Final Year Project Report

A

PROJECT REPORT ON

“DESIGN AND DEVELOPMENT OF AN ATTACHMENT TO

LOCATE THE CENTER OF AN INDENTATION FOR A

TOOL BASED MICRO-MACHINE”

SUBMITTED TO THE SYMBIOSIS INTERNATIONAL UNIVERSITY, PUNE IN

PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE

DEGREE OF

BACHELOR OF TECHNOLOGY

(MECHANICAL ENGINEERING)

BY

Mr. ABHINAV AGARWAL PRN: 09070121401

Mr. GAURAV JAIN PRN: 09070121414

Mr. SRINIVASA PRASHANTH PRN: 09070121430

Mr. NEEL PATEL PRN: 09070121442

Under The guidance of

Prof. AMOL DALAVI

DEPARTMENT OF MECHANICAL ENGINEERING

SYMBIOSIS INSTITUTE OF TECHNOLOGY, PUNE

(YEAR: 2012-13)

CERTIFICATE

This is to certify that the project report entitled

“DESIGN AND DEVELOPMENT OF AN ATTACHMENT TO LOCATE THE

CENTER OF AN INDENTATION FOR A TOOL BASED MICRO-MACHINE”

submitted by

Mr. GAURAV JAIN (PRN:09070121414)

Mr. NEEL PATEL (PRN:09070121442)

Mr. SRINIVASA PRASHANTH (PRN:09070121430)

Mr. ABHINAV AGARWAL (PRN:09070121401)

is a bonafide work carried out by them under the supervision of Prof. Amol Dalavi and it is

approved for the partial fulfillment of the requirement of the Symbiosis International

University for the award of the degree of Bachelor of Technology (Mechanical Engineering)

during the academic year 2012-2013.

This project report has not been earlier submitted to any other Institute or University for the

award of any degree.

Prof. Amol Dalavi Prof. Col. Nitin Solke Dr. T.P.Singh

Guide Head Director

Department of Mechanical Department of Mechanical Symbiosis Institute of

Engineering Engineering Technology

ABSTRACT

Micro Machining processes are capable of achieving high precision in terms of tolerance and

shape error within few tens of microns. They are extensively used for manufacturing of micro

fluidic channels, MEMS devices, medical and defence equipment’s. Micro drilling is used in

applications where holes in micron range are to be drilled. It has always been difficult to

locate the exact position at which the hole needs to be drilled. The precision Engineering

Division of Bhabha Atomic Research Centre required a suitable technique to drill a hole at

the centre of a circular indentation with better positional accuracy. From literature survey it is

seen that not many methods are available to achieve the stated objective. In this project we

have designed, developed and tested on optical based device to meet the desired objective.

CONTENTS

CHAPTER 1 – INTRODUCTION 01

CHAPTER 2 – LITERATURE SURVEY

2.1 MICRO MACHINES 04

2.2 PRINCIPLES OF MICRO-MACHINE DEVELOPMENT 04

2.3 DIFFERENT SYSTEMS IN MICRO MACHINES 05

2.3.1 Drive System

2.3.2. Transmission

2.3.3. Feedback System

2.4 QUALITY CONTROL 09

2.4.1 Standard Deviation

2.4.2 Accuracy

2.4.3 Precision

2.5 PROCESS CAPABILITY 11

2.5.1 Measuring Process Capability

2.6 LOCATING DEVICE 12

CHAPTER 3- SELECTION OF METHODOLOGY

3.1 INTRODUCTION 13

3.2 CONTACT TYPE MEASURING INSTRUMENTS 13

3.2.1 Universal Measuring Machine

3.2.2 Co-ordinate Measuring Machine

3.2.3 Vernier Calliper

3.2.4 Newall Measuring Machine

3.3 NON-CONTACT TYPE MEASURING INSTRUMENTS 14

3.3.1 Optical Measuring Instruments

3.3.1.1 Optical Projection comparator

3.3.1.2 Interferometers

3.3.1.2.1 Michelson Interferometer

3.3.1.2.2 Single Frequency DC Interferometer

3.3.1.2.3 Laser Interferometer

3.3.1.3 Image Shearing Microscope

3.4 SELECTION OF AN OPTICAL TECHNIQUE 17

3.4.1 Dual Camera Method

3.4.2 Offset Camera Method

3.5 DESIGN OF THE FIRST ATTACHMENT 20

3.6 CAMERA SELECTION 23

3.6.1 Camera Requirements

3.6.2 Dino-Lite Premier AM7013MT:

CHAPTER 4- EXPERIMENT

4.1 INTRODUCTION 26

4.2 CALIBRATION 26

4.3 FIRST EXPERIMENT 28

4.3.1 Introduction

4.3.2 Results Obtained

4.3.3 Discussion of Results

4.4 SOURCES OF ERROR 30

4.4.1 Solutions for Minimizing Error

4.4.1.1 Error due to Non-perpendicularity of camera optical axis with

respect respect to the spindle axis

4.4.1.1.1 Introduction

4.4.1.1.2 Experimental Method to find the Angle of the Optical

Axis Axis of the Camera with respect to Spindle Axis

4.4.1.1.3 Finding the error due to change in height of the

spindle spindle axis

4.4.1.2 Error due to Metal-Non-Metal Contact

4.5 SECOND EXPERIMENT 36

4.5.1 Introduction

4.5.2 Second Attachment

4.5.3 Result

4.5.4 Discussion

CHAPTER 5- RESULT AND CONCLUSION 46

CHAPTER 6- FUTURE SCOPE 47

REFERENCES 48

LIST OF TABLES

Table No. Title Page No.

1 Specification of digital microscope 24

2 X and Y offset for 1st attachment 29

3 Offset values taken by Gaurav

(2nd

attachment)

39

4 Offset values taken by Prashanth

(2nd

attachment)

39

5 Offset values taken by Abhinav

(2nd

attachment)

40

6 Offset values taken by Neel

(2nd

attachment)

40

LIST OF FIGURES

Figure

No.

Name of Figure Page No.

1 Simple micro machine 5

2 DT-110 micro machine 5

3 Drive system flowchart 6

4 Classification of transmission 7

5 Open loop system 8

6 Closed loop system 8

7 Probability density vs. value graph 10

8 Dual camera attachment design 18

9 Offset camera attachment design 19

10 CATIA model of first attachment 21

11 Actual photograph 1st attachment 21

12 Actual photograph 1st attachment 22

13 Photograph of work piece 22

14 Dino-Lite Camera 24

14a Calibration Technique 27

15 Control chart for X-axis Offset 29

16 Control chart for Y-axis Offset 30

17 Inclination of camera 32

18 Schematic for a Digital Microscopic camera

imaging a surface and for calculating the error

33

19 Trigonometric relation 34

20 Schematic for the case where the height of the

spindle is increased

35

21 CATIA model of second attachment 37

22 Photograph of second attachment 2nd

attachment 37

23 Two types of clamps 38









32 Comparing the results of all four operators 43

33 Metrology equipment 44

34 Metrology equipment and the results 44

35 Metrology equipment and the results 44

ACKNOWLEDGEMENT

We take this opportunity to thank our mentor Dr.R.Balasubramaniam of Bhabha Atomic

research Centre, Trombay. He was the backbone of this project, continuously motivating us.

