MANUFACTURING SCIENCE S5ME -NITC-2016

Some basics - you had in Foundry
Sand casting.Sand casting.
Steps:
» 1.Mechanical Drawing of the part
» 2. Making pattern- about pattern material.
» 3.Making cores- if needed
» 4.Preparing drag and cope. (Setting the core, positioning etc.)
» 5.Removal of pattern
» 6Assembling cope and drag
» 7.Pouring- factors, method, etc.
» 8.Casting removed
» 9.Trimming etc.
» 10. READY FOR SHIPMENT
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1.Mechanical Drawing of the part
2. Making pattern- about pattern
material.
3.Making cores- if needed
4.Preparing drag and cope.
(Setting the core, positioning etc.)
5.Removal of pattern
6Assembling cope and drag
7.Pouring- factors, method, etc.
8.Casting removed
9.Trimming etc.
10. READY FOR SHIPMENT
Some basics you had
in Foundry
1
4a
32
5b 6 8&9 10
5a4b
3b 3c3a

CASTINGCASTING
FUNDAMENTALSFUNDAMENTALS
Basically involves
i. Pouring molten metal into a mould patterned after the part to be made
WITHOUT TURBULANCE , SERIES OF EVENTS TAKES PLACE
INFLUENCE SIZE, SHAPE, UNIFORMITY OF THE GRAINS FORMED,
AND THUS THE OVERALL PROPERTIES.
• ii. Allow it to cool
HEAT TRANSFER DURING SOLIDIFICATION
• iii. Remove from the mold
INFLUENCE OF THE TYPE OF MOULD MATERIAL
•
SIMILARITY WITH POURING CAKE MIX INTO A PANSIMILARITY WITH POURING CAKE MIX INTO A PAN
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POURING CAKE MIX INTO A PAN (MOULD) & BAKING IT
*SELECT THE KIND AND SIZE OF PAN,
*CONTROL THE COMPOSITION OF THE MIX,
* CAREFULLY POUR THE MIX,
* SET THE PROPER BAKING TEMPERATURE,
* SET THE TIMER FOR PROPER BAKING TIME,
* LEAVE THE CAKE IN THE MOULD FOR A CERTAIN
AMOUNT OF TIME BEFORE REMOVING.
(CASTING OF PLASTICS & CERAMICS - DIFFERENT)
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Knowledge of certain fundamental relationships
is essential to produce good quality economic
castings
This knowledge helps in establishing proper
techniques for mould design and casting practice.
Castings must be free from defects, must meet the
required strength, dimensional accuracy, surface
finish
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Outline of production steps in a typical sand casting operation
- pattern making
- Core making
- Gating system
Moulding
Sand Mould
Melting Pouring casting Heat Treat Clean Inspect
Furnaces Solidification Shakeout Addl. Heat Treatment
Defects, pressure tightness, dimensions
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ADVANTAGES OF CASTING PROCESS
• Process is cheap
• More suitable for mass production
• Most suitable for manufacturing
complex/complicated/intricate shaped products.
• Large parts weighing several tonnes and also small
components weighing a few grams can be cast.
• No limitation on the size of component.
• Directional properties absent in castings. Components with
uniform properties as well as with varying properties at
different locations can be cast.
• By use of cores, saving in machining of holes achieved.
• Internal stresses are relieved during solidification in many
types of castings.
• Even some materials which cannot be made by other
processes made by casting: eg. Phosphor-Bronze.
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DISADVANTAGES
• Cast product properties inferior in many
cases when compared with other
manufacturing processes.
• Elevated temperature working in
castings, as material has to be melted.
• Thin section limitations exist.
• For number of components very small,
casting not preferred.
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SIGNIFICANT FACTORS-
•TYPE OF METAL,
•THERMAL PROPERTIES OF BOTH THE METAL
AND MOULD,
• GEOMETRIC RELATIONSHIP BETWEEN THE
VOLUME AND SURFACE AREA ,AND
•SHAPE OF MOULD.
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• SOLIDIFICATION OF METALS
• AFTER POURING MOLTEN METAL INTO
MOULD, SERIES OF EVENTS TAKES
PLACE DURING SOLIDIFICATION AND
COOLING TO AMBIENT TEMPERATURE.
• THESE EVENTS GREATLY INFLUENCE
THE SIZE, SHAPE, UNIFORMITY OF THE
GRAINS FORMED, AND THUS THE
OVERALLL PROPERTIES.
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Volumetric variation from Liquid through
Solidification and then to ambient temperature

The liquid Metal has a Volume
"A”
It solidifies to solid with a new
volume "B"
The solidified casting further
contracts (shrinks) through
the cooling process to Volume
"C"
Three Stages of Contraction (Shrinkage)

COOLING CURVE
For pure metal or compound
T
E
M
P
E
R
A
T
U
R
E
TIME, log scale
Freezing begins Freezing ends
Liquid
Liquid
+
Solid
Solid
Cooling
of Liquid
Cooling of solid
Latent heat of
solidification
given off
during
freezing-
At constant
temperature

COOLING CURVE
For Binary solid solutions
T
E
M
P
E
R
A
T
U
R
E
TIME, log scale
Freezing with drop in
temperature
And FOR ALLOYS:
Alloys solidify over a range of
temperatures
Begins when temp. drops below
liquidous, completed when it
reaches solidous.
Within this temperature range,
mushy or pasty state.
Inner zone can be extended
throughout by adding a catalyst.-
sodium, bismuth, tellurium, Mg
(or by eliminating thermal
gradient, i.e. eliminating
convection. (Expts in space to
see the effect of lack of gravity in
eliminating convection)
(refresh dendritic growth-
branches of tree, interlock, each
dendrite develops uniform
composition, etc)

The ambient
temperature is
always in a state of
transition
Minor variations in
volumetric
displacement are
negligible,
compared to the
variations that occur
from "A" to "B" and
lastly to "C".
A
C
B
B
C
A
*
*

STRUCTURE
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FOR PURE METALSFOR PURE METALS::
At the mould walls, metal cools rapidly. Produces
solidified skin or shell (thickness depends on
composition, mould temperature, mould size and
shape etc)
• These of equiaxed structure.
• Grains grow opposite to heat transfer through the mould
• These are columnar grains
• Driving force of the heat transfer is reduced away from
the mould walls and blocking at the axis prevents further
growth

Solidified structures of metal -Solidified structures of metal -
solidified in a square mouldsolidified in a square mould
(a). Pure metal
(b). Solid solution
(c). When thermal gradient is absent
within solidifying metal
Development of a preferred textureDevelopment of a preferred texture
- for pure metal at a cool mould- for pure metal at a cool mould
wall.wall.
A chill zone close to the wall and
then a columnar zone away from
the mould.
Three basic types of cast structures-
(a). Columnar dendritic;
(b). equiaxed dendritic;
(c). equiaxed nondendritic

Size and distribution of the overall grain structure throughout
a casting depends on rate & direction of heat flow
(Grain size influences strength, ductility, properties along
different directions etc.)
CONVECTION- TEMPERATURE GRADIENTS DUE TO
DIFFERNCES IN THE DENSITY OF MOLTEN METAL AT DIFFERENT
TEMPERATURES WITHIN THE FLUID - STRONGLY EFFECTS
THE GRAIN SIZE.
Outer chill zones do not occur in the absence of convectionOuter chill zones do not occur in the absence of convection
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Atm.Pressure
Pouring basin
MOULD
GATE
SPRUE
LIKE A PRESSURISED SYSTEM

MOULDING BOARD
FLASK
SHOWEL
DRAW SPIKE
RIDDLE
SLICK
RAMMER
LIFTER
STRIKE-OFF BAR
TROWELS
GATE CUTTER
BELLOWS
SPRUE PINS
VENT ROD …..
MOULDERS’
TOOLS
AND
EQUIPMENT

Making a Core; (a). Ramming Core Sand. (b). Drawing the core box
(c). Baking in an oven (d) Pasting the core halves
(e). Washing the core with refractory slurry
edc
ba

1. Make the pattern in
pieces, prepare the core.
2. Position the drag half of
pattern on mould board
in the drag half of flask
3. Prepare the drag half of
mould, roll drag over,
apply parting sand, place
the cope half of pattern
and flask, ram and strike
off excess sand
4. Separate flasks, remove
patterns, cut sprue, set
core in place, close flask
5. Now after clamping,
ready fro pouring.
2
3b
4a
1
3a
4b
5

THREE BOX MOULDING
PROCEDURE
LOAM MOULDING USING
LOAM SAND

Design of Risers and Feeding of
Castings• A simplified diagram by putting in
references to the equations (1, 2 & 4)
there is no Equation 3, diagram not changed
• EQ(1) - Freeze Point Ratio (FPR)
FPR=X
X = (Casting Surface/Casting Volume) /
(Riser Surface/Riser Volume)
• EQ(2) - Volume Ratio (VR) (Y Axis)
VR=Y=Riser Vol/Casting Vol*
Note: The riser volume is the actual poured
volume
References - AFS Text Chapter 16; Chastain's Foundry manual Vol 2, Google
• EQ(4) - (Freeze Point Ratio) Steel
X=0.12/y-0.05 + 1.0*
*The constants are from experiments and
are empirical

Volumes, Surface Areas, Castings and
Risers...
There are relationships between all these
items and values that will help in designing
a complete mold that controls progressive
solidification, and influences directional
solidification to produce castings with
minimal porosity and shrinkage defects.
This is by ensuring that the riser(s) are the
last to solidify.

4 points about the Riser/Casting
Relationship
• 1 - Risers are attached to the
heaviest sections of the casting
• 2 - Risers are the last to solidify
• 3 - A casting that has more than
one heavy section requires at
least one riser per heavy section
• 4 - Occasionally the thermal
gradient is modified at the mold-
metal interface by the introduction
of a "Chill" that can better conduct
the heat away from the casting
and lower the solidification time
for that section.

Gating / Runner Design
• A look at the flow characteristics of the metal as it
enters the mold and how it fills the casting.
Of the flow characteristics fluidity/viscosity
plays a role.
Also,
velocity,
gravitational acceleration & vortex,
pressure zones,
molten alloy aspiration from the mold and
the momentum or kinetic energy of a fluid.

The demarcation point is
Re < 2000 is considered a Laminar Flow
Re > 2000 is considered a Turbulent Flow
Objective is to maintain Re below 2000.

Basic Components of a Gating System
• The basic components of a gating system are:
Pouring Basin,
Sprue,
Runners and
Gates that feed the casting.
The metal flows through the system in this order.
Some simple diagrams to be familiar with are:

"Crucible-Mold Interface" is where the metal
from the crucible first contacts the mold
surface.
This area is lower than the area where the
Mouth of the Sprue is located.
Metal flow will be less chaotic than pouring
from the crucible down into the sprue.
"Dross-Dam" - to skim or hold back any
dross from the crucible or what is
accumulated through the act of pouring.
As the lower portion fills and the metal is
skimmed, the clean(er) metal will rise up
to meet the opening of the sprue in a
more controlled fashion.
Pouring Basin - This is the "Crucible -Mold Interface", A pouring cup and
pouring basin are not equivalents, The pouring cup is simply a larger target
when pouring out of the crucible, a Pouring Basin has several components
that aid in creating a laminar flow of clean metal into the sprue.
The basin acts as a point for the liquid metal to enter the gating system in
a laminar fashion.

Sprue Placement and Parts
The sprue is the extension of the sprue
mouth into the mold
The choke or narrowest point in the
taper is the point that would sustain a
"Head" or pressure of molten metal.
From the Pouring Basin, to reduce
turbulence and promote Laminar Flow,
the flow begins in a near vertical incline
that is acted upon by gravity and with an
accelerative gravity force
Fluids in free fall tend to distort from a
columnar shape at their start into an
intertwined series of flow lines that have
a rotational vector or vortex effect
(Clockwise in the northern hemi-sphere,
and counter clockwise in the southern
hemi-sphere).

