PDF Essay

1 | P a g e

BACHELOR OF ENGINEERING (HONOURS) MATERIAL

FACULTY OF ENGINEERING

YEAR 2 SEMESTER 2

BTMT 3043 Foundry Engineering

Assignment Title: Gating and Risering Systems for Steel Casting and Aluminium Alloy Casting

Marks Allocation

NAME : LEE JINGX UAN

ID : 17WGR10119

TUTOR : MR. KHOO KHEE TONG

DATE OF SUBMISSION : 24 DECEMBER 2018

Introduction

/10

Content

/50

Recommendation

/20

Conclusion

/15

Reference

/ 5

Total Marks

/100

2 | P a g e

1.0 Introduction ………………………….. ………………………….. ………………………….. ………………………….. . 3

2.0 Gating system ………………………….. ………………………….. ………………………….. ………………………… 3

2.1 Components of gating system ………………………….. ………………………….. ………………………….. …… 4

3.0 Riser system ………………………….. ………………………….. ………………………….. ………………………….. 6

3.1 Types of riser ………………………….. ………………………….. ………………………….. ………………………….. 6

4.0 Types of gating systems ………………………….. ………………………….. ………………………….. ………….. 7

4.1 Pressurized Gating System ………………………….

. ………………………….. ………………………….. ……….. 7

4.2 Non -Pressurized Gating System ………………………….. ………………………….. ………………………….. .. 8

4.3 Comparison table ………………………….. ………………………….. ………………………….. …………………….. 8

5.0 Recommendation ………………………….. ………………………….. ………………………….. …………………… 9

5.1 Precautions for gating system ………………………….. ………………………….. ………………………….. …… 9

6.0 Conclusion ………………………….. ………………………….. ………………………….. ………………………….. .. 9

3 | P a g e

1.0 Introduction

To be able to obtain a sound casting, the gating and ris er design plays a pivotal role in the sand casting

process. The gating system of sand casting is designed to direct the liquid to the mould cavity metal

for filling. The riser system is direct to counterbalance shrinkage cause by casting solidification. Pr oper

gating and risering design is important for producing sound castings and to improve the yield of the

casting. To achieving this the engineers to design filling and feeding system with very accurate

performance. The pattern allowances are also affects the quality of the casting. The solidification is

the important factor considering for the reason of defects as the selection of correct allowances helps

to reduce the rejections.

2.0 Gating system

Gating system is known as the simple design that is imp ortant to be able to construct a smooth and

appropriate filling of the mold cavity of the casting without any discontinuity, voids or solid inclusions.

A proper method of gating system formed are able to ensure that it leads the pure molten metal to flow

through a ladle to the casting cavity, which ensures proper and smooth filling of the cavity.

From here, there are different types of gating systems for different application which includes the

horizontal , vertical , bottom , and middle gating system. For horizontal gating system which 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. Next, for vertical

gating system that is applied in tall castings were high -pressure sand mold, shell mold and die -casting

processes are done.

Figure 2 .1: Gating system

4 | P a g e

2.1 Components of gating system

The main element needed for the gating system includes pouring basin, sprue, runner, gates and ri sers.

Pouring basins

From here, pouring basin which also known as bush or cup that are rectangular in shape collects molten

metal that is poured from the ladle that direct the flow of metal to sprue. Moreover, it helps maintaining

the required rate of liquid metal flow. While doing that, it is able to reduce the turbulence at the sprue

entrance and helps separating dross, slag and other unwanted stuff from metal before it enters the sprue.

If a pouring basins are made large, the 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. This large basins may be filled

quickly without overflowing and act as reservoir to compensate metal shrinkage or contraction.

Sprue

Next, th e sprue is circular in cross section where it leads the molten metal from the pouring basin to

the sprue well. Other than that, the runner takes the molten metal from sprue to the casting as it is

located in the horizontal plane which connects the sprue to its ingates. In other words, the sprue is

tapered with its bigger end at top to receive the liquid metal. The smaller end is connected to runner.

Figure 2.2. : Pouring basins

Figure 2 .3: Sprue

5 | P a g e

Gates

The gates plays a roles of a channel where it connects runner with the mould cavity and through which

molten metal flows to fill the mould cavity. From here, a small gate is used for a casting which

solidifies slowly and nice versa. Other than that, a gate should not have sharp edges as the may break

during the pouring and sand pieces may be carried with molten metal in the mould cavity. The different

types of gates include top gate, bottom gate and parting line side gate.

? Top gate

The top gate is sometimes called the drop gate as the molten metal just

drops on the sand in the bottom of the mould.

? Bottom gate

The bottom gate is made in the drag portion of the mould. The liquid

metal fills rap idly the bottom portion of the mould cavity and rises

steadily and gently up the mould walls.

? Parting line side gate

This gating system combine the characteristics of top and bottom

gating system. In this technique, gate is provided along the parting line

such that some portion of the mould cavity will be below the parting

line and some portion will be ab ove the parting line.

6 | P a g e

3.0 Riser system

Risers are known as the channels that allows continuous flow of m olten metal which appears to be

vertical. From here, it is able to eliminate shrinkage as solidification which occurs during the casting

process. In general, metals are generally less dense as liquids than solids which results in casting

shrinkage during c ooling process. Thus, risers plays a pivotal role on preventing this to happen by

feeding the molten metal to the casting as it solidifies.

