manufacturing science firstyear file
TRANSCRIPT
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INDEX SR
NO NAME OF EXPERIMENT DATE SIGN REMA
RK 1. Design of pattern of desired
casting.2. Pattern making using a given
design of pattern.3. Making mould for a desired
casting -Bearing Block, Machinevice moving jaw.
4. Mould sand testing(a) Permeability test (b)Moisture content test.
5. Study of oil fired tilting furnaceand melting of metal for acasting.
6. Study of jigs and fixtures anddrilling of holes with the help of
jigs.7. Tube bending on Tube Bending
Machine.8. Study of Power Press and to
perform Blanking and piercingoperation.
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PATTERN MAKING SHOP
OBJECT: To make the pattern for the moving jaw of a machine vice.
MATERIAL REQUIRED-Soft wood (Deodar, teak).
TOOLS REQUIRED-Tools required for making pattern is as follows-
1. RIP SAW : It s size is determined by its length which is about 12 to
20 cm wide near the handle and 6 to 10 cm near the tip. It cuts the
wood along the grains. The cutting action starts from near the and
gradually the whole length, or a major part of it, is used in theoperation. The pressure is applied in the forward stroke and relieved
during the backward stroke. It carries about 2 teeth per cm length of the blade.
2. CROSS CUT SAW : It is primarily designed for cutting across the
grains of woodwork. Its blade is 50 cm to 70 cm long and carries 3 to
4 points per cm. A blade with finer pitch is preferred for hard woodand that having coarse pitch for soft wood.
3. COMPASS SAW : It carries a tapered blade, which is long narrow.
The blade length usually varies from 25 to 40 cm and the width from
2.5 cm at tip to 5 cm near the handle. The blade is quite flexible andthus, it can be used easily for straight or curved cuts on outside or on
inside of the wood. For internal cutting a hole is first drilled and then
the saw blade inserted in it to commence the cut. Its blade containsabout 12 teeth per cm length.
4. FIRMER CHISEL : It is a general purpose chisel and is used for
taking wider cuts and finishing flat surfaces inside the groove. It
carries a wide blade, the common widths varying from 3mm to
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38mm at the cutting edge; the blade has a rectangular cross section
such that the longer side of the rectangle represents the width andthe smaller side the thickness of the blade at that point.
5. DOVETAIL CHISEL : It has a long carbon steel blade with abeveled back. The shape enables reduction of blade thickness on the
sides due to which it can enter sharp corners to finish them. Such arequirement usually occurs in case of dovetail joint and other V-
shaped grooves.
6. MORTISE CHISEL : It is used for taking heavy and deep cuts in
more stock removal, as in case of making mortises. It is available in
various assorted sizes, the maximum width of blade in commonlyused chisel being up to 15mm. The blade thickness varies from 6 to
15mm.
7. TRY SQUARE : It is used measuring and setting out dimensions,
testing the finish of a planed surface, draw parallel lines at right
angle to a planed surface, draw mutually perpendicular lines over a
plane surface and test squareness of two adjacent surfaces. Itconsists of a steel blade fitted into a wooden or metallic stock at
right angles. The inner surfaces, i.e. the surface that runs the job it is
provided with a brass liner. The blade carries graduation either in
inches and their parts or centimeters and millimeters.
8. MARKING GAUGE : It is made of wood and is very prominent tool
for marking. The stem is a long bar of wood of square or rectangular
cross section. The side faces are made a little curved. One of thecurved sides faces carries graduations. A sliding piece, called stock,
also made of wood, carries a brass liner at the face of it which istowards the scribing pin fitted in the stem. It is this face of the stock,
which remains in contact with the job surface during marking. The
thumbscrew helps in tightening the stock over the stem at any
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distance from the scribing pin. It is used to scribe lines parallel to and
at any desired distance from a finished face or edge.
10. WOOD TURNING LATHE :
Construction :
The wood turning lathe consists of cast iron body, a head
stock, tool rest, live and dead centers and a speed control device.
The bed carries horizontal ways as its top on which the tailstock and
tool rest move. They can be clamped at any desired place along
these ways. The work pieces are either clamped between two
centers. The live on the headstock spindle and the dead centre in the
tail stock, or on a face plate. The operation done the former case is
known as turning between centers. The different types of tools used
in wood turning lathe are : -
a) SCRAPING TOOLS: the most common used chisels in lathe
operations are round nose, square nose, spear point, diamond nose.
