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VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
RANDOM VIRATIONAL ANALYSIS ON MILLING MACHINE STRUCTURE
Dr. VVRLS GANGADHAR1, S SHASHANK
2, GYADARI RAMESH
3, V.P. RAJU
4
1,2,,3& 4 DEPARTMENT OF MECHANICAL ENGINEERNG
PRINCETON COLLEGE OF ENGINEERING & TECHNOLOGY, HYDERABAD, TELANGANA
Abstract
Beds, bases, columns and box type housings are called
“structures” in machine tools. In machine tools, 70-
90% of the total weight of the machine is due to the
weight of the structure. They provide rigid support on
which various subassemblies can be mounted i.e. beds,
bases, provide housings for individual units or their
assemblies like gear box, spindle head, support and
move the work piece and tool relatively, i.e. table,
carriage, tail stock etc.
In this thesis, tool structure of a milling
machine is designed and modeled in 3D modeling
software CREO 2.0. Static analysis is done on the
tool structure by applying weight forces, cutting
forces for different materials Cast Iron, Mild Steel,
Granite and Concrete to determine deformations
and stresses. Modal analysis and Random Vibration
analysis are done to determine frequencies and
stresses produced from frequencies. Analysis is
done in Ansys.
Key words: Cutting Forces, Metal Cutting, Vibration
I.INTRODUCTION
Milling machines were first invented and
developed by Eli Whitney to mass produce
interchangeable musket parts. Although crude,
these machines assisted man in maintaining
accuracy and uniformity while duplicating parts
that could not be manufactured with the use of a
file Development and improvements of the milling
machine and components continued, which resulted
in the manufacturing of heavier arbors and high
speed steel and carbide cutters. These components
allowed the operator to remove metal faster, and
with more accuracy, than previous machines.
Variations of milling machines were also
developed to perform special milling operations.
During this era, computerized machines have been
developed to alleviate errors and provide better
quality in the finished product.
Metal cutting is generally used in the
manufacturing industry to machine, e.g., work
pieces to desired geometries with certain
tolerances. During the machining process, a
number of different machining operations may be
involved. Today, there are many advanced
machines that have several axes and that can
perform complex milling and turning operations
about non-fixed axes by, for example, rotating or
leaning the axis of the spindle. Another example of
the type of advanced operation that modern
machines are capable of is the production of an
oval or ellipsoidal cross-section of a work piece by
controlling the tool motion in the radial direction of
the work piece during turning.
The metal cutting operation may
sometimes produce high server vibration levels.
The cause of these vibrations can be attributed to
many different factors such as the cutting
parameters, the work piece material and shape, the
tooling structure, the insert, and the stability of the
machine. Thus, there are many different parameters
that impudence the stability of the cutting process
in milling operations, and there has been a lot of
research done in this area.
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
II.LITERATURE REVIEW
In the paper by Mounir Muhammad Farid
Koura, Muhammad LotfyZamzam, Amir Ahmed
Sayed Shaaban, presented an integrated simulation
system that is employed in order to evaluate the
static and dynamic performance of a milling
machine. The paper discusses the design
consideration of the evaluation system, creates the
system based on finite element technique, applies it
to a case study, and discusses the results. Obtaining
such a reliable model could replace many
experimental tests that must otherwise be carried
out each time the parameters affecting cutting
conditions are changed. Modeling and meshing of
various machine elements including the mechanical
structure are carried out, contacts between each
adjacent element are defined, load components
generated from machining process are modeled,
and finally the static and dynamic performance of
the entire machine is evaluated. The machine
performance is identified in terms of static loop
stiffness in both x and y directions, mode shapes,
and frequency response function at tool center
point.
In the paper by F. Haase, S. Lockwood &
D.G. Ford [2], A restriction for large material
removal rates is the tendency of machines to
ch1atter (structural vibration) for large depths of
cut. This work is concerned with improving
machine tool performance by understanding and
ultimately controlling vibration in machine
structures. If vibration due to chatter under load
conditions can be controlled, then component
surface finish can be improved and the life of
components extended. The first step in this research
is to measure and interpret vibration and model the
structures, which are to be controlled. Appropriate
sensors need to be selected and designed to
measure self-excited vibrations. The vibrations of
the investigated machines need to be understood by
analyzing the sensor signals and surface finish.
