CONTENTS Foreword ... xiii Chapter 1. Introduction ... 1 1.1 Brief History of Ergonomics ... 3 1.2 The Interdisciplinary Nature of Ergonomics ... 4 1.3 Ergonomics for Productivity, Safety, Health and Comfort ... 4 Chapter 2. Case Studies of Implementation of Ergonomics in Manufacturing ... 7 2.1 Ergonomic Improvements in Card Assembly ... 7 2.1.1 Design Improvements ... 8 2.1.1.1 Illumination Level ... 8 2.1.1.2 Special Lighting for Inspection ... 8 2.1.1.3 Job Rotation and Shift Overlap ... 9 2.1.1.4 Personal Music ... 9 2.1.1.5 Ergonomic Chairs ... 9 2.1.1.6 Operator Communication and Feedback ... 9 2.1.1.7 Materials Handling ... 9 2.1.1.8 Automation of Monotonous Jobs ... 9 2.1.1.9 Metric to Decimal Conversion ... 9 2.1.1.10 Housekeeping ... 9 2.1.1.11 Noise Reduction ... 10 2.1.1.12 Ergonomics Training ... 10 2.1.1.13 Continuous Flow Manufacturing ... 10 2.1.1.14 Evaluation of Protective Gloves ... 10 2.1.2 Specific Problems ... 10 2.1.3 Cost Efficiency of Improvements ... 10 2.2 Ergonomic Improvements in the Assembly of a Printer ... 12 2.2.1 Task Considerations ... 12 2.2.2 Workstation Ergonomics ... 13 2.2.3 Design of Tools and Controls ... 14 2.2.4 Discussion ... 14 Chapter 3. Anthropometry in Workstation Design ... 17 3.1 Measuring Human Dimensions ... 17 3.2 Definition of Anthropometric Measures ... 21 3.3 Using Anthropometric Measures for Industrial Design ... 24 3.4 Procedure for Anthropometric Design ... 25 3.4.1 Exercise : Designing a Microscope Workstation ... 27 Chapter 4. Physical Work and Heat Stress ... 29 4.1 Physical Workload and Energy Expenditure ... 29 4.1.1 Metabolism ... 29 4.1.2 Individual Differences ... 30 4.1.3 Metabolism During Work ... 30 4.1.3.1 Example : Calculation of Relative Workload ... 32 4.1.4 Measurement of Physical Workload ... 33 4.1.4.1. Example : Fatigue Due to Physical Workload ... 33 4.2 Heat Stress ... 33 4.2.1 Thermeregulation ... 33 4.2.2 Measurement of Heat Exposure ... 34 4.2.3 Wet Bub Globe Temperature ... 34 4.2.4 Heat Stress Management ... 35 4.2.5 Comfort Climate ... 36 4.2.5.1 Example : Discussion of Heat Stress Measures ... 37 Chapter 5. Manual Lifting ... 39 5.1 Statistics of Back Injuries Associated with Lifting ... 39 5.2 A Biomechanical Model for Lifting ... 41 5.3 The So-called Correct Lifting Technique ... 43 5.4 Guidelines and Standards for Lifting ... 46 5.4.1 1991 Nosh-Equation for Evaluation of Manual Lifting ... 46 5.4.1.1 Example : Loading Punch Press Stock ... 48 5.4.1.2 Example : Product Packaging ... 49 5.4.1.3 Lifting Index ... 50 5.4.2 Guidelines for the European Community ... 50 5.4.3 Guidelines for Manual Lifting in the UK ... 50 5.5 Materials Handling Aids ... 50 5.5.1 Materials Handling Devices ... 52 5.6 Recommended Reading ... 54 Chapter 6. Choice of Work Posture : Standing, Sitting, or Standing? ... 55 6.1 Examples of Work Posture ... 55 6.2 Identifying Poor Postures ... 58 6.2.1 Example : Sitting in India ... 58 6.3 Sitting, Standing or Sit-Standing ... 59 6.4 Hand Height and Determination of Table Height ... 60 6.4.1 Example 1 ... 62 6.4.2 Example 2 ... 62 6.4.3 Example 3 ... 62 6.5 Work at Conveyors ... 63 Chapter 7. Repetitive Motion Injury ... 65 7.1 Carpal Tunnel Syndrome ... 65 7.2 Cubital Tunnel Syndrome ... 67 7.3 Tendonitis(or Tenoinitis) ... 88 7.4 Tenosynovitis(or Tendosynovitis) ... 68 7.5 Thoracic Outlet Syndrome ... 68 7.6 Cause of Repetitives Motion Injury ... 69 7.7 Design Guidelines to Minimize Repetitive Motion Injury ... 71 Chapter 8. Hand Tool Design ... 73 8.1 Fitting the Task ... 73 8.2 Designing for the User ... 74 8.3 Prevention of Injuries ... 75 8.4 Segmental Vibration ... 77 8.5 Design Guidelines : for Hand Tools ... 78 Chapter 9. Illumination at Work ... 79 9.1 Measurement of Illuminance and Luminance ... 79 9.2 Measurement of Contrast ... 80 9.2.1 Example : Contrast Requirements in Manufacturing ... 80 9.3 Use of a Photometer ... 81 9.4 Recommended Illumination Levels ... 82 9.5 The Ageing Eye ... 83 9.6 Use off Indirect (Reflected) Lighting ... 86 9.7 Cost Efficiency of Illumination ... 87 9.8 Special Purpose Lighting for Inspection and Quality Control ... 89 Chapter 10. Design of VDT Workstations ... 91 10.1 Sitting Work Posture ... 91 10.1.1 Viewing Angle ... 91 10.1.2 Thigh Clearance and Low-profile Keyboards ... 91 10.1.3 Chair Design ... 92 10.1.4 Supports for the Hands, Arms and Feet ... 83 10.1.5 Viewing Distance ... 94 10.2 Visual Fatigue ... 94 10.3 Effect of Radiation ... 95 10.4 Reducing Reflections and Glare on VDT Screens ... 