DOI: 10.23883/IJRTER.2017.3455.RCZ5M 74
Accuracy Improvement through CNC Machining in Step Turning
Process by changing Tool Bit specifications
Shivam Paneri1, Vishal Kumar2, Sonu Yadav3, Dr. Dipak Ranjan Jana4
Department of Mechanical Engineering, Poornima College of Engineering, Jaipur
Abstract:-For achieving greater accuracy of a product is much important for productivity improvements
In this study we have used CCMT Tool bit ,a sand wick product instead of HSS tool bit, mini Tool bit
has been used in the CNC Machining process for step turning operation, where not only the product
accuracy but also product quality in terms of low cost has been achieved .Hence the process
improvements in terms of accuracy has been shown with the help of SQC Chart which has been plotted
in the graph and from the received data which has been shown remarkable achievements in terms of
accuracy and quality when root causes of the problem have been found out through Pareto followed by
Ishikawa Analysis with taking corrective actions.
Keywords- Accuracy, Productivity, Step Turning, CNC machining, Feed, CAD, CAM.
I. INTRODUCTION Production may be defined as converting input to output where raw materials are processed in different
stages of operation in-turn produces finished or semi-finished products. Productivity is the ratio between
output and input. Poor quality of the product is due to improper raw material, inadequate knowledge of
the operator, machine problem or process synchronisation problem. Product quality also depend upon
not only those factors indirectly it produces horrible resource eaters such as waste, warranty cost,
misprocess fall out, lengthy development of cycles, excess inventory in terms of buffer stock,
engineering drawing or design changes which occurs after product launches as well as different
recurring problems. Addressing above those points is the resource eater will translate to cost reduction
thereby, improve profits. Thus, improving accuracy in-turn improves productivity also.
Productivity = Output/Input
where, Input is in term of man, material, machine, method and maintaining proper environment.
Fig.1 Tools of Accuracy Improvements
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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II. COMPUTER AIDED DESIGN
CAD or computer aided design, involve computer model design by the geometrical parameter. These
models typically appear on computer monitor as a (3D) representation of a path which can be really
allied by changing relevant parameter (CAD) system design to view object under a wide variety of
representation and to test their object by simulating real World condition. CAD is 2D wire frame
package. That used to create engineering drawing the 3D parameter feature based modelling component.
Form is created using freedom surface modelling, solid modelling or hybrid of two.
These in the detailed component are then assembled in to a 3D representation of the final product is
called bottom-up-designs the assembly model. Can be used to perform analysis to antic if the component
can be assembling and fit together as well as for simulating the dynamic at the product.
Line element analysis can also performed on the component and assembled to their strength in 3D model
are used to generated a 2D technical drawing and this has been directly transfer the data to CAM, CNC.
Rapid prototype product visualisation system is the non-geometric information being communicated to
downstream with the air CAD/CAM.
CAD tools can be defined as the intersection of three sets – Geometric modelling, Computer graphics
and design tools. The main functions that would utilize the computer are:
Pre-planning, planning and designing
Component modeling
Assembly modeling and simulation
Engineering drawings and designs
III. COMPUTER AIDED MANUFACTURING Computer aided manufacturing is the process of manufacturing a particular product with the help of
computer. During the drawing of a design of a particular product and this computer language again
doing machine interface to a machine language by which through a numerically control machine does
various operations, such as turning, milling, grinding and boring operations being carried out. Hence
initially program instruction being given to machine control unit (MCU) and through this machine unit
again the program goes to tools for manufacturing of the product.
Fig.2 CNC Processing
a) G-codes
G-code is a language in which people tell computerized machine tools how to make something. The
"how" is defined by instructions on where to move, how fast to move, and what path to move. The most
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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common situation is that, within a machine tool, a cutting tool moved according to these instructions
through a tool path and cuts away material to leave only the finished work piece.
