Production Technology Lecture Notes as per GGSIPU SYLLABUS FOR UNIT 1. Casting is a process in which molten metal is allowed to solidify in a predefined mould cavity. After the solidification by breaking the mould the component is taken out. This is known as CASTING. Pattern is a replica of a object to be made with some modifications. Pattern Materials Difference between Pattern and Casting Types of Patterns Pattern Design Considerations Pattern Allowances Pattern Making Pattern Layout Properties of moulding sand Testing of Moulding Sand Special casting process

1. UNIT-1
MOULDING
Prepared by;
ANKIT SAXENA
Assistant Professor
Dr. Akhilesh Das Gupta Institute of Technology
and Management (Formerly NIEC)
Mechanical and Automation Engineering
Department

2. Types of Manufacturing Processes

3. Metal Casting Process
Casting is a process in which molten metal is allowed to solidify
in a predefined mould cavity. After the solidification by breaking
the mould the component is taken out. This is known as
CASTING.

4. Schematic diagram of general Casting Process

5. Classification of Casting Processes

7. The Pattern and their functions
Pattern is a replica of a object to be made with some
modifications, The modifications are
(i) Allowances
(ii) Core Print
 A pattern prepares a mould cavity for the purpose of
making a casting.
 A pattern may contain projections known as core prints if
the casting requires a core and need to be made hollow.
 Runner, gates and risers may form a part of the pattern.

8. A pattern may help in establishing locating points on the
mould and therefore on the casting with a purpose to
check the casting dimensions,
Patterns establish the parting line and parting surfaces
in the mould.
A pattern may help position a core before the moulding
sand is rammed.
Properly made patterns having finished and smooth
surfaces reduce casting defects.
Properly constructed patterns minimize overall cost of
the castings.

9. Pattern Materials
1. Wood - common material because it is easy to work, but it
warps
2. Metal - more expensive to make, but lasts much longer
3. Plastic - compromise between wood and metal
Selection of pattern Materials
(i) The number of castings to be produced. Metal Pattern are
preferred when the production is large.
(ii) Method of moulding i.e., Hand or machine moulding.
(iii) Shape, complexity and size of the casting.
(iv) Type of moulding materials i.e., Sand etc.
(v) The chances of repeat orders.

10. Difference between Pattern and Casting
The main difference between a pattern and the
casting is as regards their dimensions. A pattern is
slightly larger in size as compared to the casting,
because a pattern:
(i) Carries Shrinkage allowance, it may be of the
order of 1 to 2 mm/100mm.
(ii) Is given a Machining allowance, to clean and
finish the required surfaces.
(iii) Carries a Draft allowance of the order of 1 and 3
degree for external and internal surfaces
respectively.
(iv) Carries core prints.

11. In addition;
(i) A pattern may not have all holes and slots
which a casting will have. Such holes and slots
unnecessarily complicate a pattern and
therefore can be drilled in the casting after it
has been made.
(ii) A pattern may be in two or three pieces
whereas a casting is in one piece.
(iii) A pattern and the casting also differ as
regards the material. Out of which they made.

12. Types of Patterns
Solid Pattern Split Pattern Match-plate pattern Cope and Drag pattern

13. 1. Solid or single piece pattern
If the object to be produced is very simple and
size without any complex surfaces we can select
solid pattern.
Solid pattern is kept inside the drag box such
that one of its surface will matches with parting
line.
2. Split pattern
If the complexity of the object is more i.e.,
Patterns of intricate castings cannot be made in
one piece because of inherent difficulties
associated with the moulding operations.

14. 3. Match-plate pattern
Characteristics of Match Plate Pattern
 It is a split pattern
 Cope and Drags on the opposite site
of the metallic (generally) plate.
 The gates are runners are on the
match plate.
 Can be used for large number of
casting with very little hand work.
 A match plate can be single pattern
or a combination of many small
patterns
Example : IC engine piston rings can be
produced by match plate pattern
4. Cope and drag pattern
 For big parts who are difficult to
handle.

