GA-PSO BASED OPTIMIZATION FOR PIN TYPE FIXTURE IN FREE FROM GEOMETRY MACHINING

BY

AHMAD NUKHAIE BIN BERAHIM

A dissertation submitted in fulfilment of the requirement for the degree of Master of Science in Manufacturing

Engineering

Kulliyyah of Engineering International Islamic University

Malaysia

JUNE 2011

ii

ABSTRACT

This dissertation presents the method of optimization of pin type fixture configuration

for holding a free form workpiece during machining process. The hybrid optimization

algorithm is manipulated to obtain the optimum configuration of pin type fixture.

Combination between Genetic Algorithm (GAs) and Particle Swarm Optimization

(PSO) algorithm has been enabled to determine optimum clamping respect to

minimum workpiece deformation. Spherical type pin type fixture is used to increase

the ability to conform to free from geometry. An array of these pins on two sides of

the workpiece in opposite direction will enable fixturing action with two supporting

action. Deformations that may result from clamping force and friction slip are

predicted by simulation of pin-workpiece clamping model and analyzed by Finite

Element methods. Maximum deformation and slip condition are evaluated by building

the parametric script of the model. Parameters of the model are assigned by the

algorithm through iteration process. Satisfied clamping arrangement to minimize the

deformation and prevent the slip is evaluated using GAs to arrange pin configuration.

PSO is further applied based on the result of GAs for obtaining global optimum of

objective function. Utilizing LabView to interface between DAQ and the fixture has

enabled automatic clamping of the fixture. Data format of pin configuration is

translated into actual clamping of pins proven by pin activation linked with solenoid

valve. The capability of actuating the pin for automatic operation has been tested by

changing several configurations of pins.

iii

ملخص البحث

دبوس من نوع خاص يلعب دور الأسلوب الأمثل لتحسين تثبيت تقدم ىذه الأطروحةتم تهجين وتحسين خوارزمية للحصول . اساسي لتثبيت قطعة العمل خلال عملية التصنيع

خوارزمية و ( GAs)حيث تم الجمع بين الخوارزمية الجينية .على الوضع الامثل لتثبيت الدبوستم . للحصول على قطعة العمل الافضل باقل تشوه لشكن( PSO)الأمثل سرب الجسيمات

حيث .استخدام مثبت دببابيس كروي الشكل لزيادة القدرة على مطابقة خالية من الذندسةستمكن لرموعة من الدسامير مثبتة على طرفي قطعة العمل باتجاىين لستلفين من عملية تثبيت

عملية وتنبأ التشويهات التي تحدث من قوة التحامل و تم توقع . جارية مع عمليتين تدعيموحلل باستخدام ( pin-workpiece)من خلال لزاكاة نموذج التحامل الدسمى الاحتكاك

تم تقويم الحد الاقصى للتشويو وضروف الانزلاق . (Finite Element) عملية العنصر المحدودالنموذج باستخدام معاملاتتم تعيين .من خلال بناء السيناريو الدبدئي لذذا النموذج

تم تقييم نسق مرضي للتحامل لتقليل التشوه ومنع . الخوارزمية من خلال عملية التكرارعلاوة على ذلك تم تطبيق . الدبوس تكوينلترتيب ( GAs)الانزلاق باستخدام خوارزمية

شملل والامثل الدهمة الاللحصول على ( GAs)بناء على نتائج خوارزمية ( PSO)خوارزمية والدثبت من تفعيل عملية ( DAQ)من التوصيل بين ( LabView)استخدام سهلو . للغرض

تم تحويل نسق بيانات تشكيل الدبوس الى ملزم دبابيس حقيقي . تحامل اوتوماتيكية للمثبتوقد تم اختبار القدرة على تشغيل الدبوس في .صمام لولبي مرتبط معمثبت مع تفعيل دبوس

.وتوماتيكية من خلال تغيير في خصائص عدة للدبابيسعملية ا

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APPROVAL PAGE

I certify that I have supervised and read this study and that in my opinion; it conforms

to acceptable standards of scholarly presentation and is fully adequate, in scope and

quality, as a dissertation for the degree of Master of Science in Manufacturing

Engineering.

