Laser Material Processing ||

Lasers play a major part in the processing of the disparate materials used in engineering and manufacturing. The range of procedures in which they are involved is ever increasing. The informal style of Laser Material Processing (4th Edition) will guide you smoothly from the basics of laser physics to the detailed treatment of all the major materials processing techniques for which lasers are now essential. • Helps you to understand how the laser works and to decide which laser is best for your purposes. • New chapters on laser physics, drilling, micro- and nanomanufacturing and biomedical laser processing reflect the changes in the field since the last edition, updating and completing the range of practical knowledge about the processes possible with lasers already familiar to established users of this well-known text. • Provides a firm grounding in the safety aspects of laser use. • Now with end-of-chapter exercises to help students assimilate information as they learn. • The authors’ lively presentation is supported by a number of original cartoons by Patrick Wright and Noel Ford which will bring a smile to your face and ease the learning process. Laser Material Processing (4th Edition) will be of use as university or industrial course material for senior undergraduate, graduate and non-degree technical training in optoelectronics, laser processing and advanced manufacturing. Practising engineers and technicians in these areas will also find the book an authoritative source of information on the ever- expanding use of industrial lasers in material processing. Praise for the third edition: "It is the great merit of this book to offer a compact survey on laser material processing. A useful and fascinating book, pleasant to read with many useful figures and examples of industrial applications. It is a textbook for advanced students in this field, but also a reference book for engineers." H. Weber, Technische Universität Berlin "Laser Material Processing is a clear and instructive textbook for students who will become the next generation of laser specialists, and it is a good source of updated knowledge for practicing engineers and technicians in optoelectronics, laser processing, materials treatment, and advanced manufacturing. The book also will be helpful as a reference source. The chapters are largely independent of one another, and a reader interested in only one topic may be satisfied by reading all of parts of the relevant chapter without going to other chapters. Well written, with many useful diagrams and examples of industrial applications, Steen’s book is a good guide in the field." The Industrial Physicist "Material processing is one of the most important applications of lasers.… Laser Material Processing gives a compact survey and can be used as university or industrial course material…. The book will guide the reader smoothly from the basics of laser physics to the detailed treatment of all major material processing techniques for which lasers are essential.