• The rotational effect, though not a strong
force, is causing the cork-screwing effect
of the falling fluid.
• If allowed to act on the fluid over a great
enough duration or free fall the centrifugal
force will separate the flow into droplets.
• None of the above promotes Laminar flow,
plus it aids the formation of dross and gas
pick-up in the stream that is going to feed
the casting.

The Gating System
• The Gates (in this case)
accommodate a directional
change in the fluid flow and
deliver the metal to the
Casting cavity.
• Again, the design objective
is to promote laminar flow.
The primary causes of
turbulence are sharp
corners, or un-proportioned
gate/runner sizes.
• The two dashed blue areas
when added together form a
relationship to the Choke or
base of the Sprue Area.

• The runner system is fed by the well
and is the path to the gates.
• This path should be "Balanced" with
the model of heating or AC ductwork
serving as a good illustration. The
Runner path should promote smooth
laminar flow by a balanced volumetric
flow, and avoiding sharp or abrupt
changes in direction.
• The "Runner Extension" is a "Dead-
End" that is placed after the last gate.
The R-Ext acts as a cushion to absorb
the forward momentum or kinetic
energy of the fluid flow. The R-Ext
also acts as a "Dross/Gas Trap" for
any material generated and picked-up
along the flow of the runner.
• An Ideal Runner is also proportioned
such that it maintains a constant
volumetric flow through virtually any
cross-sectional area.
• The runner becomes proportionally
shallower at the point where an in-
gate creates an alternate path for the
liquid flow.
The Runner System

Some dimensioning ratios from Chastain's
Foundry Manual (no.2)
• 1- Choke or sprue base area is 1/5th the area of the well.
• 2- The well depth is twice the runner depth.
• 3- the Runner is positioned above the midpoint of the
well's depth
•By creating a sprue with a taper, the fluid is constrained to
retain it's shape, reducing excessive surface area development
(dross-forming property) and gas pick-up.
•The area below the sprue is the "Well". The well reduces the
velocity of the fluid flow and acts as a reservoir for the runners
and gates as they fill.

Formulae, Ratios and Design Equations
• What is covered so far is comprehensive, and intuitive on a
conceptual level, but the math below hopefully offers some insight
into quick approximations for simple designs, and more in-depth
calculations for complex systems.
• Computerized Flow Analysis programs are used extensively in large
Foundry operations.
• From basic concepts, designing on a state of the art system shall be
attempted:
• Continuity Equation –
• This formula allows calculation of cross-sectional areas, relative to
flow Velocity and Volumetric flow over unit time. This is with the
assumption that the fluid flow is a liquid that does NOT
compress (that applies to all molten metals).

Here, a flow passes through A1
(1" by 1", 1 sq")
The passage narrows to a cross-
sectional area A2
(.75" by .75", 0.5625 sq")
The passage expands to a cross-
sectional area A3
(1" by 1", 1 sq").
Q= Rate of Flow
(Constant - uncompressible)
V=Velocity of flow
A=Area (Cross-section)
If A1 and A2 are considered, the Area A2 is almost half of
A1, thus the velocity at A2 has to be almost double of A1.

• The issue of sharp corners (both inner
and outer) create turbulence, low & high
pressure zones that promote aspiration of
mold gases into the flow, and can draw
mold material (sand) into the flow. None
of this is good... By providing curved
radius changes in direction the above
effects are still at play but at a reduced
level. Sharp angles impact the
solidification process and may inhibit
"Directional Solidification" with cross-
sectional freezing.
• The image is just a representation
• By proportioning the gating system, a
more uniform flow is promoted with near
equal volumes of metal entering the mold
from all points. In an un-proportioned
system the furthest gates would feed the
most metal, while the gates closest to the
sprue would feed the least.
(this is counter to what one initially thinks).

GATING RATIO is-
Areas of Choke : Runner : Gate(s)
• The base of the Sprue and Choke are the
same.
• The ratios between the cross-sectional Area can
be grouped into either Pressurized or
Unpressurized.
• Pressurized: A system where the gate
and runner cross-sectional areas are either
equal or less than the choke cross-sectional
area.

Pressurized - is a system
where the gate and runner
cross-sectional areas are
either equal or less than
the choke cross-sectional
area;
A1= Choke = 1 unit
A2 = 1st Runner c/s
Area = 0.75 unit
A3 = 2nd Runner c/s
Area = 0.66 unit
A4 = 1st Gate = 0.33 unit
A5 = 2nd Gate = 0.33 unit
Unpressurized - The key
distinction is that the
Runner must have a c/s
area greater than the
Choke, and it would
appear that the Gate(s)
would equal or be larger
than the Runner(s).
Common Ratios are;
1 : 2 : 4; 1 : 3 : 3
1 : 4 : 4; 1 : 4 : 6

• Areas A2 & A3 do not get
added as they are
positioned in line with
each other and flow is
successive between the
points and not
simultaneous.
• Areas A4 & A5 are added
together as flow does
pass through these
points simultaneously.
• This would resolve to a
pressurized flow of
1 : 0.75 : 0.66
A1= Choke = 1
A2 = 1st
Runner c/s Area = 0.75
A3 = 2nd
Runner c/s Area = 0.66
A4 = 1st
Gate = 0.33
A5 = 2nd
Gate = 0.33
Pressurized

Unpressurized:
• The key distinction is that the Runner must have
a cross sectional area greater than the Choke,
and it would appear that the Gate(s) would equal
or be larger than the Runner(s).
• Common Ratio's noted in Chastian's Vol 2 are:
• 1 : 2 : 4
• 1 : 3 : 3
• 1 : 4 : 4
• 1 : 4 : 6

• An exception is noted in Chastain with a 1 : 8 : 6
ratio to promote dross capture in the runner
system of Aero-Space castings.
• The Continuity Equation is simplified with the
use of ratios as the velocity is inversely
proportional between any 2 adjacent ratio
values. ie H : L equates to an increase in
velocity while a L : H equates to a drop in
velocity.
• Laminar Flow is harder to control at a high
velocity than a relatively lower velocity.
• Chastain's Vol 2 has much more mathematical
expressions and calculations.

PURE METALSPURE METALS-
Have clearly defined melting/freezing point,
solidifies at a constant temperature.
Eg: Al - 6600
C,
Fe - 15370
C,
and W- 34100
C.
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Solidified structures of metal -Solidified structures of metal -
solidified in a square mouldsolidified in a square mould
(a). Pure metal
(b). Solid solution
(c). When thermal gradient is absent
within solidifying metal
Development of a preferred textureDevelopment of a preferred texture
- at a cool mould wall.- at a cool mould wall.
A chill zone close to the wall and
then a columnar zone away from
the mould.
Three basic types of cast structures-
(a). Columnar dendritic;
(b). equiaxed dendritic;
(c). equiaxed nondendritic

STRUCTURE
FOR PURE METALSFOR PURE METALS::
At the mould walls, metal cools rapidly. Produces
solidified skin or shell (thickness depends on composition,
mould temperature, mould size and shape etc)
• These are of equiaxed structure.
• Grains grow opposite to heat transfer through the
mould
• These are columnar grains
• Driving force of the heat transfer is reduced away
from the mould walls and blocking at the axis
prevents further growth
NITC

FOR ALLOYS:
• Alloys solidify over a range of temperatures
• Begins when temp. drops below liquidous,
completed when it reaches solidous.
• Within this temperature range, mushy or pasty
state (Structure as in figure)
• Inner zone can be extended throughout by adding
a catalyst.- sodium, bismuth, tellurium, Mg
(or by eliminating thermal gradient, i.e. eliminating
convection. (Expts in space to see the effect of lack of
gravity in eliminating convection)
(refresh dendritic growth- branches of tree, interlock, each
dendrite develops uniform composition, etc)
NITC

SOLIDIFICATION TIMESOLIDIFICATION TIME
During solidification, thin solidified
skin begins to form at the cool mould
walls.
Thickness increases with time.
For flat mould walls
thickness ∝ √time
(time doubled, thickness by 1.414)
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CHVORINOV’S RULE
solidification time (t) is a function of volume of
the casting and its surface area
t = C ( volume/ surface area )2
C is a constant [depends on mould material, metal
properties including latent heat, temperature]
A large sphere solidifies and cools at a much slower rate
than a small diameter sphere. (Eg- potatoes, one big and
other small)
Volume ∝ cube of diameter of sphere,
surface area ∝ square of diameter
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Solidification time for various shapesSolidification time for various shapes::
Eg: Three pieces cast with the SAME volume, but different shapes.
(i)Sphere, (ii)Cube, (iii)Cylinder with height = diameter.
Which piece solidifies the fastest?
Solution: Solidification time = C (volume/surface area)2
Let volume = unity. As volume is same, t = C/ surface area2.
Cylinder: V = πr2
h = 2 π r3;
ie, r = (1/2 π) 1/3
A = 2 πr2
+ 2πrh = 6 πr2
= 5.54.
Then, t cube = 0.028C ; t cylinder = 0.033C ; t sphere= 0.043C
Metal poured to cube shaped mould solidifies the fastest.
Sphere: V= 4/3 (π r3
); i.e. r = (3/4 π)1/3
A= 4 π r2
= 4 π (3/4 π)1/3
= 4.84
Cube: V = a3
; ie a = 1; A = 6 a2
= 6.
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SHRINKAGE AND POROSITYSHRINKAGE AND POROSITY
METALS SHRINK(CONTRACT) DURING
SOLIDIFICATION
- CAUSES DIMENSIONAL CHANGES
LEADING TO CENTRE LINE SHRINKAGE, POROSITY,
CRACKING TOO
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T
Time
1
2
3
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SHRINKAGE DUE TO:
(1).CONTRACTION OF
MOLTEN METAL AS IT
COOLS PRIOR TO
SOLIDIFICATION
(2) CONTRACTION OF
SOLIDIFYING METAL,
LATENT HEAT OF
FUSION
(3) CONTRACTION OF
SOLIDIFIED METAL
DURING DROP TO
AMBIENT TEMP
OUT OF THESE, LARGEST SHRINKAGE DURINGOUT OF THESE, LARGEST SHRINKAGE DURING
COOLING OF CASTINGCOOLING OF CASTING (ITEM 3) eg:pure metal

SOLIDIFICATION CONTRACTION FOR VARIOUS METALSSOLIDIFICATION CONTRACTION FOR VARIOUS METALS
METAL Volumetric Solidification Contraction
Al 6.6
Grey cast Iron Expansion 2.5
Carbon Steel 2.5 to 3
Copper 4.9
Magnesium 4.2
Zinc 6.5
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• POROSITY DUE TO SHRINKAGE OF GASES
AND METAL TOO.
RELATED TO DUCTILITY
AND SURFACE FINISH
(DUCTILITY V/S POROSITY CURVES FOR
DIFFERENT METALS)
- ELIMINATION BY VARIOUS MEANS
(ADEQUATE SUPPLY OF LIQUID METAL, USE
OF CHILLS, NARROWING MUSHY ZONE-
CASTING SUBJECTED TO ISOSTATIC PRESSING
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POROSITY BY GASESPOROSITY BY GASES
LIQUID METALS HAVE HIGH SOLUBILITY FOR
GASES
DISSOLVED GASES EXPELLED FROM
SOLUTION DURING SOLIDIFICATION
(Hydrogen, Nitrogen mainly)
ACCUMULATE IN REGIONS OF EXISTING
POROSITY OR
CAUSE MICROPOROSITY IN CASTING
- TO BE CONTROLLED
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Effect of microporosity on the ductility of quenched and
tempered cast steel – Porosity affects the ‘pressure tightness’ of
cast pressure vesselDuctility
Porosity(%)
Elongation
Reduction of area
0 5 10 15
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FLOW OF MOLTEN METAL IN MOULDSFLOW OF MOLTEN METAL IN MOULDS
Important: pouring basin, mould cavity & riser
GATING SYSTEM Design -fluid flow, heat transfer, influence
of temperature gradient,
FLUID FLOW
Without turbulence
or with minimized turbulence
HEAT FLOW INFLUENCED BY MANY FACTORS
FLUIDITY-A characteristic related to viscosity.
TEST OF FLUIDITY - USING A SPIRAL MOULD.Fluidity Index
NITC

TEST FOR
FLUIDITY
USING A SPIRAL
MOULD.
FLUIDITY INDEX IS
THE LENGTH OF
THE SOLIDIFIED
METAL IN THE
SPIRAL PASSAGE.
GREATER THE
LENGTH, GREATER
THE FLUIDITY
INDEX.

