Laser Fabrication and Machining of Materials

Transcription

1 Laser Fabrication and Machining of Materials

2 Narendra B. Dahotre Sandip P. Harimkar Laser Fabrication and Machining of Materials

3 Narendra B. Dahotre Professor of Materials Science and Engineering 326 Dougherty Hall Department of Materials Science and Engineering The University of Tennessee Knoxville, TN Sandip P. Harimkar 420, Dougherty Hall, Department of Materials Science and Engineering The University of Tennessee Knoxville, TN ISBN e-isbn Library of Congress Control Number: Springer Science + Business Media, LLC All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science + Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now know or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper springer.com

4 Preface This book covers the fundamental principles and physical phenomena governing laser-based fabrication/machining processes and their existing and potential applications. It provides a link between advanced materials and advanced processing/ manufacturing techniques. It connects physical science and engineering aspects together. Laser machining is an emerging area in various applications ranging from bulk machining in metal forming to micromachining and microstructuring in electronics and biomedical applications. The uniqueness of lasers lies in flexible manufacturing using lasers as assist in conventional machining techniques that has emerged into new fields like laser-assisted mechanical machining (LAM), laserassisted chemical machining (LCM), laser-assisted etching, etc. The book is intended to give a comprehensive overview of the principles and applications of lasers applied to material removal as well as forming processes in manufacturing, micromachining, and medical applications. In addition, the emerging field of LAM and machining using intersecting beams is introduced. These machining techniques have the potential for direct three-dimensional machining and microstructuring for a number of applications. The content of this book is divided into four parts comprising 14 chapters. Part I deals exclusively with the basics of lasers used in materials processing and the principles of laser materials processing including physical processes during laser material interactions. This part is intended to emphasize a dire need for understanding the physical principles of the complex tool (lasers) and processes during its use. Such understanding will allow better insight into the use of lasers in various processes described in the following parts of the book and possibly trigger thoughts for the development of new uses of lasers. Part II begins with an overview of conventional manufacturing processes and their configuration for laser-based manufacturing. The remaining chapters in Part II are mostly based on laser material removal processes such as drilling, cutting, and machining. As all laser-based processes are nonphysical (nonmechanical) and mostly thermal, the thermal principles governing material removal under various conditions are explained in these chapters. Part III includes chapters on laser processes mostly based on material addition such as rapid prototyping and welding along with the governing thermodynamic principles. Part IV dwells upon new and novel uses of lasers. Although use of lasers is new in v

5 vi Preface medicine, it is rapidly making headways in the field of biomedicine. As mentioned earlier, Part I provides sufficient basics of lasers and laser processes to spawn thoughts in one s mind for new applications of lasers. Examples of such new applications are described in chapters on laser interference processing, laser shock processing, and laser dressing of grinding wheels. It is hoped that the book will provide further impetus to many more readers to take lasers into new frontiers of applications. Thus, unlike many other books on similar topics, this book deals with the subject of laser-based fabrication and machining in a comprehensive manner. The subject matter in the proposed book extends over a wide range of disciplines that include, but are not limited to, mechanical, electrical/electronics, materials, and manufacturing. Such interdisciplinary discussion of the topic is a need of the time for many undergraduate and graduate academic programs and research activities that themselves are increasingly wielding interdisciplinary flavor. Furthermore, the scope of the subject matter ranging over macro-, to micro-, to nanolevels of processing/ manufacturing is very important to educate and prepare individuals for the next generation manufacturing. In addition, the integration of fundamental principles and physical phenomena governing laser-based fabrication/machining processes and their existing and potential applications have widened the scope of the book across the sectors of academia, research, and industry. Knoxville, TN Narendra B. Dahotre July 12, 2007 Sandip P. Harimkar

6 Acknowledgments We are indebted to many individuals, publishers, and organizations for granting us the permission to reproduce copyrighted material in the present work. We also express our sincere appreciation to Jennifer Mirski, Gregory Franklin, and Alexander Greene of Springer Science+Business Media LLC for their guidance and assistance in producing this work. We also appreciate the assistance of Anoop Samant and Sameer Paital in enhancing the figures. Finally, we thank our family, friends, and teachers for their continuous encouragement and support. vii

7 Contents Part I Fundamentals of Laser Processing Basics of Lasers Introduction Nature of Electromagnetic Radiation Laser Operation Mechanism Population Inversion Stimulated Emission Amplification Properties of Laser Radiation Monochromaticity Collimation Beam Coherence Brightness or Radiance Focal Spot Size Transverse Modes Temporal Modes Frequency Multiplication Types of Industrial Lasers Solid-State Lasers Gas Lasers Semiconductor Lasers Liquid Dye Lasers Laser Materials Interactions Introduction Absorption of Laser Radiation Thermal Effects Heating Melting Vaporization Important Considerations for Thermal Analysis ix