Recent advances in micro-machining technology
have resulted in a new type of accelerometer that is
an order of magnitude lower in cost than traditional
types. Results have shown that these sensors can be
successfully used to replace their more expensive
counterparts.
In the paper H. Akesson, T. Smirnova, L.
H. akansson, T. Lag¨o and I. Claesson [3], The
vibration level depends on many different
parameters such as the material type, the
dimensions of the work piece, the rigidity of
tooling structure, the cutting data, and the operation
mode. In milling, the cutting process subjects the
tool to vibrations, and having a milling tool holder
with a long overhang will most likely result in high
vibration levels. As a consequence of these
vibrations, the tool life is reduced, the surface
finishing becomes poor, and disturbing sound
appears. In this report, an investigation of the
dynamic properties of a milling tool holder with
moderate overhang has been carried out by means
of experimental modal analysis and vibration
analysis during the operating mode. Both the
angular vibrations of the rotating tool and the
vibrations of the machine tool structure were
examined during milling. Also, vibration of the
work piece and the milling machine was examined
during cutting. This report focuses on identifying
the source/sources of the dominant milling
vibration components and on determining which of
these vibrations that are related to the structural
dynamic properties of the milling tool holder.
In the paper by SiamakPedrammehr –
Mehran Mahboubkhah – Mohammad Reza Chalak
Qazani3 – ArashRahmani – SajjadPakzad [4] ,
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Assuming a sinusoidal machining force, the forced
vibration of a machine tools’ hexapod table in
different directions is addressed in the present
study. A vibration model for the hexapod table is
developed and the relevant explicit equations are
derived. In the vibration equation of the table, the
pods are assumed as spring-damper systems and
the equivalent stiffness and damping of the pods
are evaluated using experimental results obtained
by modal testing on one pod of the hexapod table.
The results of the analytical approach have been
verified by FEM simulation. The theoretical and
FEM results exhibit similar trends in changes and
are close to each other. The vibration of the table in
different positions has been studied for rough and
finish machining forces for both down and up
milling. The ranges of resonance frequencies and
vibration amplitudes have also been investigated.
The safe functional modes of the table in terms of
its upper platform’s position have subsequently
been determined
In the paper by Huaizhong Li, Xiubing
Jing, and Jun Wang [5], An experimental study to
understand the characteristics related to chatter
occurrence in micro milling operations is
presented. Accelerometers are used to measure the
vibration signals in the machining process. The
accelerate on signals are then analyzed in the time
domain and the frequency domain. Along with the
onset of chatter, it is found that there is a
characteristic shift of the dominant frequency
components in addition to the change of vibration
amplitude. A modulation of the spindle frequency
around the chatter frequency is also found to be
present in the vibration signal. A dimensionless
chatter indicator based on revolution RMS values is
designed and used to evaluate the stability of the
micro-milling process. It is shown that the
proposed indicator provides a simple, but effective
way to detect chatter onset.
In the paper by K. Reza Kashyzadeh ,
Prof. Dr. M. J. Ostad-Ahmad-Ghorabi [6], Machine
tool chatter is one of the major constraints that limit
productivity of the turning process. It is a self-
excited vibration that is mainly caused by the
interaction between the machine-tool/work piece
structure and the cutting process dynamics. The
frictional and impact chatter are mainly due to the
nonlinearity of the dry friction and the intermittent
contact between the cutting tool and the work
piece. There are some methods that can limit the
chatter. In this paper we introduce and compare
some of these methods.
In the paper by B.V. Subramaniam, A.
Srinivasa Rao, S.V. Gopala Krishna, CH. Rama
Krishna [7], Static and Dynamic analysis of
machine tool structures plays an important role on
the efficiency and job accuracy of the machine tool.
Static analysis is useful for estimating stresses,
strains and deflections, where as dynamic analysis
deals with the prediction of natural frequencies and
corresponding mode shapes, which will inturn,
prevent the catastrophic failure of the machine tool
structures.
