Ergonomics Assessment Of Sheet Metal Cutters.

ERGONOMICS ASSESSMENT OF SHEET METAL

CUTTERS

AZIMI B AB RASHID

B050810032

UNIVERSITI TEKNIKAL MALAYSIA MELAKA 2011

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

ERGONOMICS ASSESSMENT OF SHEET METAL CUTTERS

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing

Engineering (Manufacturing Management) with Honours.

by

AZIMI B AB RASHID B050810032

FACULTY OF MANUFACTURING ENGINEERING 2011

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA Ergonomics Assessment of Sheet Metal Cutters

AZIMI B AB RASHID

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DECLARATION

I hereby declare that this report entitled “Ergonomics Assessment of Sheet Metal Cutters” is the result of my own research except as cited in the references.

Signature :

Author’s Name : AZIMI B AB RASHID

APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial fulfilment of the requirements for the degree of Bachelor of Manufacturing Engineering (Manufacturing Management) with Honours. The members of the supervisory committee are as follow:

………..…...… Supervisor

i

ABSTRAK

Penyelidikan ini bertujuan untuk perlaksanaan faktor – faktor ergonomik dalam pengunaan alat pemotong besi menggunakan tangan bagi mengelakkan masalah otot tangan seperti masalah carpal tunnel, tenditis dan juga ketegangan otot. Antara faktor ergonomik yang terdapat dalam kajian ini ialah kepuasan dan keselesaan dalam menggunakan alat pemotong besi menggunakan tangan melalui rekabentuk alat. Kajian ini juga tertumpu kepada penilaian semasa menggunakan alat pemotong besi melalui perbezaan jenis alat dan juga cara pemotongan. Selain itu kajian ini memenuhi keselamatan dalam bekerja melalui faktor ergonomik untuk pekerja pemotong besi menggunakan tangan dalam industri.

ii

ABSTRACT

This research is address to the implementations of ergonomic factors in sheet metal cutters using for prevention from musculoskeletal disorder has carpal tunnel syndrome, tendinitis and muscle strain. Ergonomic factors including in this research is comfort and satisfaction feeling from the design of sheet metal cutters tools. This research focus is on the evaluation of using the sheet metal cutters tools through different tools design and different type of cutting. This research also provide to safety working from ergonomic factors for industries using the hand tools.

iii

ACKNOWLEDGEMENT

First and foremost, I would like to thank my parents and family for the endless encouragement and undying support for me complete this report especially to my father, AB RASHID B MAMAT and my mum CHE ARIAH BINTI MAT ZAIN. They have been my inspiration to bring out the best of me in completing this study.

I also wish to thank all of lecturer in Management Department of Manufacturing Engineering Faculty Universiti Teknikal Malaysia Melaka ( UTeM). In addition, thanks and apologies to others whose contributions I may have forgotten to acknowledge.

I also would like to express my sincere thank to my friends in 4BMFU. Their idea and moral support have helped me during this project. I wish them achieve their goal successfully.

iv

TABLE OF CONTENTS

Abstrak i

Abstract ii

Acknowledgement iii

Table of Content iv

List of Tables viii

List of Figures ix

List of Abbreviations xi

1. CHAPTER 1: INTRODUCTION

1.1 Background Study of Sheet Metal Cutters 1

1.2 Problem Statement 3

1.3 Objectives of Study 3

1.4 Scope of Project 4

1.5 Potential/Benefit of Project. 4

2. CHAPTER 2: LITERATURE REVIEW

2.1 Introduction 5

2.2 Repetitive Motion Injuries of the Upper Limb 6

2.3 Hand Tools Ergonomics 7

v 2.5 Methods and Techniques Used in Evaluating Hand Tools Ergonomics 9 2.5.1 Several Considerations Regarding Hand Tool Ergonomics 10

