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Module 5 - Principles of Gating and Risering

This document discusses the principles of gating and risering systems in casting. It defines the components of a gating system, including the pouring basin, sprue, runner, gates, and riser. It explains the functions of the gating system to fill the mold cavity completely before freezing, minimize turbulence, avoid erosion, and establish directional solidification. It also discusses the different types of gates and risers, and factors to consider in the design of the gating system such as avoiding sudden changes in flow direction and controlling temperature, flow rate, and component sizes.

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Goutham Reddy
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2K views14 pages

Module 5 - Principles of Gating and Risering

This document discusses the principles of gating and risering systems in casting. It defines the components of a gating system, including the pouring basin, sprue, runner, gates, and riser. It explains the functions of the gating system to fill the mold cavity completely before freezing, minimize turbulence, avoid erosion, and establish directional solidification. It also discusses the different types of gates and risers, and factors to consider in the design of the gating system such as avoiding sudden changes in flow direction and controlling temperature, flow rate, and component sizes.

Uploaded by

Goutham Reddy
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Module 5 - Principles of Gating and Risering

• Purpose of the gating system.

• Components of the gating System and its functions.

• Design of the gating system.

• Different types of gates. Gating ratio and its functions.

• Definition and functions of the riser. Types of risers and


their application.

• Design of the riser - its shape. Size and location.

• Use of insulating material and exothermic compounds in


risers.
GATING SYSTEM
• The term gating system refers to group of elements
through which the molten metal passes while entering
the mould cavity.

• The gating system is composed of (components of gating


system)
 Pouring basin
 Sprue
 Runner
 Gates
 Risers
Typical Gating and Risering System
Functions of Gating System

 To fill the mould cavity completely before freezing


 To minimise turbulence
 To avoid erosion
 To remove inclusions
 To regulate flow of molten metal
 To consume least metal – less scrap (Casting yield)
 To establish directional solidification
Any gating system designed should aim at providing a defect
free casting. This can be achieved by considering following
requirements.

 A gating system should avoid sudden (or) right angle changes


in direction.

 A gating system should fill the mould cavity before freezing.

 The metal should flow smoothly into the mould without any
turbulence. A turbulence metal flow tends to form dross in the
mould.
 Unwanted materials such as slag, dross and other mould materials

should not be allowed to enter the mould cavity.

 The metal entry into the mould cavity should be properly controlled

in such a way that aspiration of the atmospheric air is

prevented. (Aspiration is sucking of the air because of a low pressure

zone created inside the mold)

 A proper thermal gradient should be maintained so that the casting

is cooled without any shrinkage cavities or distortions.


Metal flow should be maintained in such a way that no gating

or mould erosion takes place.

The gating system should ensure that enough molten metal

reaches the mould cavity.

It should be economical and easy to implement and remove

after casting solidification.


For proper functioning of the gating system, the following factors
need to be controlled.

 Type of pouring equipment, such as ladles, pouring basin etc.

 Temperature/ Fluidity of molten metal.

 Rate of liquid metal pouring.

 Type and size of sprue.

 Type and size of runner.

 Size, number and location of gates connecting runner and casting.

 Position of mould during pouring and solidification.


Elements of Gating System

Pouring cup
Sprue
Sprue well
Runner
Runner extension
Ingates (Gates)
Riser
POURING BASINS
• A pouring basin makes it easier for the ladle or crucible

operator to direct the flow of metal from crucible to sprue.

• Helps maintaining the required rate of liquid metal flow.

• Reduces turbulence at the sprue entrance.

• Helps separating dross, slag etc., from metal before it enters the

sprue.
If the pouring basins are made large,
Dross and slag formation will tend to float on the surface of the
metal and may be stopped from entering the sprue and hence the
mould.

They may be filled quickly without overflowing and may act as a


reservoir of liquid metal to compensate metal shrinkage or contraction.

Shapes of Pouring Basin


Pouring Cup
dimensions

Anti-swirl bar: To minimise


turbulence through vertex
formation and minimise
erosion

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