They are used for shaping different contours in faceplate work. Also
they are used in turning between centers; the round nose chisel forshaping of curved surfaces and square nose for plain cylindrical
surfaces.
Theory :
DEFINITION: A pattern may be defined as a replica or facsimile model
of the desired casting which, when packed or embedded in a suitable
moulding material, produces a cavity called mould. This cavity when
filled with molten metal produced the desired casting after the
solidification of the poured metal.
PA TTERN M AKI NG M A TERIAL
The common materials used for pattern making are :
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1. W OOD : It is the most common material used for pattern making.
The wood selected for pattern making should be straight grained,free from knots and other natural defects and should not carry sap
wood. The common wood used for pattern making is : -
(i)Pine (ii) Deodar (iii) Teak (iv) Mahogany
Advantages:-
(i) It is cheap and available in abundance.(ii) It can be easily shaped into forms and intricate designs.
(iii) Its manipulation is easy because of lightness in weight.(iv) Good surface finish can be easily obtained by only planning and
sanding.
Disadvantages:
(i) It wears out quickly due to its low resistance to send abrasion. Assuch a wooden pattern cannot stand a long constant use.
(ii) It is very susceptible to moisture, which may lead to its warpingor splitting. This needs its careful storing in a dry place and the
application of preservatives.
2. METALS: Metals used for with advantage, as the pattern material,
only when the number of castings to be made is very high and acloser dimensional accuracy is desired. They have a much longer life
than wooden pattern and eliminate the inherent disadvantage of
wood to a greater extent. But they have certain disadvantages. They
are as follows :
(a) They are costlier than wood, and therefore cannot be used withadvantage, where a smaller number of castings are to be made.
For giving different shapes and fine surfaces finish they need
machining.
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(b) Most of them are very heavy and in case f large castings theweight of the pattern always poses a problem in its manipulation.
(c) A large number of them have a tendency to get rusted. Commonmetals for purpose of pattern making are cast iron, brass,aluminum, white metal, etc.
3. PLASTER: Plaster of Paris or gypsum cement is advantageously
used as a pattern material since it can be easily cast into intricate
shapes and can be easily worked also. Its expansion can be easilycontrolled and it carries a very high compression strength. Its specific
use is in making small patterns and core boxes involving intricate
shape and closer dimensional control.4. PLASTICS: Plastics are gradually gaining favour as pattern materialsdue their following specific characteristics :
(a) Lightness in weight(b) High strength(c) High resistance to wear(d) Fine surface(e) High resistance to corrosion due to moisture(f) Low solid shrinkage(g) Very reasonable cost
5. W AX: Wax patterns are exclusively used in investment casting. For
this a die or metal mould is made in two halves into which the
heated wax is poured. The die is kept cool by circulating water
around it. As the wax sets on cooling the die parts are separated andthe wax pattern are taken out.
PATTERN ALLOW ANCES
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A pattern is always made larger than the required size of the
casting in order to allow for various factors, such as follows : -1) SHRINKAGE ALLOW ANCE: most of the metal used in castingwork contract during cooling from pouring temperature to roomtemperature. This contraction takes place in forms, viz, liquid
contraction, solidifying contraction and solid contraction. The first
two are compensated by gates and risers and the last one byproviding allowances in the patterns. The amount of contraction
varies with different metals and therefore their corresponding alsodiffers. The prominent factors, which influence the metal contraction
are the following :
(a) Pouring temperature of molten metal.(b) Type of mould material.(c) Moulding method.(d) Mould resistance to shrinkage of metal.(e) The metal of which the casting is to be made.
Thus, the correct amount of shrinkage allowance for a particular
casting can be obtained only after duly taking into consideration all
the factors.2) MACHINE ALLOW ANCE: A casting may require machining all
over or on certain specified portions depending upon the
assembly condition and the operation it has to perform. Such
portion or surface is marked duly in the working drawings. The
corresponding portion or surface on the pattern are givenadequate allowance, in addition to the shrinkage allowance, by
increasing the metal thickness there to compensate for theloss of metal due to machining on the surface. The amount of
this allowance depends on the method to be employed,
method of casting used, size and shape of casting and the
degree of finish required on the machined portion. Ferrous
metals need more Allowance than the non-ferrous metals.