… I can recommend this book as an authoritative source of information on the rapidly expanding use of industrial lasers in material processing. " Optik Prologue References 1 Background to Laser Design and General Applications 1.1 Basic Principles of Lasers 1.1.1 Stimulated Emission Phenomenon 1.1.2 Basic Components of a Laser 1.1.3 Physics of the Generation of Laser Light 1.1.4 Relationship Between the Einstein Coefficients 1.1.5 Lifetime Broadening 1.1.6 Transition Rates for Monochromatic Waves 1.1.7 Amplification by an Atomic System 1.1.8 The Laser: Oscillation and Amplification 1.2 Laser Construction Concepts 1.2.1 Overall Design 1.3 Types of Laser 1.3.1 Gas Lasers 1.3.2 Solid-state Lasers 1.3.3 Dye Lasers 1.3.4 Free-electron Lasers 1.4 Applications of Lasers 1.4.1 Powerful Light 1.4.2 Alignment 1.4.3 Measurement of Length 1.4.4 Velocity Measurement 1.4.5 Holography 1.4.6 Speckle Interferometry 1.4.7 Measurement of Atmospheric Pollution and Dynamics 1.4.8 Inspection 1.4.9 Analytical Technique 1.4.10 Recording 1.4.11 Communications 1.4.12 Heat Source 1.4.13 Medical Uses 1.4.14 Printing 1.4.15 Isotope Separation 1.4.16 Atomic Fusion 1.4.17 Stimulated Radioactive Decay? 1.5 Market for Laser Applications References 2 Basic Laser Optics 2.1 The Nature of Electromagnetic Radiation 2.2 Interaction of Electromagnetic Radiation with Matter 2.2.1 Nonlinear Effects 2.3 Reflection or Absorption 2.3.1 Effect of Wavelength 2.3.2 Effect of Temperature 2.3.3 Effect of Surface Films 2.3.4 Effect of Angle of Incidence 2.3.5 Effect of Materials and Surface Roughness 2.4 Refraction 2.4.1 Scattering 2.5 Interference 2.6 Diffraction 2.7 Laser Beam Characteristics 2.7.1 Wavelength 2.7.2 Coherence 2.7.3 Mode and Beam Diameter 2.7.4 Polarisation 2.8 Focusing with a Single Lens 2.8.1 Focused Spot Size 2.8.2 Depth of Focus 2.9 Optical Components 2.9.1 Lens Doublets 2.9.2 Depolarisers 2.9.3 Collimators 2.9.4 Metal Optics 2.9.5 Diffractive Optical Elements – Holographic Lenses 2.9.6 Laser Scanning Systems 2.9.7 Fibre Delivery Systems 2.9.8 Liquid Lenses 2.9.9 Graded-index Lenses 2.10 Conclusions References 3 Laser Cutting, Drilling and Piercing 3.1 Introduction 3.2 The Process – How It Is Done 3.3 Laser Drilling and Piercing 3.3.1 Introduction 3.3.2 Drilling Process Variations 3.3.3 Percussion and Single- or Double-shot Drilling 3.3.4 Drilling Ceramic-coated Material 3.3.5 Trepanning 3.3.6 Helical Trepanning 3.3.7 Applications of Laser Drilling 3.3.8 Monitoring the Drilling Process 3.4 Methods of Cutting 3.4.1 Vaporisation Cutting/Drilling 3.4.2 Fusion Cutting – Melt and Blow 3.4.3 Reactive Fusion Cutting 3.4.4 Controlled Fracture 3.4.5 Scribing 3.4.6 Cold Cutting 3.4.7 Laser-assisted Oxygen Cutting – the LASOX Process 3.5 Theoretical Models of Cutting 3.6 Practical Performance 3.6.1 Beam Properties 3.6.2 Transport Properties 3.6.3 Gas Properties 3.6.4 Material Properties 3.6.5 Practical Tips 3.7 Examples of Applications of Laser Cutting 3.7.1 Die Board Cutting 3.7.2 Cutting of Quartz Tubes 3.7.3 Profile Cutting 3.7.4 Cloth Cutting 3.7.5 Aerospace Materials 3.7.6 Cutting Fibre Glass 3.7.7 Cutting Kevlar'256 3.7.8 Prototype Car Production 3.7.9 Cutting Alumina and Dielectric Boards 3.7.10 Furniture Industry 3.7.11 Cutting Paper 3.7.12 Flexographic Print Rolls 3.7.13 Cutting Radioactive Materials 3.7.14 Electronics Applications 3.7.15 Scrap Recovery 3.7.16 Laser Machining 3.7.17 Shipbuilding 3.7.18 The Laser Punch Press 3.7.19 Manufacture of Bikes and Tubular Structures 3.7.20 Cutting and Welding of Railcars 3.8 Costed Example 3.9 Process Variations 3.9.1 Arc-augmented Laser Cutting 3.9.2 Hot Machining 3.10 Future Developments 3.10.1 Higher-powered Lasers 3.10.2 Additional Energy Sources 3.10.3 Improved Coupling 3.10.4 Smaller Spot Size 3.10.5 Increased Drag 3.10.6 Increased Fluidity 3.11 Worked Example