COMMON G CODES (GEOMETRIC CODING)
G00 - Positioning at rapid speed; Mill and Lathe
G01 - Linear interpolation (machining a straight line); Mill and Lathe
G02 - Circular interpolation clockwise (machining arcs); Mill and Lathe
G03 - Circular interpolation, counter clockwise; Mill and Lathe
G04 - Mill and Lathe, Dwell
G09 - Mill and Lathe, Exact stop
G10 - Setting offsets in the program; Mill and Lathe
G12 - Circular pocket milling, clockwise; Mill
G13 - Circular pocket milling, counterclockwise; Mill
G17 - X-Y plane for arc machining; Mill and Lathe with live tooling
G18 - Z-X plane for arc machining; Mill and Lathe with live tooling
G19 - Z-Y plane for arc machining; Mill and Lathe with live tooling
G20 - Inch units; Mill and Lathe
G21 - Metric units; Mill and Lathe
G31 - Skip function; Mill and Lathe
G33 - Thread cutting; Mill
G50 - Set coordinate system and maximum RPM; Lathe
G71 - Rough turning cycle
G72 - Rough facing cycle
G81 – Drill cycle; Mill and Lathe
G90- absolute programming
G91- incremental programming
b) M-codes
M-codes (general codes) actually operate some controls on the machine tool and thus affect the running
of the only one m code is supposed to be given in a single block. However some controllers allow or two
or more m codes to be given in a block, provided these are not mutually exclusive, e.g., coolant on and
off cannot be given in one block.
COMMON M CODES (MISCELLOUS CODING)
M00 - Program stop; Mill and Lathe
M01 - Optional program stop; Lathe and Mill
M02 - Program end; Lathe and Mill
M03 - Spindle on clockwise; Lathe and Mill
M04 - Spindle on counterclockwise; Lathe and Mill
M05 - Spindle off; Lathe and Mill
M06 - Tool change; Mill
M08 - Coolant on; Lathe and Mill
M09 - Coolant off; Lathe and Mill
M10 - Chuck or rotary table clamp; Lathe and Mill
M11 - Chuck or rotary table clamp off; Lathe and Mill
M19 - Orient Spindle; Lathe and Mill
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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M30 - Program end, return to start; Lathe and Mill
M97- Local sub-routine call; Lathe and Mill
M98 - Sub-program call; Lathe and Mill
M99 – End of sub program; Lathe and Mill
IV. SPEED AND FEED The speeds and feeds are two separate velocities in machine tool practice, cutting speed and feed rate.
They considerably act as a pair because of their combined effect on the cutting process.
Speed and feed goes hand in hand. The relation between speed and feed is such that on increasing speed,
feed decreases and vice-versa.
Speed = (D*π*N)/12 (ft/min)
For more accurate calculations:-
Speed = (D *π*N)/60 (mm/s)
Tool Life Expectancy:-
The Taylor's Equation for Tool Life Expectancy provides a good approximation.
Vc Tn= C
A more general form of the equation is
Vc Tn × Dx Fy = C
Where
Vc= cutting speed
T=tool life
D=depth of cut
F=feed rate
Experimentally n, x, y and C are constants
V. STATISTICAL PROCESS CONTROL AND STATISTICAL QUALITY CONTROL (SPC
& SQC)
A. SPC:- In the industrial process Statistical Process Control (SPC) has been defined as, it is an early warning
signal by which it enable us to determine the defects in ongoing production and to provide the remedy
for improvements.
B. SQC:-
Statistical Quality Control (SQC) is an industrial management technique by which an uniform and
acceptable products have been produced. Hence, we find out the quality characteristics with the help of
statistical quality control chart, one of the best tool invented by Dr. Walter A. Shewhart in Bell Lab. In
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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SQC chart three horizontal lines are been drawn over the graph known as Upper Specification
Limit(USL), Specification Limit(SL) and Lower Specification Limit(LSL) as shown in fig. 3.
Fig.3 Statistical Quality Control(SQC) Chart
Where, X-axis: Numbers of Observations
Y-axis: Quality Characteristics
VI. STEP TURNING OPERATION WITH HSS TOOL BIT
Fig.4 Job drawing for step turning operation with all dimensions in mm.
MATERIAL USED:- Copper
A. Data Collection:-
For step turning operation using HSS Tool bit the data has been collected digital micrometer whose least
count is 0.01mm made out of MITUTOYO. And the data has been shown in Table:-1.