15. 5. Gated Pattern
All the gating
elements are the
integral part of pattern.
Used to produce small
number of castings in
mass production.
6. Loose piece pattern

16.  If the object to be produced is having some web portions or
overhanging portion it is difficult to remove the pattern as a
solid pr split piece pattern.
 For easy removal of these types of pattern the web portion
made as a loose piece and they will be removed from mould
cavity after removing the main part of the pattern from mould.
7. Sweep Pattern
Used for producing large size
symmetrical castings such as
bells.

17. 8. Skelton Pattern
To Reduce the moulding material in casting of complex shapes.
Production of large size shells and drums is possible.

18. Pattern Design
1. Pattern Design Considerations
 Factors listed below must be taken into consideration while designing
a pattern:
 A pattern should be accurate as regards its dimensions and posses
very good surface finish, good surface finish may be imparted to a
pattern surface initially by sanding and then by coating shellac on it.
 A proper material for making the pattern should be selected. Metallic
patterns last longer as compared to wooden ones but are expensive.
 A Pattern must carry all those allowances which are essential to
simplify the moulding operations and impart accurate dimensions to
the final casting.
 In case of split patterns, the parting surface should be such that the
maximum portion of the pattern remains in the drag, offset parting is
beneficial.
 Jointed cores should preferably be avoided in order to obtain uniform
holes.

19.  Core prints provided with the pattern should be of optimum size and
suitably located.
 All those patterns of the castings for whom repeat orders are
expected should be coated with preservatives, suitably marked and
adequately stored.
2. Pattern Allowances
Shrinkage allowance
i. Solid shrinkage compensated by
increasing the size of pattern in the
form of shrinkage allowance.
ii. Liquid and solidification shrinkage
is concentrated by providing riser
in moulding process.
iii. It can be expressed in terms of
percentage of shrinkage of liquid
metal.
iv. Solid shrinkage can be given to
linear dimension of the casting

20. Draft allowance
i. It is given to all surfaces
perpendicular to parting line.
ii. Draft allowance is given so
that the pattern can be easily
removed from the moulding
material tightly packed around
it with out damaging the
mould cavity.
Fig shows taper in design

21. Distortion or cambered allowance
 During solidification of casting there
is a possibility of distortion of given
component due to internal stresses
which are developed because of
different shrinkage rate, the
distortion depends on the shape and
size of the object.
A casting will distort or wrap if :
i. It is of irregular shape,
ii. All it parts do not shrink uniformly
i.e., some parts shrinks while
others are restricted from during
so,
iii. It is U or V-shape
Shake or Rapping Allowance
 Pattern is shaken or rapped by striking the same with a wooden piece from side to side.
This is done so that the pattern a little is loosened in the mould cavity and can be easily
removed. In turn, therefore, rapping enlarges the mould cavity which results in a bigger sized
casting. Hence, a –ve allowance is provided on the pattern i.e., the pattern dimensions are
kept smaller in order to compensate the enlargement of mould cavity due to rapping.

22. Pattern Making
Pattern Making tools

24. Pattern Making Machines

26. Pattern Layout
Steps involved:
i. Get the working drawing of the part for which the pattern is to be
made.
ii. Make two views of the part drawing on a sheet, using a shrink rule.
A shrink rule is modified form of an ordinary scale which has already
taken care of shrinkage allowance for a particular metal to be cast.
iii. Add machining allowances as per the requirements.
iv. Depending upon the method of moulding, provide the draft
allowance.
Fig. Pattern Layout

27. Pattern Construction:
i. Study the pattern layout carefully and establish,
a. Location of parting surface.
b. No. of parts in which the pattern will be made.
i. Using the various hand tools and pattern making machines fabricate the
different parts of the pattern.
ii. Inspect the pattern as regards the alignment of different portions of the
pattern and its dimensional accuracy.
iii. Fill wax in all the fillets in order to remove sharp corners.
iv. Give a shellac coatings(3 coats) to pattern.
v. Impart suitable colours to the pattern for identification purposes and for
other information.
Fig shows no. of parts in which the pattern will be made.