of Power Requirement References 4 Laser Welding 4.1 Introduction 4.2 Process Arrangement 4.3 Process Mechanisms – Keyholes and Plasmas 4.4 Operating Characteristics 4.4.1 Power 4.4.2 Spot Size and Mode 4.4.3 Polarisation 4.4.4 Wavelength 4.4.5 Speed 4.4.6 Focal Position 4.4.7 Joint Geometries 4.4.8 Gas Shroud and Gas Pressure 4.4.9 Effect of Gas Pressure – Due to Velocity and Environment 4.4.10 Effect of Material Properties 4.4.11 Gravity 4.5 Process Variations 4.5.1 Arc-augmented Laser Welding 4.5.2 Twin-beam Laser Welding 4.5.3 Walking and Spinning Beams 4.5.4 Laser Welding of Plastics 4.6 Applications for Laser Welding in General 4.7 Costed Example References 5 Theory, Mathematical Modelling and Simulation 5.1 Introduction 5.2 What is a Model? 5.2.1 Derivation of Fourier's Second Law 5.3 Analytical Models with One-dimensional Heat Flow 5.4 Analytical Models for a Stationary Point Source 5.4.1 The Instantaneous Point Source 5.4.2 The Continuous Point Source 5.4.3 Sources Other than Point Sources 5.5 Analytical Models for a Moving Point Source 5.6 Alternative Surface Heating Models 5.6.1 The Ashby–Shercliffe Model: The Moving Hypersurface Line Source 5.6.2 The Davis et al. Model: The Moving Gaussian Source 5.7 Analytical Keyhole Models – Line Source Solution 5.7.1 Line Source on the Axis of the Keyhole 5.7.2 Line Source Around the Surface of a Cylinder: One-dimensional Transient Model for Cylindrical Bodies 5.7.3 Analytical Moving Point–Line Source 5.8 Three-dimensional Models 5.8.1 Three-dimensional Model for a Semi-infinite Plate 5.8.2 Three-dimensional Transient Model for Finite Slabs 5.9 Numerical Modelling 5.9.1 Three-dimensional Thermal Model 5.9.2 Flow Within the Melt Pool – Convection 5.9.3 Pool Shape 5.9.4 Some Model Results 5.9.5 Effect of Flow on Surface Deformation 5.9.6 Model for Flow with Vaporisation 5.9.7 Mass Additions – Surface Alloying and Cladding 5.10 Modelling Laser Ablation 5.11 Semiquantitative Models 5.12 Conclusions References 6 Laser Surface Treatment 6.1 Introduction 6.2 Laser Heat Treatment 6.2.1 Heat Flow 6.2.2 Mass Flow by Diffusion 6.2.3 Mechanism of the Transformation Process 6.2.4 Properties of Transformed Steels 6.3 Laser Surface Melting 6.3.1 Solidification Mechanisms 6.3.2 Style of Solidification 6.4 Laser Surface Alloying 6.4.1 Process Variations 6.4.2 Applications 6.5 Laser Cladding 6.5.1 Laser Cladding with Preplaced Powder 6.5.2 Blown Powder Laser Cladding 6.5.3 Applications 6.6 Particle Injection 6.7 Laser-assisted Cold Spray Process 6.8 Surface Texturing 6.9 Enhanced Electroplating 6.10 Laser Chemical Vapour Deposition 6.11 Laser Physical Vapour Deposition 6.12 Noncontact Bending 6.13 Magnetic Domain Control 6.14 Laser Cleaning and Paint Stripping 6.15 Surface Roughening 6.16 Scabbling 6.17 Micromachining 6.18 Laser Marking 6.19 Shock Hardening 6.20 Conclusions References 7 Rapid Prototyping and Low-volume Manufacture 7.1 Introduction 7.2 Range of Processes 7.2.1 Styles of Manufacture 7.2.2 Classification of Rapid Prototyping Techniques by Material 7.3 Computer Aided Design File Manipulation 7.4 Layered Manufacturing Issues 7.4.1 General 7.4.2 Stair Stepping 7.4.3 Layer Thickness Selection 7.4.4 Accuracy 7.4.5 Part Orientation 7.4.6 Support Structures 7.5 Individual Processes 7.5.1 Stereolithography 7.5.2 Selective Laser Sintering 7.5.3 Laminated-object Manufacture 7.5.4 Laser Direct Casting or Direct Metal Deposition (DMD) 7.6 Rapid