KNUSTwww.knust.edu.gh

Foundry Technology II:

Design of a Camshaft timing GearTeam Name: Stronghold

E. Odoi (2205514); J. Koomson (2204414); R. Asante Danso (2202514); E. Bosoka (2203214); E. Adade (2200614)

Kwame Nkrumah University of Science and Technology (KNUST), Ghana

College of Engineering, Materials Engineering Department

www.knust.edu.gh

Introduction Cast Design Charge Calculation

• Gears are wheels having on its periphery, equal spaced teeth

which are so designed that those wheels transmit, without

slip, rotary motion smoothly and uniformly with minimum

friction and wear at the mating tooth-profiles.

• Designing is done prior to manufacturing and includes

calculation of the gear geometry, taking into account gear,

strength, wear, characteristics of the gear teeth, material

selection, gear alignment and provision for lubrication.

• The melting, pouring and solidification calculations have

been considered. The material for the production has been

selected to be Grey cast iron, and the casting process

employed is sand casting.

• Inspection methods have also been included to check for

possible defects after the casting process. These have been

elaborated in details.

• The target structure after the production process should be as in

the figure below;

Fig1: Solid diagram and pictorial view of target object

Cast Part – Applications and Design goals

Conclusions / Recommendations

Acknowledgements

• The material chosen for the production of the timing gear

was grey cast iron because it is machinable, castable and has

high compressive strength.• A horizontal gating system was designed to produce a gear

blank using green sand mold and a non-pressurized gating

system with a gating ratio of 1: 3: 3.

• One defect which can render the whole process nil is mold

shift, it is recommended that proper alignment of cope and

drag must be ensured.

• The heat for melting and total solidification of the part was

calculated and determined. These calculations were done to

ensure the production of a cast part meeting the required

dimensions and accuracy

• During the annealing process, the product must be heated

and soaked at about 50⁰C above the austenitic region. This is

done to prevent overheating and burning.

• Since the component will be used, it is recommended that

only NDT methods are used to determine flaws.

We would like to thank our lecturer Prof. Kwofie for his

immeasurable knowledge in foundry technology that he

imparted to us and also Dr. Arthur for his guidance towards

the project. We would like to also thank our parents for their

help. We would like to say a thank you to all those who

supported us in other ways to the success of this work.

Material

• The material selected is Grey cast iron. A material for a gear

production should be hard, with good thermal and

mechanical properties with minimum elongation and high

compressive strength. A material for a gear should be

machinable and castable.

• The composition of the Grey cast Iron should fall within the

following range of composition; Carbon, C=2.7% - 4%,

Manganese, Mn=0.8% max, Silicon, Si=1.8% - 3%, Sulpur,

S=0.07% max, Phosphorus, P=0.2% max. W=1.357kg

a. Sand blow

b. Pin holes

c. Sand wash

d. Scabs

e. Penetration

f. Mold shift

g. Core shift

h. Mold Crack

i. Misrun

Cast Part

Dimension = Dimension of part+shrinkage allowance +

machining allowance

Mold Design

• Mold was designed with a sprue to runner to ingate ratio

of 1:3:3.

Table 1 : Dimensionss of parts of the mold

Cast Calculations

Sprue height, h=50mm, sprue base diameter, r=6.07mm

Cross sectional area of base of sprue, A=115.75mm2

From Bernoulli’s theory;

Velocity in the sprue, v = (2gh)0.5

= (2×9810×50)0.5

= 990.45mm/s

Volumetric rate of flow, Q = vA

= 990.452mm/s × 115.75mm2

= 114694.62mm3/s

Mold Filling Time, TMF =

Total Solidification Time, TTS

Pouring Rate, R =

Heat required, H = ρV {Cs(Tm - To)+ Hf + Cl(Tp - Tm)}H = 7.2×190.84[(0.117(1180 - 25) + 126 + 0.46(1300 - 1180)]

H = 434659.47J

Hence, the energy required for the melting process is

434.659kJ.

The areas where where gear systems are applicable are;

• Speed gear box,

• Feed gear box and some other kinetic units of machine tools,

• Gear boxes of automobiles,

• Timing and idler gears in automobiles and in several other

machanised systems and tools.

Design Goals

The camshaft timing gear is to be used to transmit rotary motion

with limited wear and friction. The cast part must therefore have

the following properties;

• The material for the production should be castable with

minimum defects.

• The mold should take minimum time in the production.

• The part must have high compressive strength and

machineable after production.

• The part should have high strength to weight ratio.

• It should take a maximum of 5hours to complete production

from melting to finished product.

• The possible defects should be able to be remedied.

GRP _ 03 METE

Aims and Objectives

The aim of the design is to produce a part (gear) that can

withstand mechanical wear and provide rotary motion with

limited slip and friction at the mating tooth profiles. The cast

part should have minimum dwefects and be machineable at the

end of the casting proces.

Objectives

1. To design a pattern for the part (camshaft timing gear).

2. To specify a mold appropriate for the production of the part.

3. To specify the casting process to be used.

4. To identify the possible defects and appropriate prevention

and remedies for the defects.

STRING Dimension

Weight of Part, W 1.357kg

Surface Area of Part, A 29665.75mm2

Volume of Part, V 190836.77mm3

Sprue Height, Hsprue 50mm

Area of Sprue inlet 115.8mm2

Area of Sprue exit 115.8mm2

Runner Cross sectional Area 347.4mm2

Volume of Riser 109.691mm3

s66.162.114694

77.190836

Q

V

1.52min

91.04s

75.29665

77.1908362.2

A

VC

2

2

m

0.5475kg/s1.357kg47.0Wb

Defects Discussions

Composition % Carbon % Silicon % Manganese % Phosphorus % Sulphur

0.4kg pig iron 1.750 1.250 0.3500 0.085 0.04350

0.28kg New scrap 1.190 0.805 0.0525 0.070 0.01050

0.12kg Foundry returns

0.495 0.375 0.0975 0.024 0.00525

Total 3.435 2.430 0.5000 0.179 0.05925

(i)

Table 2 : Composition of charge to furnace

Figure 2 : Solid diagram and pictorial view of the cast part