36. Testing of Moulding Sand
The moulding sand after it is prepared, should be properly tested to see that the
requisite properties are achieved. These are standard tests to be done as per
Indian Standards.
1. Moisture Content
2. Clay Content
3. Sand Grain Size
4. Permeability
5. Strength
6. Green Compression Strength
7. Green Shear Strength
8. Dry Strength
9. Mould Hardness

37. 1. Moisture Content
i. Moisture is an important element of the moulding sand as it affects many
properties. To test the moisture of moulding sand a carefully weighed sand test
sample of 50g is dried at a temperature of 105 degC to 110 degC for 2 hours by
which time all the moisture in the sand would have been evaporated. The
sample is then weighed. The weight difference in grams when multiplied by
two would give the percentage of moisture contained in the moulding sand.
ii. Alternatively a moisture teller can also be used for measuring the moisture
content. In this sand is dried by suspending the sample on a fine metallic
screen and allowing hot air to flow through the sample. This method of drying
completes the removal of moisture in a matter of minutes compared to 2 hours
as in the earlier method.
iii. Another moisture teller utilizes calcium carbide to measure the moisture
content. A measured amount of calcium carbide (a little more than actually
required for complete reaction) in a container along with a separate cap
consisting of measured quantity of moulding sand is kept in the moisture teller.
Care has to be taken before closing the apparatus that carbide and sand do not
come into contact. The apparatus is then shaken vigorously such that the
following reaction takes place:
CaC2 + 2 H2O → C2H2 + Ca(OH)2
The acetylene ( C2H2) coming out will be collected in the space above the sand
raising the pressure. A pressure gauge connected to the apparatus would give
directly the amount of acetylene generated which is proportional to the
moisture present. It is possible to calibrate the pressure gauge directly read the
amount.

38. 2. Clay Content
i. The clay content of the moulding sand is determined by dissolving or
washing it off the sand.
ii. To determine the clay percentage a 50 g sample is dried at 105 to 110 degC
and the dried sample is taken in a one litre glass flask and added with 475
ml of distilled water and 25ml of a one percent solution of caustic soda
(NaOH 25 g per litre). This sample is thoroughly stirred.
iii. After the stirring, for a period of five minutes, the sample is diluted with
fresh water up to a 150 mm graduation mark and the sample is left
undisturbed for 10 minutes to settle. The sand settles at the bottom and the
clay particles washed from the sand would be floating in the water.
iv. 125 mm of this water is siphoned off the flask and it is again topped to the
same level and allowed to settle for five minutes. The above operation is
repeated till the water above the sand becomes clear, which is an indication
that all the clay in the moulding sand has been removed. Now, the sand
removed from the flask and dried by heating.
v. The difference in weight of the dried sand and 50g when multiplied by two
gives the clay percentage in the moulding sand.

39. 3. Sand Grain Size
i. To find out the sand grain size, a sand
sample which is devoid of moisture and
clay such as the one obtained after the
previous testing is to be used. The dried
clay free sand grains are placed on the
top sieve of a sieve shaker.
ii. The sieves are shaken continuously for a
period of 15 minutes. After this shaking
operation, the sieves are taken apart and
the sand left over on each of the sieve is
carefully weighed. The sand retained on
each sieve expressed as a percentage of
the total mass can be plotted against
sieve number. But more important is the
Grain Finesses Number (GFN) which is a
quantitative indication of the grain
distribution.
iii. The amount retained on each sieve is
multiplied by the respective weightage
factor, summed up and then divided by
the total mass of the sample, which gives
the GFN.