Table:-1. Data Obtained Using HSS Tool Bit
Dimensions with Specifications:- Obtained Data:-
(mm)
Sample No. 1 Sample No. 2 Sample No. 3 Sample No. 4 Sample No. 5
ᶲ25±0.5mm 25.2 24.4 24.8 25.0 25.4
ᶲ20±0.5mm 20.1 20.3 19.8 19.5 20.1
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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B. Plotting the Data in SQC Charts:-
Fig.5 SQC Chart for Dimensions with Specification: ᶲ25±0.5mm processed using HSS Tool bit
Fig.6 SQC Chart for Dimensions with Specification: ᶲ20±0.5mm processed using HSS Tool bit
Fig.7 SQC Chart for Dimensions with Specification: ᶲ15±0.5mm processed using HSS Tool bit
24
24.5
25
25.5
25.2 24.4 24.8 25 25.4
ᶲ25±0.5mm
ᶲ25±0.5mm
19
19.5
20
20.5
20.1 20.3 19.8 19.5 20.1
ᶲ20±0.5mm
ᶲ20±0.5mm
14
14.5
15
15.5
14.9 14.5 15.1 15.4 14.8
ᶲ15±0.5mm
ᶲ15±0.5mm
ᶲ15±0.5mm 14.9 14.5 15.1 15.4 14.8
ᶲ5±0.5mm 4.4 4.6 4.3 5.0 5.1
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Fig.8 SQC Chart for Dimensions with Specification: ᶲ5±0.5mm processed using HSS Tool bit
NOTE:- For Fig.5-8 Row 1-(USL), Row 2-(SL), Row 3-(LSL)
Fig.9 Work-piece, so obtained after machining.
VII. OBSERVATION FROM ALL THE SQC CHART While working with HSS Tool bit there is wide variation in dimensions observe. While taking
measurements which has been plotted in above figures(Fig. 5-8). Hence, we couldn’t get adequate
accuracy in this process.
VIII. MEASURE TO BE TAKEN FOR IMPROVEMENT On this work at first we have define the problem and measure the problem with help of statistical tool.
There after problem have been analyse with the help of Pareto and Cause-effect analysis and remarkable
improvement has been achieved for the betterment of the product.
4
4.5
5
5.5
4.4 4.6 4.3 5 5.1
ᶲ5±0.5mm
ᶲ5±0.5mm
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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A. Problems Findings: -
Problems have been investigated through Pareto analysis (vital few from trivial many) followed by
Cause and Effect analysis which is shown in the fig. 10 & 11 in the histogram and Ishikawa Analysis.
In the Ishikawa Analysis we could find out vital problem lies in the machines such as machine vibration,
tool alignments, machine bed inclination, Backlash of gear etc.
Fig.10 Percentage distribution of problems causing Inaccuracy (Pareto Analysis)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
Pareto Analysis
Machine
Operator
Environment
Others
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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Fig.11 Cause and effect analysis (Fish bone & Ishikawa diagram)
IX. IMPROVEMENT TO BE IMPLEMENTED
Implementation of TPM to the machine for taking corrective actions:-
1. For the removal of machine problem following rectification have been carried out:-
•Machine Leveling checks with the help of sprit level and straight edge for longitudinal and vertical
axis.
• Bed inclination check with the help of angle dekkor and Laser Alignment.
• Topping up of lubricants with proper specifications.
• Check all the gear for its backlash with the help of Parkinson gear tester and filler gauge after
cleaning with Non-Lead Gasoline.
• Check for proper coolant used in machine process with 1:20 ratio, servo cut-s : water.
2. Check for tool for tool setting angle with respect to job with tool pre-setter.
Hence, we want to get the product with greater accuracy then we have to look into following criteria
also:-
Correct raw materials with proper specifications which we can clarify from incoming material
inspection.
Setting the sequence of operation with the help of work study (motion and time study) with proper
routing and scheduling.
Failure
Accuracy
Environment
Operator
Materials
Machine
Gear Backlash
to end
Centre alignment end
Machine Vibration
alignment
Machine bed
Procurement
Devices quality
Interferers
Fatigue
Motivation
Training
Dust Particles
Humidity
Temperature
Noise
Cause and Effect Analysis
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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Use of precession machine and tools say sophisticated measuring instrument whose least count is
better (instruments should be calibrated one).