PATTERNPATTERN
• Model of a casting constructed such that it
forms an impression in moulding sand
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PATTERNPATTERN
• 1st
step- Prepare model (pattern)
Differs from the casting
Differences Pattern Allowances.
• To compensate for metal shrinkage,
• Provide sufficient metal for machining
• Easiness in moulding
• As Shrinkage allowance, Draft allowance, Finishing
allowance, Distortion or camber allowance,
Shaking or rapping allowance
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MATERIALMATERIAL
1. WOOD.
2. METAL Al, CI, Brass,
3. For special casting processes,
Polystyrene which leaves mould as gas
when heated also used.
Types- many
Simple-Identical patterns;
Complex, intricate- with number of pieces.
Single or loose piece; Split; gated; Match Plate;
Sweep; Segmental; Skeleton(frame, ribbed), skell;
Boxed Up; Odd shaped etc. Sketches--
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MaterialMaterial
1. WOOD.
(+) Cheap, easily available, light, easiness in surfacing,
preserving (by shellac coating), workable, ease in
joining, fabrication
(-) Moisture effects, wear by sand abrasion, warp during
forming, not for rough use.
Must be properly dried/ seasoned,
free from knots, straight grained
Egs. Burma teak, pine wood, mahogany, Sal, Deodar,
Shisham, Walnut, Apple tree
NITC

2. METAL:
For durability, strength
Egs: Al alloys, Brass, Mg alloys, Steel, cast Iron for
mass production
(first, wooden pattern is made, then cast in the metal)
Type of material depends on shape, size, number of
castings required, method of moulding etc.
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TYPES OF PATTERNS
1. SINGLE PIECE PATTERN.
NITCALICUT
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2. SPLIT PATTERN (TWO PIECE )
NITCALICUT
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2. a, THREE PIECE SPLIT PATTERN
NITCALICUT
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3. LOOSE PIECE PATTERN
NITCALICUT
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4. COPE AND DRAG PATTERN
• COPE AND DRAG PARTS OF THE PATTERN
MOUNTED ON SEPARATE PLATES.
• COPE HALF AND DRAG HALF MADE BY
WORKING ON DIFFERENT MOULDING
MACHINES.
• THIS REDUCES THE SEPARATE COPE AND DRAG
PLATE PREPARATION.
• GENERALLY FOR HIGH SPEED MECHANISED
MOULDING.
NITCALICUT
NITC

5. MATCH PLATE PATTERN –
Pattern generally of metal and plate making
parting line metal/wood.
NITCALICUT
NITC

6. FOLLOW BOARD PATTERN.
For thin sections.
NITCALICUT
NITC
THIN PATTERN

7. GATED PATTERN -
Gating system is a part of the pattern.
NITCALICUT
NITC

8. SWEEP PATTERN –
For large size castings in small numbers. Template of
wood attached to a sweep used.
NITCALICUT
NITC

9. SEGMENTAL PATTERN –
For rings, wheel rims, large size gears.
NITCALICUT
NITC

10. SKELETON PATTERN.-
Stickle board used to scrape the excess sand.
Eg. Oil pipes, water pipes, pipe bends, boxes, valve bodies etc.
NITCALICUT
Stickle board
NITC

11. SHELL PATTERN
NITCALICUT
NITC

12. BUILT UP PATTERN –
Also called lagged up patterns- For barrels, pipes,
columns etc
NITCALICUT
NITC

13. LEFT AND RIGHT PATTERN –
For parts to be made in pairs.
Eg: legs of sewing machine, wood working lathe,
garden benches, J hangers for shafts, brackets for
luggage racks etc.
NITCALICUT
NITC

• Type of pattern depends on:
• Shape and size of casting,
• number of castings required,
• method of moulding employed,
• easiness or difficulties of the moulding
operations,
• other factors peculiar to the casting.
NITCALICUT
NITC

CHARACTERISTICS OF
PATTERN MATERIALS
CHARACTERISTIC RATING
WOOD AL STEEL PLASTIC CAST IRON
MACHINABILITY E G F G G
WEAR RESISTANCE P G E F E
STRENGTH E G E G G
WEIGHT E G P G P
REPAIRABILITY E P G F G
RESISTANCE TO:
• CORROSION (by water) E E P E P
• SWELLING P E E E E
E- Excellent; G- Good; F-fair, P- Poor
NITC

Functions of pattern
• Moulding the Gating system;
• Establishing a parting Line,
• Making Cores,
• Minimising casting Defects,
• Providing Economy in moulding
• Others, as needed

MOULDING SAND
• Granular particles from the breakdown of rocks by frost,
wind, heat and water currents
• Complex Composition in different places
• At bottom and banks of rivers
• - mainly silica (86 to 90%); Alumina (4% to 8 %);
Iron oxide (2 to 5%) with oxides of Ti, Mn, Ca. etc.
NITC

NATURAL SAND , called Green sand. Only water as
binder; can maintain water for long time
SYNTHETIC SAND.- (1)GREEN and (2)DRY types
(1) Artificial sand by mixing clay free sand,
binder(water and bentonite)
Contains New silica sand 25%; Old sand 70%;
bentonite 1.5%;moisture 3% to 3.5%
(2) New 15%; Old 84%;
bentonite and moisture 0.5 % each
NITC

DRY SAND- for moulding large castings. Moulds of
green sand dried and baked with venting done. Add-
cow dung, horse manure etc.
LOAM SAND- mixture of clay and sand milled with
water to thin plastic paste. Mould made on soft bricks.
The mould dried very slowly before cast. For large
regular shapes- drums, chemical pans etc.
FACING SAND- used directly with surface of pattern;
comes in contact with molten metal; must have high
strength, refractoriness.
Silica sand and clay without used sand- plumbago
powder, Ceylon lead, or graphite used. Layer of 20 to
30 mm thick---
about 10% to 15% of whole mould sand
NITC

BACKING SAND- old used moulding sand called floor
sand black in colour. Used to fill mould at back of
facing layer. Weak in bonding strength
SYSTEM SAND- used in machine moulding to fill whole
of flask. Strength, premealibility and refractoriness
high
PARTING SAND- used for separating boxes from
adhering, free from clay
CORE SAND- for making cores. Silica sand with core oil
(linseed oil, rosin, light mineral oil, binders etc)
SPECIALISED SANDS - like CO2sand, Shell sand, etc
for special applications
Mould washers- slurry of fine ceramic grains applied on
mould surface to minimize fusing
NITC

About MOULDING SAND
1. NATURAL SAND
2. SYNTHETIC SAND.- GREEN and DRY
3. DRY SAND
4. LOAM SAND
5. FACING SAND
6. BACKING SAND
7. SYSTEM SAND
8. PARTING SAND
9. CORE SAND
10. SPECIALISED SANDS
11. Mould washers
NITC

ADV - Acid Demand Value
Defined as the property of a sand or additive to affect
the cure process as a function of the materials acidity
or basicity on the pH scale.

MOULDING SAND- PROPERTIES
• Green Strength- Adequate strength after mixing, and
plasticity for handling
• Dry Strength- After pouring molten metal, adjacent surface
loses water content. Dries. Dry sand must have enough
strength to resist erosion
• Hot Strength- Strength at elevated temperature after
evaporation of moisture
• Permeability- Permeable or porous to permit gases to escape.
Ability of sand moulds to allow the escape of gases
NITC

• Thermal stability- Rapid expansion of sand surface at
mould-metal interface. May crack. Results in defect called
SCAB
• Refractoriness- Ability of sand to withstand high
temperature
• Flowability- Ability to flow & fill narrow portions around
pattern
• Surface finish- Ability to produce good surface finish in
casting
• Collapsibility- Allow easy removal of casting from mould
• Reclamation- Should be reusable and reclaimable
NITC

FURNACES
Proper selection depends on:
• Composition and melting point of alloy to be cast
• Control of atmospheric contamination
• Capacity and rate of melting required
• Environmental considerations- noise, pollution
• Power supply, availability, cost of fuels
• Economic considerations-initial cost, operating cost,
maintenance cost etc.
CUPOLAS (> 50 T, VERTICAL, HIGH RATES)
ELECTRIC FURNACES
INDUCTION FURNACES
NITC

FOUNDRIES
• From Latin word- fundere (meaning melting & pouring)
• Pattern & Mould making- automated, computer integrated
facilities- CAD/CAM
• Melting, controlling composition & impurities, pouring-
Use of conveyors, automated handling, shakeout,
cleaning, heat treatment, inspection, etc.
NITC

CUPOLA
* CHARGE PASSES DOWNWARDS
UNDER GRAVITY
* MEETS FLOW OF HOT GASES
MOVING UPWARDS
* CONTINUOUS IN OPERATION
.Vertical steel shell, lined with fire
bricks.
.Base on four steel columns
.Hinged doors in the base plate to
remove residue at the end of melt.
.Air blast through tuyeres (number on
size)
.Through charging door, coke, pig
iron, scrap & lime stone charged.
.Cold & Hot blast cupolas.

TOWER FURNACE
TO MELT ALUMINIUM
& alloys
3 main sections-
charging elevator,
melting unit, holding
furnace (Cylindrical
rotary unit).
Automatic controls
Grate above burners
supports solid charge
Molten charge runs
down

REVERBERATORY FURNACE
Small units (50kg) for melting non ferrous metals, large (about 25T)
10 T capacity to melt iron
AIR FURNACE:
One type of RB- to melt cast iron for roll mill rolls, malleable castings,
15 T capacity – Charge out of contact with fuel, less sulphur absorbed,
long melting time enables control of composition, large size scrap
handled.
Lump coal, pulverised fuel, oil used to fire. Solid coal burnt in a grate

The Sand Casting Process
The most commonly used Casting Process, in the entire
Casting Industry.
• Concept: The top and the bottom of the mold form the
flask. "holds the whole thing together." The cope and the
drag.
• An impression device, in the middle of the flask assembly,
called the pattern.
• The sand around the pattern is called the, holding medium.
• These are the basic, universal casting components, which can
be applied to all Casting and Molding Processes.
• The mold maker uses the pattern to make the impression in
the holding medium, the sand, then sets the pattern aside,
closes the cope and drag, to complete the flask, and forms
the mold, fills that void with a molten material; which could
be almost anything.
NITC

Middle support for a bike rack on public trains.
• Material:535 aluminum.
• Process: Sand casting.
• Casting Supplier: Dent
Manufacturing, Inc.,
Northampton, Pennsylvania.
• This 2-lb casting replaced four
stainless steel fittings, eliminating
the need for several nut and bolt
assemblies.
• The 8.5 x 7.5 x 3.5-in. component
is designed to hold 1.25-in. steel
pipe handrails on a bike rack.
• The foundry polishes and clear
anodizes the casting for a long-
lasting finish, which provides a
cleaner appearance when
compared to the previous
assembly.
• The casting eliminates the need
for multiple parts, reducing
manufacturing time and overall
cost. NITC

Air scoop that directs air flow for an agricultural
combine.
Material:80-55-06 ductile iron.
• Process:Sand casting.
• Casting Supplier: Neenah
Foundry Co., Neenah, Wisconsin.
• Originally manufactured as a
stamping and weldment, this 25-
lb component was converted to a
ductile iron casting at a 40% cost
reduction. Pictured is the casting
(r) and the previous
stamping/weldment (l).
• The cast component, which
measures 210 x 60 x 620 mm,
afforded the customer a simpler
design, eliminating the need for
capital resources and manpower
for extensive stamping and
welding equipment.
NITC