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Similarly large and slender castings need more allowance than
the shorter ones. This allowance varies from 1.5 mm to 16 mmbut 3mm allowance is quite common for small and medium
size castings.
3) DRAFT ALLOW ANCE: All patterns are given a slight taper on allvertical surfaces i.e. the surface parallel to the direction of theirwithdrawal from the mould. This taper is known as DRAFT
ALLOWANCE. It can be expressed in terms of linear measures, it isprovided in both internal surfaces is more than on external
surfaces. The amount of draft on internal surfaces is more than
external surfaces. The purpose of providing this taper or draft is tofacilitate easy withdrawal of pattern from the mould without
damaging the surface and edges of the latter. The amount variesfrom 10 mm to 25 mm per meter on the external surfaces and
from 40 mm to 70 mm per meter on the internal surfaces. The
factors affecting this amount are the design of pattern, its vertical
height, method of moulding.
4) RAPPING AND SHAPING ALLOW ANCE: When a pattern is to bewithdrawn from the mould, it is first rapped or shaken, by striking
over it from side to side, so it s surface may be free of the mould
cavity increase a little and a negative allowance is to be provided
on the pattern to compensate the same. However, it may be
considered negligible for all practical purposes in small andmedium sized castings.
5) DISTORTION
ALLO
WANCE
:
The tendency of distortion is notcommon in all the castings. Only castings which have an irregular
shape and some design that the contraction is not uniform
throughout will distort during cooling on account of the setting up
of thermal stresses in them. Such an effect can be easily seen in
some dome shaped or u shaped castings. To eliminate this defect
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an opposite distortion is provided on the pattern, so that the
effect is neutralized and the correct casting is obtained.6) MOULD W ALL MOVEMENT ALLOW ANCE: Movement of mould
wall in sand mould takes place on account of the excessive heatand the static pressure exerted on the surface layer of sand which
comes in contact with the molten metal. Graphitisation of another
cause of mould wall movement on case of ferrous casting. Thismovement of mould walls, obviously affects the ultimate size of
the castings and needs to be compensated by providingcorresponding allowances in the patter and by controlling the
density and temperature of the molten and composition of the
moulding sand.
TYPE OF PATTERN
1) SOLID OR SINGLE PIECE PATTERN : A single piece pattern is thepattern, is made in one- piece and carries no joint, partition orloose pieces, Depending upon the shape, it can be moulded in one
or two boxes. This pattern is the cheapest but its use can be done
to a limited extent of production only since its moulding involves alarge number of manual operations like gate cutting, providingrunners and risers and the like.
2) TW O-PIECE OR SPLIT PATTERN : many times the design of castingoffers difficulty in mould making and withdrawal of pattern, if thesolid pattern is used. For such castings, split or two piece pattern
are employed. They are made in two parts, which are joined at theparting line by means dowels. While moulding, one part of the
pattern is continued by the drag and the other cope.
3) MULTIPIECE PATTERN : casting having a more complicated designthan two parts in order to facilitate an easy moulding and
withdrawal of the pattern may consist of 3, 4 or more number of
parts, depending on their design.
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4) MATCH PLATE PATTERN : these patterns are used where a rapidproduction of small and accurate castings is desired on a largescale. These patterns find a great favor in machine moulding.
There construction cost is quiet high, but the same is easilycompensated by a high rate of production, greater dimensional
accuracy and minimum requirement for matching in the casting.
These patterns are made in 2 pieces; one piece mounted on oneside and the other side of the plate; called matching plate. The
plate may carry only one pattern, or a group of pattern mountedon the same way on its 2 sides. The plate may be of wood, steel,
magnesium, or aluminium.
5) GATE PATTERN : they are also used in mass production of smallcastings. For such castings multi-cavity moulds are produced i.e. a
single sand mould carries a number of cavities. Pattern of thesecastings are connected to each other by means of gate formers,
which provide suitable channels, or gates in sand for feeding the
molten metal to these cavities. A single runner can be used for
feeding all the cavities. This enables a considerable saving in
moulding time and a uniform feeding of molten metal. For smallquantities, these patterns may be made of wood, but for large
production metallic pattern are preferred.
