.
• Molasses sand is use for producing intricate, small thin sectioned and accurate castings.
• Small non-ferrous gears may be cast in molasses sand.
Properties of molding sandFlowability
Green strength
Hot strength
Refractoriness
Adhesiveness
Fineness
Bench of life
Coefficient of expansion
Durability
FLOWABILITY
It is the ability of the molding sand
to get compacted to uniform
density
Flowability increases as clay and
water contents increase.
GREEN STRENGTH
It is the strength of sand in green or
moist state.
Green strength help in making and
handling the molds.
HOT STRENGTH
It is strength of sand above 212’F.
In the absence of adequate hot strength,
the mold may
1.enlarge
2.break
3.get cracked
DRY STRENGTH
It is strength of molding sand in the
dry condition.
Dry sand strength is related to grain
Size ,binder ,water content.
REFRACTORINESS
It is the ability of molding sand to
withstand high temp. without
1.Fusin
2.Cracking or buckling
ADHESIVENESS
It is property of molding sand owing to
which ,it
1.Sticks with the wall of molding boxes
2.sticks with gaggers.
FINENESS
Finer sand molds resist metal
penetration & produce smooth
casting surface and it can be
maintained by using mold
coating on highly permeable
mold cavity walls.
BENCH LIFE
It is ability of molding
sand to
retain its properties during
storage or while standing.
COEFFICIENT OF EXPANSION
Molding Sand Should Possess Low coefficient of expansion.
And also molding sand is easy to prepare and control
ADDITIVES• 1. The basic constituents of molding
sand mixture are sand, binder , water.
• 2.Some of additives materials along with the specific function performed by them like…….
FACING MATERIALS
Facing materials tend to obtain Smoother and cleaner surfaces of castings and help easy peeling of sand from the casting surface during shake out……………………………
•
• 1.SEA COAL- Added to molding sand for cast iron to
improve stripping & surface apperiance.
• 2.PITCH & ASPHALT- Improve hot strength.
• 3.GRAPHITE-Improve surface finish of castings.
• 4.COKE• 5.SILICA FLOUR-Improve surface finish,add hot strength
• Cushion materials burn when the molten metal is poured and thus give rise to space for accommodating the expansion of silica sand at the surface of mold cavity.
CUSHION MATERIALS
WOOD FLOUR, CEREAL HULLS, CELLULOSE.
They minimize the sand expansion defects.Improve flowability.
PERLITEIt serves the same purpose a wood flour.
CEREALS It increse green & hot strength.It minimizes sand expansion defects.
TESTS ON MOLDING SAND • Sand test is require because a molding sand is
supposed to possess many properties for its efficient functioning.
• This properties depend upon grain shape, size, distribution, type of binders, additives and moisture.
• So for produce sound casting & good quality of mold test is require.
MOISTURE CONTENT TEST
• It determines the
• 1.Moisture content
• METHODS • 1.Using electrode probe
devices.
• 2.Employing measurements of microwave absorptiong in compacted sand samples.
• 3.Using infrared heating
MOISTURE DETERMINING APPARATUS
GRAIN FINENESS TEST
• It determines the• 1.Grain size• 2.Distribution• 3.Grain fineness
• METHODS
• Grain fineness tester
GRAIN FINENESS TESTER
STRENGTH TEST
• It determined by,
• 1.Compression• 2.Tensile• 3.shear• 4.Transverse tests
• METHOD
• Strengths testing equipment
STRENGTHS TESTER
HOT STRENGTH TEST
• It determine the
• Hot strength of molding sand.
• METHOD
• 1.Specimen is tested in a DILATOMETER
SHAPES OF SPECIMEN AND GRIPS FOR STRENGTHS
HAND MOLDING EQUIPMENT
• In hand processes , all the operations, such as ramming the sand , placing and drawing the pattern ,turning over the molding boxes , etc are performed by hand.
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