Torque arm bracket for the after-market automotive
industry.
• Material:80-55-06 ductile iron.
• Process: Sand casting.
• Casting Supplier: Farrar Corp.,
Norwich, Kansas.
• Converted from a fabricated
steel assembly, the casting saved
the customer $49/part due to
reduced grinding and no
assembly time for the component
(previously 8-10 hours per
bracket).
• Fully machined by the foundry,
the casting achieves tighter
dimensional tolerances than the
fabrication and has experienced
zero returns due to failure in the
field.
• Using rapid prototyping, the
foundry was able to deliver
sample parts for approval within
one week from design delivery. NITC

SHELL MOULDING-DEVELOPED IN 1940s
• THERMOSETTING RESINS
USED AS BINDERS
• PHENOL
FORMALDEHYDE(3% BY
WT.OF SAND)
• 15% HEXAMETHYLENE
TETRAMINE ADDED TO
GIVE THERMOSETTING
PROPERTY
• RESIN SETS AT ABOUT 2500
C
(1750
C- 3700
C)
• SHELL OF 4 to 9 MM FORMS
• SHELL MOULDING MACHINES
USED
• PATTERN MADE OF METAL
• MOUNTED ON MATCH PLATES
WITH GUIDE PINS
• PATTERN HEATED TO 2500
C
• CLEANED WITH COMPRESSED
AIR, PETROLEUM SPIRIT
APPLIED
• PATTERN INVERTED, PLACED
IN DUMP BOX CONTAINING
SAND MIX , LOCKED
• DUMP BOX INVERTED, KEPT
FOR A FEW MINUTES, (1-3 MINS)
SHELL FORMS
• RE-INVERTED, SHELL FORMED
IS TRIMMED, REMOVED USING
GUIDE PIN EJECTION,
• ANOTHER HALF ASSEMBLED,
READY FOR POURING

CARBON-DI OXIDE PROCESS
(SILICATE BONDED SAND PROCESS)
• FIRST IN 1950s
• MIXTURE OF SAND AND 1.5% TO 6 %
SODIUM SILICATE (AS BINDER)
• MIXTURE PACKED AROUND THE
PATTERN, HARDENED BY BLOWING CO2
• DEVELOPED FURTHER BY ADDING OTHER
CHEMICALS AS BINDERS
• MAINLY TO MAKE CORES-AS USE IS IN
ELEVATED TEMPERATURE APPLICATION

Na2O SiO2 + H2O +CO2 Na2CO3 + (SiO2+H2O)
(Silica Gel)
Formation of Silica Gel gives strength to the moulds
+ Points:
• Drying not necessary
• Immediately ready for pouring
• Very high strength achieved
• Dimensional accuracy very good
- Points
- Collapsibility poor, can be improved by additives
- Na2O SiO2 attacks and spoils wooden pattern

DIE CASTING
GRAVITY SEMI PERMANENT MOULD
OR PERMANENT MOULD
COLD CHAMBER HOT CHAMBER
(HEATING CHAMBER)
OUTSIDE THE MACHINE
INTEGRAL WITH THE MACHINE

PERMANENT MOULD OR GRAVITY DIE CASTING
*METALLIC MOULDS USED
*TWO HALVES OF DIES- ONE FIXED, ONE MOVABLE
•VERY CLOSE TOLERANCE CASTINGS, MORE STRENGTH, LESS
POROUS
•-BETTER SURFACE FINISH COMPARED TO SAND CASTING
•-SURFACE FREE FROM SAND & DENSITY HEAVY
ONLY FOR SMALL AND MEDIUM SIZE CASTINGS
FOR NON FERROUS, MAINLY
LARGE QUANTITY, BUT IDENTICAL PIECES ONLY

PERMANENT MOULD
OR GRAVITY DIE CASTING
*METALLIC MOULDS USED - MOULD TO
WITHSTAND TEMPERATURE
*NO EXTERNAL PRESSURE APPLIED,
*HYDROSTATIC PRESSURE BY RISERING
*LAMP BLACK/CORE OILAPPLIED TO DIE SURFACES
FOR EASY REMOVAL
*FAST CONDUCTION, RAPID COOLING
*TWO HALVES OF DIES- ONE FIXED, ONE MOVABLE NITC

• +POINTS
• - VERY CLOSE TOLERANCE CASTINGS,
• MORE STRENGTH, LESS POROUS
• - BETTER SURFACE FINISH COMPARED TO
• SAND CASTING
• - SURFACE FREE FROM SAND
• - DENSITY HEAVY
• - MORE DIMENSIONALACCURACY - 0.06 TO 0.3 MM
• - DIES LESS COSTLY THAN PRESSURE DIE CASTING DIES
• - GOOD FOR PRESSURE TIGHT VESSELS
• - LESS COOLING CRACKS
• - LESS SKILL
• - GOOD FOR LARGE QUANTITIES
NITC

- POINTS
 ONLY FOR SMALLAND
MEDIUM SIZE CASTINGS
 FOR NON FERROUS, MAINLY
 LARGE QUANTITY,
BUT IDENTICAL PIECES ONLY
 POOR ELONGATION
 STRESS AND SURFACE HARDNESS DEFECTS
OBSERVED
 CASTING TO BE WITHDRAWN CAREFULLY
FROM DIES
NITC

A TYPICAL DIE
ECCENTRIC CLAMPING
MOULD / DIE HALF
VENT
HOLE POURING
BASIN
MOULD CAVITY

SEMIPERMANENT DIECASTING
• DIE PRESSURE AT 20 TO 20,000 ATM
• PRESSURE FILL SOLIDIFICATION
• FOR NONFERROUS METALS
• FOR INTRICATE SHAPES
• CLOSE TOLERANCES POSSIBLE
• FOR MASS PRODUCTION, >10,000
NITC

FOR SEMI AND PRESSURE DIE CASTING SET UPS,
THE FOLLOWING FACTORS A MUSTA MUST
1. A GOOD DIE SET MECHANISM
2. MEANS FOR FORCING METAL
3. DEVICE TO KEEP DIE HALFS PRESSED
4. ARRANGEMENT FOR
AUTOMATIC REMOVAL OF CORES- IF ANY
5. EJECTOR PINS
NITC

TWO TYPES OF PRESSURE DIE CASTING
COLD CHAMBER-
HEATING CHAMBER OUTSIDE THE MACHINE
- FOR Al, Mg, Cu, AND HIGH MELTING ALLOYS
HOT CHAMBER-
HEATING INTEGRAL WITH THE HANDLING
GOOSE NECK MECHANISMS WIDELY USED
FOR LOW MELTING ALLOYS- Zn, Pb, Etc.
ALSO VACUUM DIE CASTING MACHINES- SPACE
BETWEEN THE DIES AND PASSAGE VACUUMISED
BEFOR POURING-
SUBMERGED PLUNGE TYPE, DIRECT AIR DIE
CASTING MACHINES

D.A.D.C. MACHINE – showing two positions of pot

ANOTHER TYPE OF D.A.D.C. MACHINE

SQUEEZE CASTING
• DEVELOPED IN 1960’S (also called liquid forging)
• SOLIDIFICATION OF MOLTEN METAL UNDER HIGH
PRESSURE (pressure application when liquid partially
solidifies 70 to 140 MPa)
• A COMBINATION OF CASTING & FORGING
• DIE, PUNCH, EJECTOR PIN
• PUNCH KEEPS ENTRAPPED GASES IN SOLUTION,
RAPID COOLING DUE TO HIGH PRESSURE DIE-
METAL INTERFACE
• PARTS OF NEAR-NET SHAPE MADE, COMPLEX AND
FINE SURFACE DETAILS OBTAINED. No riser needed
• FOR FERROUS & NON FERROUS
• AUTOMOTIVE WHEELS, SHORT BARRELED CANNONS
ETC.

VACUUM DIE CASTING MACHINES
• SOME AIR ENTRAPPED IN ORDINARY DIE CASTING MACHINES
• THIS PRODUCES BLOW HOLES
• IN VACUUM DIE CASTING TYPE, VACUUM PUMP CREATES VACUUM
IN DIE CAVITY, A SEAL CUTS OFF THE PIPE CONNECTION AFTER
EVACUATING
• THIS PREVENTS FLOW OF METAL FROM DIE TO VACUUM PIPE
• FLOW OF MOLTEN QUICK AND AUTOMATIC
• FINISHES:
• ALL DIE CASTINGS SUSCEPTIBLE TO CORROSION, HENCE
SUBJECTED TO FINISHING OPERATIONS OR PLATING
NITC

DESIGN CONSIDERATIONS
• USE OF RIBS, HUBS, BOSSES MUST BE TO REDUCE WEIGHT,
STRENGTHEN THE PART, IMPROVE THE APPEARANCE
• THICK SECTIONS MAKE DIE HOTTER AND THUS LESSEN
DIE LIFE
• LARGE SECTIONS TO BE COOLED MAY CAUSE POROSITY
• EXCESSIVE SECTIONAL CHANGES TO BE AVOIDED
• AVOID UNDERCUTS
• FILLETS DESIRABLE OVER SHARP EDGES
• DRAFTS NEEDED ON ALL CASTINGS
• EJECTOR PINS AT BACK TO AVOID VISIBILITY OF MARKS
• FLASH NECESSARY , TO BE REMOVED LATER BY
TRIMMING
NITC

DIE MATERIALS
CASTING ALLOYS DIE MATERIAL
TIN, LEAD ALLOY CAST STEEL WITHOUT HEAT
TREATMENT
ZINC, Al HEAT TREATED LOW ALLOY
STEEL
COPPER BASE
ALLOYS
HEAT TREATED SPECIAL ALLOY
STEEL
NITC

DIE CASTING ALLOYS
• MAINLY NON-FERROUS CASTINGS WITH
PROPERTIES COMPARABLE WITH FORGINGS
ZINC ALLOYS:- WIDELY USED ( > 70%)- Al 4.1%; Cu
MAX 1%, Mg 0.4%; BALANCE ZINC
• -- PERMITS LONGER DIE LIFE, SINCE TEMP. IS LOW
• GOOD STRENGTH, Tensile Strength: 300 Kg/cm2
• VERY GOOD FLUIDITY, THUS THIN SECTIONS POSSIBLE
• USESUSES: AUTOMOBILES, OIL BURNERS, FRIDGES, RADIO, TV
COMPONENTS, MACHINE TOOLS, OFFICE MACHINERIES
NITC

ALUMINIUM ALLOYS:
• BY COLD CHAMBER PROCESS-
• Cu 3 to 3.5%, Si 5 to 11 %, BALANCE Al.
• LIGHTEST ALLOYS, GOOD CORROSION
RESISTANCE, FINE GRAINED STRUCTURE
DUE TO CHILLING EFFECT
• Tensile Strength: 1250 to 2500 Kg/cm2
• GOOD MACHINABILITY,
SURFACE FINISH
• USESUSES: MACHINE PARTS, AUTOMOTIVE,
HOUSE HOLD APPLIANCES ETC.
NITC

COPPER BASED ALLOYS:
• Cu 57 to 81%;Zn 15 to 40%; SMALL QUANTITIES
OF Si, Pb, Sn
• VERY HIGH TENSILE STRENGTH: 3700 to
6700Kg/cm2;
• GOOD CORROSION RESISTANCE; WEAR
RESISTANCE
• LOW FLUIDITY, HENCE REDUCED DIE LIFE
• USESUSES; ELECTRICAL MACHINERY PARTS,
SMALLGEARS, MARINE, AUTOMOTIVE AND AIR
CRAFT FITTINGS, HARDWARES
NITC

MAGNESIUM BASED ALLOYS:
• LIGHTEST IN DIE CASTING, PRODUCTION COST
SLIGHTLY HIGH, Al: 9%; Zn: 0.5%; Mn: 0.5%; Si:
0.5%, Cu:0.3%; REMAINING Mg.
• USESUSES: IN AIRCRAFT INDUSTRY, MOTOR &
ISTRUMENT PARTS, PORTABLE TOOLS, HOUSE
HOLD APPLIANCES
LEAD & TIN BASED ALLOYS;
• Lead base: 80% Pb & ; Tin base 75% tin,
antimony, copper
• LIMITED APPLICATIONS.LIMITED APPLICATIONS. LIGHT DUTY
BEARINGS, BATTERY PARTS, X-RAY SHIELDS,
LOW COST JEWELLERY, NON-CORROSIVE
APPLICATIONS
NITC

