Foundry Technology II: KN U S T Design of a Camshaft timing Gear · 2019. 2. 5. · The aim of the...
Transcript of Foundry Technology II: KN U S T Design of a Camshaft timing Gear · 2019. 2. 5. · The aim of the...
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