40. 4. Permeability
The rate of flow of air passing through a standard specimen under a standard pressure is
termed as permeability number. The standard permeability test is to measure time
taken by a 2000 cm3 of air at a pressure typically of 980 Pa to pass through a standard
sand specimen confined in a specimen tube. The standard specimen size is 50.8 mm in
diameter and a length of 50.8 mm. Then, the permeability number, P is obtained by
V H
P
p A T


 
Where V = volume of air = 2000
cm3
H = height of the sand
specimen = 5.08 cm; p = air
pressure, g/cm2; A = cross
sectional area of sand
specimen= 20.268 cm2 ; T =
time in minutes for the
complete air to pas through

41. 5. Strength
i. Measurement of strength of moulding sands can be carried out on the universal
sand strength testing machine. The strength can be measured in compression, shear
and tension. The sands that could be tested are green sand, dry sand or core sand.
The compression and shear test involve the standard cylindrical specimen that was
used for the permeability test.
6. Green Compression Strength
i. Green compression strength or simply green strength generally refers to the stress
required to rupture the sand specimen under compressive loading. The sand
specimen is taken out of the specimen tube and is immediately (any delay causes
the drying of the sample which increases the strength) put on the strength testing
machine and the force required to cause the compression failure is determined. The
green strength of sands is generally in the range of 30 to 160 KPa.
7. Green Shear Strength
i. With a sand sample similar to the above test, a different adapter is fitted in the
universal machine so that the loading now be made for the shearing of the sand
sample. The stress required to shear the specimen along the axis is then
represented as the green shear strength. It may vary from 10 to 50 KPa.

42. 8. Dry Strength
This test uses the standard specimens dried between 105 and 1100 C for 2 hours.
Since the strength increases with drying, it may be necessary to apply larger
stresses than the previous tests. The range of dry compression strengths found in
moulding sands is from 140 to 1800 KPa, depending on the sand sample.
Fig. Sand strength testing set up

43. 9. Mould Hardness
i. The mould hardness is measured by a method similar to the Brinell hardness
test. A spring loaded steel ball with a mass of 0.9 Kg is indented into the
standard sand specimen prepared. The depth of indentation can be directly
measured on the scale which shows units 0 to 100. When no penetration
occurs, then it is a mould hardness of 100 and when it sinks completely, the
reading is zero indicating a very soft mould.

44. ASSIGNMENT 1
Que1. Describe Moulding and Core making
machines.
Que2. Constituents of moulding sand and also
define types of moulding sand used in casting
process.

45. 1. Carbon dioxide Moulding Process
i. Carbon dioxide moulding also known as sodium silicate
process is one of the widely used process for preparing
moulds and cores.
ii. In this process, sodium silicate is used as the binder. But
sodium silicate activates or tend to bind the sand particles
only in the presence of carbon dioxide gas. For this reason, the
process is commonly known as C02 process.
iii. In addition, one can be sure of getting dimensionally accurate
castings with fine surface finish. But, this process is not
economical than green sand casting process.
iv. The process is basically a hardening process for moulds and
cores.

46. Process
i. The principle of working of the co2 process is based on the
fact that if co2 gas is passed through a sand mix containing
sodium silicate, the sand immediately becomes extremely
strongly bonded as the sodium silicate becomes a stiff gel.
ii. This gel is responsible for giving the necessary strength to the
mould.
iii. The sand used for the process must be dry and free from clay.
Suitable additives such as coal powder, wood flour, graphite
may be added to improve certain properties like collapsibility.
iv. The suitable sand mixture can then be packed around the
pattern in the flask or in the core box by machines or by hand.
v. When the packing is complete, co2 is forced into the mould at
a pressure of about 1.45 kgf/cm2(142 kN/m2) . The gas is inert
up to 15 to 30 seconds.
vi. The volume of co2 required can be calculated if the quantity
of sodium silicate present is known.

47. vii. As a thumb rule, for every 1 kg of sodium silicate, 0.50-0.75
kg of gas is required.
viii. Over gassing is wasteful and results in deteriorating the sand.
ix. Patterns used in this process may be made of wood, metal or
plastic.
x. Carbon dioxide casting is favoured both by the commercial
foundry men and hobbyist for a number of reasons. In
commercial operations, foundry men can assure customers
of affordable castings which require less machining.
xi. The moulding process which can be fully automated is
generally used for casting process that require speed, high
production runs and flexibility. In home foundries this is one
of the simplest process that improves the casting quality .

