core (PPT)
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Transcript of core (PPT)
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CORE MAKING IN THE
PROCESS OF CASTING
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INTRODUCTION
A core is a device used in casting process to produce
internal cavities and reentrant angles. The core is normally
a disposable item that is destroyed to get it out of the piece.
They are most commonly used in sand casting.
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CORE BOX
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TYPES OF CORE BOXES
Half core box: When the shape of the core required is such
that it can be prepared in identical halves, a half core box
should be used.
Dump core box: If the core produced by the core box does
not require any pasting and is complete in it, the box
designed is referred to as a dump core box.
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Split core box: When the core box is in two parts and
complete cores results in single ramming, the box is split
core box. For alignment of two parts, dowel pins are fixed
in one part and corresponding holes are made in the other.
Left and right core box: When the core is required in two
parts and they are not identical, two different core boxes of
the half core type have to be provided for each part of the
core. Such boxes are called right handed and left handedcore boxes.
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Strickle core box: This is used when the core is required to
have an irregular shape, which cannot be rammed by other
methods. In this case, the desired irregular shape is
achieved by striking off the core sand from the top of thecore box with a piece of wood called strickle board. The
strickle is cut to correspond exactly to the contour of the
required core.
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Loose piece core box: In case where two parts of the
core are not identical they can be prepared from a
single core box with the help of loose pieces. One
part of the core is processed by placing the loosepiece in the left-hand recess, and the other part by
shifting the loose piece to the right-hand recess
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CORE MAKING PROCESES
In Hinduja Foundries, they are using three processes.
They are
1. Cold box process
2. Carbon dioxide (CO2) core making process3. Shell process
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COLD BOX PROCESS
Cold box machine
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Part A- Polyol- Phenolic formaldehyde resin
The usage amount of this binder varies with season.
0.8 to 1.2 %( summer season)
1.0 to 1.2 %( winter season)Part B- Polyisocyanate
The usage amount of this binder also varies season.
0.8 to 1.2 %( summer season)
1.0 to 1.2 %( winter season)
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Part C
The part C is AMINE gas which is used to harden core.
Gas time 4 to 15 sec (20 sec maximum)
Initially part A and part B both are mixed with the sand itself
and this is used to fill core box and packed tightly. The
Amine gas is introduced to harden the core
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SODIUM SILICATE/CO2 CORE MAKING:
Sodium silicate core-making process
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In this process, liquid sodium silicate is mixed with
the sand. The sand is rammed into a core box and
cured by passing CO2 through the core.
The core should be between 25C to 30C (75F to 85F).
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SHELL CORE MAKING PROCESS
Shell core making process
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The shell core making process uses silica sand mixed
with a thermo plastic resin. This mixture is shot into a
heated metal core which is heated to a temperature
of about 230c. Shell moulds are made in halves
which are then glued or clipped together. The shellthickness is dependent on the amount of time the
sand is in contact with the heated core box.
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CONCLUSION
The project has been carried out on core making in
casting process at Hinduja Foundries. Different core
making processes namely, a) Cold box process b)
co2 core making process and c) shell core making
process have been studied.
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THANK YOU