6) SKELETON PATTERN : when the size of the castings is very large,but easy to shape and only a few numbers are to be made, it is in
economical to make a large solid pattern of that size. In suchcases, a pattern consisting of a wooden frame and strips is made,
called skeleton pattern. It is filled with loam sand and rammed.The surplus sand is removed by means of a strickle.
7) SW EEP PATTERN : sweep can be advantageously used forpreparing mould so flarge symmetrical castings, particularly of
circular cross-section. This affects a great save in time, labour and
material. The full equipment consist of a base, suitably placed in
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the sand mass, a vertical spindle and a wooden template called
sweep. The outer end of the sweep carries the contourcorresponding to the shape of the desired castings. The sweep is
rotated about the spindle to form the cavity. Then the sweep andthe spindle are removed, leaving the base in the sand the hole
made by removal of spindle, is patched up filling the sand.
8) FOLLOW BOARD PATTERN : a follow board is a wooden boardused to support a pattern during moulding; it acts as a seat for the
pattern. Such single piece pattern, which have an odd shape orvery thin wall require a follow board.
9) SEGMENTAL PATTERN : these patterns are used for preparingmoulds of large circular castings, avoiding the use of a solidpattern of the exact size. In principle they work like a sweep but
the difference is that a sweep is given a continuous revolvingmotion to generate the desired shape, where as the segmental
pattern is portion of a solid pattern itself and the mould is
prepared in parts by it. It is mounted on a central pivot and after
preparing the part mould in one position; the segment is moved
to the next position. The operation is repeated till the completemould is ready.
CORE BOXES
Core boxes are made for making core. They are either made single orin 2 parts. Their classification is, generally according to the shape of
the core or the method of making the core. The common types of core boxes are :
1) HALF CORE BOX: to prepare the core into halve which are lateron cemented together to form the complete core.
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2) DUMP CORE BOX: used to prepare complete core in it generallyrectangular cores are prepared in these boxes. In constructionit is similar to half core box.
3) SPLIT CORE BOX: it is made in 2 parts, which can be joinedtogether by means of dowels to form the complete cavity for
making the core.
4) STRICKLE TYPE CORE BOX: it is used to form cores of irregular orunsymmetrical shapes.
5) LOOSE PIECE CORE BOX: it is used to prepare, in same core box,the 2 halves of a core are non-identical in shape and size.
PROCEDURE
1. Cut a rectangular piece of length 95 mm, width 66 mm andthickness 12 mm. Make the edges at right angles with the
help of tri-square and file.
2. Finish the top surface of the job with sand paper.3. Mark the required dimensions on both the sides of the job.4. Cut the job with the crosscut saw according to the given
dimensions.5. Make the groove on the top of the job with the help of a
firmer and mortise chisel.
6. Finish the surface with the help of sand paper.
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Hydraulic Pipe Bending Machine
OBJECT: To perform pipe bending operation with the help of
Hydraulic Pipe
Bending
Machine .
TOOLS: A hallow GI pipe of inch diameter, bending machine.
THEORY: The tooling used is bending operation results in the metal
being formed in localized area only the localized stress occurs only in
the bend radius. The remaining part of the blank is not stressedduring bending the metal on the outside of the bent radius is
stretched or elongated. The metal on the inside of bend radius isstretched or elongated. The metal on the inside is compressed. If
pipe fracturing occurs during bending its coiling occurs at the outside
of the bend surface of the bend. This wrecking also has to be taken into a current when designing parts and processes but visually loss of a
concern then is outside bend fracture. During bending one area of blank is usually held stationary by a press plate a pad. A leveal region
of the blank is bent and the change in contour. This free metal
movement is often called swinging and a characteristic common onlyto bending operation. In design of a bending die the swinging action
must be predicted so that no abstracts are placed in the way.Because of the related movement the larger area of the plant is
usually held stationary and the smaller blank area is allowed to
move.
Types of Bending Operations :
Angle of b ending bending at sharp angles. Curling - edge is curled around. Fo rming -bending along a curved die. Plunging -localized bending to form a hole.
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Precautions :
(i) Force should be applied slowly on the hand.(ii) Rod should be fastened correctly.
MOULDING AND CASTING
INTRODUCTION
The moulding is the process of making a cavity (or mould) outof sand by means of a pattern. The molten metal is poured intothe mould to produce casting. Some time a casting is to be made
hollow or with cavity in it. Such type of casting requires the use of cores.A core is defined as a sand shape which is exactly similar tothe cavities or holes to be provided in the casting s. The cores aregenerally made separately i.e., they are not moulded with thewith the pattern. The process of making cores is called coremaking.