…..…………………………………

Afzeri

Supervisor

I certify that I have read this study and that in my opinion it conforms to acceptable

standards of scholarly presentation and is fully adequate, in scope and quality, as a

dissertation for the degree of Master of Science in Manufacturing Engineering.

…..…………………………………

Ahsan Ali Khan

Internal Examiner

…..…………………………………

Arbeshir Bahreininejad

External Examiner

This dissertation was submitted to the Department of Manufacturing and Material and

is accepted as a fulfilment of the requirement for the degree of Master of Science in

Manufacturing Engineering.

…..…………………………………

Eri Y.T Adesta

Head, Department of Manufacturing

and Material.

This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a

fulfilment of the requirement for the degree of Master of Science in Manufacturing

Engineering.

…..…………………………………

Amir Akramin Shafie

Dean, Kulliyyah of Engineering

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DECLARATION

I hereby declare that this dissertation is the result of my own investigations, except

where otherwise stated. I also declare that it has not been previously or concurrently

submitted as a whole for any other degrees at IIUM or other institutions.

Ahmad Nukhaie Bin Berahim

Signature : …………………………… Date:………………………...

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INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

DECLARATION OF COPYRIGHT AND AFFIRMATION

OF FAIR USE OF UNPUBLISHED RESEARCH

Copyright © 2011 International Islamic University Malaysia. All rights reserved.

GA-PSO BASED OPTIMIZATION FOR PIN TYPE FIXTURE IN FREE

FROM GEOMETRY MACHINING

I hereby affirm that The International Islamic University Malaysia (IIUM), holds all

rights in the copyright of this work and henceforth any reproduction or use in any

form or by means whatsoever is prohibited without the written consent of IIUM. No

part of this unpublished research may be reproduce, stored in a retrieval system, or

transmitted, in any form or by means, electronic, mechanical, photocopying, recording

or otherwise without prior written permission of the copyright holder.

Affirmed by Ahmad Nukhaie Bin Berahim

……………………………….. ……………………..

Signature Date

vii

ACKNOWLEDGEMENTS

I would like to say Alhamdulillah, for giving me the strength and health to do this

dissertation work until it was done. Not forgotten thanking to my parents, my wife and

family for their supports, advice and patience along the way of finishing this research.

I would like to express my highest gratitude to my adviser, Dr. Afzeri for guiding me

throughout this project. Great deals of appreciation go to Kulliyyah of Engineering,

especially the Deputy Dean of Postgraduate Office, Prof. Dr. Momoh Jimoh and Sister

Mariana that have been helping me a lot in completing this dissertation. Not to forget

Dr. Eri Y.T, Head of Department Manufacturing and Material for his efforts in

helping me with this dissertation. Many thanks also to Bro. Zakaria (Tool & Die Lab)

and Bro. Suleiman who have been helping me with the experimental work.

viii

TABLE OF CONTENT

Abstract.......................................................................................................................

Approval.....................................................................................................................

Declaration..................................................................................................................

Copyright....................................................................................................................

Acknowledgements....................................................................................................

List of Tables..............................................................................................................

List of Figures.............................................................................................................

List of Abbreviations..................................................................................................

List of Symbols...........................................................................................................

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CHAPTER 1: INTRODUCTION...........................................................................

1.1 Background...........................................................................................

1.2 Problem Statement and Its Significance...............................................

1.3 Research Objectives.............................................................................

1.4 Research Methodology........................................................................

1.5 Research Scope.....................................................................................

1.4 Dissertation Outline..............................................................................

1

1

3

4

4

5

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CHAPTER 2: LITERATURE REVIEW..............................................................

