International Journal of Engineering Trends and Technology (IJETT) – Volume 24 Number 5- June 2015
Enhancement of Machine Utilization by Using Digital
Manufacturing
Putta Priyanka¹ Dr. G. Amarendar Rao²
Department of Mechanical Engineering
VBIT, Hyderabad, Telangana, INDIA
ABSTRACT
Digital manufacturing or virtual
machining Tool Kit will be a one stop
solution right from operation creation, post
process to NC validation with real time
Machine simulation. Digital manufacturing is
an off-line tool for detailed analysis and
optimization of NC programs. Depending on
the batch size (job-shop or large-volume),
reduction of setup times or shortening of cycle
times are two major benefits. Digital
manufacturing enables the user to identify and
realize potential savings in machining
processes at an early stage. In Digital
manufacturing any NC program can be
validated and optimized according to the
requirement. This optimization results in
reduction of setup time, manufacturing cost,
collision detection and finally increases
machine utilization.
In this project to validate virtual machine,
steering knuckle is taken as case study.
In automotive suspension, a steering knuckle
is that part which contains the wheel hub or
spindle, and attaches to the suspension
components.
In manufacturing environment before
development of digital manufacturing
operators used to generate NC program
manually or by using postprocessors, this
generated NC program is fed to machine
directly or through DNC (direct numerical
control) lines for CNC machines. The
generated NC program using postprocessor or
by manually result in dimensional error of
component, collision of part and spindle, tool
and work table or spindle and worktable.
Collisions leads to breakage of component or
tool sometimes results badly as damage to
machine. The generated NC program will be
edited manually to obtain component as
customer required and trails are also done for
modified NC program to find whether this
modified NC program will produce the
component as customer requirement. There
are some collisions due to error in NC
program or by considering wrong tools.
Below images shows spindle-part collision
due to length of the tool and tool-part
collision. Tool breaks the part and damages
due to error in NC program.
Aim of the project is to develop virtual
machine of DMG 5-axis using NX software
and validate machine by taking steering
knuckle component as case study.
Keywords:
Digital Manufacturing, 5-axis
milling machine, steering knuckle, Machine
tool builder, UNIGRAPHICS.
I.
Fig1. collision of spindle and part
INTRODUCTION
Manufacturing
Process
before
Development of Digital Manufacturing:
Fig 2. Breakage of work piece
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To avoid this collisions digital manufacturing
process is developed to check the generated
NC program before fed to machine. The
complete manufacturing process is examined
in digital manufacturing process and
collisions are detected and modifications in
NC program are done. Finally modified NC
program is given to machine these results in
reduction of manufacturing errors.
Fig.3 Final Assembly of DMG 5 axis CNC milling machine
II. METHODOLOGY
Virtual Machine Tool Kit will be a one
stop solution right from operation creation,
post process to NC validation with real time
Machine simulation.
VIRTUAL KIT is an off-line tool for
detailed analysis and optimization of NC
programs. Depending on the batch size (jobshop or large-volume), reduction of setup
times or shortening of cycle times are two
major benefits. VIRTUAL KIT enables the
user to identify and realize potential savings
in machining processes at an early stage.
PROCESS TO SET UP AN ISV SCENARIO
RUNNING TOGETHER WITH
DMG_MILL_5AX
Building a directory for the machine tool
resources
NX has 2 places (directories) for storing the
machine tool data: One for the resources
(geometries, Post Processor files etc.) and
another one for the ready-to-use machines
including kinematics structure and other
settings. We will build the machine model in
the resources and will copy it later into the
other directory. By default the resource
directory is located in the installation
directory of UG NX, such as
…..\NX
7.5\MACH\resource\library\machine\instal
led_machines
Create a new folder in the installed_machines
library and name it DMG_mill_ 5ax Create a
subdirectory called graphics and another
subdirectory named postprocessor so that the
structure looks like this:
3D MODELING OF VIRTUAL KIT
Fig4. List of all geometry part file of the
DMG_mill_ 5ax
My project deals with the virtual machining of
5-axis DMG milling machine
The related cse_driver folder needs to be
copied from one of the existing installed
machine tools. Copy all geometry part files
into the \graphics subdirectory
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The location of the geometry files is assigned
in the machine database later on. We will
define a directory name which clearly
identifies the machine tool (DMG_mill_ 5ax).