MOULDING MATERIALS
Following are the moulding materials commonly used infoundry practice :
1.Moulding sand, 2.Sand binders,and3.Additive materials.
MOULDING SAND
The principal material used in making a mould is sand. The Sand
is defined as the granular particles resulting from thebreakdown of rocks. Quartz and other silica rocks are the source of
silica sand, which is commonly used for moulding. The sand is found
in nature on the bottoms and banks of rivers, lakes and larger
bodies of water. The silica sand comprises from 50 to 95% of the
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total material in any moulding sand. A good moulding sand
contains the following ingredients.Silica sand(SiO 2)- 80.8%
Alumina (Al 2O3) - 14.9%
Iron oxide(Fe 2O3) - 1.3%Combined water - 4 to 6%
Other inert materials- 1.5%
SAND BINDERS
Any material added to the sand or provided by nature in thesand imparts cohesiveness to it, is called a binder. The binderhold the sand grain together, imparts strength, resistance toerosion and breakage and degree of collapsibility.The binders areclassified as :
1.Clay- type binders,2.Organic-type binders, and3.Inorganic type binders.The clay is natural earthy material, which becomes plastic when
moltened. The fire clay is a clay-type binder and widely used
with silica sand.
The organic-type binders are mostly produced from vegetables
wood. For example, molasses (from sugarcane), starches (from maizecorn and potatoes), dextrines (intermediate product in the
degradation of starch), linseed oil (from flax seed), resins (from
trees), pitch (from coal).They are mainly used in making oil sands forcores.
The inorganic binders include Portland cement, bentonites (a
form of clay), fire clays (kaolinite), sodium silicate and iron oxide.
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These binders have considerable strength at high temperatures.They may be used to obtain green strength, baked strength, hotStrength or smooth finish.
SAND ADDITIVES
Materials, which do not promote binding action, when added to
the sand by facing the mould or by mixing with heap of sand forimproving sum special feature is called a sand additive. Some
Commonly used additives are sea coal, wood flour and silica flour.The sea coal is a finely pulverized bituminous coal. It improves
the surface finish, aids in cleaning of casting and prevent burning
on sand.The wood flour is a finely pulverized or ground soft wood. It
Improves finish, prevent burning in, aids cleaning and improves
collapsibility.
The silica flour is a finely ground silica sand of less than 54
microns. It fills interstices (voids ) and thus reduces metal
penetration.
PROPERTIES OF MOULDING SAND
The moulding sand must posses the following properties :
P orosity or p ermeability : It is that property of sand, whichpermits the steam and other gases to pass through the sand mould. When hot molten metal is poured into the
sand mould, it evolves a great amount of steam and othergases while coming in contact with moist sand. If these
gases do not escape completely through the mould, the
casting will contain gas holes and pores. Thus the sand
from which the mould is made must be sufficiently
porous or permeable.
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P lasticity : It is that property of sand due to which it flows to all portion of the moulding box or flask and
acquires a predetermined shape under ramming pressure
and retains this shape when pressure is removed. The sandmust have sufficient plasticity to produce a good mould.
The plasticity is increased by adding water and clay to
sand.
Ad hesiveness : It is that property of sand due to whichit adheres or clings to the sides moulding box. A good
sand have sufficient adhesiveness so that heavy sand
masses can be successfully held in the moulding box or flax
without any danger of its falling out when the flask is
Removed.
C ohesiveness : It that property of sand due to whichthe sand grain sticks together during ramming. It may be
defined as the strength of moulding sand. It is of the
following three types :
a) GREEN STRENGTH: The green sand, after water has mixedto it, must have adequate strength and plasticity formaking and handling of the mould. The green strength
depends upon the grain shape and size, amount and type of
clay and the moisture content.
b) DRY STRENGTH: When the molten metal is poured, the sandadjacent to the hot metal quickly loses its water as steam.The dry sand must have strength to resist erosion and alsothe metallostatic pressure of the molten metal, otherwisethe mould may enlarge.
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The natural sand is one,which contains sufficient clay as minedfrom the sand pit so that it can be used directly. It needs only to betempered and conditioned. Since the natural sands have theadvantages of simplicity in their preparation, handling and use,
therefore these are used for most of the ferrous and non-ferrouscastings.