We thank the Precision Engineering Department of Bhabha Atomic Research Centre,

Trombay, especially Dr.V.K.Suri, Head, PED. His charisma rubbed on us and it is because of

him that we were able to convert this study project into a product. This product is

indigenously built for use on all kinds of precision machines. His valuable guidance shall

never been forgotten. Also, we would like to thank Mr.Prabhat Ranjan for helping us with

developing the mathematical equation. We would also like to thank Mr. Surendran for

patiently bearing with us and helping us throughout the project. A special thanks to

Mr.Ashwin Rathod, for his support and ideas. It is because of him that we made the crucial

breakthrough when our options seemed to have dried up.

We thank our project guide Prof.Amol Dalavi. His support and motivation has helped us

achieve the level of excellence in our project. It was because of his help that we were able to

write a journal article that was published by in IOSR journal. This exercise of writing a

journal paper gave us immense experience and boosted our morale.

We would also like to thank the faculty members of our college, Symbiosis Institute of

Technology. We would specially like to thank Prof. L.S.Bhargava for his valuable advice

which helped us overcoming some of the limitations of our project.

GAURAV JAIN ABHINAV AGARWAL PRN: 09070121414 PRN: 09070121401

NEEL PATEL SRINIVASA PRASHANTH

PRN: 09070121442 PRN: 09070121430

B.Tech . (Mechanical)

Department of Mechanical Engineering

Symbiosis Institute of Technology

SIT MECHANICAL ENGINEERING 2012-13 1

CHAPTER 1: INTRODUCTION

Micromachining is a precision machining process. Micro machined components find

application in medical equipment‟s, optical grade mirrors, electronic industries and defence

purposes. The positional accuracy and shape error of micro machined components are in the

order of few tens of microns. In order to attain such high level of accuracy, micro machine

are built to achieve the desired level of accuracy.

The parts of the micro machine can be categorized as drives, transmission, feedback and

machine control units. Drives include all the parts of the machine which creates motion such

as motors. Transmission system includes the various mechanisms used for transmission of

power from the drives. Transmission causes the motion of the slides and spindles. Feedback

system is used to monitor various parameters of the machine. They help in achieving high

level of accuracy. In spite of using methods to achieve high level of accuracy, errors are

introduced due to various factors. These errors can be classified as machine error, human

error and environment error. These errors may be caused due to vibration of the spindle,

thermal expansion due to heat produced by friction during the machining process or

inaccuracy due to dust particles.

Micro drilling is a micro machining process in which drilling is carried out in the micron

range. A carbide drill bit with a diameter in micrometer range is used to carry out the micro

drilling process. For drilling a micro hole, the drill has to be positioned exactly above the

point at which the hole needs to be drilled. For a precision process, it is essential that the error

between drill bit position and the location at which the hole should be drilled be minimum.

But as mentioned above, there are errors due to which the stated objective cannot be

achieved. It was noticed that there were no methods currently available to locate the point in

the micro range.

Hence, the objective of the project was to establish a suitable method to locate the position at

which the drilling process is to be carried out and also study the various errors in the method

and minimize them. We were assigned the task of drilling a hole at the centre of a circular

indentation. Thus, the project involved developing a method to locate the point at which the

hole needs to be drilled. Advantages and limitations of existing process for macro scale were


studied; later their feasibility on a micro scale was checked. Depending upon the results, a

method was finalized and the errors arising were studied. In subsequent steps, designs were

modified to minimize these errors. Along with the project, equations were derived from a

study of the behaviour of change in error with respect to change in height of the spindle.


Structure of thesis

The thesis has been divided into six chapters. The first chapter is an introduction to the

project. The second chapter is literature survey. A literature survey was carried out to

understand the parts of micro machines. Quality control procedure required to meet the

objective has also been explained in this chapter.

The third chapter describes about the various methods available to solve the objective. Each

method was extensively studied, the advantages and limitations were weighed and based on

the conclusion, a method was chosen. Also, sub classifications of the chosen method were

studied and based upon the requirements of the user, a method was finalized. Design and

fabrication of the initial attachment is mentioned in the end of this chapter.

Chapter 4 describes the experiments that were carried out using the initial attachment. The

procedure for carrying out the experiment is described in brief. The results for the first

attachment are discussed and the errors arising have been studied. The solution to minimize

these errors is proposed and a second attachment was fabricated. The results of the second

attachment are also discussed.

Results of the two experiments are compared and a conclusion is arrived at in Chapter 5. In

Chapter 6, the future scope of this project is discussed. Various techniques to improve the

efficiency of the attachment are discussed. Also, other applications of the attachment are

discussed.


CHAPTER 2. LITERATURE SURVEY

2.1 MICRO MACHINES

Limitations on the resources of energy, space and material coupled with the recent trend of

miniaturization of mechanical devices, have provided impetus to the development of meso or

micro-sized machines to manufacture micro-parts. It is observed that in these machines, the

vibrations, inertia and thermal effects decrease significantly with the scale of machines.

Micromachining is the basic technology for fabrication of micro-components or features

of size in the range of 1 to 500 micrometers. Their need arises from miniaturization of

various devices in science and engineering, calling for ultra-precision manufacturing and

micro-fabrication. There is a growing demand for industrial products not only with increased

number of functions but also of reduced dimensions. Since miniaturization of industrial

products has been the trend of technological development, micro machining is expected to

play increasingly important roles in today's manufacturing technology.

2.2 PRINCIPLES OF MICRO-MACHINE DEVELOPMENT

There are a number of reasons for which the miniaturization or development of micro

machines is always attempted at. Firstly, to date, the manufacturing of micro-components is

mainly facilitated by lithography-based techniques. However, these processes can produce

two-dimensional components on a select few materials. Whereas, many microscopic

actuation devices and mechanisms require three-dimensional components made of materials

of varying characteristics. In the past, these have been manufactured using precision or ultra-

precision machine tools. However, the ability of a machine tool to produce a precise micro-

component is proportional to its size. The smaller machines can produce smaller components

more accurately than larger machines. This is because the inertial forces decrease

proportional to the fourth power of the scaling factor. Figures of micro machines are shown

below as Figure-1 and 2. Figure-1 is a deep hole drilling micro EDM and Figure-2 is a

Universal Micro machining centre.