8 x Contents 2.4 Vapor Expansion and Recoil Pressures Plasma Formation Ablation Part II Laser Machining Manufacturing Processes: An Overview Introduction Manufacturing Processes Casting Processes Forming Processes Joining Processes Machining Processes Lasers in Manufacturing Laser Casting Laser Forming/Shaping Laser Joining Laser Machining Selection of Manufacturing Processes Properties of Materials Geometrical Complexity of Product Quality Parameters Manufacturing Economics Laser Drilling Introduction Laser Drilling Approaches Melt Expulsion During Laser Drilling Analysis of Laser Drilling Process Quality Aspects Practical Considerations Effect of Laser Parameters Effect of Focusing Conditions Effect of Assist Gas Type, Gas Pressure, and Nozzle Design Laser Drilling Applications Drilling of Cooling Holes Drilling of Diamonds Microdrilling Advances in Laser Drilling Laser Cutting Introduction Laser Cutting Approaches Evaporative Laser Cutting

9 Contents xi Laser Fusion Cutting Reactive or Oxygen-Assisted Laser Cutting Controlled Fracture Technique Quality Aspects Striations Dross Heat-Affected Zone Practical Considerations Effect of Laser Type Effect of Laser Power Effect of Optical System Effect of Nozzle Parameters Effect of Assist Gas Type Laser Cutting of Various Materials Metallic Materials Polymers Ceramics and Glasses Laser-Cutting Applications Advances in Laser Cutting Laser Cutting Assisted by Additional Energy Sources Underwater Cutting Laser Cutting of Composites and Laminates Three-Dimensional Laser Machining Introduction Laser-Assisted Machining LAM Process Analysis of LAM Process LAM Process Results Laser Machining Machining Using Single Laser Beam Machining Using Intersecting Laser Beams Applications of Three-Dimensional Laser Machining Laser Micromachining Introduction Laser Micromachining Mechanisms Laser Ablation Laser-Assisted Chemical Etching Laser Micromachining Techniques Direct Writing Technique Mask Projection Technique Interference Technique Combined Techniques

10 xii Contents 7.4 Laser Micromachining Applications Microvia Drilling Drilling of Inkjet Nozzle Holes Resistor Trimming Laser Scribing and Dicing Laser Marking and Engraving Biomedical Applications Thin Film Applications Fuel Injector Drilling Stripping of Wire Insulation Part III Laser Fabrication Laser Forming Introduction Laser Forming Processes Bending or Temperature Gradient Mechanism Buckling Mechanism Upsetting Mechanism Analysis of Laser Forming Processes Temperature Gradient Mechanism Buckling Mechanism Practical Considerations Processing Parameters Bending Rate and Edge Effects Laser Forming Strategies and Control Microstructure and Properties of Laser-Formed Components Laser Forming Applications Correction of Bending Angles Laser Forming of Complex Shapes Rapid Prototyping Flexible Straightening of Car Body Shells Microfabrication Laser Forming in Space Advances in Laser Forming Laser Forming of Tubes Laser Forming with Preload Laser Forming with Two Beams Laser Forming of Composite Materials Laser-Based Rapid Prototyping Processes Introduction Basics of Rapid Prototyping Processes Classification of Rapid Prototyping Processes

11 Contents xiii Liquid-Based RP Processes Powder-Based RP Processes Solid-Based RP Processes Concept Modelers Laser-Based Rapid Prototyping Processes Stereolithography Selective Laser Sintering Laminated Object Manufacturing (LOM) Laser Engineered Net Shaping (LENS) Applications of Rapid Prototyping Processes Applications in Rapid Prototyping Applications in Rapid Tooling Applications in Rapid Manufacturing Medical Applications Laser Welding Introduction Laser Welding Process Analysis of Laser Welding Process Quality Aspects Porosity Cracking Heat-Affected Zone Mechanical Properties of Laser Welds Practical Considerations Effect of Laser Parameters Effect of Focusing Conditions Effect of Shielding Gas Effect of Welding Speed Joint Configurations Laser Welding of Various Materials Metallic Materials Ceramics Polymers Composites Dissimilar Materials Advances in Laser Welding Arc-Augmented Laser Welding Multibeam/Dual-Beam Laser Welding Laser Welding of Tailor-Welded Blanks

12 xiv Contents Part IV Special Topics in Laser Processing Laser Interference Processing Introduction Theory of Interference Interferometry for Surface Processing of Materials Laser and Materials Aspects Interferometer Design Aspects Applications of Laser Interference Processing Crystallization and Structuring of Semiconductor Films Structuring of Monolayer and Multilayer Metallic Films Structuring of Biomaterials Laser Shock Processing Introduction Fundamentals of Laser Shock Processing Analysis of Laser Shock Processing Process Processing Parameters Effect of Laser Intensity Effect of Pulse Duration Effect of Temporal Pulse Shape Effect of Laser Wavelength Effect of Spatial Energy Distribution Effect of Coating Material Mechanical Effects During Laser Shock Processing Microstructure Modification During Laser Shock Processing Applications of Laser Shock Processing Laser Dressing of Grinding Wheels Introduction Grinding Process and Need of Wheel Dressing Laser-Based Wheel Dressing Techniques Laser-Assisted Dressing Laser Dressing Recent Approaches of Laser Dressing Lasers Processing in Medicine and Surgery Introduction Laser Tissue Interactions Photothermal Interactions Photochemical Interactions (Photoablation) Photodisruptive Interactions

13 Contents xv 14.3 Laser Applications in Medicine and Surgery Lasers in Ophthalmology Lasers in Dermatology Lasers in Otolaryngology Head and Neck Surgery Lasers in Angioplasty Lasers in Osteotomy Lasers in Dentistry Index