2.5.1.1 Design of Grip 10

2.5.1.2 Effectives Weight of Tools 10

2.5.1.3 Grip span and Handle Length 11

2.5.1.4 Duration and Repetitiveness of Use 11

2.5.1.5 Users Consideration 12

2.6 Comparison of Methods and Technique 12

2.7 Evaluation Sheet Metal Cutters (Tools and Technique) 13

2.7.1 Questionnaire Survey 13

2.8 Literature Review Summary Journal 15

3. CHAPTER 3: METHODOLOGY

3.1 Introduction 17

3.2 Planning of Study 17

3.2.1 Final Year Project 1 (FYP 1) 17

3.2.2 Final Year Project 2 (FYP 2) 18

3.3 Types of Sheet Metal Cutters 18

3.4 Evaluation of Sheet Metal Cutters 19

3.4.1 Questionnaire Survey 19

3.4.2 Usability Survey Questionnaire 19

3.4.3 Comfort Survey Questionnaire 20

3.4.4 Actual Testing of Tools 20

3.4.5 Straight Cutting 20

3.4.6 Curved Cutting 21

vi

3.6 Laboratory Testing of Sheet Metal Cutting 22

3.6.1 Subjective Grip Force Assessment for Sheet Metal Cutting Tasks 23

3.6.2 Tool Specifications 24

3.6.3 Steps of Laboratory Testing 25

3.7 Data Analysis Method 27

3.8 Flow Chart of Project 27

3.8.1 Selecting Title and Approval Stage 29

3.8.2 Research Stage 29

3.8.3 Design and Development Stage 29

3.8.4 Analysis Stage 29

4. CHAPTER 4: RESULTS AND DISCUSSION

4.1 Tin Snips Data Analysis 30

4.2 Overall Score Result 32

4.2.1 Pre and Post Estimate Force Score for Tin snips 33

4.2.2 Tin Snips Grip Force Score 34

4.3 Pre Estimate and Post Estimate Results 35

4.4 Tin Snips Ergonomics Factors Survey Results 38

4.4.1 Ergonomics Factors 39

4.5 Tin Snips Usability Factor Survey Results 48

4.5.1 Usability Factors 49

4.6 Additional Hand Tools Evaluation 55

4.6.1 Hand Tools Design Consideration 55

4.6.2 Hand Grip 55

4.6.2.1 Comparison Tin Snips Hand Grip 55

4.6.3 Handle Length 56

4.6.3.1 Comparison Tin Snips Handle Length 57

4.6.4 Handle Size 58

vii

4.6.5 Handle Material 59

4.6.5.1 Comparison Tin snips Handle Material 59

4.6.6 Weight of the Tools 60

4.6.6.1 Comparison Tin Snips Weight of Tools 61

4.6.7 Handle Shape 62

4.6.7.1 Comparison Tin Snips Handle Shape 62

4.7 Testing Limitation 63

5. CHAPTER 5: CONCLUSION & RECOMMENDATION

5.1 Conclusion 64

5.2 Recommendation 66

REFERENCES 67

APPENDICES A - Tin Snips Questionnaire Data & Calculation

APPENDICES B - Pre Estimate and Post Estimate Questionnaire Form APPENDICES C - Tin Snips Ergonomics and Usability Questionnaire Form APPENDICES D – Overall Results Ergonomics and Usability Questionnaire

from Participants APPENDICES E – Gantt Chart of PSM

viii

LIST OF TABLES

2.8 Literature Review Summary Journal 15

3.6.2 Tin snips tool specification 24

4.1 Overall score, pre and post estimate grip force for tin snips 31 4.2.1 Pre and post estimate force data for tin snips 34

