It gives the complete explanation about the sand casting process

1. STEPS INVOLVED IN SAND
CASTING PROCESS
BY
ARAVINDKUMAR B

2. MANUFACTURING:
 Manufacturing is a latin word “manufactus” means
made by hand.
 In modern context, it involves making products from
raw materials by using Various processes, by making
use of hand tools, machinery or even computers.
CLASSIFICATIONS:
 Casting Process: Die Casting
 Forming Process: Rolling, Extrusion
 Fabrication Process: Welding, Riveting
 Material Removal Process: Drilling, Turning
METAL CASTING:
 Converting molten or plastic raw materials into finished
products.

3. Steps involved in producing a cast part:
 Preparing the mould
 Preparing the molten metal
 Introducing or Pouring the molten metal into the mould
with the help of ladle
 Solidifying the molten metal
 After solidification, removing the cast part from the
mould
Applications of Metal Casting:
 Transport: Automobile, Aerospace
 Heavy Equipment: Construction, Mining
 Electrical Machines: Motors, Generators, Pumps
 Household: Kitchen and Gardening Equipments

4. SAND CASTING:
 Sand Casting is one of the metal shaping method
 It is defined as “ pouring the molten metal into a
refractory mould with the help of ladle and allowing it
to solidify. When solidified, the desired metal object is
taken out from the refractory mould either by breaking
the mould or taking the mould apart ”
MERITS:
 Very simple and inexpensive
 Any materials like ferrous or non-ferrous can be made
 Intricate shapes can be made
 Any size and weight, up to 200 tonnes can be made
 Certain metals and alloys can be made

5.  SAND CASTING

8. APPLICATIONS:
 Cylinder Block, Liners, Machine Tool Beds, Pistons,
Piston Rings, Wheels, Water Supply Pipes and Bells
MOULDING SAND:
 The ingredients of moulding sand are 80 to 90 % Silica
Sand Grains, 5 to 20 % Clay, Moisture, 2 to 5 % Water,
Oxides of Iron, Potash, Limestone, Magnesia and Soda
MOULDING SAND PROPERTIES:
 Porosity: It is the property of sand which permits the
steam and other gases to pass through the sand mould. If
the sand is too fine, the porosity will be low.
 Strength: Measurement of strength can be done by
using Universal Sand Strength Testing Machine

9.  Flowability: When rammed, sand will flow into all
portions of a mould and take up the required shape
 Refractoriness: The sand must be capable of
withstanding high temperature of the molten metal
without breaking
 Adhesiveness: It is that properties of sand must be
capable of adhering or sticking to the sides of the
moulding box
 Cohesiveness: It is the property of sand due to which
the sand grains stick together during ramming. It is
defined as the strength of the moulding sand.
 Chemical Resistivity: The moulding sand should not
chemically react with the metallic mould

10. MOULDING SAND TESTING METHODS:
(1) Grain Fineness Test: Grain size of a sand is
designated by a number called “Grain Fineness
Number” that indicates the average size as well as
portions of smaller & larger grains
 A sample of dry sand, free from clay is placed on the
upper sieve & the sieve is vibrated for 15 min
 Grain Fineness No. = Total Product / Total % of sand
saved on each sieve
(2) Moisture Content Test: The moisture content is
calculated by difference in weight between the moist
and dry sand. The drying of moist sand is carried out at
105ºC & 110ºC in a heated oven and then cooled to
room temperature.

11. (3) Clay Content Test: The method for determining the
clay content of moulding sand consists of agitating the
sand in water.
 So as to separate the clay from the sand particles and
then removing the clay which remains suspended in
distilled water at room temperature
(4) Permeability Test: Permeability is measured by the
quantity of air that will pass through a standard
specimen of the sand under a given pressure in a
prescribed time
 Permeability Number = v × h / p × a × t
 Where, v = Volume of air in cc, h = Height of the sand
specimen in cm, p = Air pressure in gm / cm², a = Cross-
sectional area of the specimen in cm², t = Time in mins

12. PATTERN:
 The pattern is used for forming an impression on the
material
PATTERN MATERIALS:
(1) Wood: The most commonly used pattern material is
wood, the main reason being the easy availability, low
weight, it can be easily shaped and cheap
 Ex: Pine, Teak wood
(2) Metal: Metal patterns are extensively for casting,
because of their strength, accuracy, good dimensional
stability, durability and smooth surface finish
 Many materials such as Cast iron, Brass, aluminium,
white metal can be used as pattern materials

