Accuracy Improvement through CNC Machining in Step Turning … · 2017-10-10 · Keywords- Accuracy, Productivity, Step Turning, CNC machining, Feed, CAD, CAM. I. INTRODUCTION Production

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]

@IJRTER-2017, All Rights Reserved 75

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



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



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



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



B. Plotting the Data in SQC Charts:-

Fig.5 SQC Chart for Dimensions with Specification: ᶲ25±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




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



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



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



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



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



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



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


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





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



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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Documents

Accuracy Improvement through CNC Machining in Step Turning … · 2017-10-10 · Keywords- Accuracy, Productivity, Step Turning, CNC machining, Feed, CAD, CAM. I. INTRODUCTION Production