Figure (1) Figure (2)

Problems faced during micro machining process:

• Vibrations of spindle and other machine tools.

• Vibration of the ground/floor of the work space.

• Thermal expansion leading to loss of accuracy

• Inaccuracies due to the cutting forces.

Applications of Precision Engineering:

• Health

• Defense

• Electronics

• Transportation

2.3 Different Systems in Micro Machines

• Drives

• Transmission

• Feed back

• Machine control unit


2.3.1 Drive System

Amplifier circuits drive motors, and ball lead screws are main component of drive

systems. Control signals i.e. position and speed of each axis is fed to amplifier circuits from

MCU. The control signals are augmented to actuate drive motors that in turn rotate ball lead-

screws to position the machine table.

Servo

Works with an FCS and is used in a closed loop control system. A servomotor is a rotary

actuator that allows for precise control of angular position.

Stepper

Stepper motor drives are the devices which convert the signals coming from the computer,

and the power coming from the power supply into high power electrical signals that will

power and move the stepper motors. Figure of flowchart is given below.

Figure (3)

2.3.2. TRANSMISSION

Requirement:

Transmission of motion is required from external source to the operative element.It can be

done by mechanical elements or by means of hydraulic and electrical circuits.

Advantages:

Hydraulic transmission provides step less regulation of the speed and feed rate. While in

mechanical transmission speeds can be achieved only in steps and feed rate may also be


stepped.

Figure (4)

2.3.3. Feedback System

A feedback system is also referred to as a measuring system. It uses position and speed

transducers to continuously monitor the position of the cutting tool at any particular time. The

MCU uses the difference between reference signals and feedback signals for correcting

position and speed errors.

Open Loop - The primary drawback of the open-loop system is that there is no feedback

system to check whether the program position and velocity has been achieved. If the system

performance is affected by load, temperature, humidity, or lubrication then the actual output

could deviate from the desired output. Figure is shown below.

For these reasons, the open-loop system is generally used in point-to-point systems where the

accuracy requirements are not critical.

Classification of

Transmission

Hydraulic transmission

Pumps Hydraulic cylinder

Throttles

Mechanical transmission

Gear transmission

Belt transmission

Chain transmission


Figure (5)

Closed Loop -The closed-loop system has a feedback subsystem to monitor the actual output

and correct any discrepancy from the programmed input. The feedback system could be

either analog or digital. The analog systems measure the variation of physical variables such

as position and velocity in terms of voltage levels. Digital systems monitor output variations

by means of electrical pulses

Closed-loop systems are very powerful and accurate because they are capable of monitoring

operating conditions through feedback subsystems and automatically compensating for any

variations in real-time. Figure is shown below.

Figure (6)

Feedback can be accomplished in one of two ways.


Linear Scales - Linear scales are high precision glass scales that can be "seen" by an

optical encoder that follows along with the axis movement. This is the type of scale

used on most DRO systems for manual mills. The accuracy of these scales are

absolute in that position of the optical encoder relative to the scale is exact from one

end of the scale to the other baring thermal expansion.

Resolvers - Resolvers work differently. The resolver is a complicated and expensive

analog device that feeds back via calibrated sine signals relative to its angle of

rotation. Prior to the extensive use of digital technology all NC machines used

resolvers as it was the only means to close a loop. Today the vast majority of

machines use optical shaft encoders which are far less expensive and more suitable to

the digital technology used with CNC machinery. However, resolvers are still used on

some newer CNC machines where high shock or vibrations are present.

2.4 QUALITY CONTROL

Juran defined quality control as

a. To degree to which a specific product satisfies the wants of a customer

b. The degree to which a specific product conforms to the design r specification.

Objectives

1. Evaluation of quality standards of incoming material, product in actual manufacture

and of outgoing product.

2. Judging the conformity of the process of the established standard and taking suitable

action when deviations are noted.

3. Evaluation of optimum quality obtainable under given conditions.

4. To improve quality and productivity by process control and experimentation.

2.4.1 Standard Deviation

It is the most useful measure of dispersion of a set of observations. It is equal to the root

mean square deviation of the observed numbers from their arithmetic mean


Here, xi are the various values of x is the mean and n is the number of readings., The SD is

the most significant characteristics of a distribution because it provides an arbitrary measure

of the probability that a certain number of measurement will fall within a particular range of

values.

2.4.2Accuracy

The accuracy of a measurement system is the degree of closeness of measurements of a

quantity to that quantity's actual (true) value.

2.4.3Precision

The precision of a measurement system, also called reproducibility or repeatability, is the

degree to which repeated measurements under unchanged conditions show the same results.

Figure (7) shows a diagram that distinguishes between accuracy precision.

Fig (7)


2.5 PROCESS CAPABILITY

A critical aspect of statistical quality control is evaluating the ability of a production process

to meet or exceed pre-set specifications. This is called process capability.To understand

exactly what this means, let‟s look more closely at the term specification. Product

specifications, often called tolerances, are pre-set ranges of acceptable quality characteristics,

such as product dimensions. For a product to be considered acceptable, its characteristics

must fall within this pre-set range.

For example, the specifications for the width of a machine part may be specified as 15 inches

+0.3. This means that the width of the part should be 15 inches, though it is acceptable if it

falls within the limits of 14.7 inches and 15.3 inches. Similarly, for Cocoa Fizz, the average

bottle fill may be 16 ounces with tolerances of +0.2 ounces. Although the bottles should be

filled with 16 ounces of liquid, the amount can be as low as 15.8 or as high as 16.2 ounces.

2.5.1 Measuring Process Capability

Process capability is measured by the process capability index, Cp, which is computed as

the ratio of the specification width to the width of the process variability:

where the specification width is the difference between the upper specification limit (USL)

and the lower specification limit (LSL) of the process. The process width iscomputed as 6

standard deviations (6σ) of the process being monitored. The reason we use 6σ is that most of

the process measurement (99.74 per cent) falls within +3 standard deviations, which is a total

of 6 standard deviations.

There are three possible ranges of values for Cpthat also helps us interpret its value:

Cp= 1: A value of Cpequal to 1 means that the process variability just meets specifications.

We would then say that the process is minimally capable.


Cp< 1: A value of Cpbelow 1 means that the process variability is outside the range of

specification. This means that the process is not capable of producing within specification

and the process must be improved.

Cp>1: A value of Cpabove 1 means that the process variability is tighter than specifications

and the process exceeds minimal capability.

A Cpvalue of 1 means that 99.74 percent of the products produced will fall within the

specification limits. This also means that .26 percent (100% - 99.74%) of the products will

not be acceptable. Although this percentage sounds very small, when we consider of it in

terms of parts per million (ppm) we can see that it can still result in a lot of defects. The

number .26 percent corresponds to 2600 parts per million (ppm) defective (0.0026 ×

1,000,000). That number can seem very high if we think of it in terms of 2600 wrong

prescriptions out of a million, or 2600 incorrect medical procedures out of a million, or even

2600 malfunctioning aircraft out of a million.