49. Advantages
i. Instantaneous strength development. The development of strength
takes place immediately after carbon dioxide gassing is completed.
ii. Since the process uses relatively safe carbon dioxide gas, it does not
present sand disposal problems or any odour while mixing and
pouring. Hence, the process is safe to human operators.
iii. Very little gas evolution during pouring of molten metal.
iv. Semi-skilled labour can be used.
v. This process can be fully automated.
Disadvantages
i. Poor collapsibility of moulds is a major disadvantage of this process.
ii. There is a significant loss in the strength and hardness of moulds
which have been stored for extended periods of time.
iii. Over gassing and under gassing adversely affects the properties of
cured sand
Applications
i. CO2 casting process is ideal where speed and flexibility is the prime
requirement.

50. 2. Shell Moulding Process
i. Shell moulding is an efficient and economical method for producing
steel castings.
ii. The process was developed by “Herr Croning” in Germany during
World war-II and is sometimes referred to as the Croning shell
process.
iii. It can produce min. shell thickness, the amount of shell thickness
depends upon how much contact time of sand and heated pattern
(Dwell time).
Procedure in shell moulding process
(a) A metallic pattern having the shape of
the desired casting is made in one half from
carbon steel material. Pouring element is
provided in the pattern itself. Refer figure
(a).

51. 1. The pattern is inverted and is placed
over a box as shown in figure (1). The
box contains a mixture of dry silica
sand or zircon sand and a resin binder
(5% based on sand weight).
2. The box is now inverted so that the
resin-sand mixture falls on the heated
face of the metallic pattern. The resin-
sand mixture gets heated up, softens and
sticks to the surface of the pattern. Refer
figure (2).
3. After a few seconds, the box is again
inverted to its initial position so that the
lose resin-sand mixture falls down leaving
behind a thin layer of shell on the pattern
face. Refer figure (3).

52. 4. The pattern along with the shell is removed
from the box and placed in an oven for a
few minutes which further hardens the
shell and makes it rigid. The shell is then
stripped from the pattern with the help of
ejector pins that are provided on the
pattern. Refer figure (5).
Fig 5
5. Another shell half is prepared in the
similar manner and both the shells are
assembled, together with the help of
bolts, clips or glues to form a mould. The
assembled part is then placed in a box
with suitable backing sand to receive the
molten metal. Refer figure (6).

53. 6. After the casting solidifies, it
is removed from the
mould, cleaned and
finished to obtain the
desired shape as shown in
figure (7).
Fig7
Advantage
Better surface finish and dimensional tolerances.
Reduced machining.
Requires less foundry space.
Semi-skilled operators can handle the process easily.
Shells can be stored for extended periods of time.
Disadvantages
Initially the metallic pattern has to be cast to the desired shape, size and finish.
Size and weight range of castings is limited.
Process generates noxious fumes.

54. 3. Fluid sand process or Dicalcium silicate process
i. Dicalcium silicate has been found to be very effective hardening
agent when used with sodium silicate as a binder.
ii. Unlike Fe-Si process where hardening is due to exothermic
reaction, the chemical reaction taking place in this process do not
cause any evolution of heat.
iii. Synthetically produced dicalcium silicate can be used for this
purpose.
iv. Slag from certain melting or reduction process; such as Basic hot
blast Cupola, open hearth furnace etc. contains an appreciable
quantity of dicalcium silicate and are quite suitable.
v. The rate of hardening depends upon the grain fineness of the
silicate and the temperature of the sand.
vi. Fineness of the silicate grain should not be less than 200 mesh.
The higher the production, the quicker the reaction and shorter
the bench life.

55. vii. To prepare the mix, about 2-3%of dicalcium silicate and 5% sodium
silicate are mixed with sand , along with suitable foaming chemicals.
viii. The mix can flow easily in the mould, thus eliminating any need for
ramming.
ix. Mixing time is from 3-5 min, the sodium silicate used in the process
should have a high mass ratio (1:2.3 to 1:2.8) and specific gravity
1.48 to 1.50.
x. The fluid sand process finds its application in medium and heavy
castings both in Grey iron steel such as ingot, moulds, heavy
machine tool.
xi. The main advantage of the process is great saving in labour input &
moulding equipment.
xii. No dying and baking needed.
xiii. Defect free casting are produced.