1. ANALYSIS ON MILLING MACHINE
TOOL STRUCTURE
The reference paper for the analysis is
taken from “Simulation approach to study the
behavior of a milling machine’s structure during
end milling operation” by Mounir Muhammad
Farid Koura, Muhammad LotfyZamzam, Amir
Ahmed Saied Shaaban, Turkish J EngEnvSci
(2014) 38: 167 – 183, as specified in Reference
chapter as [1].
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
The material properties are specified in the below
table which are taken from website
www.matweb.com
MATERIAL
Density
(kg/m3)
Young’s
modulus
(Mpa)
Poisson’s
ratio
Mild steel 7850 210000 0.303
Cast iron 7810 240000 0.370
Granite 2660 60000 0.3
2300 30000 0.18
Table 1 - Material Properties
III.STRUCTURAL ANLYSIS
Condition 1- Force 1000 N
MATERIAL – MILD STEEL
Save Creo Model as .iges format
→→Ansys → Workbench→ Select analysis
system → static structural → double click
→→Select geometry → right click → import
geometry → select browse →open part → ok
→→ Select mesh on work bench → right click
→edit
Imported model
Double click on geometry → select geometries →
edit material
Select mesh on left side part tree → right click →
generate mesh →
Meshed model
Select static structural right click → insert → select
Force –1000N
Force
Select fixed support → select required area →
click on apply →
Fixed support
Select solution right click → solve →
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Solution- right click → insert → deformation →
total
Solution right click → insert → strain → equitant
(von-misses) →
Solution right click → insert → stress → equitant
(von-misses) →
Right click on deformation → evaluate all result
Total deformation
Von-misses stress
Von-misses strain
MATERIAL – CAST IRON
Total deformation
Von-misses stress
Von-misses strain
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
MATERIAL -GRANITE
Total deformation
Von-misses stress
Von-misses strain
MATERIAL – CONCRETE
Total deformation
Von-misses stress
Von-misses strain
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
MODAL ANALYSIS
MATERIAL – STEEL
Save Creo Model as .iges format
→→Ansys → Workbench→ Select analysis
system → model → double click
→→Select geometry → right click → import
geometry → select browse →open part → ok
→→Select modal → right click →select edit →
another window will be open
Imported model
Double click on geometry → select geometries →
edit material →Select mesh on left side part tree →
right click → generate mesh →
Meshed model
Select fixed support → select required area → click
on apply → Select solution right click
Fixed support
Solution right click → insert → deformation →
total deformation → model Solution right click →
insert → deformation → total deformation2 →
mode 2
Solution right click → insert → deformation →
total deformation 3→ mode 3
Right click on deformation → evaluate all result
Mode 1
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Mode 2
Mode 3
MATERIAL – CAST IRON
Mode 1
Mode 2
Mode 3
MATERIAL – CONCRETE
Mode 1
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Mode 2
RANDOM VIBRATIONALANALYSIS
MATERIAL – MILD STEEL
Enter frequencies and deformation values
Solution –right click-solve-select solution –right
click –directional deformation
Select solution –right click –shear stress
Select solution –right click –shear strain
Directional deformation
Shear stress
Shear strain
MATERIAL – CAST IRON
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Directional deformation
Shear stress
Shear strain
MATERIAL - GRANITE
Directional deformation
Shear stress
Shear strain
MATERIAL – CONCRETE
Directional deformation
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Shear stress
RESULT & DISCUSSION STATIC ANALYSIS
Force
Material
Deformation
(mm)
Stress
(Mpa)
Strain
1000N
Steel 0.0013823 0.081035 4.264e-7
Cast iron 0.00011753 0.081752 3.7182e-7
Granite 0.00048436 0.081007 1.4928e-6