13.  Aluminium and White metal are most commonly used,
these materials are light weight, it can be easily worked,
corrosion resistant
(3) Plastics: This are also used as pattern materials
because of their low weight, easier formability, good
dimensional stability, smooth surfaces and durability
 Ex: Epoxy resin
(4) Plasters: It has high strength, it can be easily formed
into complex shapes and it can be used only for small
pattern
 Ex: Gypsum cement
(5) Waxes: Excellent material for investment casting and
it has good surface finish, high tensile strength, hardness
 Ex: Paraffin Wax, Bees Wax

14. (6) Rubbers: Mainly used for investment casting
 Ex: Silicon Rubber
 Wooden pattern for a cast-iron gear with curved
spokes:

15. TYPES OF PATTERNS:

17.  THE DETAILS OF A CAST IRON WHEEL
THE DETAILS OF A CAST
IRON WHEEL
THE SPLIT PIECE OR TWO PIECE
PATTERN OF A CAST IRON WHEEL

19. 4. Shell Pattern:
 Shell Pattern is a Hollow Pattern. These patterns are
made of metal.
 Its outer shape is used for making the mould. The core is
prepared using the inner surface of the pattern itself.

20.  This is made into two halves and joined accurately by
dowels. Ex: Drainage Fittings, Pipe Work like Short
Bends
5. Gated pattern:
 A gated pattern is simply one or more loose patterns
having attached gates and runners.

21. 6. Sweep pattern:
 Sweep patterns are used for the castings which are
symmetrical and regular in shape like cylinder or pipe
etc.
 This type of pattern is used when the castings required
are very large.
 In sweep pattern a simple sweep which is rotated about a
central axis is used to produce a mould cavity.

22. PATTERN ALLOWANCES:
 A duplicate of the product to be cast, modified
dimensionally to reflect process of material to be cast
 Modification incorporated in pattern are allowance or
pattern allowance

23. (1) Shrinkage or Contraction Allowance: Generally
metals shrink in size during solidification and cooling
in the mould
 So casting becomes smaller than the pattern and the
mould cavity
 Therefore, to compensate for this, mould and the pattern
should be made larger than the casting by the amount of
shrinkage.
 The amount of compensation for shrinkage is called the
shrinkage allowance.
 Generally shrinkage of casting varies not only with
material but also with shape, thickness, casting
temperature, mould temperature, and mould strength.

24.  (2) Draft or Taper Allowance: When the pattern is to be
removed from the sand mold, there is a possibility that
any leading edges may break off, or get damaged in the
process
 To avoid this, a taper is provided on the pattern, so as to
facilitate easy removal of the pattern from the mold, and
hence reduce damage to edges.
 The draft is expressed in millimeters per meter on a side
or in degrees.
 The amount of draft needed depends upon (1) the shape
of casting, (2) depth of casting, (3) moulding method,
and (4) moulding material.

26. (3) Machining or Finish Allowance: The surface finish
obtained in sand castings is generally poor
(dimensionally inaccurate)
 Hence in many cases, the cast product is subjected to
machining processes like turning or grinding in order to
improve the surface finish
 During machining processes, some metal is removed
from the piece
 To compensate for this, a machining allowance
(additional material) should be given in the casting
(4) Distortion Allowance: During cooling of the mold,
stresses developed in the solid metal may induce
distortion in the cast

27.  For example, a U-shaped casting will be distorted during
cooling with the legs diverged or deviated, instead of
parallel (Figure).
 For compensating this, the pattern is made with the legs
converged or jointed but, as the casting cools, the legs
straighten and remain parallel.
(a) Casting without camber or bend
(b) Actual casting
(c) Pattern with camber or bend

28. (5) Shake or Rapping Allowance:
 Additional size tolerances must be built into the pattern
 When the pattern is shaken for easy withdrawal from the
mould cavity, hence the casting is slightly increased in
size.
 In order to compensate for this increase, the pattern
should be initially made slightly smaller.
 In this process, the final cavity is enlarged. To
compensate for this, the pattern dimensions need to be
reduced
 Usually during removal of the pattern from the mould
cavity, the pattern is rapped or cracked all around the
faces, in order to facilitate or help easy removal

