In this paper, a machine bed will be selected for the complete analysis for both static and dynamic loads. Then investigation is carried out to reduce the weight of the machine bed without deteriorating its structural rigidity and the accuracy of the machine tool by adding ribs at the suitable locations.

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International Journal of Research and Innovation (IJRI)
International Journal of Research and Innovation (IJRI)
GEOMETRIC OPTIMIZATION OF CNC VERTICAL MILLING
MACHINE BED
S.Ravi Kiran 1
, G Nagendra Krishna2
, Kandathil Abraham Mathew3
, Godi Subba Rao4
1 Research Scholar, Department of Mechanical Engineering, Hyderabad Institute of Technology and Management, Hyderabad, India
2 Assistant professor, Department of Mechanical Engineering, HyderabadInstituteOf Technology and Management,Hyderabad, India
3 Professor, Department of Mechanical Engineering, Hyderabad Institute of Technology and Management,Hyderabad, India.
4 Professor, Department of Mechanical Engineering, HyderabadInstitute of Technology and Management,Hyderabad, India
*Corresponding Author:
S.Ravi Kiran,
Research Scholar, Department of Mechanical Engineering,
Hyderabad Institute af Technology and Management,
Hyderabad, India
Published: July 04, 2015
Review Type: peer reviewed
Volume: II, Issue : IV
Citation: S.Ravi Kiran, Research Scholar (2015)
GEOMETRIC OPTIMIZATION OF CNC VERTICAL
MILLING MACHINE BED
INTRODUCTION
The machine bed plays a crucial role in providing the
strength and rigidity to a machine. It accommodates all
the accessories and cutting tools and other necessary
equipments for the running of the machine. It is subject-
ed to various static and dynamic forces during the ma-
chine operation. Its design is vital for the performance
and accuracy of the machine tool.
A milling machine is a machine tool used to machine solid
materials. Milling machines are often classed in two basic
forms, horizontal and vertical, which refer to the orienta-
tion of the main spindle. Both types range in size from
small, bench-mounted devices to room-sized machines.
Unlike a drill press, which holds the work piece stationary
as the drill moves axially to penetrate the material, mill-
ing machines also move the work piece radially against
the rotating milling cutter, which cuts on its sides as well
as its tip? Work piece and cutter movement are precise-
ly controlled to less than 0.001 in (0.025 mm), usually
by means of precision ground slides and lead screws or
analogous technology. Milling machines may be manually
operated, mechanically automated, or digitally automat-
ed via computer numerical control. Milling machines can
perform a vast number of operations, from simple (e.g.,
slot and keyway cutting, plaining, drilling) to complex
(e.g., contouring, die-sinking). is often pumped to the cut-
ting site to cool and lubricate the cut and to wash away
the resulting swarf.
Vertical milling machine. 1: milling cutter 2: spindle 3:
top slide or overarm 4: column 5: table 6: Y-axis slide 7:
knee 8: base
In the vertical mill the spindle axis is vertically oriented.
Milling cutters are held in the spindle and rotate on its
axis. The spindle can generally be extended (or the table
can be raised/lowered, giving the same effect), allowing
plunge cuts and drilling. There are two subcategories of
vertical mills: the bed mill and the turret mill.
Horizontal mill
Abstract
In this paper, a machine bed will be selected for the complete analysis for both static and dynamic loads. Then investiga-
tion is carried out to reduce the weight of the machine bed without deteriorating its structural rigidity and the accuracy
of the machine tool by adding ribs at the suitable locations.
In this work, the 3D CAD model for the base line and the optimized design has been created by using commercial 3D
modeling software PRO/Engineer. The analyses were carried out using ANSYS and Design Optimization is done with the
help of OptiStruct (FEM Based geometric modification). The results were shown with the help of graphs to analyze the
effect of weight reduction on the structural rigidity of the machine bed before and after the weight reduction and conclu-
sions were drawn about the optimized design.
Keywords: Structural rigidity, Design optimization, Dynamic Analysis
1401-1402