V-Process 1. Pattern (with vent holes) is placed on hollow carrier
plate.
2. A heater softens the .003" to .007" plastic film.
Plastic has good elasticity and high plastic deformation
ratio.
3. Softened film drapes over the pattern with 300 to
600 mm Hg vacuum acting through the pattern vents
to draw it tightly around pattern.
4. Flask is placed on the film-coated pattern. Flask
walls are also a vacuum chamber with outlet shown.
5. Flask is filled with fine, dry unbonded sand. Slight
vibration compacts sand to maximum bulk density.
6. Sprue cup is formed and the mold surface leveled.
The back of the mold is covered with unheated plastic
film.
7. Vacuum is applied to flask. Atmospheric pressure
then hardens the sand. When the vacuum is released
on the pattern carrier plate, the mold strips easily.
8. Cope and drag assembly form a plastic-lined cavity.
During pouring, molds are kept under vacuum.
9. After cooling, the vacuum is released and free-
flowing sand drops away leaving a clean casting, with
no sand lumps. Sand is cooled for reuse.
NITC

Benefits Of Using The V-Process:
• Very Smooth Surface Finish
• 125-150 RMS is the norm. Cast surface of 200 or better, based on The Aluminum
Association of America STD AA-C5-E18.
• Excellent Dimensional Accuracy
• Typically +/-.010 up to 1 inch plus +/-.002 per additional inch. Certain details can
be held closer.
• +/-.010 across the parting line.
• Cored areas may require additional tolerances.
• Zero Draft
• Eliminates the need for machining off draft to provide clearance for mating parts
and assembly.
• Provides consistent wall thickness for weight reduction and aesthetic appeal.
• Allows for simple fixturing for machining and inspection.
NITC

• Pattern construction becomes more accurate and efficient.
• Total tolerance range becomes more accurate and efficient.
• Geometry/tolerance of part is at its simplest form. Draft does not use up
tolerance.
• Design/drafting is less complex. Calculations and depictions related to draft are
eliminated.
• Thin Wall Sections
• Walls as low as .100 in some applications are possible.
• Excellent Reproduction Of Details
• Very small features and lettering are possible.
• Consistent Quality
• All molding is semi-automatic. Variable "human factor" has been reduced.
• Superior Machining
• Sound metal and no hidden sand in the castings means fewer setups, reduced
scrap and longer tool life.
• Low Tooling Costs
NITC

• All patterns are made from epoxy, machined plastics, SLA or LDM. There
is no need to retool for production quantities.
• Unlimited Pattern Life
• Patterns are protected by plastic film during each sand molding cycle.
• Easy Revisions To Patterns
• No metal tooling to weld or mill. Great for prototypes.
• Short-Run Production Capability
• Excellent for short-run production while waiting for hard tooling. The V-
PROCESS method can outproduce traditional prototype methods such as
plaster or investment castings.
• Fast Turnaround
• From placement of order to sample casting in as little as two to four weeks.
NITC

• Known for several hundred years.
• But its evolution into a sophisticated production method for other
than simple shapes has taken place only in this century.
• Today, very high quality castings of considerable complexity are
produced using this technique.
CENTRIFUGAL CASTING
AN OVERVIEW
NITC

• To make a centrifugal casting, molten metal is poured into a
spinning mold.
• The mold may be oriented horizontally or vertically, depending on
the casting's aspect ratio.
• Short, square products are cast vertically while long tubular
shapes are cast horizontally. In either case, centrifugal force holds
the molten metal against the mold wall until it solidifies.
• Carefully weighed charges ensure that just enough metal freezes
in the mold to yield the desired wall thickness.
• In some cases, dissimilar alloys can be cast sequentially to produce
a composite structure.
NITC

CENTRIFUGAL CASTING
TRUE-
C.I. PIPES, LINERS, BUSHES, CYLINDER BARRELS
ETC.
SEMI-
CENTRE CORE FOR INNER SURFACE-
SHAPE BY MOULD AND CORE,
MAINLY NOT BY CENRTRIFUGALACTION-
Eg:FLYWHEELS
PRESSURE OR CENTRIFUGAL CASTING-
ALSO TERMED AS CENTRIFUGING
FOR NON SYMMETRICAL SHAPES
MOULD WITH ANY SHAPE PLACED
AT CERTAIN DISTANCE FROM AXIS

• SEMI-
• CENTRE CORE FOR INNER SURFACE-
SHAPE BY MOULD AND CORE,
MAINLY NOT BY CENRTRIFUGALACTION-
Eg:FLYWHEELS
• SPEED OF ROTATION-
60 TO 70 TIMES GRAVITY FOR HORIZONTAL
AND INCLINED TYPES
ABOVE 100 FOR VERTICAL TYPES.
NITC

CENTRIFUGING
PROPERTIES OF CASTING DEPEND ON
DISTANCE FROM AXIS
SQUEEZE CASTING
DIE, PUNCH, EJECTOR PIN
PARTS OF NEAR-NET SHAPE MADE,
COMPLEX AND FINE
SURFACE DETAILS OBTAINED
FOR FERROUS & NON FERROUS

CENTRIFUGAL CASTING
• + points:
• Denser structure, cleaner, foreign elements
segregated (inner surface)
• Mass production with less rejection
• Runners, risers, cores avoided
• Improved mechanical properties
• Closer dimensions possible, less machining
• Thinner sections possible
• Any metal can be cast
NITC

- points:
- Only for cylindrical and annular parts with limited
range of sizes
- High initial cost
- Skilled labour needed
- Too high speed leads to surface cracks- (high
stresses in the mould )
NITC

• For copper alloy castings, moulds are usually made from carbon
steel coated with a suitable refractory mold wash.
• Molds can be costly if ordered to custom dimensions, but the
larger centrifugal foundries maintain sizeable stocks of molds in
diameters ranging from a few centimetres to several metres.
• The inherent quality of centrifugal castings is based on the fact
that most nonmetallic impurities in castings are less dense than
the metal itself. Centrifugal force causes impurities (dross, oxides)
to concentrate at the casting's inner surface. This is usually
machined away, leaving only clean metal in the finished product.
• Because freezing is rapid and completely directional, centrifugal
castings are inherently sound and pressure tight.
• Mechanical properties can be somewhat higher than those of
statically cast products.
NITC

• Centrifugal castings are made in sizes ranging from
approximately 50 mm to 4 m in diameter and from a few
inches to many yards in length.
• Size limitations, if any, are likely as not based on the
foundry's melt shop capacity.
• Simple-shaped centrifugal castings are used for items such
as pipe flanges and valve components, while complex
shapes can be cast by using cores and shaped molds.
• Pressure-retaining centrifugal castings have been found to
be mechanically equivalent to more costly forgings and
extrusions.
NITC

PRODUCTS
• Material:Gray iron.
• Process: Centrifugal casting.
• This 84-lb brake drum is produced by casting
gray iron centrifugally into a steel shell. This
shell acts as a protective jacket, resulting in
superior drum strength and allowing for the
removal of iron in the drum band and
mounting areas normally required in a full
cast brake drum.
• Through concerted efforts between the
foundry, machine shop and engineering/testing
resources, 6 lb were removed from the brake
drum while providing the same performance,
balance and reliability as the standard drum.
With the weight optimized at 84 lb, the drums
are ideal for weight sensitive applications such
as refrigerated trailers, tankers and bulk
haulers.
• Utilizing these drums on an 18-wheel
tractor/trailer application can provide up to
224 lb of weight savings.
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Brake drum for commercial highway Class 8 trucks and trailers.

Commercial products made by centrifugal
casting
• Belt buckles, battery lug nuts, lock parts, "pot
metal" gears and machine parts, bushings,
medallions, figurines, souvenirs, memorial coins
and plaques, toy and model parts, concrete
expansion fasteners, hardware such as drawer
pulls and knobs, handles, decorative wall switch
plates etc. etc.
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INTRODUCTION
• Investment casting, often called lost wax casting, is
regarded as a precision casting process to fabricate near-
net-shaped metal parts from almost any alloy. Although its
history lies to a great extent in the production of art, the
most common use of investment casting in more recent
history has been the production of components requiring
complex, often thin-wall castings. A complete description
of the process is complex. But, the sequential steps of the
investment casting process are as below, with emphasis on
casting from rapid prototyping patterns.
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Fig: 1- Investment casting process
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• The investment casting process begins with fabrication of a
sacrificial pattern with the same basic geometrical shape as
the finished cast part
• Patterns are normally made of investment casting wax that
is injected into a metal wax injection die. Fabricating the
injection die is a costlier process and can require several
months of lead time.
• Once a wax pattern is produced, it is assembled with other
wax components to form a metal delivery system, called
the gate and runner system. The entire wax assembly is
then dipped in a ceramic slurry, covered with a sand
stucco, and allowed to dry. The dipping and stuccoing
process is repeated until a shell of ~6-8 mm (1/4-3/8 in) is
applied.
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Fig. 2- Investment casting process - dewaxing
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• Once the ceramic has dried, the entire assembly is placed in a
steam autoclave to remove most of the wax.
• After autoclaving, the remaining amount of wax that soaked
into the ceramic shell is burned out in a furnace. At this point,
all of the residual pattern and gating material is removed, and
the ceramic mold remains.
• The mold is then preheated to a specific temperature and filled
with molten metal, creating the metal casting. Once the casting
has cooled sufficiently, the mold shell is chipped away from the
casting.
• Next, the gates and runners are cut from the casting, and final
post-processing (sandblasting, machining) is done to finish the
casting.
(The CAD solid model, the shell, and the pattern produced in the QuickCast
process is schematically shown)
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Fig. 3. Investment casting process –Preheating and pouring
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INVESTMENT CASTING
Also called LOST WAX PROCESS- used during 4000-3000 BC
• Die for casting wax pattern made with
allowances for wax and metal.
• Pattern and gating systems made of
wax (bee wax, aera wax, paraffin) or
plastic (polystyrene) by injecting -in
molten condition - into the metal die
• PRECOATING- The pattern dipped
in a slurry of refractory material (fine
325 mesh silica &binders, water, ethyl
silicate, acids), and sprinkled with
silica sand
• This pattern with initial coating
dried, coated repeatedly to increase
thickness
• The one piece mould is dried
• DEWAXING- Inverted and
heated to 900
C-1750
C for 12
hours
• Wax melts. Can be reclaimed
and reused.
• Mould fired to 6500
C-10500
C
for about 4 hours
• POURING- Metal poured,
allowed to solidify
• Mould broken, casting taken
out

Plus and Minus points
• Very good dimensional
accuracy
• No or very little finishing
• Intricate and thin shapes
possible
• About 40 kg parts cast
• Both for ferrous and
nonferrous alloys
• Suited for mechanization
• Careful handling
needed,as the patterns are
not strong.
• Close control of process
needed
• Labour and material costs
high, but high melting
point alloys cast with
good surface finish &
close tolerances.
• Eg: gears, cams, valves,
ratchets, turbine blades,
electrical & electronic
components etc.

CAD solid model (top), SLS polycarbonate pattern (left),
A356 aluminum casting (right).

• The major impact rapid prototyping processes have had on investment casting is
their ability to make high-quality patterns (Fig. 5) without the cost and lead times
associated with fabricating injection mold dies.
• In addition, a pattern can be fabricated directly from a design engineer's computer-
aided design (CAD) solid model. Now it is possible to fabricate a complex pattern in
a matter of hours and provide a casting in a matter of days.
• Investment casting is usually required for fabricating complex shapes where other
manufacturing processes are too costly and time-consuming.
• Another advantage of rapid prototyping casting is the low cost of producing
castings in small lot sizes.
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1. Vacuum Vessel for the power
generation industry
• Material:Inconel 625
• Process: Investment
• Casting Supplier:
Bescast, Inc.,
Willoughby, Ohio

Vacuum Vessel for the power generation industry
Material:Inconel 625
• Process: Investment Casting
• The 5-lb casting is one-tenth scale of the vacuum vessel
for the National Compact Stellarator Experiment
(NCSX) being developed by the Princeton Plasma
Laboratory and the Oak Ridge National Laboratory as
the next generation of fusion experiment. The scale
model was investment cast to determine the feasibility of
using a casting for a vacuum vessel with complex
geometry.
• To meet the rush timeline (with the help of
buycastings.com), SLS rapid prototyping techniques
were employed to make the complicated wax patterns
from a CAD/STL file in 2 weeks. Solidification modeling
predicted the potential “hot spots” and ways to optimize
the pour parameters.
• The foundry employed a vacuum-assist casting method
to cast the Inconel 625 air melt alloy with a consistent
wall thickness of 0.1 in. The entire vessel is assembled by
welding three equal segments cast by the foundry.
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2.Cam clamp used to secure
ambulance gurnees.
• Material: Stainless
steel.
casting.
Independent Steel
Castings Co., Inc.,
New Buffalo,
Michigan.