Cpis valuable in measuring process capability. However, it has one shortcoming: it assumes

that process variability is centred on the specification range. Unfortunately, this is not always

the case. In the Cocoa Fizz example, the specification limits are set between 15.8 and 16.2

ounces, with a mean of 16.0 ounces. However, the process variation is not centred; it has a

mean of 15.9 ounces. Because of this, a certain proportion of products will fall outside the

specification range.

2.6 LOCATING DEVICE

Currently, no locating devices are available for locating a point in micro scale. However,

edge detection devices are available. But, the objective of the project is to locate a point and

not an edge. Hence a mechanism has to be devised in order to locate the point. The probe

system which is used for edge detection cannot be used in this case.


CHAPTER 3: SELECTION OF METHODOLOGY

3.1 INTRODUCTION

A method had to be chosen for developing the methodology. For this purpose, methods

existing for similar problems on the macro scale were studied and their feasibility was

checked for micro scale. In this chapter, the advantages and limitations of each method have

been given. Also the selection of the camera and design of the first attachment have been

discussed in the end of the chapter.

There are two main methods for testing or quality control. The first method is contact method

and the other method is non-contact method. The sub classifications of these methods are

discussed below.

3.2Contact Type Measuring Instruments

In this method, contact is established between the object to be measured or tested and the

measuring device (probe). Some of the contact methods are:

3.2.1Universal Measuring Machine

In the world that has the concept of interchangeable manufacture parts, measurements of size

and with tolerances that are specified in terms of fractions of a micron, UMM is an important

part of manufacturing process. The four essential components measured by the UMM are

length, geometry, division of circle and roundness.Advantages of UMM are it relies on end

standard and is capable of measuring work which differs in size from the standard by several

millimetres. The limitations are these work only up to range of 6 to 150 mm diameter and 50

mm depth.

3.2.2Co-ordinate Measuring Machine

CMM‟s are useful where precise movements in x-y-z components are necessary. The

movement of the slides can be easily controlled and measured by linear measurement

transducer. The measuring head incorporated a probe tip, which can of different kinds viz.


taper tip, ball tip. The advantages of CMM are that it has a very low measuring uncertainty.

Also, it can be used with computer aided measuring to get a vibration free mechanical

structure. But following are the limitations:

1. Dimensional errors may be influenced by scale-division and adjustment of scales.

2. Probe system calibration is required before it can be operated.

3.2.3VernierCalliper

The principle of the Vernier Calliper is that when two scales or divisions slightly different in

size are used, the difference between them can be utilised to enhance the accuracy of

measurement. It consists of two steel rules that can slide along each other. One end of the

frame contains a fixed jaw which is shaped into a contact tip at its extremity. Advantages are

1. It is simple in construction, is easy to use and has a low cost

The limitations are:

1. It has a low accuracy as compared to other Linear Measuring instruments.

3.2.4Newall Measuring Machine

This machine is used level the work piece. It carries a sensitive spirit level at its upper end

and the level has graduations, each graduation corresponds to movement of about 0.0001mm.

Advantages are the movement of anvil in the order of 0.00025 mm can be detected and it is a

high precision instrument with low cost. The limitations are that it is bigger in size and thus

has a large weight. It is difficult to be used in mobile applications.

3.3Non-Contact type Measuring Instruments

In a non-contact type measuring instrument, there is no contact between the work piece and

the measuring instrument. The following are some of the non-contact methods:

3.3.1Optical Measuring Instruments

In these instruments Light beam is used as the amplifying lever.Light can travel in straight

lines with almost no deviation, providing higher accuracies than other measurement

components. Advantages are that they are used for high precision measurements and the light


beam has advantage of straightness and weightlessness thus gives high accuracies. The

limitations are that a small deflection of mirror may cause a large error.

There are three types of optical measuring instruments

a. Vertical optimeter

b. Horizontal optimeter

c. Tool maker‟s microscope

3.3.1.1 Optical Projection comparator

It is a measuring instrument which projects an enlarged shadow of the part being measured

on a screen, where it is compared to a master drawing. The instrument contains four essential

instruments viz. source of light, collimating or condensing lens, projection lens and screen.

Advantages:

1. Parts that are complicated in shape can be easily checked and measured

2. It can measure with a High precision.

Disadvantages:

1. Shadow distortion is possible, resulting in errors in measurement.

3.3.1.2Interferometers

These are the optical instruments used to measure the flatness and determining the length

of slip gauges by direct reference to the wavelength of light.

3.3.1.2.1 Michelson Interferometer

It consists of a monochromatic light source, a beam splitter and two mirrors. It relies on

the principle of constructive and destructive interference as one mirror remains fixed and the

other is moved.


Advantages: A monochromatic light source is required.

Disadvantages: It relies on the principle of constructive and destructive interference hence;

accuracy of measurement is not very high as it is not possible to maintain the sharpness of

interference fringes beyond certain distance.

3.3.1.2.2 Single Frequency DC Interferometer

It uses a single frequency circular polarised laser beam, thus can be used to measure

flatness, straightness, rotary axis calibration. Arrangements also need to be made for

environmental compensation because the refractive index of the air varies with temperature,

pressure and humidity.

Advantages: Improved form of Michelson interferometer uses a single frequency circular

polarised laser beam to have high resolution measurement and high accuracy.

Disadvantages: complex arrangement of apparatus, difficult to calibrate.

3.3.1.2.3 Laser Interferometer

The measuring capacity of a lamp based interferometer is limited as it is not possible to

maintain sharpness of interference fringes at certain distances. Thus , a laser which is a

source of intense monochromatic optical energy can be collimated into a directional beam.

Advantages:

1. It uses AC lasers as their light source thus enabling it to measure over a long distance.

2. It has high repeatability and resolution of displacement measurement.

3. It is easy to install.

Disadvantages:

1. It is much more expensive than a traditional interferometer.

2. Conversion instrumentation is required for conventional read out.


3.3.1.3 Image Shearing Microscope

In this instrument an optical system is used to produce two identical images of the object

which can be superimposed or sheared across each other by means of a precisely calibrated

mechanism. This method yields very high precision in making the setting for the two

contacting edges to virtually vanish.

Advantages:

1. Used for precise measurement of lateral dimensions of objects.

2. Can be applied to the accurate measurement of integrated circuits,

3. It does not strain eyes during the process of experimentation.

4. It has a precision up to 0.01 microns.

Disadvantages:

1. A skilled operator is required to carry out the measurements.

2. The apparatus is expensive, thus has a limited applications in industry.

From this study, it is concluded that the non-contact method is suited over contact method

for this application. The optical method is most suited for this method because of its low

costs and simplicity compared to other techniques.