Machine should be fully serviceable including no vibration should be allowed as well as should
have proper levelling and this can be done with the help of vibro meter and sprit level.
Copper material should be maintained as per the required specification.
Ensure no backlash in the machines gear elements and no other gear defects such as pitch, profile,
teeth to teeth composite error, run out etc.
NOTE:-
i. If the specification of the material is not known the heat treatment process will be affected as a
result the defects of the products will occur at the end.
ii. Ensuring System design, Parameter design and design margin while doing production process.
Measure to be taken as follows before manufacturing process:-
• Material selection as per the required specification.
• Proper Speed and feed calculation with different depth of cut.
• Sequence of operation as per scheduling.
• Check the tool to tool setting angle with respect to the job with the help of tool pre-setter.
• Use of sophisticated measuring appliance such as Digital micrometer and V.C. (Vernier callipers of
L.C. 0.01 mm)
• Atmospheric condition of the workshop shall be maintained as follows:
I. Temperature should be maintaining 68◦F.
II. Humidity should be maintaining 50% of the relative humidity.
III. Dust particles should not increase more than 3.3*105 m3 /unit area.
• Drawing dimensions should be clearly indicating the accuracy of the product.
X. STEP TURNING OPERATION IN CNC MACHINE AFTER IMPROVEMENTS WITH
CCMT TOOL BIT
Table:-2. Planning and operations sheet
Table:-3. Tool offset sheet
Sr
NO.
OPERATION TOOL HOLDER TOOL TIP TOOL
STATION
NO
TOOL
OFFSETS
NO
SPINDLE
SPEED
(RMS)
FEED
(mm/min.)
1 Multiple
Rough Facing
SDJCR1212H11 CCMT11T304 1 1 1000 50
2 Finishing SDJCR1212H11 CCMT11T302 2 2 1250 22
Tool OFFSET
NO
TOOL COMPENSATION
(mm)
TOOL NOSE
RADIUS(mm)
STAND TOOL
NO
X Z R
1 0.4 3
2 0.2 3
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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Fig.12 Performing step turning operation over CNC-Lathe Machine
Fig.13 CCMT11T304 Tool Bit
CNC Programming for Step Turning Operation:-
N000 M03 S1000
N008 M08
N010 G00 X27 Z5
N020 G00 X25 Z0
N030 G01 Z-100 F50
N040 G00 X27 Z10
N050 G00 X24 Z0
N060 G01 Z-75 F50
N070 G00 X30 Z5
N080 G00 X23 Z0
N090 G01 Z-75 F50
N100 G00 X28 Z10
N110 G00 X22 Z0
N120 G01 Z-75 F50
N130 G00 X30 Z10
N140 G00 X21 Z0
N150 G01 Z-75 F50
N160 G00 X30 Z10
N170 G00 X20 Z0
N180 G01 Z-75 F50
N190 G00 X30 Z8
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N200 G00 X19 Z0
N210 G01 Z-50 F50
N220 G00 X30 Z10
N230 G00 X18 Z0
N240 G01 Z-50 F50
N250 G00 X30 Z5
N260 G00 X17 Z0
N270 G01 Z-50 F50
N280 G00 X30 Z5
N290 G00 X16 Z0
N300 G01 Z-50 F50
N310 G00 X30 Z8
N320 G00 X15 Z0
N330 G01 Z-50 F0
N340 G00 X28 Z10
N350 G00 X14 Z0
N360 G01 Z-25 F50
N370 G00 X28 Z10
N380 G00 X13 Z0
N390 G01 Z-25 F50
N400 G00 X27 Z10
N410 G00 X12 Z0
N420 G01 Z-25 F50
N430 G00 X26 Z5
N440 G00 X11 Z0
N450 G01 Z-25 F50
N460 G00 X30 Z5
N470 G00 X10 Z0
N480 G01 Z-25 F50
N490 G00 X27 Z5
N500 G00 X09 Z0
N510 G01 Z-25 F50
N520 G00 X28 Z10
N530 G00 X08 Z0
N540 G01 Z-25 F50
N550 G00 X29 Z5
N560 G00 X07 Z0
N570 G01 Z-25 F50
N580 G00 X30 Z5
N590 G00 X06 Z0
N600 G01 Z-25 F50
N610 G00 X27 Z5
N620 G00 X05 Z0
N630 G01 Z-25 F50
N640 G00 X35 Z15
N650 M05
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N660 M10
N670 M30
MATERIAL USED: Copper
A. Data Collection:-
For step turning operation using CCMT Tool bit the data has been collected digital micrometer whose
least count is 0.01mm made out of MITUTOYO. And the data has been shown in Table:-4.