Cam clamp used to secure ambulance gurnees.
Material:Stainless steel.
• Process: Investment casting.
• The casting design requires intricate angles
and surface profiles—the dimensional
integrity of the profile angles have to be
held to ±0.005 in./linear in. tolerances while
helix and spiracle angles move both
horizontally and vertically.
• The foundry redesigned the component to
remove material from the rear casting
section for weight reduction. In addition,
the founry designed in a tapered bore for
mounting a bearing during assembly.
• The casting requires slotting at the top and
bottom to align mating components. Holes
at the top and bottom are cast-in and sized
as ready-to-tap.
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3. Mounting bracket for
medical centrifuge.
• Material:CF3M
stainless steel.
casting.
Vestshell, Inc.,
Montreal, Quebec,
Canada.
•

Mounting bracket for medical centrifuge.
Material:CF3M stainless steel.
Process: Investment casting.
• This casting provides balanced,
vibration-free support to a centrifuge
that turns at more than 1000 RPM.
• Originally designed as a machined
weldment, investment casting
reduced costs by 450% and provided
this precision component with
dimensional repeatability and high-
strength qualities.
• To date, the customer has received
800 parts without encountering
casting-related defects.
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4. Duck bill for White Cap, L.L.C. to
seal caps on food jars.
• Material:316L
stainless steel.
casting.
Northern Precision
Casting Co., Lake
Geneva, Wisconsin.

Duck bill for White Cap, L.L.C. to seal caps on food jars.
Material:316L stainless steel.
• Casting Supplier: Northern Precision
Casting Co., Lake Geneva, Wisconsin.
• Originally constructed as a three-piece
stamping/weldment, the 3.9-oz, 3.44 x 3.15 x
1.49-in. new casting design offers lighter
weight (29% reduction), a one-piece
construction, increased strength and a
smooth sanitary finish (an important
requirement for the food service industry).
• The conversion to casting from a multi-piece
weldment resulted in a 70% cost savings for
the customer.
• To accommodate the thin sections of the
component, the foundry designed a unique
gating and tooling system that uses wedge
gates and gating into the top of the
component to ensure against porosity.
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5. Fan Frame Hub
• Material: Titanium.
casting.
Precision Castparts
Corp. (PCC), Portland,
Oregon.

A fan frame hub for General Electric’s CF-6-80C engine
for Boeing’s 747, 767 and MD-11 aircraft.
Material:Titanium.
• This single 52-in. titanium investment
casting replaced 88 stainless steel parts
(from five vendors) that were
previously machined and welded
together.
• The casting, which supports the front
fan section of the engine and ties it to
the compressor section, provides
improved strength and dimensional
control in addition to a 55% weight
reduction.
• Conversion to a metal casting allowed
GE to include several unique details
including bosses, flanges and a 2-in.
larger overall diameter.
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This single 52-in. titanium investment
casting replaced 88 stainless steel parts
(from five vendors) that were previously
machined and welded together.
The casting, which supports the front fan
section of the engine and ties it to the
compressor section, provides improved
strength and dimensional control in addition
to a 55% weight reduction.
Conversion to a metal casting allowed GE to
include several unique details including
bosses, flanges and a 2-in. larger overall
diameter.

6. Racing car upright
• Material: Titanium
6246.
casting.
Coastcast Corp.,
Rancho Dominguez,
California.

Normally manufactured via machining or
welding, four of these one-piece cast
components were manufactured via rapid
prototyping and investment casting from design
to delivery in 8 weeks.
Using rapid prototyping with the investment
casting process eliminated an up-to-$50,000
tooling cost for these components.
manufacture the components, they don’t
require any rework during use. The cast
titanium provided the same strength—but at a
reduced weight—as 17-4PH steel (the other
material considered). In addition, with no welds
required to

7. Housing actuator for an engine for
Hamilton Sundstrand.
• Material: A203
aluminum alloy.
casting.
Cabiran, Ltd., Kibbutz
Cabri, Israel.

With wall thickness to 0.12 in., this casting
requires moderate strength, good stability
and resistance to stress-corrosion cracking
to 600F (316C).
This casting exhibits mechanical properties
at room temperature of 32-ksi tensile
strength, 24-ksi yield strength and 1.5%
elongation, while maintaining a 16-ksi
tensile strength and 4% elongation at 600F.
The component's as-cast surface finish
meets the customer's requirements, and
the invest casting process reduced the
customer's finishing and machining costs.

SEMI-PERMANENT MOLD CASTING
Semi-permanent mold is a casting process -
producing Aluminum alloy castings - using
re-usable metal molds and sand cores to
form internal passages within the
casting. Molds are typically arranged in two
halves - the sand cores being put into place
before the two halves are placed together.
The molten metal flows into the mold cavity
and surrounds the sand core while filling the
mold cavity. When the casting is removed
from the mold the sand core is removed
from the casting leaving an internal passage
in the casting.

The re-usable metal molds are used
time and again, but the sand cores
have to be replaced each time the
product is cast, hence the term semi-
permanent molding.
Semi-permanent molding affords a
very high precision quality to the
casting at a reduced price compared
to the sand casting processes.

8. Aluminum composite alloy
• Material: 359/SiC/20p
aluminum composite
alloy.
• Process:Semi-
permanentmold casting.
• Casting Supplier: Eck
Industries,Inc.,
Manitowoc, Wisconsin.

The brake rotor was converted to an
aluminum metal matrix composite (MMC)
alloy casting at a 50% weight reduction,
with the same casting yield and without a
loss in performance.
In terms of mechanical properties, the
aluminum MMC brake rotor’s modulus and
its wear rate in application are the same as
cast iron.

9. Bucket chain link for a
conveyor system
• Material:C95410
nickel aluminum
bronze.
• Process:Permanent
mold casting.
Piad Precision
Casting Corp.,
Greensburg,
Pennsylvania.

PERMANENT MOLD CASTING
PRODUCTS
• Material:C95410 nickel
aluminum bronze.
• Process: Permanent
mold casting.
• Casting Supplier: Piad
Precision Casting Corp.,
Greensburg,
Pennsylvania.
10. BUCKET CHAIN

Previously made from two steel stampings
welded together with two tube sections and
subsequently tin-plated for corrosion
resistance (r), this bronze cast component
(l) now is a one-piece permanent mold
casting.
The cast component (l) exhibits good
corrosion resistance (without plating or

11. Manual Trip
• Material:Copper
aluminum bronze alloy.
mold casting.
• CastingSupplier: Piad
Precision Casting Corp.,
Greensburg,
Pennsylvannia.

Originally manufactured by fabricating and
welding 7 components, pressing in a steel
spring pin, and adding a zinc chromate
coating for corrosion protection, this part was
converted to a single permanent mold casting
with a cast-in stainless steel pin.
By casting in the pin, the foundry reduced the
component's cost by eliminating the reaming
and pressing operations.
The foundry's alloy provides the necessary
corrosion resistance to the component, thus
eliminating the zinc-chromate coating
previously required.

12. Felsted Division/Furon’s foot
pedal control lever.
• Material: Zamak 3.
• Process: Diecasting.
CrecoCast, Seville,
Ohio.

The lever originally was designed as a steel
sand component with machining operations to
size the shaft, pivot hubs and cable connection
holes.
The die cast component combined two levers
(for 2- and 3-in. cable travel) and provided
connecting holes for different cable travel
lengths.
The redesign held the required hole diameter
tolerance of ±0.001 in. and the hub diameter
tolerance of +0.002, -0.001 in. while
eliminating a lever and machining
requirements. This reduced component cost by
91%.

13. Instrument panel frame for the
Cadillac DeVille.
• Material: AZ91
magnesium alloy.
Intermet Corp’s
Hannibal Plant,
Hannibal, Missouri.

Originally manufactured as a steel
stamping, this component was redesigned
into a two-piece die casting to better
control tolerances and to fit the end-user’s
mounting requirements. The design also
allows more flexibility for future vehicle
platform changes.
The 15-lb cast component reduced the
part’s original weight by 45 lb while
reducing tool-building time, delivery cost
and lead time.
The foundry assembles the frame before
delivery to the end-user for installation.

14. Valve spacers for Warren Rupp’s
Sandpiper II air-actuated pumps.
• Material: ZA-8 zinc
alloy.
CrecoCast, Seville,
Ohio.

Previously machined from stainless steel
bars, the valve spacers now are hot
chamber die cast at net shape, eliminating
secondary machining.
In addition to the cost reductions achieved
by casting, Warren Rupp’s designers were
able to maximize air flow with the cast
spacers by designing for fit and function
without the restrictions of machining from
bar stock.

NO BAKE CASTING
The No-Bake Sand
Casting process consists
of sand molds created
using a wood, metal or
plastic pattern. Sand is
mixed with a urethane
binder and deposited into
a box containing the
pattern (and all necessary
formers and inserts) for
pouring.Filling a wood mold with
sand

PRODUCTS
15. TENSIONER PULLEY
Material: Gray iron
Process: Nobake sand
Casting Supplier: Wellsville Foundry, Wellsville, Ohio

This 175-lb component is used as a
brake that puts tension on a 4 ft. wide
roll of rubber feeding into a tire press.
Converted from a steel fabrication (two
ring burn-outs with spokes), the
foundry provided the end-user with a
50% cost savings.

Previously made from two steel stampings
welded together with two tube sections and
subsequently tin-plated for corrosion
resistance (r), this bronze cast component (l)
now is a one-piece permanent mold casting.
The cast component (l) exhibits good
corrosion resistance (without plating or
painting), 50 ksi yield strength and 95 ksi
tensile strength.
By converting this part to a copper-based
permanent mold casting, the

16. Suspension crossmember
• Material:B356
aluminum alloy.
mold casting.
CMI-Precision Mold,
Inc., Bristol, Indiana.

This 26-lb safety-critical component was
redesigned to an aluminum casting from a
steel weldment, resulting in a 14-lb weight
reduction.
The casting’s dimensional tolerances are
held to 0.5 mm across the length of the part,
a threefold reduction over the previous
design.
The casting’s mechanical properties include
44 ksi ultimate strength, 32 ksi yield strength
and 10.4 x 106 psi Young’s modulus.

17. Bracket for a piston cooling system
• Material:953
aluminum bronze.
• Process:Permanentmol
d casting.
Aurora Metals, L.L.C.
(Hiler Industries),
Montgomery, Illinois.

This 0.8-lb component was converted to
permanent mold casting to eliminate the
leaks inherent in the previous
manufacturing method. In addition, the
conversion realized a cost savings by
reducing man-hours and eliminating heat
treatment as permanent mold casting
achieves the required mechanical
properties.
Permanent mold casting allows a stainless
steel tube insert to be cast directly into the
bracket.

18. Cleaning Brush
• Material: 65-45-12
ductile iron.
• Process:Green sand
casting.
Smith Foundry Co.,
Minneapolis

Previously manufactured as a four-piece
weldment, this component was
redesigned as a single casting at a
$3/casting, $72,000/year savings to the
customer.
The weldment experienced failure and
breakage under heavy shock loading.
The conversion to cast ductile iron
eliminated the field failure and also
incorporated the three holes in each
blade as-cast to eliminate post-process
drilling.