4.2.2(a) Tin Snips 1 grip force Average score 34

4.2.2(b) Tin Snips 2 grip force Average score 34

4.2.2(c) Tin Snip 3grip force average score 34

4.3 Pre estimate and post estimate grip force result for tin snips 35

4.4 Ergonomic rating for tin snips 38

4.5 Usability rating for tin snips 48

4.6.2.1 Comparison tin snips hand grip 56

4.6.3.1 Comparison tin snips handle length 57

4.6.4.1 Tin snips comparison of handle size 58

4.6.5.1 Comparison tin snips handle material 60

4.6.6.1 Tin snips comparison for weight 61

ix

LIST OF FIGURES

3.3(a) Universal lever tin snip (Tool 1) 18

3.3(b) Aviation tin snip (Tool 2) 18

3.3(c) Tinman’s tin snip (Tool 3) 19

3.4.5 Straight cutting 20

3.4.6 Curved cutting 21

3.6(a) Type of tin snips laboratory testing 22

3.6(b) Material for tin snips testing cutting 23

3.6.3(a) Cutting tasks for tin snips 1 25

3.6.3(b) Cutting tasks for tin snips 1 25

3.6.3(c) Cutting tasks for tin snips 2 26

3.6.3(d) Cutting tasks for tin snips 2 26

3.6.3(e) Cutting tasks for tin snip 3 26

3.6.3(f) Cutting tasks for tin snip 3 26

3.8 Flow chart of the overall project process 28

4.2 Overall score result for tin snips 32

4.3 Pre estimate and post estimate force result for tin snips 36 4.3(b) Participants cutting tasks using tin snip 1 37

4.4.1(a) Tin snips 1 rectangle shape 39

4.4.1(b) Tin snip 2 curve shape 39

4.4.1(c) Tin snips 3 design of scissors principle 40 4.4.1(d) Tin snip 2 design of handles and jaws 42 4.4.1(e) Cause peak pressure on hand agrees percentage for tin snips 43

x 4.4.1(f) Feeling numb agrees percentages for tin snips 43 4.4.1(g) The tool will promote a comfortable hand posture agree

percentage for tin snips 44

4.4.1(h) Feeling slippery at handle agrees percentage for tin snips 44 4.4.1(i) Needs low hand grip force supply for tin snips 45

4.4.1(j) Has a nice feeling handle for tin snips 45

4.4.1(k) Feels clammy for tin snips 46

4.4.1(l) Good friction force between my hand and each tool for

tin snips 46 4.4.1(m) Has a good force transmission for tin snips 47

4.5.1(a) Tin snips 2 with spring return concept 49 4.5.1(b) Using this tools enable to accomplish tasks more quickly for

tin snips 51

4.5.1(c) Using this tool in my job would increase my productivity for

tin snips 51

4.5.1(d) Learning to operate this tool would be easy to me for tin snips 52 4.5.1(e) 1 would find it easy to perform cutting task for tin snips 52 4.5.1(f) 1 would find this tool easy to use for tin snips 53 4.5.1(g) Using this tool would enhance my effectiveness on the job for

tin snips 53

4.5.1(h) Using tool would make it more difficult to do my job for tin snip 54

xi

LIST OF ABBREVIATION

CM - Centimeter

CTS - Carpel Tunnel Syndrome

EMG - Electromyography

F - Female

FYP 1 - Final Year Project 1

FYP 2 - Final Year Project 2

KG - Kilogram

M - Male

P1-P11 - Participant 1 to Participant 11

Q1-Q16 - Question1 to Question 16

1

CHAPTER 1

INTRODUCTION

1.1 Background Study of Sheet Metal Cutters

Using of hand tools lead to feeling of comfort and discomfort factor. These feeling of discomfort can reduce efficiency and satisfaction of workers. Using hand tools can also cause musculoskeletal disorders for the long term. Comfortable hand tools can reduce the occupational injury for the workers. Design of hand tools very important for discomfort user and provide worker satisfaction. Comfort is considered for construct of a subjectively defined personal nature, affected by factors of various nature (physical, physiological, psychological) and reaction to environment.

Manufacturers recognize comfort as a major selling point, as it is thought to play an increasingly important role in product buying decisions. Therefore, they pay more attention to the design of comfortable hand tools, which reduce the risk of occupational injury and result in high product quality for customers, and of course, comfort for users. The major question here is, how to design hand tools that are characterized by much comfort for the user .Therefore, a clear definition of the concept of comfort is important to the designer, as well as knowledge about which factors contribute to the comfort of the end user. Comfort and discomfort have been as two discrete state ( Hertzberg, 1972; Branton, 1962), as two opposites on a continuous scale and as two separate entities underlied by different factors (Zhang et al.,1996).

2

The idea of comfort in hand tools would also extend to sheet metal cutters. The design of sheet metal cutters can highly influence comfort for users, as well as reducing the risk of upper limb musculoskeletal disorders. Sheet metal cutting may cause neck and upper limb disorder. The force, posture and frequency of movement of the hand, forearm, and wrist posture, high torque forces, high repetition, friction and shoulder has been associated with such disorder. Interaction between user and hand tool posture and muscles, irritation and pain hand fingers, irritation hand surface and handle characteristic.

Ergonomic sheet metal cutting tools expose factors are the following hand tools user considerations. Firstly in sheet metal cutting design of grip, weight, duration frequency use and gloves using would influence hand tool comfort. Worker characteristic such as left and right handed, gender and age, strength, technique, body size and posture profoundly influence both risk of injury and productivity in work with hand tool for user consideration.