Kinematics to the Geometric Model
Now that we have built up the geometric
structure of the model we have to define in
which way the different components of the
machine will move later on when we are
going to simulate the machining process.
Basically the kinematics definition procedure
can be split in 4 areas:
 Definition of kinematics components
(k-components)
which
are
placeholders for further kinematics
information. K-components are nodes
in the kinematics tree

Definition of junctions for the kcomponent. A junction or coordinate
system defines the location and
orientation of all components
referring to that coordinate system.
By way of example the junction of the
fixture defines how the cam part is
mounted.

Selection of axes for determining the
moving direction of the k-component.
Axes can be regarded as one of the
properties of k-components. Axes are
selected according to the respective
junctions.

Classification of k-components. By
assigning classes for the components
a proper handling of the collision
calculation and other information will
be achieved later. Let’s build the
kinematics for the current example:
Select menu Start → All
Applications → Machine Tool Builder
Open the Machine Tool Navigator, click twice
on the item NONAME and change the name
to "DMG_mill_ 5ax"
Highlight this name and open the context
menu by clicking with the right mouse
button.
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Select Insert → Machine
Base Component
In the Create K-component Dialog, press
Add to add the geometry. Select the geometry
of the machine (BED) directly in the graphics
window. Use the Class selection dialog to
apply the classification “MACHINE_BASE"
Below image shows getting in to machine
tool builder
Fig.5. Getting in to machine tool builder
 Next step is to add a junction with a
specified name. This will be the basic
junction for further handling of
components in the machine model.
 Select the item MACHINE_BASE,
click the right mouse button and
select →Junctions →Add.
 Enter
the
designation
“MACHINE_ZERO” as name.
 Leave the dialog open and define a
coordinate system. In the current case
the zero coordinate system is located
at the intersection of the vertical axis
of the B_rotary table and the
horizontal axis of the fixture (part
holder). For the orientation it is a rule
that the Z-axis is always pointing
towards the tool. In principle the
orientation of the X and Y axis are
arbitrary but you should always
contact
the
machine
tool
documentation for the exact definition
for orientation and position of the
machine zero.
 Change the selection scope to “Entire
Assembly” if not already done. This
makes sure that you can select all
components inside the graphics.
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 Measure the distance between the
centre of the B_ROTARY component
and the centre of the C-axis_Rotary
(refer to the assembly navigator).
 Activate the information window
when the measurement is done.
(Results Display→Show Information)
Read the Delta in Z-direction which is
85 mm.
 Place the coordinate system at the
centre of the fixture, then make an
adjustment of 85 mm in z-direction.
Be sure that Z is pointing towards the
tool (away from the fixture)
 Select OK to complete the junction
definition.
Below image shows creating junction to
machine base component
Fig. 6. creating junction to machine base
component
Below image shows display of the machine
zero junction and classification of the
machine zero junction
“Classify”. Select “Machine Zero” as
classification.
 The next task is the definition of
further k-components for building the
kinematics chain. Be sure to keep in
mind the two major rules for
kinematics definition:
 Every component or assembly that
can move has to be a separate
kinematics component
If the component or assembly which you are
defining is itself mounted on another
moveable component / assembly then the
latter one has to precede the first one in the
kinematics chain. If you click on the
respective components in the assembly
navigator you can identify the machine
components.
MACHINE
CONFIGURATION
MOVEMENT
AXIS LIMITS
1. X SPINDLE
X = 880 to -220
2. Y SPINDLE
Y = 630 to 0
3. Z TABLE
Z = 0 to -630
4. B SPINDLE
B = +30 to -120
5. C TABLE
C = 360deg
FINAL KINEMATIC MACHINE MODEL:
This is the required CNC machine model with
kinematics given to x-slide ,y-slide, table
rotary and spindle.
Fig7. Display of the machine zero junction and
Classification of the machine zero junction
 With the Junction definition dialog
still open highlight the item
MACHINE_ZERO
and
click
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Fig.8. Final Kinematic Machine Model
Adding the Machine To Machine Database:
Machine data base file is located in
…\ProgramFiles\UGS\NX7.5\MACH\
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resource\library\machine\ascii\
machine_database.dat
Fig.11. postprocessor input window
Fig.9. machine data base file
III. POST PROCESSOR:
For every CNC machine there will be a
specified post processor to generate NC
program. Postprocessor is created using post
builder application.