2.1 Introduction.........................................................................................

2.2 Type of Fixtures...................................................................................

2.2.1 Plate Fixtures..............................................................................

2.2.2 Angle-Plate Fixtures...................................................................

2.2.3 Vise-Jaw Fixtures.......................................................................

2.2.4 Indexing Fixtures.......................................................................

2.2.5 Multi-station Fixtures.................................................................

2.2.6 Profiling Fixtures.......................................................................

2.2.7 Pin-type Fixtures........................................................................

2.3 Criteria of Fixture................................................................................

2.4 Fixture Holding Methods.....................................................................

2.5 Software Application...........................................................................

2.5.1 Utilization of FEA......................................................................

2.5.2 Genetic Algorithm......................................................................

2.5.3 Particle Swarm Optimization......................................................

2.6 Summary..............................................................................................

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CHAPTER 3: METHODOLOGY..........................................................................

3.1 Introduction.........................................................................................

3.2 Vibration analysis................................................................................

3.1.1 Design of pin-type fixture........................................................

3.1.2 Pin type fixture prototype..........................................................

3.1.3 Clamping stability evaluation...................................................

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3.3 Clamping configuration optimization...................................................

3.3.1 CAD Model for clamping..........................................................

3.3.2 Static clamping model...............................................................

3.3.3 Clamping formulation................................................................

3.3.4 Clamping optimization..............................................................

3.3.5 Automated Clamping................................................................

3.4 Summary...............................................................................................

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CHAPTER 4: RESULTS AND DISCUSSION......................................................

4.1 Introduction.........................................................................................

4.2 Results on vibration analysis..............................................................

4.2.1 Varying spindle speed (conventional fixture)............................

4.2.2 Varying spindle speed (pin type fixture)...................................

4.2.3 Varying Depth of Cut................................................................

4.3 Results on clamping optimization......................................................

4.4 Results on hybrid optimization using PSO........................................

4.5 Results on automatic clamping...........................................................

4.6 Summary............................................................................................

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CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS.........................

5.1 Conclusions........................................................................................

5.2 Future Work.......................................................................................

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BIBLIOGRAPHY.....................................................................................................

APPENDIX A............................................................................................................

APPENDIX B.............................................................................................................

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APPENDIX C............................................................................................................ 76

APPENDIX D............................................................................................................ 78

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LIST OF TABLES

Table No. Page No.

3.1 Cutting parameter used in the experiment 38

4.1 GAs parameters selected based on optimum value suggested in

literature 58

4.2 Pin Configurations to Activate Clamping 61

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LIST OF FIGURES

Figure No. Page No.

2.1 Plate fixture 8

2.2 Angle-plate fixture 9

2.3 Modified angle-plate fixture 9

2.4 Vise-jaw fixtures 10

2.5 Indexing fixture 10

2.6 Parts machined using an indexing fixture 10

2.7 Duplex fixture 11

2.8 Profiling fixture 12

2.9 Generic schematic diagram of the main concept of a pin-type fixture 12

2.10 Prototype of pin-type fixture 13

2.11 Tooling Apparatus (US Patent No. 5722646) by Soderberg 14

2.12 Effect of setting and handling time (th) on production efficiency λ 16

2.13 Effect of handling and machining times (th & tm) on production rate, Q 16

2.14 Fixture body (Base plate) 18

2.15 Locators applied onto workpiece 19

2.16 Example of a clamp on a fixture 19

2.17 Direction of acting forces for a pin clamp against the workpiece 22

2.18 Two springs connected in series each with constant k1, and k

2 25

2.19 Element ‘e’ with nodes fi and fj 25

3.1 Base plate for pin-type fixture 36

3.2 Locking plate for pin-type fixture (highlighted) 36

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3.3 Pin location obtained from solid interferes generated from pin and workpiece

surface

40

3.4 Programming flowchart for clamping simulation. 41

3.5 Pin-Workpiece contact model 43

3.6 Hybrid optimization flowchart 47

4.1 Frequency and amplitude effect of variable spindle speed during machining

when using conventional fixture; (a) Spindle speed 500rpm, (b) Spindle speed

700rpm, (c)Spindle speed 900rpm, (d) Spindle speed 1100rpm with cutting

direction normal to pin and (e) Spindle speed 1100rpm with cutting direction in

axial direction of pin

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4.2 Frequency and amplitude effect of variable spindle speed during machining

when using pin type fixture; (a) Spindle speed 500rpm, (b) Spindle speed

700rpm, (c)Spindle speed 900rpm, (d) Spindle speed 1100rpm with cutting

direction normal to pin and (e) Spindle speed 1100rpm with cutting direction in

axial direction of pin.

