moulding machine

1. COURSE: MANUFACTURING PROCESSS
CODE: AMEC11
IV Semester
Regulation: IARE UG-20
Institute of Aeronautical Engineering
(Autonomous)
Dundigal, Hyderabad- 500043
Mr. G. Praveen Kumar
Assistant Professor
Mechanical Engineering
Prepared by

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Cores and Core making
 Cores are made of sand which are used to make cavities
and hallow projections.

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Characteristics of Core
 Green strength – sufficient strength to hold up its shape till it is baked.
 Dry strength – sufficient strength to resist bending forces due to hydrostatic
pressure from the liquid (molten metal), when core is placed inside the mould
 Refractoriness – core is surrounded on all sides by molten metal and should
have high refractoriness.
 Permeability – gases evolved may pass through the core to escape and
should posses sufficient permeability.
 Collapsibility – should shrink as molten metal shrinks during solidification
 Friability – should get dismantled easily once the casting is completely
cooled.
 Smoothness – surface of core should be smooth to have better surface finish.
 Low gas emission – emission of gases from core should be as low as
possible to avoid voids formed inside core

4. Core sand
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 Core sand must be stronger than moulding sand
 Core sand = Sand grains + Binders + Additives Sand grains
 Sand containing more than 5% clay is not used to make core Excessive
clay reduces the permeability and collapsibility of the core.
 Coarse silica used for making steels and finer one for cast iron an non-
ferrous alloys Binders
 Organic binders tend to burn away under the heat of molten metal and
hence increases the collapsibility of the core. Organic binder develop
strength by polymerisation and cross-linking and hence cores are baked.
 Some of the binders are linseed oil, dextrin, molasses, resins etc.

5. Core Prints
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 Core Prints
 Core prints are extra projections provided on the pattern
that form a seat in the mould. Core prints support the core
in the mould cavity.

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Core shifts and chaplets
Core shifts and chaplets
Chaplets are used to support the cores which tend to sag
without adequate supports.
Chaplets are made of the same material as that of the
casting

7. Types of Cores
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 Horizontal cores
 It is held horizontally along the parting
line of the mould.
 Ends of core rests in the seats
provided by core prints on the pattern.
 Vertical cores
 Two ends of the mould sits on the cope
and drag portion of the mould.
 Amount of taper on the top is more than
the taper at the bottom of the core

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When openings are required at only one
end, balanced cores are used.
 Core prints are available at one end of
the pattern.
Core prints need to be sufficiently longer
to support the core in case of longer
holes.
 Balanced cores
Types of Cores

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Types of Cores
In cover core, core hangs from the cope
portion and is supported by the drag.
Core acts as a cover and hence termed as
cover core.
 Cover cores
 A Drop core is used when hole or recess is
to be obtained in casting.
 Core print is given sufficient amount of taper
so that core is placed readily in the mould.
 Drop cores

10. Gating system in mould
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 Pouring basin
 Sprue
 Sprue Base
 Runner
 Gate
 Riser
 The gating system refers to all those elements which are concerned with
the flow of molten metal from ladle to the Mould Basin cavity.
 The various elements that comes under gating system are

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 To provide continuous, uniform feed of molten metal in to
mould cavity and to reduce the turbulence flow.
 Proper directional solidification
 To fill the mould cavity in a less time to avoid thermal
gradient
 To provide minimum excess metal
 To prevent erosion of mould walls
 To prevent the foreign materials to enter in mould cavity
Functions of the Gating system

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Elements of Gating system
1. Pouring basin
 It is the conical hollow element or tapered hollow
vertical portion of the gating system
 It makes easier for the ladle operator to direct the flow
of molten metal from crucible to pouring basin and
sprue.
 It helps in maintaining the required rate of liquid metal
flow.
 It reduces turbulence and vortexing at the sprue
entrance.
 It also helps in separating dross, slag and foreign
element etc.
 Skim core plays very important role in removing slag.

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Elements of Gating system
2. Sprue
 It is channel in cope side connected at bottom of pouring basin which
will carry molten metal to the parting plane.
 In straight sprue due to vortex flow air bubbles may enter in to the cavity
this can be compensated by providing taper to it.
 It is tapered with its bigger end at to receive the molten metal the smaller
end is connected to the runner.
 It some times possesses skim bob at its lower end.

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Elements of Gating system
3. Sprue Base Well
 It acts as a reservoir for metal at the bottom of sprue in order to reduce
moment of molten metal.
 The molten metal gains velocity while moving down the sprue, some of
which is lost in the sprue base well by which the mold erosion is reduced.

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Elements of Gating system
4.Runner
 It is located in parting plane and connects the sprue to the in-gates.
 The runners are normally made trapezoidal in cross-section.
 The slag trapping takes place in the runner, when runner flows full. If
the amount of molten metal coming from sprue base is more than the
amount flowing through the in-gates.
 A partially filled runner causes slag to enter the mold cavity.

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Elements of Gating system
5. Gate or Ingate
 It is a small passage or channel being cut by
gate cutter which connect runner with the mould
cavity.
 It feeds the liquid metal to the casting at the
rate consistent with the rate of solidification
Types of Gates
 Top Gate
 Bottom Gate
 Parting Gate

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 In this type of gate the molten metal from the top flows down directly
into the mould. As all the molten metal enters the casting at the top,
the hottest metal comes to rest at the top of casting with the result,
proper temperature gradient is formed to enable directional
solidification of casting from the bottom side towards the riser.
Top Gate
Elements of Gating system

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 In this type of gate, the molten metal from the pouring basin flows down
and enter the mould cavity at or near its bottom. Bottom type of gate
facilities the mould to be prepared in two moulding boxes. During
pouring the molten metal, bottom types of gate enable to reduce the
erosion of mould and core and minimize the turbulence of metal.
Bottom Gate
Elements of Gating system

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 Middle or side or parting gating systems combine the characteristics of
top and bottom gating systems. In this technique gate is provided along
the parting line such that some portion of the mould cavity will be below
the parting line and some portion will be above the parting line. The cavity
below the parting line will be filled by assuming top gating and the cavity
above the parting line will be filled by assuming bottom gating..
Parting Gate
Elements of Gating system

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 Oxidation of metal
 Cold shuts
 Mould erosion
 Shrinkages
 Porosity
 Misruns
 Penetration of liquid metal into mould walls.
Defects occurring due to improper design of gating
system

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Metal flow rate and velocity calculations

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Metal flow rate and velocity calculations

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Design criteria for pouring basin

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Design of sprue

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Design of sprue

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Design of sprue

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Design of sprue

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Design of sprue

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Design of sprue

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Design of Runner and Gate

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GATING RATIO

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GATING RATIO

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GATING RATIO

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