3.4 SELECTION OF AN OPTICAL TECHNIQUE

Using optical technique, we have two options:

1. Dual Camera Method

2. Offset camera method

3.4.1 Dual Camera Method

In this method we find the centre of the indentation by using two cameras that are

mounted on the same vertical axis and shown in the figure (8)


Figure (8)

The camera provides a live feed to the user of the work piece thereby enabling the operator to

locate the centre of the indentation. The camera diagonally opposite to the work piece helps

in aligning the tool with the axis of the camera. Since, axis of both the cameras are aligned to

each other the tool centre and the centre of the indentation are thus on a common axis.

Advantages:

1. Very accurate as both the cameras are aligned with each other and hence less chances of

human error.

Disadvantages:

1. The camera is very costly with low magnification power.

2. Cannot be used where the distance between the tool and work piece is less.

3.4.2 Offset Camera Method

In this type of method a camera with high magnification power is used. It is mounted on an

attachment as shown in the figure (9).

Dual side camera

Spindle


Figure (9)

The camera is mounted in the external mounting bracket provided on the attachment. The L-

shaped bracket helps in adjusting the position of the camera bracket in order to maximize

positional accuracy. The camera mounted on the bracket is a high magnification power

camera with optical zoom up to 150x. This scale of magnification provides a clear real-time

live feed of the work piece. The offset between the camera and the spindle can be calculated

by drilling a sample hole and then moving the camera to the centre of the drilled hole. The

distance moved by the tool post helps in calibrating the offset value up to a few 10‟s of

microns.

Advantages:

1. High magnification power of the camera provides high quality image at fairly low prices.

2. Can be readily used where the distance between the tool and the work piece is small.

Disadvantages:

1. Due to non-perpendicularity of the camera axis delivers fairly high value of positional

errors.

2. Highly skilled operator required to obtain high levels of positional accuracy.

After studying the advantages and limitations of both methods, it was concluded that the

offset method was much more beneficial and economical than the dual camera method due to

Attachment

to hold

camera


its significantly lower cost as compared to dual camera and because of its higher zooming

capability.

3.5 DESIGN OF THE FIRST ATTACHMENT

For holding the optical device, a clamp had to be developed. Upon selection of the

camera, the dimensions of the camera body were known. Moreover, no force was acting on

the body of the clamp. One major aspect that was to be considered was the dimension and

shape of the attachment as it should not interfere with the parts of the machine.

A clamp with a bore of 33mm was fabricated to hold the camera. It was bolted to a frame

which in turn was bolted to the machine frame. The dimensions of the attachment were

chosen empirically. Weight and dimensions were the major consideration. Aluminium was

chosen because of its light weight. Moreover, it served in damping the vibrations produced by

the spindle and it was also easy to fabricate. The dimensions were chosen according to the

machine dimensions such that the attachment did not interfere with the machine. The

thickness was selected empirically. If the thickness was less than 8mm, it would bend

because of its weight. Having greater thickness did not serve any purpose. The attachment

was held to the machine frame using four screws to arrest all six degrees of freedom.

Provision was provided in the attachment such that partial rotational motion in the X-Z

plane was provided. The clamp was attached to the frame using two screws such that it had

one degree of freedom when one of the screws was loosened. Shown in fig (10) to fig (12)

are the CATIA model and actual photograph of the first attachment. Figure (13) shows an

enlarged view of the work piece shown in figure (12).


Figure (10)

Figure (11)

First attachment

with rotation in

X-Z plane

Hinges for

rotation

Dino-Lite Digital

Microscope


Figure (12)

Figure (13)

Spindle

Work-Piece

First attachment

with rotation in

X-Z plane

Dino-Lite Digital

Microscope


3.6 CAMERA SELECTION

Micro-machining demands higher accuracy. To attain higher machining accuracy higher

positional is accuracy has to be attained. Measuring devices are used to know the position of

machining to be done on the work piece. There are two types of probing devices:

1. Contact type

2. Non-contact type

When it comes to micro-machining, the components machined are of micro dimensions

and therefore positional accuracy up to 10microns is required. Contact type measuring

devices involve human interaction therefore leading to less positional accuracy. On the other

hand, Non-contact type measuring devices involve lesser human intervention and therefore

are more accurate.

Digital cameras are used as non-contact measuring devices. They provide clear images

and progressive scanning ability which with the help of Image processing provide accurate

position of machining and 2-D dimensions of the component

3.6.1 Camera Requirements

To attain higher positional accuracy the microscope should consist of the following

specifications:

1. High Pixels - A pixel is a physical point in a raster image or the smallest addressable

element in a display device, so it is the smallest controllable element of a picture

represented on the screen. The address of a pixel corresponds to its physical

coordinates.

2. Greater Pixel per inch (PPI) – PPI is the number of pixels per inch. It gives the pixel

density. The greater the PPI, the more accurate position determination can be done.

3. Higher Magnification – Since the components are of micro-dimensions, therefore to

gain clear images of the component higher magnification power is required.


3.6.2 Dino-Lite Premier AM7013MT:

The Dino-Lite Premier AM7013MT digital handheld microscope fulfilled all the

requirements.The specifications are mentioned in table (1). Fig (14) shows Dino-Lite.

Figure (14)

Specifications

Model AM7013MT Dino-Lite Premier

Interface USB 2.0

Product Resolution 5M pixels (MJPEG codec may be required to

run at 2592 x 1944 resolutions)

Magnification Rate 20x~50x, 200x

Sensor Color CMOS

Frame Rate Up to 30fps

Save Formats

Image:

DinoCapture2.0: BMP ,GIF ,PNG ,MNG ,TIF

,TGA ,PCX ,WBMP ,JP2 ,JPC ,JPG ,PGX

,RAS ,PNM

DinoXcope: PNG ,JPEG

Movie:

DinoCapture2.0: WMV, FLV, SWF

DinoXcope: MOV


Microtouch Touch sensitive trigger on the microscope for

taking pictures

LED lighting 8 white LED lights switched on/off by software

Measurement Function Yes

Calibration Function Yes

Operating System Supported Windows 8 ,7 ,Vista, XP

MAC OS 10.4 or later

Unit Weight 140(g)

Unit Dimension

10cm (H) x 3.2cm (D)

Package Dimensions 21.5cm(L) x 18cm(W) x 7cm(H)

Table (1)

* Both Digital Microscope and Camera are interchangeable terms. In this project, they refer to the

same thing.


