18543038 sand casting presentation
TRANSCRIPT
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SANDCASTING
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PRESENTED BY
GROUP 1ANG PHEI CHEE
CHUNG YU NING
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CONTENTS
INTRODUCTION
THE SAND
EQUIPMENTS GATING SYSTEM
THE PROCESS
FLOW CHART OF PROCESS CYCLE
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PRODUCTS OF SAND CASTING
cast model
bronze cast model
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INTRODUCTION
Sand casting, the most widely used casting
process, utilizes expendable sand moulds to
form complex metal parts that can be made of
nearly any alloy.
The sand casting process involves the use of a
furnace, metal, pattern, and sand mould.
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MATERIALS
Sand casting is able to make use of almost any alloy. An advantage of sandcasting is the ability to cast materials with high melting temperatures,including steel, nickel, and titanium.
The four most common materials that are used in sand casting are shownbelow, along with their melting temperatures.
Materials Melting temperature
Aluminum alloys 1220 F (660 C)
Brass alloys 1980 F (1082 C)
Cast iron1990-2300 F (1088-
1260 C)
Cast steel 2500 F (1371 C)
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ADVANTAGES
Can produce very large parts
Can form complex shapes
Many material options Low tooling and equipment cost
Scrap can be recycled
Short lead time possible
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DISADVANTAGES
Poor material strength
High porosity possible
Poor surface finish and tolerance Secondary machining often required
Low production rate
High labor cost
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THE SAND
Different types of sand are used in sand casting;
Petro-bond This is a mixture of quality sand andoil or synthetic resin.
Green sand A mixture of sand, clay, water andsometimes other additives. It is called green sandbecause it is re-usable. The right amount of waterhas to be added to prevent porosity.
Sand mixed with water glass can be hardened
with CO2 gas .(This transforms the sand into a solid mould, whichcan be used after the cope & drag are removed.)
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CHARACTERISTICS OF SAND
FLOWABILITY
The ability to pack tightly around the pattern.
PLASTIC DEFORMATION
Have the ability to deform slightly withoutcracking so that the pattern can be withdrawn.
GREEN STRENGTH
Have the ability to support its own weight whenstripped from the pattern, and also withstandpressure of molten metal when the mold is cast.
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PERMEABILITY
This allows the gases and steam to escapefrom the mold during casting.
THERMAL STABILTY
Ability to resist damage, such as cracking,from the heat of the molten metal.
REUSABILITY
Ability of the sand to be reused for futuresand molds.
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EQUIPMENTS
CASTING FLASK
Consists of the cope (top halve) and the drag
(bottom halve) to receive the pattern.
The drag (left) and cope
(right) of a casting flask
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PATTERN
Model of products, made of wood, plastic or
metals.
CORE
To produce cavities within the casting, made of
plaster, metals and ceramics.
Left:- Corebox, with resulting (wire reinforced)
cores directly below.
Right:- Pattern (used with the core) and
the resulting casting below
(the wires are from the remains of the core)
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STRAIGHT EDGE BAR
To level the sand above or below the casting flask,made of metals.
RAMMER
Consists of 2 different ends, an wedge-shaped end
and a flat shape end. Use to compress the sand.
PARTLING SAND
Put on the pattern to make it easier to remove.
LADLE
Use to melt the metals and pour into the mould.
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GATING SYSTEM
This picture shows the cross section of a sand casting mould.
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DEFINATIONS
POURING CUP
This is where the metal is poured into the mold.
SPRUE
The vertical channel from the top of the mold tothe gating and riser system. Also, a generic termused to cover all gates, runners and risers.
RUNNER The portion of the gate assembly that connectsthe sprue to the casting in gate or riser.
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GATE
The end of the runner in a mold where moltenmetal enters the mold cavity.
RISER
A reservoir of molten metal provided to
compensate for the contraction of the metal as it
solidifies.
MOLD CAVITY
The impression in a mold produced by theremoval of the pattern. When filled with molten
metal it forms a casting.
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COPE
Upper or top most section of a flask, mold orpattern.
PARTING LINE
A line on a pattern or casting corresponding to the
separation between the parts of a mold.
DRAG
Lower or bottom section of a flask, mold or
pattern.
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THE PROCESS
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A wooden pattern
of the required
casting shape ismade. A metal or
plastic can also be
used.
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A metal or
wooden flask isused to contain the
sand.
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The pattern is
placed in the flaskand packed in with
sand.
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The other half of
the mould is
placed on top,again staring with a
wooden or metal
frame.
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Sand is added
around the pattern
through a sieve, sothat it packs
together better.
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The sand is then
packed around the
pattern using thewedge-shaped end
of a rammer.
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More sand is
added, this timenot sieved.
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The sand is then
rammed in firmly
using a peen or theflat end of the
rammer.
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The sand is then
leveled off, and theexcess removed.
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A piece of pipe is
carefully pushed
through the sandto the pattern to
create a runner,
and some risers.
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Small holes arecreated in the
surface of the
sand, and CO2 gas
is passed throughto harden the
molding sand
mixed with the
water glass.
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The 2 halves of the
mould are thenseparated and the
pattern removed.
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The entrance to
the mould ( the
runner ) is then
connected to themould cavity, and
the other half
mould is hardened
with CO2.
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The 2 halves of the
mould are placed
back together,ready to make the
casting.
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Molten metal is
poured through
the runner until itfills the mould and
starts to flow up
the risers.
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The metal is left to
cool and solidify,
and then themould is broken
apart to reveal the
casting.
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The metal is left to
cool and solidify,
and then themould is broken
apart to reveal the
casting.
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The runner and
risers can then be
cut off, and thecasting polished to
give a better
surface finish.
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PROCESS CYCLE
MOULD
MAKINGCLAMPING POURING
COOLINGREMOVALTRIMMING
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PROCESS CYCLE
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THE END