Design and Finite Element Analysis of Fixture for Milling of Cummins Engine Block

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 08 | Aug -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2215
Design And Finite Element Analysis Of Fixture For Milling Of Cummins
Engine Block
Shrihari Bukkebag1, Dr. S.R. Basavaraddi2
1PG Scholar, Dept. of Mechanical Engineering KLE Dr MSSCET, Belagavi
2Profesor, Dept. of Mechanical Engineering KLE Dr MSSCET, Belagavi
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Abstract - One of the critical elements involved in mass a
production facility is Fixture. Fixtures are used in machining
components with high accuracy and efficiency. The aim ofthis
project is to design a milling fixture to mill the top surface of
the B-6 Cummins Engine block to a depth of 1 millimeter with
a cycle time less than 3 minutes and meet the production
target of 400 units per day. Hydraulic elements are also used
in the fixture to make the process more efficientandtoachieve
the given targets. The fixture is also tested for its design
feasibility by performing static analysis on ANSYS.
Key Words: Fixture, Milling, Cycle time, Static Analysis,
Engine Block.
1.INTRODUCTION
The jigs and fixtures are the economical ways to produce a
component in mass. So jigs and fixtures serve as one of the
most important means ofmassproductionsystem.These are
special work holding and tool guiding device. Quality of the
performance of a process is largely influenced by the quality
of jigs and fixtures used for this purpose. What makes a
fixture unique is that each one is built to fit a particular part
or shape. The main purpose of a fixture is to locateandin the
cases hold a workpiece during an operation.
1.1 Background of the Problem
A six cylinder Cummins engine block is cast in grey cast
iron with all the necessary locating points to mount the
engine over a fixture. The majorrequirementofthisprojectis
to design and fabricate a milling fixture for milling of the top
face of B-6 Cummins Engine block to a depth of 1millimeter
over a bed type milling machine with a cycle time less than 3
minutes and meet the production targets of 400 units per
day.
1.2 Methodology
The steps involved in designing this fixture include 1.
Fixing the Constraints 2. Fixing the dimensions of the fixture
based on the dimensions of the engine 3. Building solid 3D
model 4. Carrying out Finite Element Analysis on ANSYS to
find out the Stress 5. Calculating the results theoretically
6.Comparison of results.
2. LIRATURE REVIEW
K.Srinivasulu et al [1] in his work based on design of
machining fixture for turbine rotor blades discusses about
his work based on the industry requirement for machining
the turbine blade on a vertical machining centre (VMC).
Fixture Design consists of High product rate, low
manufacturing operation cost. Thefixturewastobedesigned
in such-away that part/product change overtimeis veryless.
Victor Songmene et al [2] published his experimental
results of Analytical modelling of slot milling exitburrsize.In
this work, a computational modelling algorithm was
proposed to predict the radial and tangential cutting forces
(Fr, Ft), friction angle λ and burrthickness Bt in slotmillingof
ductile materials. A new force model, so-called “mechanistic
approach” that comprises an algorithm for simultaneous
calculation of average cutting forces, chip thickness and
cutting force coefficients K was then used to build new
computational modelling algorithm.
S. S. Mohite & M. A. Sutar et al [3] Their work establishes
the FEA model of fixture unitassembly to predict fixture unit
stiffness and FEA model of rough surface contact to predict
contact stiffness. Based on this study the appropriate
boundary conditions were derived, thetypeofelementstobe
employed and the degree of meshing to be produced were
also considered.
Shailesh S Pachbhai & Laukik P Raut et al [4] This paper
discusses in detail the steps involved indesigningahydraulic
clamp it also discusses in length the time taken to machine
the same component on a manual fixture and compares it
with the time taken on a hydraulic fixture and the amount of
time saved leading to an increase in production of the
component it also takes into account the cost savings given
that the ideal time of the machine is reduced. The hydraulic
fixture also improves repeatability and also reduces
workpiece distortion.
3. DESIGN OVERVIEW
The dimensions of the fixture were finalized based upon the
dimensions of the engine and the saddle.

3.1 Length of fixture
The length of the engine is 748 mm hence the fixture length
was made to be 970 mm giving a clearance for clamping
bracket on either side as shown in figure 3.1 & 3.2.
3.2 Width of fixture
The width of the fixture was based on width of the saddle
which holds the fixture in its place. The width of saddle of is
600 mm. Hence the width of the fixture was fixed to be 400
mm by giving a clearance of 100 mm on either side as shown
in the figure 3.3.
3.3 Dimensions of height bracket
The height of the clamping bracket was fixed on the heightof
the engine cam bore which is at height of 319 mm as shown
in figure 3.2.
Fig -3.1: Top View
Fig -3.2: Side View
Fig -3.3: End View

