UNIVERSITI TEKNIKAL MALAYSIA MELAKA

ENGINEERING DESIGN ANALYSIS ON 5KG PAYLOAD

GRIPPER FOR COMAU ROBOT

This report submitted in accordance with the requirements of the Universiti Teknikal

Malaysia Melaka (UTeM) for the Bachelor Degree of Engineering Manufacturing

(Robotic and Automation) with Honours.

By

BONG KUAN FUNG

FACULTY OF MANUFACTURING ENGINEERING

2009

UTeM Library (Pind.1/2007)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PSM

JUDUL:

ENGINEERING DESIGN ANALYSIS ON 5KG PAYLOAD GRIPPER FOR COMAU ROBOT

SESI PENGAJIAN: Semester 2 2008/2009

Saya BONG KUAN FUNG mengaku membenarkan laporan PSM / tesis (Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:

1. Laporan PSM / tesis adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis.

2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan untuk tujuan pengajian sahaja dengan izin penulis.

3. Perpustakaan dibenarkan membuat salinan laporan PSM / tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. *Sila tandakan (√)

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA

RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh

organisasi/badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS) Alamat Tetap:

NO. 324, KPG TAPAH,

BATU 22 ½, JLN KCH SERIAN,

94200 SARAWK.

Tarikh: _______________________

(TANDATANGAN PENYELIA)

Cop Rasmi:

Tarikh: _______________________

* Jika laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak organisasi berkenaan

dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.

DECLARATION

I hereby, declared this report entitled “ENGINEERING DESIGN ANALYSIS ON

5KG PAYLOAD GRIPPER FOR COMAU ROBOT” is the result of my own

research except as cited in the references.

Signature : …………………………………

Author’s Name : BONG KUAN FUNG

Date : ………………………………...

APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a

partial fulfillment of the requirements for the degree of Bachelor of Manufacturing

Engineering (Robotic and Automation) with Honours. The members of the

supervisory committee is as follow:

………………………………………

(PSM Supervisor)

i

ABSTRACT

Gripper is general purpose robot hands, which are end effectors element in robot

applications, have been used widely in various industrial operations such as

transferring, assembling, and related manufacturing process. There are various

technological actuators of robot hands which give the power for the gripper motion.

Hydraulic, pneumatic and electrical motor system is very common actuator

technologies. In this paper, the engineering design analysis on 5kg payload gripper

for Comau robot is described. Finite element analysis is used to simulate deflections

of the gripper components under load to determine critical design parameters.

Besides that, gripper will also test under motion simulation. The system provides a

graphical and integrated environment for modeling and graphically simulating the

robot gripper when contact with the product. The result of the present study can be

used to developing the robot griper devices, optimizing their parameters and other

relevant aspects.

ii

ABSTRAK

Pencengkam merupakan penggunaan utama bagi tangan robot seperti mana

pencengkam tersebut akan disambungkan pada penghujung sesebuah tangan robot

untuk aplikasi tertentu bagi robot tersebut. Penggunaan gripper adalah luas dalam

pelbagai operasi industri seperti pemindahan barangan, pemasangan, dan

pengendalian dalam process pembuatan. Terdapat berbagai teknologi cara

mekanisme untuk gerakkan tangan robot yang memberi kuasa bagi pergerakkan

pencengkam. Contohnya, hidraulik, pneumatic, dan elektrik motor system adalah

mekanisme penggerak yang umum digunakan. Dalam projek ini, analisis rekabentuk

kejuruteraan terhadap 5kg muatan gripper untuk Comau robot akan dijalankan.