54

4.3 Frequency and amplitude effect of varying depth of cut during machining when

using pin type fixture; (a) Depth of cut 0.5mm, (b) Depth of cut 1.0mm, (c)

Depth of cut 1.5mm, (d) Depth of cut 2.0mm, (e) 1.0mm with cutting direction

axial to the pin.

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4.4 Result of Genetic Algorithm for 20 generations 58

4.5 Dynamics of workpiece positions during PSO evaluation 59

4.6 Port 2.3 ON and whilst Port 1.3 is OFF 62

4.7 Activated pin pushed by air flow from solenoid valve 62

4.8 LED Port 1.3 is ON and Port 2.3 is OFF 62

4.9 The Respective Pin is deactivated 63

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LIST OF ABBREVIATIONS

AISI American Iron and Steel Institute

APDL ANSYS Programming Development Language

ARX AutoCAD Runtime eXtension

CAD Computer Aided Drafting

CNC Computerized Numerical Controlled

DAQ Data AQuisition

FEA Finite Element Analysis

GA Genetic Algorithm

HSS High Speed Steel

LED Light Emitting Diode

NURBS Non-Uniform Rational B-Spline

PSO Particles Swarm Optimization

RPM Round Per Minute

PCI Peripheral Component Interconnect

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LIST OF SYMBOLS

µ Coefficient of friction

C1 Positive constant

C2 Positive constant

E Modulus of elasticity

f Acting force

Faxial Axial force

Ffriction Friction force

G Shear modulus

k Spring constant

L Distance from pin host to sphere centre

Q Production rate

Qt Ideal production rate

R Relative curvature at the contact between workpiece and pin tip

Rp Tip radius of fixture element

Rw Local radius of workpiece surface

th Handling time

tm Machining time

u Deflection

v Poisson’s ratio

w(t) Inertia ratio

δ Spherical tip deflection

λ Production efficiency

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

Fixturing is used for locating and restraining the workpiece in position and to ensure

that dimensional accuracy is maintained during machining operations. Fixturing has

been considered as one of the main problems to improve flexibility, productivity and

part quality. According to Al-Habaibeh, Gindy and Parkin (2003), fixturing is one of

the most direct threats to cost effectiveness and operation efficiency.

A fixture is a work holding device used in the manufacturing industry,

particularly in machining operations. What makes a fixture unique is that each one is

built to fit a particular part or shape of a certain product. The main purpose of a fixture

is to locate and hold a workpiece during machining operation.

According to Oberg, Jones, Horton and Ryffel (2000), a fixture holds the

workpiece while the cutting tools are in operation, but does not contain any special

arrangements for guiding the tools. On the contrary, jigs hold the workpiece and at the

same time, contain guides such as bushings and stops for the various cutting tools.

Fixtures must be securely held or fixed to the machine in which the operation

is performed. It is sometimes provided with a number of gauges and stops, but without

bushings or other devices for guiding and supporting the cutting tools. Fixtures are

normally designed for a definite operation to process a specific workpiece and are

designed and manufactured individually.

2

Fixturing probably represent the best value in today's machining technology.

The fixturing system normally costs only a fraction of the cost of a CNC machine tool,

the cutting tools, tool holders and tool changer with both the programming and design

software. Yet, the potential for time savings and process improvements offered by a

good fixturing solution is substantial. Al-Habaibeh et al (2003) suggested fixturing

systems can be divided into two types, which are: dedicated modular contact fixturing

and pin-type fixturing systems.

A modular fixture is a single-purpose device which is designed to locate and

constrain a specific part or component. Once the manufacturing process is completed,

the fixture is then stored for later use. This traditional approach is considered costly

and time consuming since it requires a special fixture to be manufactured for every

part or component.