Process to open post builder
Start
all programs
UGS NX7.5
manufacturing tools
post builder
File
new postprocessor
specify
name of the processor going to create and
specify all required data.
Fig.10. creating new postprocessor
The below image shows generated Post
processor of DMG_mill_5ax.
Specify all required machine specifications to
generated postprocessor for virtual kit
DMG_mill_5ax.
3 Post processor files will be generated as def,
tcl, pui
DMG_mill_5ax.PUI: Post User Interface file
(.pui) used by post builder to edit the event
handler (.tcl) and definition files (.def).This
file contains static information on how to
write out the .tcl file.
DMG_mill_5ax.TCL:
Tool
Command
Language or Event handler (.tcl) contains a
set of instructions dictating how each event
type is to be processed. Post also uses this file
at run time to generate NC code.
DMG_mill_5ax.DEF: Definition file (.def)
This file defines all the static information for
the postprocessor. This includes formats,
address and NC blocks. This file is used by
Post to postprocess the tool path and generate
NC code.
DMG_mill_5ax.CDL: User defined events
and machine control events are how NX sends
messages to the postprocessor that are outside
of the normal tool path messages. this would
be a message to turn on high pressure coolant
or unclamp a rotary axis. These events are
added to a program using the User Defined
Events.
The below image shows Post processor files
of DMG_mill_5ax.
Fig.12. Post processor files of DMG_mill_5ax
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This generated file should be pasted in
DMG_mill_5ax postprocessor which is
located in C folder installed machines. Along
these 3files another .cdl file is generated,
paste .cdl file in user_def_event.
3d Model of Steering Knuckle
The below image shows installed machine
folder.
Fig.15 final 3D model of Steering Knuckle
COMPUTER AIDED MANUFACTURING
(CAM)
Fig.13. installed machine folder
The below image shows user_def_event
folder.
Along these 3files another .cdl file is
generated, paste .cdl file in user_def_event.
The generation of tool path on 3D model of
Steering knuckle will be done using NXCAM software. By generating tool path NC
program will be generated. This NC program
is given input to the CNC machine to run
operations.
The main objective of the project is to obtain
to reduce machining errors and collision of
tools and rotary table by developing virtual
kit.
Methodology
knuckle


Fig.14. user_def_event folder
This post process files helps virtual machine
to run according to generated NC program
and shows exact simulation of machine.
Errors and collisions can be detected while
simulation of virtual machine is going on, NC
program will be edited to remove collisions
and errors according to the simulation of tools
and part.





of
manufacturing
Steering
Identify suitable machine.
Selecting
suitable
tools
for
manufacturing
Steering
knuckle
component.
Selection of fixture.
Listing down the Sequence of
operation performed on Steering
knuckle component.
Generating tool path at specified
cutting speed.
Retrieving virtual machine in NXCAM and simulating machine.
Verification of machining process in
virtual machine simulation.
Generating NC program using NX-CAM
software.