19. Carrier component
• Material: Steel
• Casting Supplier: The
Falk Corp.,
Milwaukee, Wisconsin

Converted from a fabrication, this
component design was the result of
foundry and end-user engineering
collaboration.
The casting design (especially its volume)
was optimized through casting process
modeling, resulting in weight and cost
savings for the component.
The casting meets all necessary
mechanical properties while fitting in the
same application envelope as the previous
fabrication.

20. Powerhead for a pallet truck.
• Material: A356-T6
aluminum.
molding.
Wisconsin Aluminum
Foundry Co., Inc.,
Manitowoc, Wis.

This single-piece casting replaced a 21-piece
weldment. The casting eliminated the need for
extensive and complicated fixturing of the
weldment. The cast component also allowed
for the addition of features for accessory
mounting points that would have been difficult
to accomplish as a weldment.
The largest benefit of the casting is the
increased throughput of the parent product,
resulting in savings in purchasing, receiving,
stocking, distribution, fabrication and
assembly. With the conversion, there was a
15% reduction in assembly time, 18% cost
reduction per part and a 45% weight reduction.

Lost foam process
The Lost Foam Casting process originated in
1958 when H. F. Shroyer was granted a patent
for this cavityless casting method, using a
polystyrene foam pattern imbedded in traditional
green sand. The polystyrene foam pattern left in
the sand is decomposed by the molten metal.
The molten metal replaces the foam pattern,
precisely duplicating all of the features of the
pattern. Like investment casting (Lost Wax), a
pattern must be produced for every casting
made. The Evapcast Division of Advanced Cast
Products began producing lost foam castings in
1987, after three years of research and
development.

21. Center ring for a fall
protection system
• Material: Manganese
bronze.
• Process: Lost foam
casting.
Irish Foundry and
Seattle, Washington.

Redesigned to a lost foam component, the 1-
lb casting provided a 70% cost savings to the
customer due to reduced machining and
production time.
Cast in high-tensile manganese bronze, the
component must withstand 5000 lb of
pressure in application.
The casting incorporates thin to thick to thin
wall designs without defects, a detail made
easier in lost foam casting.

22. Lifeline horizontal slide for safety
equipment.
• Material: Manganese
bronze.
• Process: Lost foam
casting.
Irish Foundry &
Seattle.

By redesigning this 2-lb, 4 x 3-in.-diameter
component as a two lost-foam castings with a
near-net-shape, the foundry was able to
reduce grinding time by 80% (because risers
are eliminated as well as the riser contacts
that must be ground) and eliminate
machining.
The redesign to lost foam resulted in higher
aesthetic qualities, including rounded edges
and smooth passageways.

CASTING TECHNIQUES FOR SINGLE
CRYSTAL GROWING (S.C.G.)
• POLYCRYSTALLINE- ANISOTROPY
• SINGLE CRYSTAL- PROPERTIES SAME IN
ALL DIRECTIONS
• CASTING OF GAS TURBINE BLADES BY
S.C.G.

CASTING TECHNIQUES FOR SINGLE
CRYSTAL GROWING (S.C.G.)
CONVENTIONAL
USE OF CERAMIC MOULD
GRAINS WITH THE ABSENCE OF THERMAL
GRADIENT
DIRECTIONAL SOLIDIFICATION PROCESS
CERAMIC MOULD PREHEATED.
MOULD SUPPORTED BY WATER COOLED CHILL PLATES.
AFTER POURING, ASSEMBLY LOWERED
CRYSTALS GROW AT CHILL PLATE SURFACE UPWARD.
COLUMNAR GRAINS FORM

CONVENTIONAL
• USE OF CERAMIC MOULD
GRAINS- AS WITH THE ABSENCE OF THERMAL
GRADIENT
PRESENCE OF GRAIN BOUNDARIES- MAKES
STRUCTURE SUSCEPTIBLE TO CREEPAND
CRACKING ALONG BOUNDARIES

DIRECTIONAL SOLIDIFICATION
PROCESS, (1960’s)
CERAMIC MOULD PREHEATED.
MOULD SUPPORTED BY WATER COOLED CHILL
PLATES.
AFTER POURING, ASSEMBLY LOWERED
CRYSTALS GROW AT CHILL PLATE SURFACE
UPWARD. COLUMNAR GRAINS FORM
BLADE DIRECTIONALLY SOLIDIFIED WITH
LONGITUDINAL- NOT TRANSVERSE- GRAIN
BOUNDARIES. THUS STRONGER

SINGLE CRYSTAL BLADES, (1967),
MOULD HAS CONSTRICTION IN THE SHAPE
OF CORK SCREW
THIS CROSS SECTION ALLOWS ONLY ONE
CRYSTAL TO FIT THROUGH
WITH THE LOWERING, SINGLE CRYSTAL
GROWS UPWARD THROUGH
CONSTRICTION
STRICT CONTROL OF MOVEMENT NEEDED
THERE IS LACK OF GRAIN BOUNDARIES,
MAKES RESISTANT TO CREEP AND
THERMAL SHOCK.--EXPENSIVE

SINGLE CRYSTAL GROWING (S.C.G.)
• FOR SEMICONDUCTOR INDUSTRY
• CRYSTAL PULLING METHOD-
CZOCHRALSKI PROCESSCZOCHRALSKI PROCESS
• SEED CRYSTAL DIPPED INTO THE MOLTEN
METAL, PULLED SLOWLY, (AT 10 µm/ s), WITH
ROTATION
• LIQUID METAL SOLIDIFIES ON THE SEED AND
CRYSTAL STRUCTURE CONTINUED
THROUGHOUT

FLOATING –ZONE METHOD
• POLYCRYSTALLINE ROD (SILICON)- ALLOWEDALLOWED
TO REST ON A SINGLE CRYSTALTO REST ON A SINGLE CRYSTAL
• INDUCTION COIL HEATS THE PIECES
• COIL MOVED UPWARD SLOWLY (20 µm/ s)
• SINGLE CRYSTAL GROWS UPWARD WITH
ORIENTATION MAINTAINED
• THIN WAFERS CUT FROM ROD, CLEANED,
POLISHED
• USE IN MICROELECTRONIC DEVICES

PLASTER MOULD CASTING
• For casting silver, gold, Al, Mg, Cu, and alloys of brass and
bronze.
• Plaster of Paris (Gypsum) (CaSo4.nH2O) used for cope and drag
moulding
• A Slurry of 100 parts metal casting plaster and 160 parts water
used.
• Plaster added to water and not water to plaster. To prevent cracks,
20-30% talc added to plaster. Lime and cement to control expansion
• Stirred slowly to form cream Poured carefully over a match plate
pattern (of metal)
• Mould vibrated to allow plaster to fill all cavities.
• Initial setting at room temperature(setting time reduced by either
heating or by use of terra-alba/ magnesium oxide)
• Pattern removed
• Cope and drag dried in ovens at 200- 425 C(about 20 hours)
• Mould sections assembled

+ points
• Dimensional accuracy 0.008 t0 0.01 mm per mm
• Excellent surface finish as no sand used.. No further
machining or grinding
• Non ferrous thin sectioned intricate castings made.
- points
• Limited to non ferrous castings.(sulphur in gypsum
reacts with ferrous metals at high temperatures)
• Very low permeability as metal moulds used. Moulds
not permanent, destroyed when castings removed.

FROZEN MERCURY MOULDING
(MERCAST PROCESS)
• Frozen Mercury used for producing precision castings
• Metal mould prepared to the shape with gates and sprue holes
• Placed in cold bath and filled with acetone (to act as lubricant)
• Mercury poured into it, freezes at –20 C, after a few minutes
(10mins)
• Mercury Pattern removed and dipped in cold ceramic slurry
bath.
• A shell of 3 mm is built up. Mercury is melted and removed at
room temperature.
• Shell dried and heated at high temperature to form hard
permeable shape.
• Shell placed in flask- surrounded by sand-, preheated and
filled with metal.
• Solidified castings removed.

• For both ferrous and non ferrous castings.(melting
temperature upto 16500
C)
• Very accurate details obtained in intricate shapes
• Excellent surface finish, machining and cleaning
costs minimum.
• Accuracy of 0.002 mm per mm obtained.
• But, casting process costly.
• Casting cost high.

23.An ice cutter used in an industrial ice machine.
Material:316 stainless steel.
• Converted from a stainless steel fabrication
consisting of 4 stampings, bar stack and a
form rolled base, this one-piece casting has an
enhanced overall efficiency and performance.
• The conversion to casting reduced the
customer's annual cost by more than
$100,000, eliminated extensive straightening
operations due to warping in the welding
process, and reduced the component's high
scrap.
• The finished cast component is supplied by
the foundry after being completely machined
to print specifications and solution-annealed.
NITC

24.Racing car upright for Minardi Formula 1.
Material:Titanium 6246.
• Normally manufactured via machining or
welding, four of these one-piece cast
components were manufactured via rapid
prototyping and investment casting from
design to delivery in 8 weeks.
• Using rapid prototyping with the
investment casting process eliminated an
up-to-$50,000 tooling cost for these
components.
• The cast titanium provided the same
strength—but at a reduced weight—as 17-
4PH steel (the other material considered).
In addition, with no welds required to
manufacture the components, they don’t
require any rework during use.
NITC

25. Housing actuator for an engine for Hamilton
Sundstrand.
Material:A203 aluminum alloy.
• With wall thickness to 0.12 in., this
casting requires moderate strength,
good stability and resistance to stress-
corrosion cracking to 600F (316C).
• This casting exhibits mechanical
properties at room temperature of 32-
ksi tensile strength, 24-ksi yield
strength and 1.5% elongation, while
maintaining a 16-ksi tensile strength
and 4% elongation at 600F.
• The component's as-cast surface
finish meets the customer's
requirements, and the invest casting
process reduced the customer's
finishing and machining costs.
NITC

26. Spacer component for an aerospace radar
system.
Material:17-4PH steel.
• Converted from a
weldment, the cast design
reduced component weight
and machining time
required.
• The 1-lb component is cast
near-net-shape with zero
draft and webbed walls.
NITC

27. A laser chassis (housing) for an Israeli Aircraft
Industries night targeting system.
Material:A357 aluminum alloy.
• Process: Investment (lost wax) casting.
• Previously machined from A6061
aluminum wrought alloy, the
component was redesigned for
investment casting at a cost savings of
$25,000/part.
• The casting achieves mechanical
properties of 41 ksi tensile strength, 31
ksi yield strength and 3% elongation
in areas up to 2.5 mm thick and 38 ksi
tensile strength, 28 ksi yield strength
and 5% elongation in areas over 2.5
mm thick.
NITC

DESIGN CONSIDERATIONS
CAREFUL CONTROL OF LARGE NUMBER OF
VARIABLES NEEDED-
• CHARACTERISTICS OF METALS &
ALLOYS CAST
• METHOD OF CASTING
• MOULD AND DIE MATERIALS
• MOULD DESIGN
• PROCESS PARAMETERS- POURING,
TEMPERATURE,
• GATING SYSTEM
• RATE OF COOLING Etc.Etc.
NITC

• Poor casting practices, lack of control of process
variables- DEFECTIVE CASTINGS
• TO AVOID DEFECTS-
• Basic economic factors relevant to casting
operations to be studied.
• General guidelines applied for all types of castings
to be studied.
NITC

CORNERS, ANGLES AND SECTION THICKNESS
• Sharp corners, angles, fillets to be avoided
Cause cracking and tearing during solidification
• Fillet radii selection to ensure proper liquid metal flow-
3mm to 25 mm.
Too large- volume large & rate of cooling less
• Location with largest circle inscribed critical.
Cooling rate less
shrinkage cavities & porosities result-
Called HOT SPOTS
NITC

• LARGE FLAT AREAS TO BE AVOIDED-
WARPING DUE TO TEMPERATURE GRADIENTS
• ALLOWANCES FOR SHRINKAGE TO BE PROVIDED
• PARTING LINE TO BE ALONG A FLAT PLANE-
GOOD AT CORNERS OR EDGES OF CASTING
• DRAFT TO BE PROVIDED
• PERMISSIBLE TOLERANCES TO BE USED
• MACHINING ALLOWANCES TO BE MADE
• RESIDUAL STRESSES TO BE AVOIDED
ALL THESE FOR EXPENDABLE MOULD CASTINGS.
NITC