Analisis ‘finite element’ akan dilaksanakan bagi simulasi pesongan komponen

gripper apabila dikenakan muatan. Analisis tersebut penting bagi penentuan rekaan

parameter. Selain itu, simulasi pergerakan ataupun dikenali sebagai ‘motion

simulation’ juga akan dijalankan. Sistem tersebut memberi paparan grafik dan

intergrasi ruangan pergerakan untuk peragaan simulasi secara grafik terhadap

pencengkam bila mengendalikan tugas. Keputusan analisis akan digunakan untuk

perkembangan dan pernambahbaikan bagi parameter-parameter serta aspek-aspek

yang berkaitan.

iii

DEDICATION

To my beloved family and friends.

iv

ACKNOWLEDGEMENT

There are many people who deserve thanks for the contributions they have made to

this project. Firstly, I would like to express my endless grateful to my Final Year

Project’s Principal Supervisor, Encik Khairol Anuar Bin Rakiman. He directed and

instructed me through every phase of the project, and his guidance has been

invaluable. He also spent time and effort helping to resolve new issue by giving

advice and suggestion as the project developed and checking the report a number of

times.

I would like to thank my beloved parent, for their abiding love and endless patience.

Their support has been constant and enduring through the process of this project.

They deserve an enormous amount of recognition for their moral support throughout

this project. I am also grateful for all of my friends, who had giving their help and

idea in completing this project. Finally, I am deeply indebted to the lab technician

and all of the people that had directly or indirectly helped me during the period of

completing the project. Thank you.

