Mold and mold making

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DEFINATIONPreparing molding sand is packed rigidly around the pattern is withdrawn , a cavity corresponding to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.