• DESIGN MODIFICATIONS TO AVOID DEFECTS-
• AVOID SHARP CORNERS
• MAINTAIN UNIFORM CROSS SECTIONS
• AVOID SHRINKAGE CAVITIES
• USE CHILLS TO INCREASE THE RATE OF COOLING
• STAGGER INTERSECTING REGIONS FOR
UNIFORM CROSS SECTIONS
• REDESIGN BY MAKING PARTING LINE STRAIGHT
• AVOID THE USE OF CORES, IF POSSIBLE
• MAINTAIN SECTION THICKNESS UNIFORMITY
BY REDESIGNING (in die cast products)
NITC

PROPERTIES AND TYPICALAPPLICATIONS OF
CAST IRONS, NON FERROUS ALLOYS etc.
Tables shall be supplied
NITC

General Cost Characteristics of
Casting Processes
PROCESS COST PRODUCTION
RATE (pc/hr)
DIE EQUIPMENT LABOUR
SAND L L L-M <20
SHELL L-M M-H L-M <50
PLASTER L-M M M-H <10
INVESTMENT M-H L-M H <1000
PERMANENT
MOULD
M M L-M <60
DIE H H L-M <200
CENTRIFUGAL M H L-M <50 NITC

THIXOTROPIC DIE
CASTING
Some of the die-cast joints used in the Insight's aluminum
body are made using a newly developed casting technology
invented by Honda engineers, called Thixotropic Die
Casting.
Thixotropic Die Casting uses aluminum alloy that has been
heated to a semi-solid condition, instead of the molten, liquid
state normally used in die casting.
Pieces made with molten aluminum must be more highly
processed and refined before casting.
NITC

However, Thixotropic Die Casting requires less energy for
smelting (an important consideration since aluminum is more
expensive than steel), and owes much of its strength to the
controlled formation of discrete aluminum crystals within the
metal casting.
Thixotropic casting involves vibratory casting of highly
thixotropic slips of very high solids loadings that are fluid only
under vibration, using porous or nonporous molds.
It is quite different from other conventional and new methods
for solid casting ceramics, including vibroforming,
vibraforming, in situ flocculation, direct coagulation casting,
and gel casting.
This is demonstrated in Table 1.
NITC

Casting Method and Major Features Differentiating Properties of Thixotropic
Casting
Vibroforming – Requires a cement for
setting
Cement is not required for setting
Vibraforming – Requires excess counter
ions and centrifugation for settling
Addition of organic deflocculant/binder
and vibration are the only necessary
steps
In situ flocculation – requires the
addition of urea and heating to control
the pH to the isoelectric point
No urea additions, heating, control of
pH, or attainment of the isoelectric point
are required
Injection moulding – required large
quantities (15-30wt%) of entraining
polymer and pressurized mould feeding
Only traces (<1%) of binder are needed
and no pressure needed for filling of
moulds
Direct coagulation casting – requires
control of the pH through an enzyme
catalysed decomposition reaction
No enzyme additions or control of pH
are required
Gel casting – requires use of a
neurotoxin to cause polymeric gelling
No polymer additive or polymerization
are required
Table 1. Thixotropic casting in comparison with the alternatives.
NITC

Thixotropic casting is a little-known derivative of solid slip
casting, having reportedly been used in the refractories industry
in the early 1970's.
Since then, the refractories industry has since largely embraced
low-cement and ultra-low-cement castables.
It is also a suitable process for forming ceramic matrix
composites and metal-ceramic functionally gradient materials.
Thixotropic casting involves vibratory casting of highly
thixotropic slips of very high solids loadings that are fluid only
under vibration, using porous or nonporous molds.
It is quite different from other conventional and new methods
for solid casting ceramics, including vibroforming,
vibraforming, in situ flocculation, direct coagulation casting,
and gel casting.
(This is demonstrated in Table 1)
NITC

Ejector Pump
The ejector pump is a type
of vacuum pump. Gas is
removed from a container
by passing steam or water
at a high velocity through a
chamber that is connected
to the container. The mixing
chamber contains both the
gas from the container and
the steam or water. At the
inlet port, the ejector pump
is connected to the
container that is being
evacuated. NITC

• For both ferrous and non ferrous castings.(melting
temperature upto 16500
C)
• Very accurate details obtained in intricate shapes
• Excellent surface finish, machining and cleaning
costs minimum.
• Accuracy of 0.002 mm per mm obtained.
• But, casting process costly.
• Casting cost high.
NITC

• PRODUCTION OF ALLOY WHEELS
• METHOD OF PRODUCTION; COUNTER
PRESSURE DIE CASTING
•
• The manufacturing process commences
with the smelting of pure aluminium
ingots in a 5-ton basin type furnace.
NITC

• The furnace is a dry sole type furnace
whose function is to smelt the primary
raw material, and reprocess alloy
scraps consisting of:- wheels used in
destructive testing by the quality
control department, and the risers and
gates removed from the wheels
following the casting process. From
the dry sole furnace, the molten
aluminium is transferred to the alloy
induction furnaces via a feed channel
to enable the mixing and smelting of
the elements required in the
preparation of the alloy – AlSi 7.
NITC

• A spectrometer equipped quality control laboratory is
used during the process of alloy preparation to ensure
the composition of the alloy meets the required
specification during this stage of the preparation
process. Spectrometer analysis sampling is also applied
randomly to finished wheels.
NITC

• Molten alloy is transferred to holding furnaces for
eventual transfer to the casting machines. After the
molten alloy has been tested for conformance to
specifications, it is transported to the alloy treatment
station where the alloy is submitted to three procedures
performed by an automatic process control system. The
treatment unit introduces salts into the molten alloy
using a high-speed spinner, where the alloy purification
is assisted by the use of nitrogen gas jets. The three
procedures to which the molten alloy is submitted are:-
∀ • Degassing
∀ • Refining
∀ • Modifying
NITC

These processes are intrinsic to the removal of all
undesirable impurities in the molten alloy.
The automation of these processes improves the
product quality control, production rates and
importantly minimizes wastage by reducing the
possibilities of rejection of the finished product.
Following the procedures to ensure that the
molten alloy conforms to precise specification, it
is transported in holding furnaces to the low
pressure casting machines. These furnaces are
designed to produce casting by employing
pressurised air within a range of 0.3 – 1.0 atm.,
the pressurization being monitored and varied by
a computerized process control system according
to flow requirements
NITC

Computerized process technology automatically controls the casting
process, and then, at the end of the 4.5 minute casting cycle, cools and
ejects the wheel onto a catcher arm designed for this purpose.
Holding furnaces contain between 500-750kg of molten alloy - sufficient
for up to approx. 4 hours of casting operations. When the holding
furnace is exhausted it is exchanged for a full replacement furnace using
the transfer shuttle - illustrated above - without interruption to the
casting process.
Hydraulic systems control many of the unit’s operating movements, and,
due to high operating temperatures many measures have to be taken to
enable minimization of risk and reduction of maintenance of these
systems. For example, it is necessary for all hydraulic systems to employ
fire resistant fluids thereby eliminating fire risk.
Likewise, all hydraulic hoses have to be metal covered and insulated
against accidental splashes of molten metal.
NITC

NITC
The operators of the Counter Pressure Casting
Machines perform an initial visual quality
control as the wheels are ejected from each
unit and palleted ready for transport to the
Riser cutting department.
At this first stage in the machining process
following casting, the removal of the gates and
risers is carried out by automated machines
designed for this purpose – with a cycle time of
50 seconds per wheel. The CNC riser-cutting
unit performs the following operations

∀ • Pre-boring of the central hole of the wheel
• · Removal of the channel burrs corresponding to the surface joints on the Die’s
moving parts
• · Trimming upper and lower edges of the wheel
• The working cycle of the Riser cutting unit is completely automated to improve both
quality control and production rate per machine. All waste products are collected for
recycling at the foundry. The machine operations are performed under a suction hood to
remove aluminium dust and particulates from the environment in proximity to this unit.
• Customarily, after the machining processes have been completed on the newly cast
wheels, the wheels are passed to the quality control unit for examination under a variety
of non-destructive and destructive tests. Batch sampling of the wheels may involve
taking a 1-2mm scrape taken using a lathe, and running a spectrometer analysis of the
resulting alloy sample.
NITC

• X-Ray analysis machine in Quality control department
• Non-destructive testing is undertaken using radiography processes. It is common
practice for the VM customers to include within their contractual requirements testing
volumes and timescales (i.e. before or after machining). The X-ray control equipment
can be pre-set with information from up to 1000 wheel designs, and wheels can be
inspected on a wide variety of positions / angles (normally 20 position variants).
• The wheel manipulator for handling the wheels during the inspection cycle has 5 fully
computerized axes and a roller conveyor automatically provides loading/unloading of
the machine with the wheels for inspection.
• The X-Ray unit takes 2 wheels at a time - one in process of inspection cycle, and a
second wheel in a ‘holding’ position. As the testing machine completes the automated
inspection cycle, it simultaneously ejects the inspected wheel, puts the second wheel
into position for inspection and draws another wheel into the ‘holding’ position. Thus
the performance inspection cycle is enhanced to its maximum possibility. During an
inspection, the operator monitors the x-ray image on a viewing console and has the
possibility of magnifying the image or ‘replaying’ the process to precisely identify any
casting defect exposed by this machine.
NITC

• The next stage of the quality control process is undertaken on Geometrical
control benches where the physical dimensions of the wheels are compared
with the specification standard using pantographs and micrometers.
• The semi- finished product, having been submitted to various machining
and quality control procedures are passed to the finishing dept. which -
dependent upon client specification - either submits the wheels through an
automated paint shop - or polishing line where a bright lacquer finish has
been specified.
• The finished wheels are then palleted and wrapped in polyethylene film -
ready for transfer to a wheel/tyre assembly plant - prior to final shipment
to the production lines of the VM customer
NITC

• The pallet/box wrapping equipment consists of a motorized wrapping
machine – allowing pallets to be placed on a rotating turntable, and
providing film wrapping through this rotation with a fixed unit holding
the polyethylene roll.
• The finished wheels are stored on pallets/boxes until shipping.
• COUNTER PRESSURE DIE CASTING MACHINES
• The casting machines have evolved over 25 years of development and
manufacturing experience of counter-pressure & low pressure casting
machines.
• Simplicity of design, operating convenience and ease of maintenance are
the core attributes that produce highest levels of egonomics and safety.
• The above principles are well emphasised by the rugged vertical tie-bar
construction incorporating an integral holding furnace.
• The well tried and proven technical solutions provide stability, accuracy
in guiding and controlling the precision of the moving parts, and include
essential rigidity, operational dependability and longevity of the machines.
• All machines are designed to withstand heavy-duty service in foundries
operating continuous 24 hour cycles.
NITC

CASTING DEFECTS
SURFACE
METALLIC PROJECTION (4)
DEFECTIVE SURFACE (11)
CHANGE IN DIMENSION- WARP
INCOMPLETE CASTING
MISRUN, RUNOUT
CAVITY-
BLOWHOLES, SHRINKAGE
PINHOLES
DISCONTINUITY
HOT CRACK
COLD SHUT, COLD CRACK
SUBSURFACE
SUBSURFACE CAVITY
INCLUSIONS
DISCONTINUITY
NITC

Casting Defects
• Metal casters try to produce perfect castings.
• A few castings, however, are completely free of
defects.
• Modern foundries have sophisticated inspection
equipment which can detect small differences in
size and a wide variety of external and even
internal defects.
For example, slight shrinkage on the back of a
decorative wall plaque is acceptable whereas
similar shrinkage on a position cannot be
tolerated.
• No matter what the intended use, however, the
goal of modern foundries is zero defects in all
castings

MANUFACTURING SCIENCE S5ME -NITC-2016

MANUFACTURING SCIENCE S5ME -NITC-2016

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