The synthetic sand is one, which is artificially compounded bymixing sand grains and selected type of clay. These sands have theadvantages of lower cast in larger volume; wide spread availabilityand the possibility of sand reclamation and reuse.
The special sand contains mixtures of inorganic compounds.
Though these sands cost more, yet they offer better hightemperature stability than ordinary silica sand. These sandsproduce better cast surface. The special sands used most often arezircon, olivine, chromotte, and chrome magnesite.
The moulding sands, according to their use, further classified asbelow :
1) Green sand . The sand in its natural or moist state is calledgreen sand. It is also called tempered sand. It is a mixture of silica sand with 20 to 30 percent clay having total amount of water from 6 to 10 percent. The mould prepared with this sandare called green sand moulds. The molten metal is poured inthe green sand moulds without any prior baking. The greensand moulds are used for small size castings of ferrous andnon-ferrous metals.
2) Dry sand. The green sand moulds when baked or dried before
pouring the molten metal are called dry sand moulds. Thesand in this condition is called dry sand. The dry sand mouldshave greater strength, rigidity and thermal stability. Thesemould are used for large and heavy casting.
3) Loam sand. A mixture of 50 percent sand grains and 50percent clay is called loam sand. It is used for loam moulding
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of large grey-iron castings.4) Facing Sand . Sand use for facing of the moulding is called
facing sand .It is specially prepared sand from silica sand andclay, without the addition of used sand. The thickness of layer of
facing sand in a mould ranges from 20 to 30 mm and isused directly next to the surface of the pattern .Since it comescontact with the molten metal when poured, therefore it mustpossess high strength and refractoriness .
5) Backing or floor sand. Sand used to back up the facing sand
and not used next to the pattern, is called backing sand. the
sand, which has been repeatedly used, may be employed for
this purpose. It is sometimes called black sand because of its
black colour.
6) System sand. Sand employed in mechanical sand preparation
and handling system is called system sand .this sand has high
strength, permeability and refractoriness .
7) Parting sand. Sand employed on the faces of the pattern
before moulding is called parting sand. The function of the
parting sand is that when the pattern is withdrawn, the face of
the mould impression is damaged by adhesion of grains of
or section of the mould. The parting sand consists of dried
silica sand, sea sand or burnt sand.
8) Core sand. sand used for the preparation of cores is called
core sand. It is sometimes called oil sand. It is the silica sandmixed with linseed oil or any other oil as binder.
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9) Molasses sand. Sand, which carries molasses as a binder iscalled molasses sand. It is very useful for making moulds of small castings of intricate shapes and their sections. Thecores are also made from this sand.
PREPARATION OF MOULDING SAND
The preparation of sand is required in order to good castings. Itconsists of mixing sand, tempering of sand, conditioning of
sand. The efficient mixing of sand ingredients in proper ratio is
very important. It may be done manually or mechanically. Thenatural sand does not possess all qualities, which the
moulding sand should posses. It is, therefore, necessary that thenatural sand should be mixed with other sands or other
substances (such as clay, coal, dust etc.), which posses that
characteristics in a high degree. The clay is a necessary bond to
the moulding sand and coal dust is the most widely used
substance. The process of mixing consists of removing of all
foreign particles such as fins, nails, etc. From the sand grain by
passing it through a sieve or by magnetic separators. The sandingredients are mixed either by hand or by sand mixing
machines. The mixing is continued till there is a uniform
distribution of ingredients. The more uniform is this
distribution; the better is the quality of sand.
The preparation of moulding sand by adding water in properproportion is known as tempering of sand. The exact amount of
water to temper a given amount of sand is impossible to state,because, the sand conditions always vary. It can be mastered onlythrough practical experience.
The preparation of moulding sand so that it becomes suitable formoulding purposes is called conditioning of sand. The properconditioning of sand accomplishes uniform distribution of binder
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around the sand grains, control the moisture content, eliminatesforeign particles and aerates the sand so that it flows readily aroundand takes up the detail of the pattern.
METHODS OF MOULDING
The various methods used in making the mould are as follows : 1. Bench moulding . The moulding done on a bench of a
convenient height to the moulder, is called bench moulding.It is usually used for small castings, which are light in
weight.
