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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