A pin-type fixturing system has been documented in several patents within

the past 30 years (Robert, 1977; Ronald, 1978; William 1984; Soderberg, 1998). A

pin-type fixture can be used for locating and clamping of workpiece of irregular shape

during manufacturing processes.

The main concept of a pin-type fixture consists of a main body or base plate

that contains two-dimensional array of orthogonal to the base pins which protruded

upward through the surface and can be moved upwards and downwards individually,

either manually or by springs or by fluid pressure. These pins are then clamped or

locked in position so that the tips of the pin form a cradle conforming to the shape of

the workpiece, in which the workpiece is fixed for manufacturing operations. Al-

Habaibeh et al (2003) for example, proposed a pin-type fixture which incorporating

low melting metal as the source of clamping forces asserted during clamping. After

the pin tips conform the part geometry, molten metal were introduced into the system,

3

which later on set as it cools and providing a fairly good rigidity in the fixturing

system. This will be explained more in the literature study.

1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE

Selection of best fixture for holding variety of workpiece geometry tend to be time

consuming and costly. Special fixture has to be designed for specific part geometry

only. This especially occurred in the low repetitive production, where, design of new

fixture for new part geometry will affect the production cost significantly.

Reconfigurable fixturing is becoming a necessary component in order to reduce the

cost of fixture development. Afzeri et al(2005) stated that comparing with the

development of new fixturing system for new part product, pin type fixture have

possibility to reduce the production cost significantly especially for low repetitive

machining.

A setup free fixturing system not only will reduce the production cost due to

factors of the above, it will also enable remote machining system to become more

possible into realization.

Some of previous studies (Afzeri and Hoshi, 1998; Afzeri, 2004), [8] utilized

round tipped pins as locator whilst end tipped pins acting as the clamps. This will not

allow flexibility of the fixture. The end tipped pins provide lower flexibility for free-

form geometry as it cannot conform to the curved surfaced workpiece or any such

feature within a part to be machined. This research shall also investigate the clamping

capability of round tipped pins for both locating and clamping functions from both

sides of the fixture.

4

1.3 RESEARCH OBJECTIVES

The objectives of this study would be as follows:

i) To design a reconfigurable fixture and suitable for variety of part

geometries.

ii) To optimize the pin configuration by Finite Element Analysis using

intelligent algorithm.

iii) To implement automatic operation of clamping process.

iv) To evaluate the performance of pin type reconfigurable fixture by

means of vibration measurement.

1.4 RESEARCH METHODOLOGY

The dissertation is accomplished by a few methodologies which are literature reviews,

development of pin type fixture prototype, optimization of pin configuration, testing

methods and utilization of softwares, data collection from experiment and discussion

on the results.

Literature review is conducted to study the fixture concepts, fixture types and

comparison between conventional fixtures and pin type fixtures. Utilization of

intelligent algorithm is also reviewed as well as the usage Finite Element Analysis

(FEA) in fixture designs.

Prototype of the pin type fixture is developed in order to be utilized during

vibration test and automatic clamping test.

Pin configuration is optimized using intelligent algorithms. The optimization

process shall consider the deflection of workpiece during clamping as well as pin

position during clamping as fitness value.

5

Methods of testing are designed to obtain optimized pin configuration,

parameters for vibration test and automatic actuation of clamping action. Suitable

softwares are used in the development of programming language for FEA and

optimization using intelligent algorithm.

The collected data from the testing will be analyzed and discussed to support

the conclusions.

1.5 RESEARCH SCOPE

The scope of this research shall revolve around pin type reconfigurable fixture,

optimization on pin configuration of the fixture as well as stability of the fixture

during simple machining process for testing purpose.

The research will investigate the stability of pin type reconfigurable fixture

during machining free form geometry. The size of the workpiece is expected to be

proportioned against the size of the fixture.