4. CALCULATIONS
Design parameters
Power of Motor = 10 hp = 7.5 KW
Speed of milling cutter = 145 rpm
Dia. of cutter Dc = 315 mm
Depth of cut ap = 1 mm
Table Feed Vf = 428.62 mm/min
No. of Teeth z = 24
Cutting Speed Vc [5]
Vc = πDn/1000
Vc = π*315*145/1000
Vc = 143.49 m/min
Feed rate per tooth Fz
Fz = Vf /Z*n
Fz = 428.62/24*125
Fz = 0.123 mm/tooth
Power Pc
Pc = Kc*ap*ae* Vf /60*106
Pc = 1750*1*252*429/60*106
Pc = 3.15 KW
Torque Mc
Mc = Pc*30*10-3/ πn
Mc = 3.15*30*10-3/ π*140
Mc = 214,859.17 N-mm
Force F
F = Mc/r
F= 214,859.17/157.5
F = 1364.18 N
4.1 Calculating Stress on Pin 1 & 2
A double Shear Stress is acting on the Pins as illustrated in
the figure 4.1 below, a force of 1364.18 N is acting on the
centre of the pin and both the ends are fixed. Material used is
mild steel with Yield Strength of 250 Mpa.
Fig -4.1: Double Shear on pins
Calculating stress on pin 1 [6]
τ1 = F/2A
τ1 = F/2*(π/4*d2)
τ1 = 1364.18/2* (π/4*122)
τ1 = 6.03 Mpa
Calculating stress on pin 2 [6]
τ2 = F/2A
τ2 = F/2*(π/4*d2)
τ2 = 1364.18/2* (π/4*102)
τ2 = 8.68 Mpa
4.2 Design of bolt
Allowable upper limit of force[7]
F= σ * As
Where As is the stress area of the bolt which is 58 mm2
F = 420 * 58
F = 24360 N
Initial Tightening load
F = 1400 * do
Where, do = outer diameter of bolt = 10 mm
F = 1400 * 10
F = 14000 N
Tightening torque
T = c*d*Fi
where, c= 0.15 coefficient of friction
T= 0.15 * 10* 1400
Tensile stress on bolt
σ = F/A
σ = 16800/113.1
σ = 148.54 Mpa
Torsonial Shear Stress
τ = 16*T/π*dc
3
τ = 16*21000/ π*9.02573*4 (No. of bolts = 4)
τ = 36.36 Mpa
Factor of saftey
FOS = Yield Strength/Allowable Strength
FOS = 310/36.36
FOS = 8.4
4.3 Clamping Pressure
The Clamping Cylinder has an operating pressure range of 1
Mpa to 7 Mpa , which translates to a clamping force of range
1809 N to 12666 N , by operating the cylinder at 1.2 Mpa we
have a Clamping Force of 2714 N , which is approximately
1.5 times the force exerted by the milling cutter.[8]

4.4 Table of values
Table -4.1: Table of values
SL.No PARAMETERS VALUES
1 Torque of Milling Cutter 214,859.17
N-mm
2 Force exerted by Milling
Cutter
1364.18 N
3 Tightening torque on Bolt 21000 N-mm
4 Tensile stress on Bolt 148.54 Mpa
5 Torsional Shear stress on
Bolt
372.06 Mpa
5.SOLID MODELLING
Fig -5.1: Assembled fixture
Fig -5.2: Assembled fixture with engine block
6. FEM RESULTS AND DISCUSSIONS
Figure 6.1 shows equivalent Von-Mises stress of 45.31 Mpa
acting on Clamp Strap.
Fig -6.1: Von-Mises Stress acting on Clamp Strap
Figure 6.2 shows maximum principal stress of 60.65 Mpa
acting on the Clamp Strap.

Fig -6.2: Max Principal stress acting on Clamp Strap
Figure 6.3 shows equivalent Von-Mises stress of 87.44
Mpa acting on Height Bracket.
Fig -6.3: Von-Mises Stress acting on Height Bracket
acting on the Height Bracket.
Fig -6.4: Max Principal stress acting on Height Bracket
Figure 6.5 shows shear stress of 5.82 Mpa acting on Pin 1.
Fig -6.5: Shear Stress acting on pin 1
Figure 6.6 shows the equivalent von mises stress of 44.80
Mpa acting on Pin 1.
Fig -6.6: Von Mises Stress on Pin 1
Figure 6.7 shows Shear stress of 7.13 Mpa acting on Pin 2
Fig -6.7: Shear Stress acting on pin 2
Figure 6.8 shows Equivalent Von Mises stress of 93.55
Mpa acting on Pin 2

