The document discusses the key elements and design considerations of a gating system used in metal casting. A gating system includes components like the pouring basin, sprue, runners, gates, risers, and mould cavity. It aims to distribute molten metal with minimal turbulence, fill the mould cavity quickly, and establish favorable temperature gradients. Proper gating ratios and avoiding abrupt changes are important design factors. Common types of gates include parting line, top, and bottom gates.

1. GATING SYSTEM
By: SamirJariwala

2. INTRODUCTION:-
All the channels or passages through which the molten
metal is delivered to mould cavity is termed as gating
system.
Gating system includes the runner, riser, pouring basin
and gate etc.

3. FUNCTION OF AN IDEAL GATING
SYSTEM:-
a) Distribute the molten metal with the least disturbance in
order to reduce erosion of the mould material.
b) Facilitate complete filling of the mould cavity.
c) Fill the mould cavity with molten metal at the earliest
possible time to avoid temperature gradient.
d) Develop such temperature gradient in molten metal and
the mould which will led to the directional solidification of
the casting towards riser.
e) prevent the formation of oxide and dross in the molten
metal while flowing through it.
f) Prevent the entry of slag, sand and the other particle from
the mould.

4. ELEMENT OF A GATING SYSTEM:-
POURING BASIN:-
 This is where the molten metal employed to manufacture
the part enters the mould. The poring basin should have a
projection with a radius around it to reduce turbulence. It
is the conical hollow element or tapered hollow vertical
portion of the gating system to mould cavity. It may be
made out of core sand or it may be cut in cope portion of
the sand mould.

5.  Down sprue:-
From the pouring basin the molten metal for the casting travels
through the down sprue. This should be tapered so its c/s is reduced as
it cause downward.
 Sprue base:-
The down sprue end at the sprue base.It is here that the casting’s
inner cavity begins.

7. • Ingate/Chock area:-
Once at the sprue base the molten material must pass
through the ingate inorder to enter the inner area of the
mold.The ingate is very important in flow regulation
during the metal casting operation.
• Main Cavity:-
The impression of the actual part to be cast is often
refferd to as the main cavity.
• Vents:-
The vent helps to assist in the escape of gases that are
expelled from the molten metal during the sodification
phase of the metal casting process.

8.  Gate:-
It is a small passage or channel being cut by get
cutter which connect runner with the mouldcavity and
through which molten metal flows to fill the mould
cavity.It feeds the liquid metal to the casing at the rate
consistant with the rate of solidification.
 Runners:-
Runners are passages that distribute the liquid
metal to the different areas inside the mold.

9. • Risers:-
Risers are reservoirs of molten material.They feed this
material to sections of the mould to compensate for shrinkage as
the casting solidifies.
There are different classifications for risers.
i) Top risers:-
Risers that feed the metal casting from the top.
ii) Side risers:-
Risers that feed the metal casting from the side.
iii) Blind risers:-
Risers that are completely conained within the mould.
iv) Open risers:-
Risers that is open at the top to the outside environment.

11. TYPES OF GATE:-
 A gat is a passage or channel through which the molten
metal flow s from the runner to the mould cavity. However,
it should be located where it can easily removed without
any loss to the casting. As per their position in the mould
cavity, gates may be classified as follows:
- parting line gate
- top gate
- bottom gate

12. PARTING LINE GATE:-
 It is the simplest type of gate and the molten metal enters the
mould cavity at the parting line. Such type of gate is cut by
hand when the cope and drag are separated or it can be formed
by an attached gate to the pattern.
 Parting line allows the use of devices that can effectively trap
any slag, dirt, or sand, which passes with the metal down the
sprue.

14. TOP GATE:-
 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.

16.  The principle advantages of top gating are its simplicity for
moulding, its low consumption of additional metal and, above
all the generation of temperature gradients favorable to feeding
from top heads.
 The main disadvantages of this type of gating is the erosion of
the mould, which takes place by the falling metal.
 The cavity of mould, therefore should be much harder and
strong to resist this impact.

17. BOTTOM GATE:-
 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.

19. GATING RATIO:-
 The dimensional characteristic of any gating system can
be generally expressed in terms of the gating ratio.
 A:B:C
Where,
A=cross sectional area of down runner
B=total cross sectional area of runners
C=total cross sectional area of ingates

20.  It is used to describe the relative cross sectional area of the
component of a gating system.
 It is defined as the sprue area to the total runner area to the
total gate area.
 A gating system having a sprue of 1 sq cm cross section,
runner of 3 sq cm cross section, and three gates, each of 1
sq cm cross section, will have a gating ratio of 1:3:3.

21. GATING SYSTEM DESIGN:-
 The following factors must be considered while designing
gating system:
(a) sharp corner and abrupt changes in at any section or
portion in gating system should be avoided for suppressing
turbulence and gas entrapment.
(b) the most important characteristic of gating system are
location and dimension of runners and type of flow.

22. (c) gating ratio should reveal that the total cross section of
sprue, runner and gate decreases towards the mould cavity
which provides a choke effect.
(d) bending of runner if any should be kept away from mould
cavity.
(e) developing the various cross sections of gating system to
nullify the effect of turbulence or momentum of molten metal