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International Journal of Research and Innovation (IJRI)
Horizontal milling machine. 1: base 2: column 3: knee 4
& 5: table (x-axis slide is integral) 6: overarm 7: arbor (at-
tached to spindle)
A horizontal mill has the same sort of x–y table, but the
cutters are mounted on a horizontal arbor (see Arbor mill-
ing) across the table. Many horizontal mills also feature a
built-in rotary table that allows milling at various angles;
this feature is called a universal table. While endmills and
the other types of tools available to a vertical mill may
be used in a horizontal mill, their real advantage lies in
arbor-mounted cutters, called side and face mills, which
have a cross section rather like a circular saw, but are
generally wider and smaller in diameter. Because the cut-
ters have good support from the arbor and have a larger
cross-sectional area than an end mill, quite heavy cuts
can be taken enabling rapid material removal rates. These
are used to mill grooves and slots. Plain mills are used
to shape flat surfaces. Several cutters may be ganged to-
gether on the arbor to mill a complex shape of slots and
planes. Special cutters can also cut grooves, bevels, ra-
dii, or indeed any section desired. These specialty cut-
ters tend to be expensive. Simplex mills have one spindle,
and duplex mills have two. It is also easier to cut gears
on a horizontal mill. Some horizontal milling machines
are equipped with a power-take-off provision on the table.
This allows the table feed to be synchronized to a rotary
fixture, enabling the milling of spiral features such as hy-
poid gears.
Variants
A miniature hobbyist mill plainly showing the basic parts
of a mill.
• Bed mill:
• Box mill or column mill:
• C-Frame mill:
• Floor mill:
• Gantry mill:
• Horizontal boring mill:
• Jig borer:
• Knee mill or knee-and-column mill
• Planer-style mill:
• Ram-type mill:
• Turret mill:
Computer numerical control
Thin wall milling of aluminum using a water based cut-
ting fluid on the milling cutter
Most CNC milling machines (also called machining cent-
ers) are computer controlled vertical mills with the ability
to move the spindle vertically along the Z-axis. This extra
degree of freedom permits their use in diesinking, engrav-
ing applications, and 2.5D surfaces such as relief sculp-
tures. When combined with the use of conical tools or a
ball nose cutter, it also significantly improves milling pre-
cision without impacting speed, providing a cost-efficient
alternative to most flat-surface hand-engraving work.
Five-axis machining center with rotating table and computer in-
terface
MODELING OF MACHINE BED
The above image shows milling machine base frame
The above image shows milling machine bed supports
The above image shows milling machine

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International Journal of Research and Innovation (IJRI)
The above image shows milling machine bed base view
The above image shows milling machine bed T slut cuts
The above image shows milling machine with bed assembly view
INTRODUCTION TO FEA
Finite Element Analysis (FEA) was first developed in 1943
by R. Courant, who utilized the Ritz method of numerical
analysis and minimization of variational calculus to ob-
tain approximate solutions to vibration systems. Shortly
thereafter, a paper published in 1956 by M. J. Turner,
R. W. Clough, H. C. Martin, and L. J. Topp established a
broader definition of numerical analysis. The paper cen-
tered on the "stiffness and deflection of complex struc-
tures".
FEA consists of a computer model of a material or de-
sign that is stressed and analyzed for specific results. It
is used in new product design, and existing product re-
finement. A company is able to verify a proposed design
will be able to perform to the client's specifications prior
to manufacturing or construction. Modifying an existing
product or structure is utilized to qualify the product or
structure for a new service condition. In case of structural
failure, FEA may be used to help determine the design
modifications to meet the new condition.
There are generally two types of analysis that are used
in industry: 2-D modeling, and 3-D modeling. While 2-D
modeling conserves simplicity and allows the analysis to
be run on a relatively normal computer, it tends to yield
less accurate results. 3-D modeling, however, produces
more accurate results while sacrificing the ability to run
on all but the fastest computers effectively. Within each of
these modeling schemes, the programmer can insert nu-
merous algorithms (functions) which may make the sys-
tem behave linearly or non-linearly. Linear systems are
far less complex and generally do not take into account
plastic deformation. Non-linear systems do account for
plastic deformation, and many also are capable of testing
a material all the way to fracture.
FEA uses a complex system of points called nodes which
make a grid called a mesh. This mesh is programmed to
contain the material and structural properties which de-
fine how the structure will react to certain loading condi-
tions. Nodes are assigned at a certain density throughout
the material depending on the anticipated stress levels of a
particular area. Regions which will receive large amounts
of stress usually have a higher node density than those
which experience little or no stress. Points of interest may
consist of: fracture point of previously tested material, fil-
lets, corners, complex detail, and high stress areas. The
mesh acts like a spider web in that from each node, there
extends a mesh element to each of the adjacent nodes.
This web of vectors is what carries the material properties
to the object, creating many elements.
STRUCTURAL ANALYSIS OF CNC VERTICAL MILLING
MACHINE BED WITH “T” SLOT
The above image shows imported model
The above image shows meshed model

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International Journal of Research and Innovation (IJRI)
BED MATERIAL: CAST-IRON
The above image shows total deformation
The above image shows stress
MODEL ANALYSIS OF CNC VERTICAL MILLING MA-
CHINE BED WITH “T” SLOT
The above image shows total deformation mode 1
The above image shows total deformation mode 2
FATIGUE ANALYSIS OF CNC VERTICAL MILLING MA-
CHINE BED WITH “T” SLOT
The above image shows life
STRUCTURAL ANALYSIS OF CNC VERTICAL MILLING
MACHINE BED WITH “T” SLOT
BED MATERIAL: S2-GLASS EPOXY
The above image shows total deformation