CHAPTER 4: EXPERIMENT

4.1 INTRODUCTION

In order to test the methodology developed, the attachment was tested on DT110. The

attachment was clamped to the frame of z-axis. By calibrating the device, the offset values of

the camera from the spindle were obtained. These offset values were then used for locating

the indentation. Experiments were carried out using the first attachment. The results of the

first experiment were used to understand the sources of errors. By applying suitable

techniques, these errors were minimized. Also, a study was conducted on the error due to non

perpendicularity of the camera axis with respect to the machining plane due to change in

height of camera (z-axis movement). A second attachment was developed based on the

studies conducted after the first experiment. Then, experiments were conducted on the new

attachment and the results were studied.

4.2 CALIBRATION

In order to find the offset between the camera and spindle axis, calibration was carried out.

Calibration has to be done after the attachment is clamped to the z-axis frame.

The procedure involves clamping of the attachment to the z-axis frame. Initially a drill is

made on a work piece. The x-axis, y-axis and z-axis coordinates are noted down. The spindle

is then moved manually such that the indentation comes within the camera range. The

camera is focused in order to obtain a clear image. The co ordinates of the centre of the

circular indentation are recorded. Offset is obtained using the following formulae

X-offset= X(spindle reading)-X(camera reading)

Y-offset= Y(spindle reading)-Y(camera reading)


STEP 2:

The spindle containing the drill bit

is retreated from the work piece.

The drilled hole is cleaned.

STEP 3:

The spindle is annually moved

such that the digital microscope is

directly over the drilled hole. The

co-ordinates of this position are

noted down. The difference

between the spindle co-ordinates

and the camera co-ordinates

gives the offset between the

spindle axis and the optical axis of

the digital microscope

CALIBRATION TECHNIQUE

STEP 1:

A drill is made on the work piece.

The machine co-ordinates are

noted from the screen.

Frame of the machine

Spindle

Drill bit

Work piece

Digital microscope

Figure (14a)


4.3 FIRST EXPERIMENT

4.3.1 Introduction

Experiments were carried out for calibration. A copper work piece was used for

experimentation purpose. Drilling was carried out at ten different points and their spindle co-

ordinates were noted down. Then the spindle was manually moved such that the camera

cross hair coincided with the centre of the circular indentation. This reading was noted down.

The spindle was then moved to some random position and again the procedure of manually

bringing the camera over the drilled hole was carried out. Similar procedure was performed

for all ten drill holes. Also the change in the offset value was monitored wrt time.

Experiments were conducted after fixed time intervals.

4.3.2 Results Obtained

The offset values were studied in order to obtain the results. The performance

characteristic curve was plotted in order to understand the results. First, the offset values were

calculated by subtracting the camera co-ordinates from the spindle co-ordinates. The mean

value and the standard deviation (σ)values were calculated. Then, the upper control limits

(UCL) and lower control limits (LCL) were calculated using 3σ. Fig (15) shows the

performance character chart for the X-offset values and Fig (16) shows the performance

character chart for the Y-offset values.


X offset Y Offset

99.0757 10.587

99.0847 10.584

99.0817 10.576

99.0737 10.591

99.0837 10.58

99.0857 10.591

99.0847 10.584

99.0557 10.592

99.0687 10.582

99.0617 10.592

Table (2)

Figure (15)


Figure (16)

4.3.3 Discussion of Results

In the previous sub-topic, the results of the experiment were mentioned. Fig (15) shows

the performance character curve for X-offset. The UCL and the LCL values are 99.1074 and

99.0438. The mean value is 99.0756. The peak value (P-V) was found out to be around

30µm. From this we can infer that the maximum deviation while carrying the calibration

process is 30µm. Similar results were found from the Y-offset performance characteristic

curve. The P-V value was found out to be around 20µm. The machine error is approximately

4µm. Thus, in order to reduce these errors, sources of these errors have to be studied and

methods have to found out to minimize the errors.

4.4 SOURCES OF ERROR

A study was carried out to understand the source of error while obtaining positional

accuracy. Positional error is caused due to combination of Machine error, human error,

alignment error and environmental factors. Machine error includes error due to spindle run-

out and error in positioning. Human error is caused by locating error. Locating error is the

error between the actual centre of indentation and the centre of indentation located by the


operator. Alignment error arises due to the lack of parallelism between the camera axes to the

spindle axis. The error varies with the angle between the optical axis of the camera with

respect to the spindle axis. Environmental errors are caused due to factors like vibration, dust

particles and chips formed during machining.

Of the four types of error mentioned above, only error due to alignment and environment

factors can be reduced. The environmental error could be reduced by carrying out the

machining process in a controlled environment such as a clean room. Alignment error was

caused due to non-parallelism between optical axis of the camera and the spindle axis. Also,

another error was due to contact between the plastic body of the camera and the metallic part

of the attachment. Since the error of the machine was of the order of 1µm, in order to obtain a

positional accuracy of less than 100µm, the error permitted due to the attachment was 99µm.

Hence these errors had to be minimized in order to maximize positional accuracy.

4.4.1 Solutions for Minimizing Error

In this sub chapter, methods to minimize the errors are discussed.

4.4.1.1 Error due to Non-perpendicularity of camera optical axis with respect to the

spindle axis

Solutions to minimize two kinds of errors have been addressed. The first error is the error

arising due to non-parallelism of spindle axis and the optical axis of camera. This translates to

the non-perpendicularity of camera axis with respect to the work piece plane.

4.4.1.1.1 Introduction

When the camera axis is not perpendicular to the work piece plane (or not parallel to the

spindle axis), the magnitude of error increases (or decreases) due to the error introduced by

the angle made by the optical axis of camera with respect to the work piece plane. Thus, in

order to minimize this error, the angle should approach zero degrees, i.e., it should be almost

perpendicular to the work piece axis. To reduce the angle to zero, it is essential to know the

angle of the optical axis of the camera/ digital microscope when it is mounted on the

attachment. Therefore an experimental method was devised to find out the angle of the

camera when it is mounted, which has been explained below in Figure (17).


Figure (17)

4.4.1.1.2 Experimental Method to find the Angle of the Optical Axis of the Camera with

respect to Spindle Axis.

Figure (18) shows a schematic for a digital microscopic camera imaging a surface where the

lens of camera is tilted about the x axis by an angle θ. The surface rigidly translates along the

direction by a distance and for clarity the positions of the surface before and after the

translation are shown separately.

Optical Axis of the

camera

Spindle Digital Microscope/

Camera

P (offset distance b/w spindle and the

optical axis of the camera if it was

perpendicular to the work piece plane

Error due to non perpendicularity

of optical axis of camera with the

work piece plane


Figure (18)

The experiment is carried out to find the angle θ and α. Shown in the figure are two positions

of the camera. At the initial position, the camera is at a height of Z1. The offset between the

spindle axis and the camera when the camera axis is assumed to be parallel to the spindle axis

is represented as „P‟. „Pnet‟ is the distance between the actual camera axis and the spindle

axis. Thus, the error due to non perpendicularity is

Error = Pnet - P

By trigonometry, it can be seen that

Error = Z1 * tanθ


But in the above equation, value of Z1 is not known. So, we move the spindle to a new

position, in this case Z2. We get new value of Pnet, that is in this case „Pnet2‟.As shown in

figure (19), Δ z and (Pnet2 - Pnet1) are the two sides of the right angle triangle.