v

TABLE OF CONTENT

Abstract i

Abstrak ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Tables viii

List of Figures ix

1. INTRODUCTION 1

1.1 Overview 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Scope 4

2. LITERATURE REVIEW 5

2.1 Overview on Gripper 5

2.2 Gripper Operation 6

2.3 Gripping Action 6

2.3.1 Internal Gripping 6

2.3.2 External Gripping 7

2.3.2.1 Friction Gripping (Force closure) 7

2.3.2.2 Retention or Encompassing Gripping (Form closure) 7

2.4 Classification of Common End Effectors 8

2.4.1 Passive End Effectors 9

2.4.1.1 Non-Prehensile Gripper 9

2.4.1.2 Warp Gripper 10

vi

2.4.1.3 Pinch Gripper 10

2.4.2 Active End Effectors and Hands 11

2.5 Component Features Considered In the Selection Process 12

2.5.1 Weight of Component 12

2.5.2 Material of Compoment 13

2.5.3 Surface Properties of the Component 13

2.5.4 Geometry of the Components 14

2.5.5 Gripper Features Considered In the Selection Process 16

2.5.6 Number of Different Components 17

2.5.7 Positional accuracy 17

2.5.8 Cycle Time 17

2.5.9 Environmental Conditions 18

2.5.10 Weight of Gripper 19

2.5.11 Gripping Force 19

2.5.12 Actuation Principle 20

2.5.13 Range of Jaw Openings 22

2.5.14 Area of Contact 22

2.5.15 Cost 22

2.6 Gripper Selection Process 23

2.6.1 Gripper Types Consideration in the Selection Process 23

2.6.1.1 Clamping Grippers 23

(a) Two-jaw Grippers 24

(b) Three-jaw Grippers 24

2.6.1.2 Flexible Grippers 25

(a) Multifingered Grippers 25

(b) Soft Grippers 26

(c) Bladder Grippers 27

(d) Adjustable-Jaw Grippers 28

(e) Single-Surface Grippers 29

(f) Magnetic grippers 29

vii

(g) Vacuum Gripper 30

(h) Adhesive Gripper 31

2.7 Conclusion 32

3. METHODOLOGY 33

3.1 Overview 33

3.2 Clarification of Task 35

3.3 Conceptual Design 35

3.4 Embodiment Design 36

3.5 Detail Design 36

4. GRIPPER DESIGN 37

4.1 Overview 37

4.2 Evaluation on Existing Gripper 38

4.3 Combination Solution Principles to Fulfill the Overall Function 40

4.4 Technical Rating Rt and Economical Rating Re 42

4.5 Selection Suitable Combinations 45

4.6 Improvement Base on Solution Variants 47

4.6.1 Improvement on Base 47

4.6.2 Improvement on Support Bar 47

4.6.3 Improvement on Slider 48

4.6.4 Improvement on Jaw 48

4.7 Optimization on gripper design 49

4.7.1 Optimization on gripper’s jaws 49

5. RESULT AND DISCUSSION 56

5.1 Overview 56

5.2 Formation of Conceptual Design 57

5.3 Griper Feature 58

5.3.1 Stability 58

viii

5.3.2 Low Cost 58

5.3.3 Minimum Gripper Weight 58

5.3.4 Flexibility 59

5.3.5 Easy of Assembly or Disassembly 59

5.4 Parts and Function of New Design 60

5.5 Cylinder Selection 62

5.6 Design Analysis 66

5.6.1 Force Acting on Parts 66

5.6.1.1 Moment Inertia of Holder with Jaws 67

5.6.1.2 Force Acting on Robot Mount 69

5.6.1.3 Force Acting on Gripper Mount 70

5.6.1.4 Force Acting on Bracket 70

5.6.1.5 Force Acting on Support 70

5.6.1.6 Force Acting on Base 71

5.6.1.7 Force Acting on Holder 71

5.6.1.8 Force Acting on Slider 72

5.6.1.9 Force Acting on Jaw 72

5.6.1.10 Force Acting on Rod 72

5.6.2 Design Analysis Using Software 73

5.7 Design Simulation 80

5.8 Conclusion on Result Obtain 80

6. CONCLUSION 84

6.1 Further Improvement Works and Suggestion 85

REFERENCES 86

ix

APPENDICES

A Engineering Drawing For Gripper

B Stress analysis on Gripper Parts

C Data Sheet for Pneumatic Cylinder

x

LIST OF TABLES

Table 2.1. Summarize of part characteristics and associated end

effector solutions. 14

Table 2.2a. Lower Power Actuator Principles. 20

Table 2.2 b. Comparison between common actuators. 21

Table 4.1 Existing griper parts and function. 39

Table 4.2 Combination scheme for different solution principle. 41

Table 4.3 Technical rating for variants. 43

Table 4.4 Economic rating for variants. 43

Table 4.5 Operation sequence for existing gripper design. 50

Table 4.6 Operation sequence for new gripper’s jaw design. 52

Table 5.1 New gripper parts and function. 60

Table 5.2 Parts quantities and weights. 61

Table 5.3 Cylinders characteristic and specification. 64

Table 5.4 Evaluation on cylinders. 65

Table 5.5 Result of base design analysis. 77

Table 5.6 Summarize result of design analysis for griper parts. 78

Table 5.7 Simulation of gripper attached on Comau robot. 80

xi

LIST OF FIGURES

Figure 2.1. Types of gripper action. 6

Figure 2. 2. External griping action. 8

Figure 2.3. A classification of the basic end effectors types. 8

Figure 2.4. A noncontact end effector for acquiring and transporting

delicate wafers. 9

Figure 2.5. Compliant pneumatic gripper executes a gentle wrap grasp. 10

Figure 2.6. A gripper with pivoted fingers designed. 11

Figure 2.7. Two-finger servo gripper with force sensing and

changeable fingertips. 12

Figure 2.8. Type of power driven shown in force versus speed. 21

Figure 2.9. Gripper classification for selection process. 23

Figure 2.10a. Two-jaw grippers. 24

Figure 2.10b. Three-jaw grippers. 24

Figure 2.11. Flexible gripper material handling. 25

Figure 2.12. Multifingers gripper material handling. 26

Figure 2.13. The flexible gripping action of the soft gripper. 27

Figure 2.14. Pulley-and-wire mechanism for soft finger. 27

Figure 2.15. Bladder Clamps handle fragile products gently. 28

Figure 2.16. (a) Adjustable jaw with laminated plate cams.

(b) Flexibility of jaw stacks arrangement.