2. Floor moulding. The moulding done on the foundry floor iscalled floor moulding. In this method, the foundry floor
itself acts as a drag and it may be covered with a cope on themould may be cast open. It is used for all medium sized and
large castings.
3. Pit moulding. The moulding done in a pit instead of a flaskis called pit moulding. It is used for extremely large castings.
The pit acts as a drag part of the flask and a separate cope isused above it. The sides of the pit are brick lined and on the
bottom there is a thick layer of cinders with connecting vent
pipes to the floor level. Since pit moulds can resist highpressure developed by hot gases, therefore it greatly saves
pattern expenses.
4. Machine moulding. The moulding done by machine iscalled machine moulding. The moulding machine perform
the number of operations which the moulder does by hand.
The ramming of sand, rolling the moulding over, forming
the gate and drawing out of pattern can be done by these
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machines much better and more efficiently than by hand.
5. Sweep moulding. The moulding done by using a sweeppattern is called sweep moulding. It is used for making
moulds of large size and symmetrical in shape particularlyof circular section.
CASTING
The sand moulds may be used for casting ferrous and non-
ferrous metals, but these moulds can be used only once, because
the moulds are destroyed after the metal has solidified. This will
increased the cast of production. The sand moulds also, cannot
maintain better tolerances and smooth surface finish. In order to
meet these requirements, following casting methods may be used :
Permanent mould casting Semi-permanent mould casting, Slush casting,
Die casting, Centrifugal casting, Investment or last wax casting, and Shell moulding process.
DESIGN OF CASTING
An engineer must know how to design the casting so that theyCan effectively and efficiently render the desired service and can
be produce easily and economically. In order to design a casting,
the following factors must be taken into consideration :
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PROCEDURE:
1- Take a sample of green sand,50gm weight the sand with theWeighing mechanism and take calculated amount of sand.
2- Place the sand in the cylinder of moisture tester .3- Add in it calcium carbide in required proportion one bowl.4- Shake the cylinder well fir few seconds.5- The amount of moisture present in the sand
RESULT: The given sample of sand containing moisture content 5.5% istested.
PRECAUTION :
1- Sand is to be homogeneous.2- Proper weighing of moisture should be3- Accurate weighing sand and proper amount of calcium carbide
should be taken.4- Mixing should be well .
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Power Press
OBJECT: -Study of Pow er Press and to perform Blanking and Piercing
operation.THEORY: -The constructional feature of power press is almost thesame as ram instead of driven by hand it is driven by power thePOWER PRESS may be designated as mechanical or hydraulicaccording to the type of working mechanism used to transmit powerto ram. In this mechanism, the rotary motion obtained from anelectric motor is converted into reciprocating movement of the ramby using different mechanical devices. In a hydraulic press the fluid
under high pressure is pumped on one side of the piston and then onthe other in a hydraulic cylinder to device. The reciprocatingmovement of a power press driven by crank and converting rodmechanism. The working of the press is similar to that of a handpress the punch is fitted on the end of ram and die is attached on thehole, the flywheel mounted on the end of crankshaft stores up theenergy for maintaining a constant downward speed of the ram whenthe sheet metal is pressed between the punch and the die.
Pow er Press Parts
The different parts of power press are described below :
Base : The base is the supporting member of press and providesarrangement for tilting and clamping the frame.
Frame : All press except the straight side types have C shapedframe to take up the vertical thrust of ram.
Bo lster Plate : The bolster plate is a flate plate fitted on thebase for supporting the die block.
Ram : The ram is the reciprocating member of the press that iswithin press and guide.
Pitman : The pitman is the connecting rod in crank or electricpower press.
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Crank Eccentric or Other Driven Mechanism : The rotarymovement of the motor is converted into the reciprocatingmovement of the ram, crank and connecting rod.
Flywheel : The flywheel is mounted at the end of the driving
shaft and is connected to it through a clutch. The flywheel isdirectly connected with the electric motor.
Clutch : The clutch is used for connecting and disconnecting themoving shaft with the flywheel.
Brakes : The brakes are used to stop the movement of thedriving shaft immedeately after it is disconnecting from theflywheel.
Result:- Both surfaces of given metal piece were grinded.
Precauti o ns: 1. In order to avoid chattering of the wheel it should be
correctly mounted at ram at prescribed speed.2. Face of wheel should be flat and dressed properly.3. Small depth of cut should be given.