Figure (19)

Using trigonometry, we can find out the value of θ using the following equations

tanθ = (Pnet2 - Pnet1) / ΔZ

The angle in the Y-Z plane, i.e., α is found out using similar technique. The equation for

finding out „α‟ is

tanα = (Qnet2 - Qnet1) / ΔZ

Thus, once we get the values of α and θ, we can use these values to adjust the optical axis

of the camera and bring it as close to zero as possible. This will help us in minimizing the

error due to non perpendicularity. More research needs to be carried out to find out the exact

value of offset, since the present methods do not give us the exact value of the error due to

non perpendicularity. However, the values of α and θ can be used to compute the error due to

change in height of spindle, which has been discussed in the next sub topic.

4.4.1.1.3 Finding the error due to change in height of the spindle axis

While machining process, the height of spindle may be increased or decreased with reference

to the calibration height due to factors like machine error or to avoid obstacles during

machining. As seen in the previous topic, error due to non perpendicularity increases with

ΔZ

θ

Pnet2 - Pnet1


increase in height and decreases with decrease in height. The values of α and θ can be used to

find the increase or decrease in error. Figure (20) shows an example where the height of the

spindle is increased.

Figure (20)

In this case, „dZ in the increase in the height and „dPnet‟ is the increase in the error. By

trigonometry, the value of dPnetcan be found out.

dPnet= dZ * tanθ

Similarly,

dQnet= dZ * tanα

By using these equations, the change in error due to change in height of the spindle axis

with respect to the height of spindle due to calibration can be found out.


4.4.1.2 Error due to Metal-Non-Metal Contact

Error could also arise due to the adhesive bond between the plastic body of the digital

microscope and the metallic body of the attachment. Various methods were studied to

understand and overcome this problem. Industrial grade glue could have been used to solve

the problem. But, the adhesive deteriorates with time. This would lead to varying offset with

respect to time. Hence industrial glue couldn‟t be used. Either a camera with metal body

could be used with the metal attachment or a plastic clamp could be used for plastic body

camera. Both these methods were tested and satisfactory results were obtained.

4.5 SECOND EXPERIMENT

4.5.1 Introduction

A second attachment was fabricated in order to overcome the errors created by the first

attachment. The attachment has two rotational movements in order to compensate for the non

perpendicularity of the optical axis of the microscope with the work piece plane. Similar

experiments were conducted as of the first experiment. The offset value between the spindle

and digital micro scope were recorded and the difference between the maximum and

minimum offset values of x and y axes were calculated. Later the results of the first and

second attachment were compared.

4.5.2 Second Attachment

As mentioned in the previous topic, the attachment was developed to overcome the error

due to non perpendicularity in both axes. Thus the second attachment was given an additional

freedom in rotation in the Y-Z plane. Thus, the camera is free to rotate in two axes. Shown in

fig (21) is the design of the second attachment. This attachment, like the first attachment was

fabricated using dimensions that were obtained empirically. Fig (23) shows the two types of

clamps that could be used for the different types of camera body.


Figure (22)

Attachment with partial

freedom of rotation in X-Z

plane and Y-Z plane.

Dino-Lite digital

microscope

Spindle

Figure (21)


Figure (23)

4.5.3 Result

A total of ten performances characteristic graphs were plotted based on the offset values

of the five experiments that were conducted. The first experiment using the new attachment

was performed by the machine operator. Table (3) shows the readings of spindle co-

ordinates, camera co-ordinates and the offset values. Figure (24) and Figure (25) shows the

performance character curve X-offset and Y-offset respectively.

Also, four different operators performed the calibration technique using the second

attachment. Figure (26) to Figure (31) shows the performance characteristic of each operator.

This was done to find out how the human error varies with operators. Figure (32) compare

the results of all four operators in the same graph.


Operator Name: Gaurav

X co-

ordinate of

spindle

Y co-

ordinate

of spindle

X co-

ordinate of

camera

Y co-

ordinate of

camera X offset Y Offset

0 0 -114.415 16.736 -114.425 16.736

-1 0 -113.438 16.742 -114.438 16.742

-1.75 0 -112.669 16.739 -114.429 16.739

-2.5 0 -111.947 16.736 -114.447 16.736

-3 0 -111.442 16.735 -114.442 16.735

-3 -0.75 -111.445 17.455 -114.445 16.725

-2.5 -0.75 -111.938 17.472 -114.438 16.722

-1.75 -1.5 -112.683 18.253 -114.433 16.743

-1 -1.5 -113.432 18.268 -114.432 16.748

0 -0.75 -114.423 17.498 -114.423 16.748

Table (3)

Operator Name: Prashanth

X co-

ordinate

of spindle

Y co-

ordinate

of spindle

X co-

ordinate

of camera

Y co-

ordinate

of camera X offset Y Offset

0 0 -114.42 16.728 -114.452 16.735

-1 0 -113.428 16.731 -114.45 16.723

-1.75 0 -112.67 16.729 -114.459 16.728

-2.5 0 -111.946 16.726 -114.451 16.725

-3 0 -111.409 16.728 -114.456 16.733

-3 -0.75 -111.411 17.5 -114.448 16.742

-2.5 -0.75 -111.949 17.503 -114.435 16.721

-1.75 -1.5 -112.652 18.24 -114.435 16.742

-1 -1.5 -113.432 18.251 -114.435 16.749

0 -0.75 -114.42 17.495 -114.438 16.741

Table (4)


Operator Name: Abhinav

X co-

ordinate of

spindle

Y co-

ordinate

of spindle

X co-

ordinate

of camera

Y co-

ordinate


0 0 -114.422 16.735 -114.42 16.728

-1 0 -113.44 16.723 -114.428 16.731

-1.75 0 -112.689 16.728 -114.42 16.729

-2.5 0 -111.901 16.725 -114.436 16.726

-3 0 -111.396 16.733 -114.419 16.728

-3 -0.75 -111.398 17.492 -114.411 16.75

-2.5 -0.75 -111.935 17.471 -114.439 16.753

-1.75 -1.5 -112.695 18.252 -114.412 16.74

-1 -1.5 -113.445 18.249 -114.432 16.741

0 -0.75 -114.418 17.46 -114.42 16.745

Table (5)

Operator Name: Neel

X co-

ordinate

of spindle

Y co-

ordinate

of spindle

X co-

ordinate

of camera

Y co-

ordinate


0 0 -114.419 16.732 -114.419 16.732

-1 0 -114.432 16.732 -115.432 16.732

-1.75 0 -114.412 16.739 -116.162 16.739

-2.5 0 -114.43 16.727 -116.93 16.727

-3 0 -114.418 16.728 -117.418 16.728

-3 -0.75 -114.425 16.738 -117.425 15.988

-2.5 -0.75 -114.436 16.755 -116.936 16.005

-1.75 -1.5 -114.439 16.729 -116.189 15.229

-1 -1.5 -114.419 16.753 -115.419 15.253

0 -0.75 -114.414 16.755 -114.414 16.005

Table (6)


Figure (24)

Figure (25)






Figure (32)

After taking the mean offset value, holes were drilled on the indentations. The centre of the

indentation was computed using the offset values. This was done by adding the offset values

to the camera co-ordinate. This brought the spindle directly over the indentation. Then a hole

was drilled. The camera was again taken to the position in order to view the hole. The centre

of the hole was computed. Theses co-ordinates were noted down.