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SEQUENCE OF OPERATIONS
PERFORMED ON STEERING KNUKCLE
DRILLING_
Drilling
TOOL
Tool
DRILLING_
Drilling
TOOL_D
Tool
DRILLING_
Drilling
7.5000
118.0 35.00
000
00
 Setup_1
Face milling
3.0000
118.0 35.00
000
00
Planar milling
Fixed contour
TOOL_D3.58 Tool
3.5800
118.0 35.00
000
00
Spot drilling
Drilling
DRILLING_
Drilling
TOOL_D2
Tool
DRILLING_
Drilling
TOOL_D2.1
Tool
DRILLING_
Drilling
2.0000
118.0 35.00
000
00
 Setup_2
Face milling
2.1200
118.0 35.00
000
00
Planar milling
Spot drilling
TOOL_D1.22 Tool
1.2200
118.0 35.00
000
00
Drilling
DRILLING_
Drilling
TOOL_D3
Tool
DRILLING_
Drilling
TOOL_1
Tool
DRILLING_
Drilling
TOOL_2
Tool
3.0000
7.5000
3.0000
118.0 35.00
000
00
118.0 35.00
000
00
118.0 35.00
000
00
MILLING TOOLS
Fig.16 Final cam part
TOOL
NAME
DESCRIP
TION
DIAMETER
COR
FLUTE
RAD
LEN
TOOLING LIST
MILL
DRILLING TOOLS
TOOL
DESCRIPT DIAME TIP
NAME
ION
SPOTDRILLI Drilling
NG_TOOL
Tool
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TER
2.0000
ANG
FLUT
MILL_1
E
Tool
Milling
Tool
20.0000
0.0000 50.0000
20.0000
0.0000 50.0000
3.6000
0.0000 50.0000
LEN
120.0 35.00
000
Milling
MILL_2
Milling
Tool
00
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BALL_
MILL
MILL_3
MILL_4
MILL_5
MILL_6
MILL_7
MILL_8
MILL_9
MILL_10
MILL_11
MILL_12
MILL_D4
MILL_13
MILL_14
Milling
Tool
Tool-Ball 3.4000
1.7000 50.0000
Mill
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
Tool
Milling
MILL_15
4.0000
0.0000 50.0000
MILL_16
3.0000
0.0000 50.0000
MILL_17
12.0000
0.0000 50.0000
10.0000
0.0000 50.0000
3.0000
0.0000 50.0000
8.0000
0.0000 50.0000
5.0000
0.0000 50.0000
2.4000
0.0000 50.0000
4.0000
0.0000 50.0000
Milling
Tool
Milling
Tool
Milling
Tool
3.0000
0.0000 50.0000
2.4000
0.0000 50.0000
4.0000
0.0000 50.0000
Integrated Simulation Verification process
Fig 17. Dialog to load objects like machine tool,
tool or devices from the library
6.0000
0.0000 50.0000
4.0000
0.0000 50.0000
10.0000
0.0000 50.0000
2.0000
0.0000 50.0000
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Creating the machining scenario For building
a complete simulation scenario where the
machine is simulated it is expected that a
CAM part which already has some operations
defined so that the tool path can be generated.
Furthermore this method requires that the
machine is a member of the machine tool
library, this is true for our sample. Open the
CAM sample part in NX. It is called
cam_sample.prt and has some common parts
in a subdirectory.
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Time taken to manufacture steering knuckle
Below image shows only machining time of steering knuckle with defined speed and feed
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Tool used before collision
Simulation verification
Tool used after collision detection
Fig. 18 Simulation verification to check the errors
developed while machining the component
Collision of spindle and fixture when spindle is
tilted to 90 deg for milling operation
Fig.19 Simulation verification
Again the same operation is verified to check
whether collision is occurs with new tool.
Remedy for collision is to increase tool
length.
Flute length and total length of the tool is
increased to overcome collision of spindle and
fixture
Fig.20. No collision observed with new tool
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Collision occurred between spindle house and
rotating work table while doing fixed contour
operation.
Below image shows the fixture used after
collision detection to avoid the collision
between spindle house and work table
Fig.21 Collision occurred between spindle house
and rotating work table
Remedy to overcome from this collision is to
increase the fixture height.
Below image shows the fixture used before
collision
Fig.23. 2D input and 3D model of new fixture
Fig.24. Remedy to overcome from this
collision is to increase the fixture height
Machine vice is fixed on the work table along
with fixture and raw material of steering
knuckle to increase the height of fixture.
Fig.22. 2D input and 3D model of fixture
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Manufacturing time of steering knuckle after virtual simulation verification
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SET UP
Product cost reduction, Reduction of
setup times
Milling&drill
ing operations
TIME
REQUIR
ED IN
MINS.
Manufacturing component on CNC machine
without virtual simulation
Milling
279
RS.1000/HR
RS.4650
Drilling
3
RS.800/HR
RS.40
TOTAL
282
IV. RESULTS
The component directly machined on the
CNC machine with trial and error and after
each operation machine will be stopped and
inspection will be done this increases
manufacturing time of the part and as well as
increases cost and reduces machine
utilization.
Time and cost calculation for manufacturing
steering knuckle as shown below including
setup time and manual modification of NC
program on CNC machine.