Manufacturing Technologies 7.6.1 Silicone Rubber Moulding 7.6.2 Investment Casting 7.6.3 Sand Casting 7.6.4 Laser Direct Casting 7.6.5 Rapid Prototyping Tooling 7.7 Applications 7.8 Conclusions References 8 Laser Ablative Processes – Macro- and Micromachining 8.1 Introduction 8.2 Basic Mechanisms During Short Radiant Interactions 8.2.1 Thermal Models 8.2.2 Nonthermal Models 8.3 Case 2: Nanosecond Pulse Impact 8.4 Case 3: Ultrashort Pulses 8.5 Applications 8.5.1 Low-energy Pulses (Less than 150nJ) 8.5.2 Medium-energy Pulses (150–500nJ) 8.5.3 High-energy Pulses (More than 500nJ) 8.6 Summary References 9 Laser Bending or Forming 9.1 Introduction 9.2 The Process Mechanisms 9.2.1 The Thermal Gradient Mechanism 9.2.2 The Point Source Mechanism 9.2.3 The Buckling Mechanism 9.2.4 The Upsetting Mechanism 9.2.5 Laser-induced Shock Bending 9.3 Theoretical Models 9.3.1 Models for the Thermal Gradient Mechanism 9.3.2 The Buckling Mechanism Model 9.3.3 The Upsetting Mechanism Model 9.4 Operating Characteristics 9.4.1 Effect of Power 9.4.2 Effect of Speed – ``Line Energy'' 9.4.3 Effect of Material 9.4.4 Effect of Thickness – Thickening at the Bend 9.4.5 Effect of Plate Dimensions – Edge Effects 9.4.6 Effect of the Number of Passes 9.5 Applications 9.6 Conclusions References 10 Laser Cleaning 10.1 Introduction 10.2 Mechanisms of Laser Cleaning 10.2.1 Selective Vaporisation 10.2.2 Spallation 10.2.3 Transient Surface Heating 10.2.4 Evaporation Pressure 10.2.5 Photon Pressure 10.2.6 Ablation (Bond Breaking) 10.2.7 Dry and Steam Laser Cleaning 10.2.8 Angular Laser Cleaning 10.2.9 Laser Shock Cleaning 10.3 An Overview of the Laser Cleaning Process 10.4 Practical Applications References 11 Biomedical Laser Processes and Equipment 11.1 Introduction 11.2 Interaction of Laser Radiation with Biological Tissue 11.2.1 Optical Properties of Biological Tissue 11.2.2 Thermal Properties of Tissue 11.2.3 Mechanical Properties of Tissue 11.2.4 Tissue Heating Effects – Nonablative Heating 11.2.5 Tissue Heating Effects – Ablation 11.2.6 Tissue Heating – Nonlinear Interactions with a Laser Beam 11.3 Medical Applications of Lasers 11.3.1 Ophthalmology 11.3.2 Surgical Applications 11.4 Medical Diagnostics 11.4.1 Absorption Techniques 11.4.2 Spectral Techniques 11.4.3 Visualisation Techniques 11.5 Laser Manufacture of Medical Devices 11.5.1 Laser Cutting 11.5.2 Marking 11.5.3 Wire Stripping 11.5.4 Laser Welding 11.5.5 Nanomedicine 11.5.6 Scaffolds for Tissue Engineering 11.6 Conclusion References 12 Laser Automation and In-process Sensing 12.1 Automation Principles 12.2 In-process Monitoring 12.2.1 Monitoring Beam Characteristics 12.2.2 Monitoring Worktable Characteristics 12.2.3 Monitoring Process Characteristics 12.3 In-process Control 12.3.1 In-process Power Control 12.3.2 In-process Temperature Control 12.4 ``Intelligent'' In-process Control 12.5 Conclusions References 13 Laser Safety 13.1 The Dangers 13.2 The Standards 13.3 The Safety Limits 13.3.1 Damage to the Eye 13.3.2 Damage to the Skin 13.4 Laser Classification 13.5 Typical Class 4 Safety Arrangements 13.6 Where Are the Risks in a Properly Set Up Facility? 13.7 Electrical Hazards 13.8 Fume Hazards 13.9 Conclusions References Epilogue 14.1 Power Intensity 14.2 Power Transmission 14.3 Power Shaping 14.4 Automation 14.5 Beam Coherence 14.6 Beam Spectral Purity 14.7 Multiphoton Events 14.8 Frequency-related Events 14.9 Equipment Developments 14.10 Unthought-of Concepts Index