Ergonomic sheet metal cutting important for avoid feeling of discomfort during the job and reduce musculoskeletal disorder on a long term. Hand tools design must be ergonomic and comfortable for workers because related with productivity.Discomfort may also reduce job satisfaction and avoid to the workers from give high performance during using the hand tool especially sheet metal cutting tools. Poor design and discomfort sheet metal cutting tools can increase the incident of chronic musculoskeletal problem disorders for hand.

3

1.2 Problem Statement

Poor design and excessive use of sheet metal cutting may be associated with increased incidence chronic disorders of the hand, wrist and forearm. Dissatisfaction using the sheet metal cutting for the long time because discomfort factor.

Short term fatigue and discomfort has been considered risk factors for musculoskeletal syndromes and have therefore been used been used as criteria in ergonomic guidelines and standard. Type of tools, the majority of injury is inflicted by non power hand tools due to the widespread use of non powered hand tools. Sheet metal cutter is a non powered hand tools. Therefore this project will focus on the evaluation and improving the design of sheet metal cutting.

1.3 Objectives of Study

The main objectives this project is to conduct an ergonomics evaluation of sheet metal cutters. This project can improve the sheet metal cutters more comfort and less comfort for users during their job. To achieve the main objectives, these sub objectives are described:

To perform a hand tool ergonomics assessment for sheet metal cutters. To conduct a usability assessment of sheet metal cutters.

To assess the subjective grip force requirements while operating sheet metal cutters.

4

1.4 Scope of Project

This project focuses to sheet metal cutting hand tools about comfort and discomfort factors, related from ergonomic sheet metal cutting design. Focus to the musculoskeletal disorder and injury factors from the type of sheet metal cutting design. Comparison and evaluate good design of sheet metal cutting from different types of tools user. Scopes in sheet metal cutters laboratory testing is curved and straight cutting only with material plate thickness 0.8 mm. Subjective of grip force testing focus for right handed users only.

1.5 Potential/Benefit of Project.

Benefit in this project is identifying musculoskeletal effect for the long term and musculoskeletal disorders using the sheet metal cutting tools. Reduce injury from the sheet metal cutting design and improve the ergonomic factor for the tools. Other benefit in this project is improving the comfort user from sheet metal cutting design and prevention worker dissatisfaction during user sheet metal cutters. Overall project benefit is sheet metal cutting improving from user aspect, design aspect and ergonomic aspect prevention long term and short term musculoskeletal problem to the workers.

5

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapters contains the literature review of the study relates to the scope of the study. Design aspect very important for develop ergonomic sheet metal cutters tools. Using hand tools must be comfort to workers for the job satisfaction.

Design of comfortable sheet metal cutters can be reduce the risk of occupational injury. Basic ergonomic principles of hand tools design have been known for several decades, limited attention has been paid these principles in designed widely used industrial tools. Guidelines has been general, lacking specify and frequently conflicting.

Using hand tools relate with musculoskeletal disorder problem especially repetitive motion injuries of the upper limb symptom. This symptom occurs when used the hand tools for the longer time period and involving repetitive work. Basic ergonomic principle can be reducing for this problem from the design of ergonomic hand tools. Design of ergonomic related with comfortable using and prevent for repetitive motion injuries problem.

6

2.2 Repetitive Motion Injuries of the Upper Limb

The concept repetitive work refers to similar tasks performed again and again. Repetitive work of the upper extremity implies motor component, which can defined in terms of time and force. Repetitive work of the upper extremity is considered one of several physical work load factor, associated with symptoms and injuries of the musculoskeletal system. Other important factors are static loads, posture, and exertion of external forces. Static load occurs when muscles are kept motionless for a long time and this is undesirable in any work situation, especially while using hand tools. The muscles become more vulnerable to fatigue and future injury.

Body posture is an effect of posture on torque exertion capability was studied in detail Mital (1986) and Mital and Channaveeriah (1988). Body posture influence using the hand tools because prevention from the awkward posture, wrist posture and effected to the musculoskeletal injuries and repetitive motion injuries.

Exertion of external forces related with type of material or working material for the tools whether give the high strength to the musculoskeletal and give the repetitive motion injuries of the upper limb.

