This document provides an overview of manufacturing processes and gating systems for casting. It discusses the key elements of a gating system including the pouring basin, sprue, runner, gates, and riser. The objectives and factors affecting the performance of gating systems are outlined. Different types of gating systems like vertical, bottom, and horizontal are described. Formulas related to fluid flow and solidification time are also provided.

1. Manufacturing Technology II
(ME-202)
Overview of
Manufacturing
Processes
Dr. Chaitanya Sharma
PhD. IIT Roorkee

2. Title of slide
Lesson Objectives
In this chapter we shall discuss the following:
Need for gating system
Elements of gating system
Learning Activities
1. Look up
Keywords
2. View Slides;
3. Read Notes,
4. Listen to
lecture
Keywords:
Pouring basin, sprue, runner, riser, gates, in-gate, dross formation

3. Gating System
• A good gating design should ensure proper distribution
of molten metal without excessive temperature loss,
turbulence, gas entrapping and slags.
• Very slow pouring, require longer filling time and
solidification will start even before filling of mould.
• This can be restricted by using super heated metal, but
in this case gas solubility will be a problem.
• Faster pouring can erode the mould cavity.
• So gating design is important and it depends on the
metal and molten metal composition. For example,
aluminium can get oxidized easily.

4. Casting Design and Fluidity Test
Figure 10.8 Schematic illustration of a typical riser-
gated casting. Risers serve as reservoirs, supplying
molten metal to the casting as it shrinks during
solidification.
Figure 10.9 A test method for
fluidity using a spiral mold. The
fluidity index is the length of the
solidified metal in the spiral
passage. The greater the length of
the solidified metal, the greater is its
fluidity.

5. Gating System
۞Gating systems refer to all those elements which are
connected with the flow of molten metal from the
ladle to the mould cavity.
Following are the elements of gating systems:
۞Pouring Basin
۞Sprue
۞Sprue Base Well
۞Runner
۞Runner Extension
۞Gate or Ingate
۞Riser

6. CHARACTERISTICS OF GATING
SYSTEM
o The purpose of gating system is to deliver the molten metal to mold.
A gating system should be able to do the following:
1. Permit complete filling of the mold cavity
2. Requires minimum time to fill the mold cavity
3. Minimum turbulence so as to minimize gas pickup
4. Regulate rate at which molten metal enters the mold cavity.
5. Prevent unwanted material from entering mould cavity
6. Establish suitable temperature gradients.
7. No mould erosion
8. Simple and economical design
9. Easy to implement and remove after solidification
10. Maximum casting yield

7. Factor Affecting Performance
Of Gating System
• To achieve sound casting and other objectives following
factors should be controlled properly:
1. The type of ladle and ladle equipment.
2. The size, type, and location of sprue and runner.
3. The size, number & location of gates entering mold cavity.
4. The rate of pouring.
5. The position of the mold during casting.
6. The temperature and fluidity of the metal.

8. Objective of The Gating
System
The four main points, which enables a proper gating system,
are:
1. Clean molten metal.
2. Smooth filling of the casting cavity.
3. Uniform filling of the casting cavity.
4. Complete filling of the casting cavity.
• The mold cavity must be filled with a clean metal so that
it prevents the entry of slag and inclusions into the mold
cavity, which in turn minimizes the surface instability.
• If the mold has smooth filling then it helps to reduce the
bulk turbulence. If it has a uniform filling it means that
the casting fill is in a controlled manner.
• Complete filling of the cavity makes the metal thin with
minimum resistance at the end sections.

9. Elements of Gating System
1. Pouring basin : This is otherwise called as bush or cup. It is
circular or rectangular in shape. It collects the molten
metal, which is poured, from the ladle.
2. Sprue : It is circular in cross section. It leads the molten
metal from the pouring basin to the sprue well.
3. Sprue Well : It changes the direction of flow of the
molten metal to right angle and passes it to the runner.
4. Runner : The runner takes the molten metal from sprue to
the casting. Ingate: This is the final stage where the molten
metal moves from the runner to the mold cavity.
5. Slag trap : It filters the slag when the molten metal moves
from the runner and ingate. It is also placed in the runner

10. Elements of Gating System
Pouring basin
• A reservoir for the molten metal poured from the ladle.
• This is otherwise called as bush or cup.
• It is circular or rectangular in shape.
• It collects the molten metal, which is poured, from ladle.
• It prevent the mould erosion.
• Prevent slag and other impurities from entering the
mould cavity.

11. Different Shape of Pouring Cup

12. Pouring Basin Proportions

13. Elements of Gating System
• Sprue : It is circular in cross section. It leads the
molten metal from the pouring basin to the sprue well.
• Sprue Well : It changes the direction of flow of the
molten metal to right angle and passes it to the runner.