Figure (33)

Figure (34)

Figure (35)


The difference between the drilled co-ordinates and the camera co-ordinates for the

indentation gives the error. In order to confirm the shape of the indentation, the work piece

was measured using metrology equipment at the Precision Engineering Division of Bhabha

Atomic Research Centre. Figure (35) shows the image of the equipment and the image of the

results obtained on the equipments monitor.

4.5.4 Discussion

The results obtained using second attachment is similar to the first attachment. The second

attachment helped reduce the angle α. The maximum P-V values obtained from were

approximately of the order of 20µm. Inspite of experimenting with different operators, from

fig (35), it is seen that the P-V value does not exceed 28µm for X-offset and 36µm for Y-

offset. Moreover from the experiment performed on the drilled hole using the metrology

equipment, it was seen that the form error of the circle was less than 10µm. The error due to

other sources such as environment error and machine error sums up to 5µm. Thus, it can be

concluded from the second experiment that the errors are limited between the ranges of 20µm

to 30µm. Fig (33) to fig (35) show the metrology equipment and the results that were

obtained using the equipment.

It is seen from the results that error changes with respect to the operators. The P-V has

maximum value in case of the operator being Gaurav. The P-V of other operators was almost

similar. It ranged between 15µm to 20µm. Operators Neel and Abhinav had consistent

results, which were close to the mean values. Some errors were introduced because of the

surface finish of material as well. It causes the drill to slide away from the desired point of

drill. But it has been neglected as the error is insignificant compared to the other errors.

From fig(32) is a comparison of results of all operators. Except for the case of operator

Gaurav, all other results are fairly consistent. Thus it can be concluded that human error is a

significant factor while locating the centre of an indentation. The maximum P-V value is

aroud 35µm. Neglecting the readings of operator Gaurav, the readings are around 25µm.

Hence in order to achieve high level of accuracy, the human error has to be minimized.


CHAPTER 5: CONCLUSION

The following conclusions were arrived at:

At present, no methods are available to detect the point in a micro scale. There are

methods available for edge detection, but they cannot be used for point detection

An optical based device was chosen for the method to be employed. The optical

device was selected because it was economical and can be coupled with other

applications, such as image processing. These functions are not available with other

methods that were studied.

Two attachments were developed. Both attachments had similar performances.This

led us to conclude that the major source of the error was the human error, which can

only be reduced effectively by introducing software packages that use methods such

as image processing to study the shape of the indentation. The second attachment help

reduce the angle in the Y-Z plane, which was not possible with the initial attachment.

Reducing the angle helped reduce the eccentricity.

Equations were derived for measuring the change in the offset error due to non-

perpendicularity of the optical axis of the camera and the spindle axis due to change

in height of the spindle. These equations helped minimize the error due to change in

height of the spindle.

A method was successfully developed to locate a point in micro scale. The offset error

was minimized, but human error still needs to be minimized. It is concluded that the

human error was the major source of error. The only way to minimize this error is

using computer based software such as image processing to further reduce this error.


CHAPTER 6: FUTURE SCOPE

The methodology was specifically developed for locating the centre of a circular

indentation for a tool based micro machine. However, there is scope for development of this

model. If integrated with suitable software, much higher level of precision can be achieved.

Moreover, measurement tools can be integrated with the software. The measurement tools

can be used for real time monitoring of the dimensions of work piece. This allows ease of

operation and since the components dimension can be measured without removing it for

quality control purpose. A self-focusing camera can also be used instead of the manually

focused camera that is being currently used.

Also, it has been noticed that no such facility is available for conventional CNC machine.

Thus not only can it be used for micro machines, but it can be also mounted on CNC

machines to measure real time dimensions and shape of the components. This attachment can

be used as a multipurpose device for quality control as well as real time monitoring of the

machining process.

Image processing can be used to study the shape of the indentation. Using suitable

algorithms, various parameters such as centre and area of irregular shaped object can be

calculated. Image processing technology will also help in finding out defects on the

component. The defect may be burrs, micro cracks or dust particles. This helps us to monitor

the component without unclamping it from the machine. Thus, it increases the process

efficiency.

Thus the precision of the process can only be increased by use of software or image

processing. The development will solely depend on the software available. Also, it can be

used for conventional CNC machines to monitor real time parameters.


REFERENCES

[1] Cliff Mirman; “Development of a Micro-Machining Support Platform” Proceedings of

The 2006 IJME - INTERTECH Conference.

[2] Douglas C. Montgomery; “Statistical Quality Control” Sixth Edition, Arizona State

University.

[3] Chih-Liang Chu, Tzu-Yao Tai; “Development of High-precision Micro CNC Machine

with Three-dimensional Measurement System” ICMES 2010Department of Mechanical

Engineering, Southern Taiwan University, Tainan, Taiwan.

[4] E.J.C. Bos; “Aspects of tactile probing on the micro scale” Eindhoven University of

Technology, Eindhoven, The NetherlandsDecember 27, 2010.

[5] HuaQiu, Hironobu Nisitani, Akio Kubo, Yong Yue; “Autonomous form measurement on

machining centers for free-form surfaces” Department of Mechanical Engineering, Kyushu

Sangyo University, 2-3-1 Matsukadai, Higashi-ku, Fukuoka City, 813-8503, Japan in 2004.

[6] A. Weckenmann, T. Estler, G. Peggs , D. McMurtry; “Probing Systems in Dimensional

Metrology” CIRP, 53/2/2004, pg. 657-684.

[7] G. K. Jain, A. A. Agarwal, A. M. Dalavi; “Optimization of an Error due to Non-

Perpendicularity of optical axis of Digital Microscope with the plane of Micro machine Base”

2013, IOSR-JCME 2nd National Conference on "Recent Developments in Mechanical

Engineering" (RDME-2013) Vol. 2 ISSN(e) : 2278-1684, Pg. 50.

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