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International Journal of Research and Innovation (IJRI)
The above image shows stress
STRUCTURAL ANALYSIS OF CNC VERTICAL MILLING
MACHINE BED WITH “T” SLOT
BED MATERIAL: ZAMAK
The above image shows total deformation
The above image shows stress
STRUCTURAL ANALYSIS OF CNC VERTICAL MILLING
MACHINE WITH “DOVETAIL” SLOT
The above image shows “DOVETAIL” SLOT
BED MATERIAL: CAST IRON
The above image shows total deformation
The above image shows stress

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International Journal of Research and Innovation (IJRI)
STRUCTURAL ANALYSIS GRAPHS
The above image shows displacement graph
The above image shows stress graph
The above image shows strain graph
DYNAMIC ANALYSIS T- SLOT FOR S2 GLASS EPOXY
The above image shows T- slot Total deformation
The above image shows T- slot Stress
The above image shows T- slot Strain
DYNAMIC ANALYSIS “DOVETAIL” - SLOT FOR S2
GLASS EPOXY
The above image shows “DOVETAIL” - slot Total deformation
The above image shows “DOVETAIL” – slot Stress

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International Journal of Research and Innovation (IJRI)
Results table
STRUCTURAL ANALYSIS
“T” SLOT “DOVETAIL” SLOT
Total
defor-
mation
0.066494 0.02077 0.073073 0.065038 0.0207 0.071426
Stress 3.4113 4.0632 3.343 3.6862 4.3676 3.6138
Strain 4.382e-2 1.7647e-
5
4.9107e-
5
4.6479e-5 1.7646e-
5
5.2101
e-5
MODEL ANALYSIS
Total
defor-
mation
HZ
144.94 144.94 144.94 144.94 144.94 144.94
Total
defor-
mation
HZ
168.77 274.92 167.42 170.29 274.92 168.98
Total
defor-
mation
HZ
258.71 287.58 257.81 260.14 287.6 259.23
Total
defor-
mation
HZ
262.89 322.2 260.44 264.33 322.22 262.08
Total
defor-
mation
HZ
274.85 336.63 274.73 274.87 336.63 274.84
DYNAMIC ANALYSIS -“T” SLOT -- BED MATERIAL: S2-GLASS EPOXY
250HZ 500HZ 750HZ 1000HZ
Total defor-
mation
0.023288 0.068505 0.054208 0.021232
Stress 2.3258 17.613 28.121 10.472
Strain 2.5396e-5 9.0944e-5 7.938e-5 2.6878e-5
DYNAMIC ANALYSIS -“ DOVETAIL” SLOT -- BED MATERIAL: S2-GLASS EPOXY
250HZ 500HZ 750HZ 1000HZ
Total defor-
mation
0.023253 0.06915 0.058086 0.023151
Stress 2.3224 18.61 29.984 12.307
Strain 2.5344e-5 9.0381e-5 8.5479e-5 3.1111e-5
CONCLUSION
This project work deals with “GEOMETRIC OPTIMIZA-
TION OF VERTICAL CNC MACHINE BED USING FEM” to
reduce cost and weight
Bed is the main part in CNC machine which holds the
entire work piece weight in moving condition. Machine is
consuming more power to move bed along with parts, so
this is an attempt to reduce the bed weight without reduc-
ing its strength and capacity.
Initially literature survey and data collection was done to
understand methodology.
Parametric models of CNC machine parts are prepared
and assembly is made using prepared parts and convert-
ed into IGES file to transfer into Ansys.
Structural and model analysis is conducted to find stress
concentration locations, structural behavior according to
the material & natural frequency values.
Dynamic analysis is conducted to evaluate results in load
and vibration conditions.
As per the analysis results S-2 glass bed with T-slots is
showing good strength than previous models also by us-
ing S-2 glass weight of the bed can be reduced up to 65%
so better to use bed with T-slot with S-2 glass material.
References
1.Performance Analysis of Vertical Machining Center through
Process Capability
2.A Study on Design and Manufacturing for the Side Wall of
Large CNC Portal Milling Machine
3.Structural Redesigning Of A Cnc Lathe Bedimprove Its Static
And Dynamic Characteristics
4.Design And Structural Analysis Of Cnc Vertical Milling Ma-
chine Bed
5.Implementation of neural network for monitoring and predic-
tion of surface roughness in a virtual end milling process of a
CNC vertical milling machine
6.Optimization of Input Process Parameters in CNC Milling Ma-
chine of EN24 Steel
7.Design Optimization of Machining Fixture for the Slant Bed
CNC Lathe
author
S.Ravi Kiran
Research Scholar,
Department Of Mechanical Engineering,
HyderabadInstituteOf Technology And Management,
Hyderabad,India
G Nagendra Krishna
Assistant professor
Department of Mechanical Engineering,
HyderabadInstitute of Technology and Management,
Hyderabad,India
Kandathil Abraham Mathew,
Professor, Department of Mechanical Engineering,
Hyderabad Institute of Technology and Management,
Hyderabad,India
Godi Subba Rao, (HOD)
Professor,Department of Mechanical Engineering,
Hyderabad Institute of Technology and Management,
Hyderabad, India