15. Elements of Gating System
• Slag trap : It filters the slag when the molten metal
moves from the runner and ingate.
• It is also placed in the runner.

16. Elements Of Gating System
• Runner : The runner takes the molten metal from
sprue to the Ingates of casting.
• This is the final stage where the molten metal moves
from the runner to the mold cavity.

17. Types of Runners
a) Straight runner
b) Tapered runner
c) Step gate (may also act as feeder)
d) Uniform size runner( may cause uneven distribution)
e) Runner for even distribution of metal (reduction in
size of runner after each gate)

18. Types of Gating System
Main types of gates are following:
1. Vertical Gating System
2.Bottom Gating System
3.Horizontal Gating System

19. Types of Gating System
1. Vertical Gating System : Lliquid metal is poured vertically, directly
to fill the mould with atmospheric pressure at the base end. This is
applied in tall castings, where high-pressure sand mold, shell mold
and die-casting processes are used.
2. Bottom Gating System : Molten metal is poured from top, but filled
from bottom to top of in tall castings . This minimizes oxidation
and splashing while pouring.
Bottom GatingVerticalGating

20. Types of Gating system
4. Horizontal Gating System : Horizontal gating is a modification of
bottom gating, in which some horizontal portions are added for
good distribution of molten metal and to avoid turbulence. This is
used most widely. This type is normally applied in ferrous metal's
sand casting and gravity die-casting of non-ferrous metals. They are
used for flat casting, which are filled under gravity
5. Top Gating System : This is applied in places where the hot metal is
poured form the top of the casting. It helps directional solidification
of the casting from top to bottom. It suits only flat castings to limit
the damage of the metal during the initial filling.
6. Middle Gating System : It has characteristics of both top and
bottom. Horizontal Gating
Top

21. Analysis of Vertical Gating
Vertical Gating : Use Bernoullis’ equation for energy balance

22. continued
• As the metal flows into the down side of sprue opening, it
increases in velocity and hence the cross-sectional area of the
channel must be reduced.
• Otherwise, as the velocity of the flowing molten metal
increases toward the base of the sprue, air can be aspirated
into the liquid and taken into the mould cavity.
• To prevent this condition, the sprue is designed with a taper,
so that the volume flow rate, Q = AV remains the same at the
top and bottom of sprue.
• The mould filling time is given by,
• Note: This is the minimum time required to fill the mould
cavity. Since the analysis ignores friction losses and possible
constriction of flow in the gating system; the mould filling
time will be longer than what is given by the above equation.

23. Analysis of Bottom Gating

24. Example: 1
• Find the filling time for both the mould types. Area of C.S. of
gate = 5 cm2 (Answer: tf = 21.86 sec; 43.71 sec.)

25. Aspiration Effect
• Aspiration effect: entering of gases from baking of
organic compounds present in the mould into the molten
metal stream.
• This will produce porous castings.
• Pressure anywhere in the liquid stream should not
become negative.
Free falling liquid,
Metal flow with aspiration effect
A tapered sprue without aspiration effect
Case : straight Vs tapered sprue

26. Design of Sprue: Vertical Gating

27. Continued

28. Formulas Related with Fluid
Flow and Solidification Time
Sprue design

A1
A2

h2
h1
Mass continuity

Q  A1v1  A2v2
Bernoulli’s theorem

h
p
g

v2
2g
 constant
Reynolds number

Re 
vD

Chvorinov’s Rule Solidification time = C
Volume
Surface Area






n

29. Casting Design
1
2
11
1 F
g
vP
h 

2
2
22
2 F
g
vP
h 

v2A2
v1A1
)( ossc TTAhq 

30. Fludity
Fludity of metal is determined generally by sprial mold test.
The fludity index is the length of the solidified metal in the
sprial Passage.
Greater the length of the solidified metal, greater is its fludity.

31. Fluidity of Molten Metal
Fluidity: The capability of a molten metal to fill mold cavities
Viscosity: Higher viscosity decreases fluidity
Surface tension: Decreases fluidity; often caused by oxide
film
Inclusions: Insoluble particles can increase viscosity,
reducing fluidity
Solidification pattern: Fluidity is inversely proportional to
the freezing temperature range

32. Factor Affecting Fluidity of
Molten Metal
1. Mold design: The design and size of the sprue, runners, and
risers affect fluidity
2. Mold material and surface: Thermal conductivity and
roughness decrease fluidity
3. Superheating: The temperature increment above the
melting point increases fluidity
4. Pouring: Lower pouring rates decrease fluidity because of
faster cooling
5. Heat transfer: Affects the viscosity of the metal