96 10.4.1 Example : Calculating the Effect of a Neutral Density Filter on the Display contrast Ratio ... 99 Chapter 11. Design of Controls ... 101 11.1 Appropriateness of Manual Controls for the Task ... 101 11.2 Computer Input Devices ... 103 11.3 Control Movements Stereotypes ... 104 11.3.1 Example : Controls for an Overhead Crane in Manufacturing ... 105 11.4 Control-Response Compatibility ... 106 11.5 Coding of Controls, Hand, Tools, Part Bins and Parts ... 108 11.5.1 Coding by Location ... 108 11.5.2 Coding by Colour ... 108 11.5.3 Coding by Size ... 108 11.5.4 Coding by Shape ... 109 11.5.5 Coding by Labelling ... 110 11.5.6 Coding by Mode of Operation ... 110 11.5.7 Coding of Parts and Other Things Touched by the Hand ... 110 11.6 Emergency Controls ... 111 11.7 Organization of Items at a Workstation ... 111 11.8 Principles for the Design of Workstations ... 112 11.9 Recommended Reading ... 114 Chapter 12. Design of Symbols, Labels and Visual Displays ... 115 12.1 Symbols ... 115 12.1.1 Example : Standardization of Symbols ... 115 12.2 Labels and Written Signs ... 117 12.3 Warning Signs ... 117 12.3.1 Warning Signs ... 118 12.3.1.1 Information Overload ... 118 12.3.1.2 Attention and Active Processing ... 118 12.3.1.3 Comprehension and Agreement ... 119 12.3.1.4 Selecting and Performing a Response ... 120 Chapter 13. Development of Training Programmes and Skill Development ... 121 13.1 Establishing the Need for Training ... 121 13.2 Determining Training Content and Training Methods ... 122 13.3 The 'Why?','What?' and 'How?' of Training Development ... 123 13.4 Use of Task Analysis ... 124 13.7 Use of Job Aids ... 126 13.7.1 Example : Remembering Error Codes ... 127 13.7.2 Example : Study of Job Aids ... 127 13.8 The Power Law of Practice ... 128 13.8.1 Example : Prediction of Future Assembly Time ... 129 13.9 Recommended Reading ... 130 Chapter 14. Noise ... 131 14.1 Measurement of Sound ... 131 14.1.1 Example : Calculation of Noise Dose ... 132 14.2 Noise Exposure and Hearing Loss ... 133 14.3 Hearing Protectors ... 134 14.4 Analysis and Reduction of Noise ... 134 14.4.1 Reduction of Noise in Manufacturing Plant ... 136 14.5 Effects of Noise on Performance ... 136 14.5.1 Broadbent and Poulton's Theories ... 138 14.5.2 Example : Discussion of Theories ... 139 14.6 Annoyance of Noise and Interference with Communication ... 139 14.6.1 Interference of Noise with Spoken Communication ... 140 14.6.1.1 Preferred Noise Criteria(PNC) Curves ... 140 14.6.1.2 Preferred Speech Interference Lever(PSIL) ... 141 Chapter 15. Shift Work ... 143 15.1 Example : How Not to Schedule Shift Work ... 144 15.2 Circadian Rhythms ... 144 15.3 Problems with Shift Work ... 145 15.4 Effects on Performance and Productivity ... 146 15.5 Improving Shift Work ... 147 15.5.1 Type of Work ... 147 15.5.2 Shift Work Schedules ... 148 15.5.3 Selecting Individuals for Shift Work ... 149 15.6 Recommended Reading ... 150 Chapter 16. Whole Body Vibration ... 151 16.1 Sources of Vibration Discomfort ... 151 Chapter 17. Design for Manufacturing Assembly ... 155 17.1 The Desire to Automate ... 155 17.2 What to Do and What to Avoid in Product Design ... 157 17.2.1 Using a Base Part as the Product Foundation and Fixture ... 157 17.2.2 Minimizing the Number of Components and Parts ... 158 17.2.3 Facilitating Handling of Parts ... 159 17.2.4 Facilitating Orientation of Parts ... 160 17.2.5 Facilitating Assembly ... 161 17.2.6 Consideration of Stability and Durability ... 161 17.3 Designing Automation using Boothroyd's Principle ... 163 17.4 MTM Analysis of an Assemble Process ... 163 17.5 Human Factors Principles in Design for Assembly ... 165 17.5.1 Example : Design for Job Satisfaction ... 169 Chapter 18. Design for Maintainability ... 171 18.1 Ease of Fault Identification ... 171 18.2 Design for Testability and Troubleshooting ... 173 18.3 Design for Accessibility ... 174 18.4 Design for Ease of Manipulation ... 174 18.5 Summary ... 174 Chapter 19. Machine and Robot Safety ... 177 19.1 Safety Devices ... 177 19.1.1 Physical Barriers ... 177 19,1.2 Photoelectric Beams ... 178 19.1.3 Pressure-sensitive Mats ... 178 19.1.4 Infrared Sensors ... 179 19.1.5 Cameras and Image Processing ... 179 19.1.6 Ultrasound(Sonar) ... 179 19.1.7 Capacitive Sensors ... 179 19.2 Example : Case Study of Robot Safety at IBM Corporation/Lexmark ... 180 19.3 Recommended Reading ... 180 References ... 131 Appendix The Use of an Ergonomics Checklist in Manufacturing ... 197 Index ... 205