Fig -6.8: Von Mises stress on Pin 2
Mpa acting on round head pin.
Fig -6.9: Von-Mises Stress acting on Round Head pin
acting on the round head pin.
Fig -6.10: Max Principal stress acting on Round Head pin
Mpa acting on diamond head pin.
Fig -6.11: Von-Mises Stress acting on Diamond Head pin
acting on the diamond head pin.
Fig -6.12: Max Principal stress acting on Diamond Head
pin
6.1 Discussions
Clamp Strap: as shown in figure 6.1 & 6.2 is made of Mild
Steel with an yield strength of 250 MPa , the equivalent Von-
Mises stress of 45.31 Mpa is acting on it and maximum
principal stress of 60.65 Mpa acting on the Clamp Strap. The
type of element used is Triangular element total no.ofnodes
113671 and total no. of elements are 66029.
Height Bracket :as shown in figure 6.3 & 6.4 ismadeof Steel
with an yield strength of 250 MPa, equivalent Von-Mises
stress of 87.44 Mpa is acting on the bracket and maximum
principal stress of 88.96 Mpa is acting on the HeightBracket.
The type of element used is Triangular element total no. of
nodes 5609 and total no. of elements are 2889.

Pins: as shown in figures 6.5 to 6.8 are made of Hardened
Steel with an yield strength of 270 Mpa. Shear Stress and
Von Mises Stress acting on pin 1 are 5.82Mpa and44.80Mpa
respectively. Shear Stress and Von Mises Stressactingon pin
2 are 7.13 Mpa and 93.55 Mpa respectively. The total no. of
nodes on pin 1 are 62445 and total no. of elements are
30884 and the total no. of nodes on pin 2 are 56572 and
total no. of elements are 27883. The type of element used is
rectangular element.
Round Head Pin : as shown in figure 6.9 & 6.10 is made of
En-31 with an yield strength of 450 Mpa and case hardened,
equivalent Von-Mises stress of 13.01 Mpa acting on round
head pin and maximum principal stress of 2.55 Mpa acting
on it. The type of element used is Triangular element total
no. of nodes 3374 and total no. of elements are 1837.
Diamond Head Pin : as shown in figure 6.11 & 6.12 is made
of En-31 with an yield strength of 450 Mpa and case
hardened, equivalent Von-Mises stress of 11.93 Mpa acting
on round head pin and maximum principal stress of 6.79
Mpa acting on it. Type of element used is Triangularelement
total no. of nodes 3354 and total no. of elements are 1820.
For all the Critical Parts that have been analyzed itshasbeen
found that the stresses acting on them are well below the
Yield Strength Limits of the materials used hence we can say
that the design is feasible.
7. RESULTS
Machining Time
Table -7.1: Machining Time
No of Trials Machining Time (Mins.)
1 2.56
2 2.52
3 2.54
4 2.58
5 2.53
Comparison of Theoretical Calculations with FEM
Results
Table -7.2: Comparison of results
Parameters Theoretical
Values
Mpa
Analytical
Values
Mpa
Remarks
Shear Stress
on Pin 1
6.03 5.82 Safe
Shear Stress
on Pin 2
8.68 7.13 Safe
8. CONCLUSION
 The Fixture has been effectively designed for the given
problem, the critical components have been analytically
tested in Static Analysis, the results of these testsfall well
below the yield strength limits of the materials used,
rendering the design feasible.
 The dowel pins and rest pads have beencasehardenedto
provide extra robustness for heavy duty mass
production.
 Pneumatic sensors have been incorporated into the rest
pads to provide feedback to the operator as to whether
the engine has been clamped properly or not before the
operation begins this will ensure that the component is
aligned properly and also help avoid machining errors.
 The average machining time oftheengine withthefixture
is 2.54 Minutes. On an average this fixture machines
around 400 engines per day.
REFERENCES
[1] C.Radha Madhavi, B. Ramu, K. Srinivasulu “Design of
Machine Fixture for Turbine Rotor Blade”, International
Journal of research in engineering and technology
eISSN: 2319-1163, pISSN: 2321-7308.
[2] Seyed Ali Niknam & Victor Songmene, “Analytical
modelling of slot milling exit burr size”, Springer-Verlag
London 2014.
[3] S. S. Mohite & M. A. Sutar, “Finite ElementModellingAnd
Analysis Of Workpiece-Fixture System”, Dept. of
Mechanical Engineering, Govt. College of Engineering,
Karad, Dist- Satara, Maharashtra, India.
[4] Shailesh S Pachbhai1 and Laukik P Raut, “Design And
Development Of Hydraulic Fixture For Machining
Hydraulic Lift Housing”, ISSN 2278 – 0149 Vol. 3, No. 3,
July, 2014.
[5] Tungaloy cutting tools “Technical Reference”.
[6] Balveer Reddy “Engineering Data Handbook”.
[7] Standard Handbook of Machine Design 3ed - Shigley,
Mischke.
[8] CLASP Product Manual.

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