7

2.3 Hand Tools Ergonomics

Using hand tools that require awkward and forceful hand exertions can cause (carpal tunnel syndrome, tendinitis, muscle strain, and other problems).

Carpal Tunnel Syndrome (CTS) is associated by symptoms and signs, which are caused by compression of the median nerve travelling through the carpal tunnel. Carpal Tunnel Syndrome affects the hands since it is an upper limb neuropathy that results in motor and sensory disturbance of the median nerve.

Tendinitis meaning inflammation of a type of tendinopathy often confused with the more common tendinitis, which has similar symptoms but requires different treatment. The term tendinitis should be reserved for tendon injuries that involve larger-scale acute injuries accompanied by inflammation. Generally tendinitis is referred to by the body part involved, such as Achilles tendinitis (affecting the Achilles tendon), or patellar tendinitis (jumper's knee, affecting the patellar tendon).

Muscle strain or muscle pull or even a muscle tear implies damage to a muscle or its attaching tendons. You can put undue pressure on muscles during the course of normal daily activities, with sudden, quick heavy lifting, during sports, or while performing work tasks.

8

2.4 Recent Studies on Hand Tool Ergonomics.

There have been a number of studies on the ergonomic evaluation of hand tools. One such study involved Groenesteijn et al (2004) where the authors evaluated pliers in a laboratory setting and in a field study. 3 different plier designs were evaluated. The subjects in the field study consisted of industrial workers and in the laboratory study it consisted of students. The results of the study showed that the multitask plier appeared to result in more comfort during working, more relaxed working and more satisfaction. No differences in productivity were found. Groenesteijn et al (2004) concluded that the multitask pliers can replace the originally used pliers and were suitable for more tasks than the original pliers.

Studies in an EU company from de Jong and Vink (2002) showed a high physical workload among employee. Awkward posture , heavy lifting and repetitive handling are often seen. This problem not occurs in one company and increase each of years. Awkward postures are postures that when used repetitively or for prolonged periods result in increased risk of fatigue, pain or injury. These postures are sustained either actively by muscle contractions or passively by compressive or tensile loads on bones, muscles, tendons, ligaments,etc. (Chaffin et al., 1984). Which the type of musculoskeletel disorder case is a neck and upper limb disorders.

Frequent use of hand tools could imply health risks, for the example stressful wrist posture , high torque and forces, high repetittions, frictions and pressure and vibration van der Griten (1999).

1.2 Problem Statement

Poor design and excessive use of sheet metal cutting may be associated with increased incidence chronic disorders of the hand, wrist and forearm. Dissatisfaction using the sheet metal cutting for the long time because discomfort factor.

Short term fatigue and discomfort has been considered risk factors for musculoskeletal syndromes and have therefore been used been used as criteria in ergonomic guidelines and standard. Type of tools, the majority of injury is inflicted by non power hand tools due to the widespread use of non powered hand tools. Sheet metal cutter is a non powered hand tools. Therefore this project will focus on the evaluation and improving the design of sheet metal cutting.

1.3 Objectives of Study

The main objectives this project is to conduct an ergonomics evaluation of sheet metal cutters. This project can improve the sheet metal cutters more comfort and less comfort for users during their job. To achieve the main objectives, these sub objectives are described:

To perform a hand tool ergonomics assessment for sheet metal cutters. To conduct a usability assessment of sheet metal cutters.

To assess the subjective grip force requirements while operating sheet metal cutters.

1.4 Scope of Project

This project focuses to sheet metal cutting hand tools about comfort and discomfort factors, related from ergonomic sheet metal cutting design. Focus to the musculoskeletal disorder and injury factors from the type of sheet metal cutting design. Comparison and evaluate good design of sheet metal cutting from different types of tools user. Scopes in sheet metal cutters laboratory testing is curved and straight cutting only with material plate thickness 0.8 mm. Subjective of grip force testing focus for right handed users only.