Concrete 0.0010038 0.08013 3.0505e-6
500N
Steel 6.9117e-6 0.040517 2.132e-7
Cast iron 5.8764e-5 0.040876 1.8591e-7
Granite 0.00024218 0.040504 7.4642e-7
Concrete 0.0005019 0.040065 1.5252e-6
Static analysis results
MODAL ANALYSIS
Materials Modes Deformation
(mm)
Frequency
(Hz)
Mild steel
Mode1 1.1555 47.855
Mode2 1.0219 48.88
Mode3 1.3766 139.59
Cast iron
Mode1 1.1597 50.946
Mode2 1.025 52.593
Mode3 1.3939 149.36
Granite
Mode1 1.985 43.958
Mode2 1.7355 44.878
Mode3 2.3638 128.19
Concrete
Mode1 2.1363 33.967
Mode2 1.8966 34.001
Mode3 2.5022 98.182
Modal analysis results
0
0.0005
0.001
0.0015
500 1000
DE
FO
RM
AT
ION
(m
m)
FORCE (N)
COMPARISON OF
DEFORMATION VALUES AT
DIFFERENT FORCES AND
MATERIALS
Mild Steel
Cast Iron
Granite
Concrete
0.00E+00
1.00E-06
2.00E-06
3.00E-06
4.00E-06
500 1000
STR
AIN
FORCE (N)
COMPARISON OF STRAIN VALUES AT DIFFERENT FORCES AND
MATERIALS
Mild Steel
Cast Iron
Granite
Concrete
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
RANDOM VIBRATION ANALYSIS RESULT
Material
Directional
deformation
(mm)
Shear stress
(MPa)
Strain
Mild
steel
65.885
507.05
0.0062923
Cast iron
69.797
631.05
0.0072045
Granite
82.628
181.53
0.0078664
IV.CONCLUSION
In this thesis, tool structure of a milling
machine is designed and modeled in 3D modeling
software CREO. Static analysis is done on the tool
structure by applying weight forces, cutting forces
for different materials Cast Iron, Mild Steel,
Granite and Concrete to determine deformations
and stresses. Modal analysis and Random Vibration
analysis are done to determine frequencies and
stresses produced from frequencies. Analysis is
done in Ansys.
By observing the static analysis results,
the stress values for all materials are less than their
respective yield stress values. The deformation and
strain values are less when Cast Iron is used. By
observing the modal analysis results, the
deformation values are less when Cast Iron is used
but the frequencies are less when concrete is used.
Thereby the vibrations on the structure due to
cutting forces will be reduced when Concrete is
used.
By observing Random Vibration analysis,
due to frequencies from modal analysis, the
directional deformation and shear stress values are
less when Concrete is used.
But the strength of the concrete is very
less when compared with that of Steel or Cast Iron.
So using Cast Iron for milling machine tool
structure is better.
REFERENCES
[1] Muhammad Farid Koura, Muhammad
LotfyZamzam, Amir Ahmed Sayed Shaaban,
Turkish J EngEnvSci (2014) 38: 167 – 183 ⃝c
TUB¨ ˙ITAK doi:10.3906/muh-1404-6
[2] F. Haase, S. Lockwood & D.G. Ford,
Transactions on Engineering Sciences vol 34, ©
2001 WIT Press, www.witpress.com, ISSN 1743-
3533
[3] H. Akesson, T. Smirnova, L. H. akansson, T.
Lag¨o and I. ClaessonBlekinge Institute of
Technology Research Report No 2009:07 ISSN:
1103-1581, November, 2009.
[4] SiamakPedrammehr – Mehran Mahboubkhah –
Mohammad Reza Chalak Qazani3 – ArashRahmani
– SajjadPakzad.
[5] HuaizhongLi ,Xiubing Jing, and Jun Wang,
Sydney, NSW 2052, Australia 2 School of
050
100150200
FREQ
UEN
CY
(H
z)
Modes
COMPARISON OF FREQUENCY WITH DIFFERENT MATERIALS AND MODES
Mild steel
Cast iron
Granite
Concrete
VVRLS Gangadhar* et al ISSN: 2250-3676
[IJESAT] [International Journal of Engineering Science & Advanced Technology Volume-7, Issue-1, 080-092
IJESAT | Jan-Feb 2017 Available online @ http://www.ijesat.org
Mechanical Engineering, TianJin University,
China.
[6] K. Reza Kashyzadeh , Prof. Dr. M. J. Ostad-
Ahmad-Ghorabi, International Journal of Emerging
Technology and Advanced Engineering. Website:
www.ijetae.com (ISSN 2250-2459, Volume 2,
Issue 4, April 2012)
[7] B.V. Subrahmanyam, A. Srinivasa Rao, S.V.
Gopala Krishna, CH. Rama Krishna, Imperial
Journal of Interdisciplinary Research (IJIR) Vol-2,
Issue-12, 2016 ISSN: 2454-1362
http://www.onlinejournal.in