Lasers in 3D Printing and Manufacturing

The following sections are included:

• FOREWORD
• PREFACE
• ACKNOWLEDGEMENTS
• ABOUT THE AUTHORS
• LIST OF ABBREVIATIONS
• CONTENTS

This book will cover the basics of lasers, optics and materials used for 3D printing and manufacturing. It will also include several case studies for readers to apply their understanding of the topics, provide sufficient theoretical background and insights to today’s key laser-assisted AM processes, and conclude with the future prospects of this exciting technology. Non-Traditional Manufacturing (NTM) processes refer to processes in which non-traditional energy transfer mechanism and/or non-traditional media for energy transfer are involved. NTM processes can machine precision components from conventional and advanced materials such as superalloys, composites and ceramics. A reduced number of machining steps and a higher product quality are some of the advantages they offer. NTM offers an attractive alternative and often the only choice for the processing of these materials. The new and potential applications require enhanced process capabilities and more precise process design and optimisation capabilities. In response, substantial progress in research has been made in recent years, especially in the areas of process innovation, modelling, simulation, monitoring and control. Laser-assisted manufacturing and 3D printing falls into these categories. This book will give a clear and concise coverage of the fundamentals and the applied technological aspects of this exciting and highly impactful technology.

In this chapter, the fundamentals of light-matter interaction are discussed with illustrative examples. It begins with the description of electromagnetic radiations and the three types of phenomena that occur when light interacts with matter. This is followed by the working principle of lasers and their characteristics. The chapter concludes with collimation optics, polarisation and different but related optical components which form the basic optics for laser-assisted manufacturing and 3D printing.

For realising higher resolution and higher productivity in laser-based 3D printing and manufacturing over various materials, photon interaction with target materials should be carefully considered. Materials for 3D printing and manufacturing are categorised into different ways depending on their applications, but generally can be categorised as either polymers, metals or ceramics. In the field of 3D printing, materials are better to be categorised by their original form as solid-, liquid- or powder-based ones. In this chapter, various materials in laser-based 3D printing and manufacturing will be discussed for the best quality material rocessing.

In this chapter, the fundamentals of laser-assisted manufacturing are discussed with illustrative examples. Both continuous wave and short pulse laser-assisted manufacturing are illustrated; showing the differences in their material removal mechanisms. The chapter begins with an introduction on laser machining, highlighting the advantages it can offer compared to conventional machining processes. A detailed account on one-, two- and three- dimensional laser machining processes are discussed. The chapter ends with a discussion on the various laser material processes and the role of focusing the laser beam for the purpose of achieving the desired effects.

There are three fundamental manufacturing processes for 3D structures: subtractive, additive and formative. Conventional manufacturing processes have long been based on subtractive and formative ones. Additive manufacturing (also called 3D printing) was first demonstrated for rapid prototyping in the 1990s and is now expanding its territories to include the efficient production of complex multi-material structures over a wide range of manufacturing applications. Lasers can be applied to all of these subtractive, additive and formative processes as highly efficient energy sources. Based on the initial form of a material, all 3D printing system can be categorised into (1) liquid-based, (2) solid-based and powder-based ones; the basic principle, system design, laser characteristics and applications of laser-based 3D printing systems will be studied in this chapter based on this categorisation.

Patterning and printing 2D and 3D structures on different materials, which also include photosensitive materials, found tremendous interest among the scientific and industrial communities. Laser interference based concepts and methodology can make a significant impact in this area. In this context, the main aim of this chapter is to give the fundamental aspects of patterning at the micro and nanoscale dimensions using the laser interference principle. It is to be emphasised here that these patterning concepts can be employed to print 2D and 3D structures on different materials. The chapter begins with an introduction and covers the fundamentals of laser interference. It then details patterning based on 2-beam and 4-beam interference with the help of a multiple beam interference lithography system. The effects of intensity and polarisation of the interfering beam on the structures are also detailed in this chapter. And finally, it finishes by covering ultrafast laser machining.

Laser-based 3D printing and manufacturing utilises high power lasers whose power exceeds certain thresholds required to change the status of materials, such as melting, evaporation or a direct change to the plasma state. These high power lasers are very hazardous; a direct or indirect exposure can burn the retina of the eye or the skin. In order to control the risk of laser related injury, the sale and usage of lasers are subject to government regulations depending on the power and wavelength. These regulations prescribe how to label lasers with specific warnings and how to select proper safety goggles when operating the lasers. This chapter covers the topics of safety design and the proper use and implementation of lasers for minimal risks and hazards.

The global 3D printing market is expected to grow at a compound annual growth rate (CAGR) of 32% to €20 billion by 2020. In this everincreasing market, the portion of laser-based 3D printing in the overall 3D printing market is increasing as well. This is because, metal-based 3D printing is growing at higher rates than polymer-based 3D printing. From 2010, the major applications of 3D printing are moving from product design (i.e. prototyping and customisation) to the actual production of end products. For 3D printing of functional parts and units, metals are better than polymers in material characteristics. A high-power laser beam (or electron-beam) is the most appropriate energy source for 3D printing of metals (and ceramics) because of their high melting temperature. Here, in this chapter, we will discuss the trends of laser-based 3D printing technology and the applications in which 3D printing could find its role in near future.