56. 4. Hot-box method
i. This process is refinement of shell moulding . A resin similar to that
used in shell moulding is applied for coating. The resin sand mix is
blown over the heated pattern. In this case mould not turned over
to allow shell formation.
ii. The Core or mould obtained are relatively free from distortion or
shrinkage and the accuracy of the dimension is greater than in case
of shell moulding.
iii. For small size, very high rate of production are achieved. The
process has been applied particularly in core making.
5. Hot Curing Process
i. The curing of resin takes place due to the dual effect of heat and
chemical reaction of an and catalyst such as hexamine. It contains:
ii. Heating the dry silica sand to a temperature between 120 to 175
DegC.
iii. Mixing the heated sand thoroughly with the resin and hexamine, so
that the sand grains get uniformly coated with the resin.

57. iv. Screening the mix to eliminate lumps and agglomerates which may
have been produced during mixing.
v. Cooling the sand mix to about 45 DegC to prevent lump formation
and to impact flowability.
vi. Aerating the cooled sand mix to further improve its flowability and
power to quickly form the shell.
It is the most economical method for mass production the process is
safe as no alcohol is used and there is no explosion hazard.
6. Cold curing Process
i. When heating of sand grains is not required, the sand is first mixed
with the requisite quantity of hexamine and then resin, duly dissolved
region at room temperature. The method is more expensive.
ii. Great quantity of resin is required . The strength of the shell produced
is also relatively less.
iii. No special equipment is required, small quantity of sand mix can be
prepared.

58. Flask less Moulding Process
i. This process is a sand casting, or a green sand moulding variation, that has been automated for
speed and high volume output, of identical castings. Despite the name which is misleading, a
flask-less moulding does use flasks. The flasks “ holds the whole thing together ”.
ii. A Flask must be used on all sand moulding for the containment of the sand, while the pattern is
surrounded by sand.
iii. In flask-less moulding, in either a vertical or a horizontal stance, a sand filled flask is rebuilt and
used over and over, in totally mechanized and automated way. In sand casting or green sand
casting, a tight fitting, individual−most likely sand filled flask is used for each mould produced.
iv. The benefits of these systems are very impressive like uniformity, high density moulds, high
output of products, elimination of mould shift, just to mention a few, all of which drastically
reduce labour expense.
v. Flask-less moulding provides a mould hardness that is consistent throughout the mould. The
operator can adjust to different cope, drag heights and total squeeze pressure to accommodate
different mould densities and mould hardness to meet the moulding application.
vi. The operator can adjust the sand fill allowing the adjustment for variations in each pattern. It is
possible to produce complex moulds and mould with deep pockets, which are difficult with
traditional, normal sand casting procedures.
vii. Rapid core setting, easy inspection of cores used, utilization of existing tooling, high casting
quality, reduced finishing time, quick pattern change, exceptional mould to mould consistency,
high productivity are some of the many reasons to use flask-less moulding

59. Advantages of Flaskless Moulding
i. It does not use flasks, which avoids a need of their transporting, storing
and maintaining.
ii. No repair expenditure on flasks
iii. By adopting aeration sand filling technology, energy saving and noise
reduction have been achieved
iv. Stable pattern draw is secured by automatic pattern spray
v. Minimize turbulence and porosity in casting

60. Video links
1. https://www.youtube.com/watch?v=Y7c9Lby0u-0&t=69s
2. https://www.youtube.com/watch?v=oZxaQ971s7k&t=23s
3. https://www.youtube.com/watch?v=Yk1JOYzwRP4&t=2s
4. https://www.youtube.com/watch?v=nCoostMdU3c
5. https://www.youtube.com/watch?v=Jk2PC2o_XSg
6. https://www.youtube.com/watch?v=m4qBETv7bX0
7. https://www.youtube.com/watch?v=rf8n9J2CDV4&t=6s

61. THANKYOU