3.1 Types of riser

Open riser

Open risers are the ones tha t are exposed to the atmosphere and are easy to be moulded. This risers

allows to know whether the mould is completely filled or not. Open riser includes top risers or side

risers. Open riser must be large in size. The advantage of top riser is that the pr essure occurred due to

the height of the metal causes feeding through thin sections and is preferred for light metals such as

aluminium. And in the case of side riser it should be placed at a higher level for proper feeding which

help the riser to receive hot metal.

Blind riser

Blind risers on the other hand are completely enclosed in the mould. Blind risers must be smaller in

size than open risers as it loses heat slowly. If a riser solidifies before the cavity it is to feed, it is useless

and produc es unsound casting. A blind riser which is in contact with the mould on all surfaces. Thus

a blind riser may be made smaller. Blind riser reduces the energy and time required in removing the

riser from the casting.

Figure 3.1 : Open Riser

Figure 3.2 : Blind Riser

7 | P a g e

4.0 Types of gating systems

In general, diffe rent materials such as ferrous (steel) and non -ferrous (aluminium alloy) requires

different process of casting which therefore leads to two types of gating systems:

? Pressurized gating system

? Un -pressurized gating system

4.1 Pressurized Gating System

This type of gating system are known as Gate Control System and is used for steel casting which are

ferrous metal s. From Figure 2.1 above, it can be seen that the total cross sectional area decreases

towards the mold cavity. Moreover, the back pr essure is maintained by the restrictions in the metal

flow. With that, the flow of liquid (volume) is almost equal from all gates. Other than that, the back

pressure helps in reducing the aspiration as the sprue always runs full. More turbulence will happe n

and higher chances of mold erosion due to the restrictions of metal flows at high velocity. This type

of gating system normally provide casting yield since the volume of metal used up in the runners and

gates are reduced. Due to the turbulence of this t ype of gating system is not used for light alloys but

can be advantageously used for ferrous castings. The gating system of a typical pressurized gating

system is sprue are: Runner area: Ingate area 1:2:1 or 1:0.75:0.5 .

Figure 4 .1: Pressurized Gating System

8 | P a g e

4.2 Non -Pressurized Gating Syst em

For this gating system, which known as Choke Control System are used for aluminium alloy casting

which are for non -ferrous metals. From Figure 2.2 above, it can be seen that the total cross sectional

area increases towards the mold cavity. With that, the restriction is only at the bottom of the sprue.

Furthermore, the flow of liquid is different from all gates. Thus, the aspiration in the gating system as

system never runs full. With that, there will be less turbulence. Because of the turbul ence this type of

gating system is used for light alloys such as aluminium and magnesium alloys. This type of gating

system have tapered sprues, sprue well and pouring cup. On top of that, the gating system of a typical

un -pressurized gating system is spru e are: Runner area: Ingate area of 1:2:2 or 1:3:3, 1:1:3 .

4.3 Comparison table

No Pressurized gating systems Unpressurized gating systems

1 Gating ratio may be of the order of 1:2:1 or

1:0.75:0.5 .

Gating ratio may be of the order of 1:2:2 or

1:3:3, 1:1 :3.

2 Air aspiration effect is minimum. Air aspiration effect is maximum.

3 Volume flow of liquid from every ingate is

almost equal.

Volume flow of liquid from every ingate is

different.

4 They are smaller in volume for a given flow

rate of metal. There fore the casting yield is

higher.

They are larger in volume because they involve

large runners and gates as compared to

pressurized system and thus lower cast yield

5 Velocity is high, severe turbulence may

occur at corners.

Velocity is low and turbulen ce is reduced.

Figure 4.2: Non -Pressurized Gating System

9 | P a g e

5.0 Recommendation

5.1 Precautions for gating system

Moving on, any gating system designed should be able to provide a defect free casting. There are

various steps to b e done on making a perfect casting. The steps are as shown below.

? A gating system must avoid of having sudden or right angle changes in direction.

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

? All undesirable 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 at mospheric air is prevented.

? A proper thermal gradient should be maintained so that the casting is cooled without any shrinkage

cavities or distortions.

? The metal flow should be maintained in such a way that no gating or mould erosion takes place.

? The gatin g system should ensure that enough molten metal reaches the mold cavity.

6.0 C onclusion

In conclusions, it cannot be denied that each materials require s different gating system to obtain a

sound and clean casting for different applications. From here, the pressurized and non -pressurized

gating system both supply di fferent structure and purposes. T he structure of the gating systems are

pivotal to ensure the mold are completely filled with metals without having turbulence and mould

erosion in casting. Moreover, it is importa nt to have defect free casting using the correct gating system .

7.0 Referenc es

1. HAWORTH CASTINGS. (21 January, 2016). Retrieved from Risers and runners:

-and -runners

2. J.Yokesh Kumar, M. S. (October, 2016). Volume 2 Issue 10. Retrieved from Review on DEsign and

Optimization of Gating and Risering System for Sand Casting Process:

3. Levture 13&14. (n.d.). Retrieved from Gating system: –

contents/IIT -ROORKEE/MANUFACTURING -PROCESSES/metalcasting/lecture13&14.htm

4. Nandagopal M, S. K. (November, 2017 ). International Journal of Recent Engineering Research and

Development (IJRERD). Retrieved from Study of Sand Casting Gating System:

jrerd.com/papers/v2 -i11/5 -IJRERD -B555.pdf

5. Tyagi, V. (16 December, 2014). Slideshare. Retrieved from Elements of gating system:

-system -in-casting