Table:-4. Data Obtained Using CCMT Tool Bit
Dimensions with
Specifications:-
Obtained Data:-
(mm)
Sample No.
1
Sample No.
2
Sample No.
3
Sample No.
4
Sample No.
5
ᶲ25±0.1mm 25 24.99 25.02 24.99 25.01
ᶲ20±0.1mm 20 20.02 20.01 20.02 20.01
ᶲ15±0.1mm 15.02 15.01 15.02 15.01 15.01
ᶲ5±0.1mm 4.99 5.01 5.01 5.02 5
B. Plotting the Data in SQC Charts:-
Fig.14 SQC Chart for Dimensions with Specification: ᶲ25±0.1mm processed using CCMT Tool bit
Fig.15 SQC Chart for Dimensions with Specification: ᶲ20±0.1mm processed using CCMT Tool bit
24.8
24.9
25
25.1
25 24.9925.0224.9925.01
ᶲ25±0.1mm
ᶲ25±0.1mm
19.8
19.9
20
20.1
20 20.02 20.01 20.02 20.01
ᶲ20±0.1mm
ᶲ20±0.1mm
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Fig.16 SQC Chart for Dimensions with Specification: ᶲ15±0.1mm processed using CCMT Tool bit
Fig.17 SQC Chart for Dimensions with Specification: ᶲ5±0.1mm processed using CCMT Tool bit
NOTE:- For Fig.14-17 Row 1-(USL), Row 2-(SL), Row 3-(LSL)
XI. OBSERVATIONS After taking the measurement data have been plotted in the graph where it has been observed in the
graphs the remarkable improvements have been achieved in terms of not only accuracy but also quality
of the products.
XII. CONCLUSION In the CNC machining, application of HSS tool bit does not provide accuracy in terms of quality of the
job. Changing the tool bit Specification to CCMT11T304 along with carrying out Total Productive
Maintenance (TPM) all the machine defects have been eliminated, before carrying the next operation.
There after it provide better quality of the product in terms of higher accuracy which has been shown in
SQC chart after obtaining the data. Hence, it increases the productivity but also quantity of product.
Hence, we conclude the following:-
1. Accurate blueprint reading.
2. Knowledge of shop floor mathematics.
3. Use of machine tools theory with TPM activity.
4. Use of SPC & SQC tools.
5. Quality Assurance and Accuracy Improvements.
6. CNC Programming (G,M-codes).
which will provide not only the product accuracy improvements but also the productivity improvements
in terms of both internal and external customers satisfaction.
14.8
14.9
15
15.1
ᶲ15±0.1mm
ᶲ15±0.1mm
4.8
4.9
5
5.1
4.99 5.01 5.01 5.02 5
ᶲ5±0.1mm
ᶲ5±0.1mm
International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 03, Issue 10; October- 2017 [ISSN: 2455-1457]
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ACKNOWLEDGMENT We, the authors take the opportunity to express immense gratitude to our supervisor Dr. Dipak Ranjan
Jana, Professor of Mechanical Engineering Department for his guidance, encouragement and
motivation towards real-time research work right from the beginning of the research. We have taken
efforts in this project work report. Without his support and timely guidance the completion of our
project and its report would be farfetched dream.
We would like to thank those persons whose name could not figure here, once again for their valuable
guidance, support and kind attention given to me throughout the project work.
Finally we bow to our parents, our all-family members, well-wishers for their blessing.
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