29. DIFFERENT TYPES OF CASTINGS DEFECTS:
 Blow: Blow is relatively large cavity produced by gases
which displace molten metal form
 Pin holes: Pin holes are small gas holes either at the
surface or just below the surface. When these are present,
they occur in large numbers and are fairly uniformly
dispersed over the surface

30.  Blow holes: Blow holes, gas holes or gas cavities are
well rounded cavities having a clean and smooth surface.
They appear either on the casting surface or in the body
of a casting
 Misrun or short run: This defect is incomplete cavity
filling. The reasons are - inadequate metal supply, too-
low mould or melt temperature, improperly designed
gates, etc

31.  Hot tear: Hot tears are hot cracks which appear in the
form of irregular crevices with a dark oxidized fracture
surface
 Shrinkage: A shrinkage cavity is a depression or an
internal void or empty space in a casting that results from
the volume contraction that occurs during solidification

32. CORE:
 A core is a device used in casting and molding processes
to produce internal cavities.
 It is made of green sand
 The core is normally a disposable item.
 They are most commonly used in sand casting, but are
also used in injection molding
 Cores are placed in the mold, and remain there during the
pouring phase of the sand casting process.
 The metal casting will solidify around the core
 Cores has good strength, good permeability, high
refractoriness and sufficient

33. TYPES OF CORES:
 Green Sand Core: When a pattern leaves a core as a
part of the mould, that body of sand used to make the
core is called Green Sand Core as this core is formed by
pattern itself.
 Horizontal Sand Core: The core is placed horizontally
in the mould and it is very commonly used in foundries.
 These are usually cylindrical in shape. It may also have
any other shape depending upon the shape of the cavity
required.
 Vertical Core: These cores are positioned vertically in
the mould.
 Balanced Core: This core is supported and balanced at
one end only. It extends horizontally in the mould.

34. TYPES OF CORE BOXES:
 Half Core Box: It is used to form two halves of the
symmetrical core. After baking, the two core pieces will
be pasted together to form the full core.
 Dump Core Box: It is used for making a full core in
one box. The box is used for making slabs or rectangular
cores.
 Split Core Box: This box has similar halves. They are
aligned by dowel pins. After ramming the core sand, the
box is separated and the core is removed.
 Gang Core Box: When a no. of cores needed are more,
a gang core box is used. At one time, many cores may
be made in this box.

35. MELTING FURNACES:
 These are used in the foundry industries. The selection
of furnace depends on,
 The temperature required to melt the alloy
 The quantity of molten metal required
 Environmental and Waste disposal requirements
 The economy of installation and operation
(1) CUPOLA FURNACE:
 This type of furnace is used for melting Cast Iron
(2) BLAST FURNACE:
 This type of furnace is used for melting Metal Ore,
usually Iron Ore

36. MOULDING MACHINES:
 Moulding involves packing the moulding sand
uniformly around a pattern placed in a moulding box.
Two types of moulding are as follows:
(a) Hand Moulding: It is economical only when castings
are required in very small number
(b) Machine Moulding: High rate of production, Low
cost, uniformity in size and shape and accuracy
 Moulding machines will do the following operations:
 Ramming the moulding sand
 Removing the pattern from the sand

37. TYPES OF MOULDING MACHINES :
(1) Jolt Squeeze Moulding Machine: The pattern is
placed in the flask on the table.
 The flask rests on the machine table and the table with
flask is raised to 80 mm by jolting mechanism and
suddenly dropped.
 The sudden dropping
of table from a height makes
the sand pack evenly around
the pattern.

38.  This machines are used for ramming horizontal surfaces
on the mould. Operation is noisy because of jolting or
shaking.
(2) Vibratory Squeeze Moulding Machine: The
moulding sand is squeezed or pressed between the
machine table and a squeezer head.
 The mould board is clamped on the table. The pattern is
placed inside the flask. The sand is filled up and leveled.
 The table is raised up by the table lift mechanism
against the squeezer head.
 The platen enters the sand frame and packs the sand
tightly. After squeezing the flask, the table comes down
to the starting position.

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