1.5 Potential/Benefit of Project.

Benefit in this project is identifying musculoskeletal effect for the long term and musculoskeletal disorders using the sheet metal cutting tools. Reduce injury from the sheet metal cutting design and improve the ergonomic factor for the tools. Other benefit in this project is improving the comfort user from sheet metal cutting design and prevention worker dissatisfaction during user sheet metal cutters. Overall project benefit is sheet metal cutting improving from user aspect, design aspect and ergonomic aspect prevention long term and short term musculoskeletal problem to the workers.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapters contains the literature review of the study relates to the scope of the study. Design aspect very important for develop ergonomic sheet metal cutters tools. Using hand tools must be comfort to workers for the job satisfaction.

Design of comfortable sheet metal cutters can be reduce the risk of occupational injury. Basic ergonomic principles of hand tools design have been known for several decades, limited attention has been paid these principles in designed widely used industrial tools. Guidelines has been general, lacking specify and frequently conflicting.

Using hand tools relate with musculoskeletal disorder problem especially repetitive motion injuries of the upper limb symptom. This symptom occurs when used the hand tools for the longer time period and involving repetitive work. Basic ergonomic principle can be reducing for this problem from the design of ergonomic hand tools. Design of ergonomic related with comfortable using and prevent for repetitive motion injuries problem.

2.2 Repetitive Motion Injuries of the Upper Limb

The concept repetitive work refers to similar tasks performed again and again. Repetitive work of the upper extremity implies motor component, which can defined in terms of time and force. Repetitive work of the upper extremity is considered one of several physical work load factor, associated with symptoms and injuries of the musculoskeletal system. Other important factors are static loads, posture, and exertion of external forces. Static load occurs when muscles are kept motionless for a long time and this is undesirable in any work situation, especially while using hand tools. The muscles become more vulnerable to fatigue and future injury.

Body posture is an effect of posture on torque exertion capability was studied in detail Mital (1986) and Mital and Channaveeriah (1988). Body posture influence using the hand tools because prevention from the awkward posture, wrist posture and effected to the musculoskeletal injuries and repetitive motion injuries.

Exertion of external forces related with type of material or working material for the tools whether give the high strength to the musculoskeletal and give the repetitive motion injuries of the upper limb.

2.3 Hand Tools Ergonomics

Using hand tools that require awkward and forceful hand exertions can cause (carpal tunnel syndrome, tendinitis, muscle strain, and other problems).

Carpal Tunnel Syndrome (CTS) is associated by symptoms and signs, which are caused by compression of the median nerve travelling through the carpal tunnel. Carpal Tunnel Syndrome affects the hands since it is an upper limb neuropathy that results in motor and sensory disturbance of the median nerve.

Tendinitis meaning inflammation of a type of tendinopathy often confused with the more common tendinitis, which has similar symptoms but requires different treatment. The term tendinitis should be reserved for tendon injuries that involve larger-scale acute injuries accompanied by inflammation. Generally tendinitis is referred to by the body part involved, such as Achilles tendinitis (affecting the Achilles tendon), or patellar tendinitis (jumper's knee, affecting the patellar tendon).

Muscle strain or muscle pull or even a muscle tear implies damage to a muscle or its attaching tendons. You can put undue pressure on muscles during the course of normal daily activities, with sudden, quick heavy lifting, during sports, or while performing work tasks.

2.4 Recent Studies on Hand Tool Ergonomics.

There have been a number of studies on the ergonomic evaluation of hand tools. One such study involved Groenesteijn et al (2004) where the authors evaluated pliers in a laboratory setting and in a field study. 3 different plier designs were evaluated. The subjects in the field study consisted of industrial workers and in the laboratory study it consisted of students. The results of the study showed that the multitask plier appeared to result in more comfort during working, more relaxed working and more satisfaction. No differences in productivity were found. Groenesteijn et al (2004) concluded that the multitask pliers can replace the originally used pliers and were suitable for more tasks than the original pliers.

Studies in an EU company from de Jong and Vink (2002) showed a high physical workload among employee. Awkward posture , heavy lifting and repetitive handling are often seen. This problem not occurs in one company and increase each of years. Awkward postures are postures that when used repetitively or for prolonged periods result in increased risk of fatigue, pain or injury. These postures are sustained either actively by muscle contractions or passively by compressive or tensile loads on bones, muscles, tendons, ligaments,etc. (Chaffin et al., 1984). Which the type of musculoskeletel disorder case is a neck and upper limb disorders.

Frequent use of hand tools could imply health risks, for the example stressful wrist posture , high torque and forces, high repetittions, frictions and pressure and vibration van der Griten (1999).