The stability of pin type fixture is measured using vibration of sample

workpiece during simple machining process, however it will not be discussing on

surface finish, chips produced during machining or any means of research methods

regarding interest on vibration in machining. The clamping stability of pin type fixture

is measured by comparing vibration measurements of both conventional fixture

(control experiment) and pin type fixtures.

FEA is utilized in this research in order to predict workpiece and pin deflection

under given clamping force, which will be used in the optimization process. The

meshing characteristics of the sample will not be discussed.

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1.6 DISSERTATION OUTLINE

There are five chapters in this dissertation.

Chapter 1 will be an introduction to pin type fixtures. The introduction consists

of background, objectives and thesis outline.

Chapter 2 contains literature reviews on the pin type fixtures and criteria of

fixtures. Comparison of pin type fixture against other type of fixtures also will be

discussed. It also will be discussing on intelligent algorithms and software application

that is used in the research.

In Chapter 3, the research methodology will be discussed. It will explain the

vibration analysis, design of the pin type fixtures as well as prototype of pin type

fixtures, pin configuration optimization and automated clamping system.

Chapter 4 contains results obtained from pin configuration optimization,

vibration test and automatic clamping system test. Discussion on the results also will

be available in this chapter.

Last but not least, chapter 5 shall contain conclusions of the research and

recommendation on future work.

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CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

The scope of this chapter, as mentioned in chapter 1, spans on the literature reviews

on type of fixtures and comparison between conventional fixtures and pin type

fixtures. Comparison of pin type fixture against other type of fixtures also will be

discussed

For low repetitive machining job, parts received to be machined are different

against one another. Each of these parts needs its own properly designed fixture before

it can be mounted on the machine table. Designing and developing a fixture can be

time consuming. Also, setup time in changing of two different fixtures on the machine

table as well as workpiece setup for each particular part against its fixture can be

excruciating. Pin type reconfigurable fixture may have potential of reducing the setup

time for this type of production shop. However, the clamping stability of pin type

fixture must first be tested.

Utilization of intelligent algorithms is to optimize the clamping position of the

pin as well as deflection of the workpiece under given clamping force. Therefore a

review of these algorithms such as Genetic Algorithm and Particle Swarm

Optimization is made in this chapter.

In order to investigate the workpiece deflection, FEA is utilized in this

research. Therefore a brief review on FEA also has been done.

8

2.2 TYPE OF FIXTURES

The names used to describe the various types of fixtures are determined mainly by

how the fixture is built.

2.2.1 Plate Fixtures

This is the simplest form of fixture (Figure 2.1). The basic fixture is made from a flat

plate that has a variety of clamps and locators to hold and locate the part.

The simplicity of this fixture makes it useful for most machining operations.

Its adaptability makes it popular.

Figure 2.1: Plate fixture by McCauley et al (2000)

2.2.2 Angle-plate Fixtures

This fixture is a variation of the plate fixture (Figure 2.2). With this tool, the part is

normally machined at a right angle to its locator. While most angle-plate fixtures are

made at 90 degrees, there are times when other angles are needed. In these cases, a

modified angle-plate fixture can be used (Figure 2.3).

9

Figure 2.2: Angle-plate fixture by McCauley et al (2000)

Figure 2.3: Modified angle-plate fixture by McCauley et al (2000)

2.2.3 Vise-jaw Fixtures

Vise-jaw fixtures are used for machining small parts (Figure 2.4). With this type of

fixture, the standard vise jaws are replaced with jaws that are formed to fit the part.

Vise-jaw fixtures are the least expensive type of fixture to make. Their use is limited

only by the sizes of the vises available.

10

Figure 2.4: Vise-jaw Fixtures by McCauley et al (2000)

2.2.4 Indexing Fixtures

Indexing fixtures are very similar to indexing jigs (Figure 2.5). These fixtures are used

for machining parts that must have machined details evenly spaced. The parts shown

in Figure 2.6 are examples of the uses of an indexing fixture.

Figure 2.5: Indexing fixture by Hoffman (2004)

Figure 2.6: Parts machined using an indexing fixture by Hoffman (2004)