Manufacturing time taken
component= 4hrs 42min
by
single
Machining cost per
operations = 1000rs
hour
for
milling
Machining cost per
operations = 800rs
hour
for
drilling
Machining cost per piece for milling
operations (machining cost per min x
machining time in min) = 1000/60*279 min=
4650 rs
Machining cost per piece for drilling
operations (machining cost per min x
machining time in min) = 800/60*3 min= 40
rs
Total machining cost per piece= milling +
drilling= 4650 + 40 = 4690 rs
Table 1: time and machining cost of
MACHINING
COST
MACHINING
COST/PIECE
PER HOUR
RS.4690
Manufacturing component on
machine with virtual simulation
CNC
There is no time waste for trial and error
operations on machine and time consumption
will be less because every operation is
virtually verified and modification will be
done in software itself. Speed and feed is
increased along depth of cut to reduce
machining time. Increased parameters are
verified using virtual simulation.
This
reduces setup time and product cost.
Manufacturing time taken by single
component= 3hrs 9min
Machining cost per
operations = 1000rs
hour
for
milling
Machining cost per
operations = 800rs
hour
for
drilling
Machining cost per piece for milling
operations (machining cost per min x
machining time in min) = 1000/60* 186min=
3100 rs
Machining cost per piece for drilling
operations (machining cost per min x
machining time in min) = 800/60* 3min= 40
rs
Total machining cost per piece= milling +
drilling= 3100+40 = 3140 rs
operation without VMS
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Table 2: time and machining cost of operation
with VMS
SET UP
Milling&dri
lling
operations
Milling
TIME
REQUI
RED IN
MINS.
MACHIN
ING
COST
MACHIN
ING
COST/PI
ECE
186
RS.1000/
HR
RS.3100
RS.800/H
R
RS.40
Drilling
3
TOTAL
189
5000
4000
3000
2000
1000
0
which reduces machine idle time and
increases machine utilization.
Table 3: cycle time with and without VMS
NO.OF
PARTS
cycle
time(hrs)
without VMS
cycle time(hrs)
with VMS
50
235
157.5
100
470
315
150
705
472.5
200
940
630
250
1175
787.5
300
1410
945
350
1645
1102.5
400
1880
1260
RS. 3140
4690
3140
282
189
without virtual
simulation
TIME (min)
with virtual
simulation
VMS = virtual machining simulation
COST (rs)
Optimization of cycle times
GRAPH
2000
Manufacturing time taken by single part in
mins = 282mins
Cycle time (hrs) with VMS= no.of parts x
manufacturing time taken by single part in
hrs.
Manufacturing time taken by single part in
mins = 189mins
1800
1600
cycle time in hrs
Optimization of cycle times
Cycle time (hrs) without VMS= no.of parts x
manufacturing time taken by single part in
hrs.
1400
1200
1000
cycle time(hrs)
with out VMS
800
cycle time(hrs)
with VMS
600
400
200
0
50
150 250 350
no.of parts
Cycle time is optimized by using virtual
simulation. In virtual simulation complete
manufacturing process can be checked and
verified in offline if any modification in NC
program will be edited in software itself
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Increase in machine utilization
The values are directly taken when
component is manufacturing on the machine
without virtual simulation. First component
on CNC machine is run in block mode, means
component is inspected after every operation
by stopping machine. At that time machine is
idle which decreases machine utilization.
Table 4: machine utilization with and without
VMS
Single
part
Machine
Machine
manufacturing
utilization
utilization with
time
without
VMS
VMS (min)
(min)
Total time
Machine
cutting
4hrs 42min
3hrs 9min
3hrs 28min
2hrs 48min
1hr 14min
21min
time
Machine idle time
Total manufacturing time is reduced by 33%
Machine idle time and machine utilization
time are inversely proportional. When idle
time is reduces then machine utilization time
will increases.
Machine utilization is increased by 71%
V.
CONCLUSION
By developing virtual machine, spindle house
and work table collision is detected, spindle
and fixture collision is detected. Remedy for
this collisions is done in software itself by
increasing tool length and changing fixture.
Manufacturing time taken for steering knuckle
without virtual simulation verification and
with virtual simulation verification is shown
in results by plotting graphs as well as
optimization of cycle time and machine
utilization also shown in results. Finally
concluding using virtual simulation process
will benefits small scale and large scale
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industries investment for this process is very
less and results in more profits for industries.
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