(c) Gripping odd shaped work piece. 29

Figure 2.17. Magnetic gripper, handling ferromagnetic workpieces. 30

Figure 2.18. Type of vacuum gripper. 30

Figure 2.19. Adhesive gripper for fabric handling. 31

xii

Figure 3.1 Flow of Work for Design and Analysis Process. 34

Figure 4.1 Existing gripper design. 38

Figure 4.2 Comparison of the technical and economic rating of the

concept variants. 44

Figure 4.3 Selection of combinations of solution principles (variants). 46

Figure 4.4 Optimization on gripper’s jaw. 51

Figure 4.5 Bottom view of gripper’s jaw arrangement. 52

Figure 4.6 Optimized gripper operates with roller conveyor. 53

Figure 4.7 Holder. 54

Figure 4.8 Rubber pad. 55

Figure 5.1 Conceptual design. 57

Figure 5.2 Forces acting on gripper. 62

Figure 5.3 Rotation of holder. 67

Figure 5.4 Force acting on robot mount. 69

Figure 5.5 Force acting on gripper mount. 70

Figure 5.6 Force acting on bracket. 70

Figure 5.7 Force acting on support. 70

Figure 5.8 Force acting on base. 71

Figure 5.9 Force acting on holder. 71

Figure 5.10 Force acting on slider. 72

Figure 5.11 Force acting on jaw. 72

Figure 5.12 Force acting on rod. 72

Figure 5.13 Forces acting at the base. 73

Figure 5.14 Stress occur on base due to applied forces. 74

Figure 5.15 Displacement changes due to applied forces. 75

Figure 5.16 Strain analyses due to applied forces. 76

Figure 5.17 Design check on factor of safety. 77

xiii

Figure 5.18 Graph of stress analysis results. 79

1

CHAPTER 1

INTRODUCTION

1.1 Overview

According to dictionary of McGraw-hill（2003）, gripper is define as a component of

robot that grasp an object, generally through the use of suction cups, magnets, or

articulated mechanism. Gripper provides the capacity to do a wide variety of

manipulative task. Robotic hand or gripper is the integral part in most of the robot

application. A robot arm itself can serve no purpose until a load or a tool is

suspended from or attached to it. The robotic application in assembly and material

handling is growing more rapidly in industrial environment. Thus, design of robotic

gripping mechanism always becomes the key element for a specific operation.

The main function of a gripper is to grasp and to release workpieces during the

material transfer route. Generally, the gripper for industrial robots is a specialized

device that is used to handle only one or a few objects of similar shape, size and

weight in a repetitive operation, which requires minimum gripping dexterity and is

limited in its versatility. However, in other applications, the robot gripper will be

required to handle many different objects of varying weights, shapes, and material.

Then, we shall refer to a more universal or versatile grippers. Gripper types will be

discussed furthers in literature review.

2

The gripper is the mechanical interface between the robot and the work and the

device with which the robot performs its programmed handling functions. Correctly

selecting the gripper for an application is essential to the success of the application.

Arthur G. Erdman (1986) explained that gripper selection is a may not be an easy

task since there are wide variety of gripper types and configurations and many

different factors to consider. Information on the factors which are relevant to the

selection process is incomplete and tends to be qualitative. The material available

and ease or manufacturing is also an important consideration.

In this study, a robot gripper that has been design by the previous students is required

be to fully analyses for its physical properties when handling load. Solid Work will

be use as the analysis software for finite element analysis to the gripper. Finally, the

gripper has to go through workspace testing by using simulation software to observe

its performance in real time working situation.

1.2 Problem Statement

The design analysis of robotic gripper is highly complex and environment dependent.

To deal with complexity, the entire design project has to be broken down into several

sub problems which are then treated independently as optimization problem.

However, the constraints are generally dependent on each other. Its also appear that

more than one constraint have to be minimize simultaneously. It may require

minimize weight of gripper and the stability of the grasp.

The study of this project is focus on improvement and continuation work on the

previous PSM project which is a 10kg payload gripper for Comau robot. Basically

the gripper design has been carried out in the last PSM. Since the current task is

design analysis on 5kg payload gripper for Comau robot, this mean there would be a

reducing in weight of payload from previous design while maintains it efficiency.

3

Often, very little time is spent in optimal kinematics structure design in the early

stages of a design process. D. T. Pham (1988) describes that a time pressures

sometimes force engineers to repeat topologies that have worked in similar

application in the past rather than try to create better design. It is always encourages

to follow the previous design unless the design analysis really proven that it was not

good. Thus, modification and optimization are requires to upgrade the design to

achieve a better performance.

Generally, a physical prototype is necessary to truly test a hand’s ability to perform

tasks, but this can be quite costly and design changes are not easy to make. Thus it

would need a simulation system that able to load a gripper hand design, to interact

with it and perform grasps of objects, and to visualize and evaluate the space of

performance and error that might occurs.

1.3 Objectives

The objective of this project is to design analysis the existing design gripper to

perform a pick and place operation for 5kg payload boxes. Below are important

objective has to be achieved:

a) Analysis on existing design

b) Finalize complete engineering design analysis and relevant aspects

c) Simulate the gripper performance

4

1.4 Scope

The scope is focused on related aspect in this project so that the objectives are able to

accomplish. Scope on this project will cover up the below task:

a) Improvement on existing design or drawing.

b) Design analysis on finite element using SolidWorks.

c) Run complete simulation on predefined layout.

5

CHAPTER 2

LITERATURE REVIEW

2.1 Overview on Gripper

A gripper is a device that grasps, retains and eventually releases a workpiece. It can

hold, tighten, handle and release an object just like a human hand. It can be attached

to a robot or be part of a fixed automation system. Because this component handles

the workpiece, the gripper must be selected and applied carefully. The design and

construction of highly dexterous robot hands has been a major research and

development objective for at least the past two decades. It was inspired by the

well-known Utah/MIT robot hands during the 1980’s explained by S .C. Jacobson

(1986).

The analysis of mechanical fixture and jig goes back to the work of Releaux (1875).

He analyzed the condition under which object or part can be completely restrained

and define form closure. While gripper and fixture have been used extensively in

industry, the field of robot grasping started with the work of Asada and Hanfusa

(1979) first attempts to develop three fingered robotic hand.

6

2.2 Gripper Operation

Consider an object grasped at a contacts, it is generally assumed that all contacts are

point contacts and idealizations such as a line or surface contact can be approximated

by two ore more point contacts. Each point contact can be modeled as either a

frictionless point contact, a frictional point contact, or a soft contact. A frictionless

contact is defined as a contact in which the finger can only exert force along common

normal at the point of contact. A frictional contact is contact that can transmit both a

normal force and a tangential force at the point of contact. While soft contact also

allows the finger to exert a pure torsion moment about common normal at the point

of contact.

2.3 Gripping Action

2.3.1 Internal Gripping

In some applications, the object geometry or the need to access the exterior of the

object will require that the object is held from the center. In this case the opening

force of the gripper will be holding the object. Figure 2.1 below shown an internal

and external grip.

Figure 2.1: Types of gripper action.

7

2.3.2 External Gripping

This is the most popular method of holding objects, it is the most simplistic and it

requires the shortest stroke length. When the gripper jaws close, the closing force of

the gripper holds that object.

External gripping action can be classified into two categories as shown in Figure 2.1.

2.3.2.1 Friction Gripping (Force Closure)

Friction gripping relies totally on the force of the gripper to hold the part. They are

the easiest to fabricate and may require more force to hold the object. This is

especially useful for objects that do not have flat surfaces. Parts can be removes by

forces applied from any direction. The coefficient of friction between the workpiece

and the gripper fingers can vary greatly depending on the material and surface finish.

For consistency in sizing purpose, the recommended coefficient of friction always is

0.25. Force closure is also known as frictional contact since it transmits both a

normal force and a tangential force at the point of contact.

2.3.2.2 Retention or Encompassing Gripping (Form closure)

The gripping jaws will hold the object and support it in the jaws. It is the preferred

method since it adds stability to holding the object and requires less force to hold the

object, to drop the object we must overcome the force to open the jaws. The travel

stroke of the gripper may have to be increased to encompass the object. While an

encompassing grip is preferred, less pressure required to grip the part, more stable

during movement throughput the work cell. It can be consider as a line or surface

contact can be approximated by two or more point contacts.