Additive Manufacturing Technologies

Frontmatter

1. Introduction and Basic Principles

Abstract

The technology described in this book was originally referred to as rapid prototyping. The term rapid prototyping (RP) is used in a variety of industries to describe a process for rapidly creating a system or part representation before final release or commercialization. In other words, the emphasis is on creating something quickly and that the output is a prototype or basis model from which further models and eventually the final product will be derived. Management consultants and software engineers both use the term rapid prototyping to describe a process of developing business and software solutions in a piecewise fashion that allows clients and other stakeholders to test ideas and provide feedback during the development process. In a product development context, the term rapid prototyping was used widely to describe technologies which created physical prototypes directly from digital data. This text is about these latter technologies, first developed for prototyping, but now used for many more purposes.

Ian Gibson, David Rosen, Brent Stucker

2. Development of Additive Manufacturing Technology

Abstract

It is important to understand that AM was not developed in isolation from other technologies. For example it would not be possible for AM to exist were it not for innovations in areas like 3D graphics and Computer-Aided Design software. This chapter highlights some of the key moments that catalogue the development of Additive Manufacturing technology. It will describe how the different technologies converged to a state where they could be integrated into AM machines. It will also discuss milestone AM technologies and how they have contributed to increase the range of AM applications. Furthermore, we will discuss how the application of Additive Manufacturing has evolved to include greater functionality and embrace a wider range of applications beyond the initial intention of just prototyping.

Ian Gibson, David Rosen, Brent Stucker

3. Generalized Additive Manufacturing Process Chain

Abstract

Every product development process involving an additive manufacturing machine requires the operator to go through a set sequence of tasks. Easy-to-use “personal” 3D printing machines emphasize the simplicity of this task sequence. These desktop-sized machines are characterized by their low cost, simplicity of use, and ability to be placed in a home or office environment. The larger and more “industrial” AM machines are more capable of being tuned to suit different user requirements and therefore require more expertise to operate, but with a wider variety of possible results and effects that may be put to good use by an experienced operator. Such machines also usually require more careful installation in industrial environments.

Ian Gibson, David Rosen, Brent Stucker

4. Vat Photopolymerization Processes

Abstract

Photopolymerization processes make use of liquid, radiation-curable resins, or photopolymers, as their primary materials. Most photopolymers react to radiation in the ultraviolet (UV) range of wavelengths, but some visible light systems are used as well. Upon irradiation, these materials undergo a chemical reaction to become solid. This reaction is called photopolymerization, and is typically complex, involving many chemical participants.

Photopolymers were developed in the late 1960s and soon became widely applied in several commercial areas, most notably the coating and printing industry. Many of the glossy coatings on paper and cardboard, for example, are photopolymers. Additionally, photo-curable resins are used in dentistry, such as for sealing the top surfaces of teeth to fill in deep grooves and prevent cavities. In these applications, coatings are cured by radiation that blankets the resin without the need for patterning either the material or the radiation. This changed with the introduction of stereolithography, the first vat photopolymerization process.

Ian Gibson, David Rosen, Brent Stucker

5. Powder Bed Fusion Processes

Abstract

Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at the University of Texas at Austin, USA, selective laser sintering (SLS) was the first commercialized PBF process. Its basic method of operation is schematically shown in Fig. 5.1, and all other PBF processes modify this basic approach in one or more ways to enhance machine productivity, enable different materials to be processed, and/or to avoid specific patented features.

Ian Gibson, David Rosen, Brent Stucker

6. Extrusion-Based Systems

Abstract

Extrusion-based technology is currently the most popular on the market. Whilst there are other techniques for creating the extrusion, heat is normally used to melt bulk material in a small, portable chamber. The material is pushed through by a tractor-feed system, which creates the pressure to extrude. This chapter deals with AM technologies that use extrusion to form parts. We will cover the basic theory and attempt to explain why it is a leading AM technology.

Ian Gibson, David Rosen, Brent Stucker

7. Material Jetting

Abstract

Printing technology has been extensively investigated, with the majority of that investigation historically based upon applications to the two-dimensional printing industry. Recently, however, it has spread to numerous new application areas, including electronics packaging, optics, and additive manufacturing. Some of these applications, in fact, have literally taken the technology into a new dimension. The employment of printing technologies in the creation of three-dimensional products has quickly become an extremely promising manufacturing practice, both widely studied and increasingly widely used.

This chapter will summarize the printing achievements made in the additive manufacturing industry and in academia. The development of printing as a process to fabricate 3D parts is summarized, followed by a survey of commercial polymer printing machines. The focus of this chapter is on material jetting (MJ) in which all of the part material is dispensed from a print head. This is in contrast to binder jetting, where binder or other additive is printed onto a powder bed which forms the bulk of the part. Binder jetting is the subject of Chap. 8. Some of the technical challenges of printing are introduced; material development for printing polymers, metals, and ceramics is investigated in some detail. Models of the material jetting process are introduced that relate pressure required to fluid properties. Additionally, a printing indicator expression is derived and used to analyze printing conditions.

Ian Gibson, David Rosen, Brent Stucker

8. Binder Jetting

Abstract

Binder jetting methods were developed in the early 1990s, primarily at MIT. They developed what they called the 3D Printing (3DP) process in which a binder is printed onto a powder bed to form part cross sections. This concept can be contrasted with powder bed fusion (PBF), where a laser melts powder particles to define a part cross section. A wide range of polymer composite, metals, and ceramic materials have been demonstrated, but only a subset of these are commercially available. Some binder jetting machines contain nozzles that print color, not binder, enabling the fabrication of parts with many colors. Several companies licensed the 3DP technology from MIT and became successful machine developers, including ExOne and ZCorp (purchased by 3D Systems in 2011). A novel continuous printing technology was been developed recently by Voxeljet that can, in principle, fabricate parts of unlimited length.

Ian Gibson, David Rosen, Brent Stucker

9. Sheet Lamination Processes

Abstract

One of the first commercialized (1991) additive manufacturing techniques was Laminated Object Manufacturing (LOM). LOM involved layer-by-layer lamination of paper material sheets, cut using a CO₂ laser, each sheet representing one cross-sectional layer of the CAD model of the part. In LOM, the portion of the paper sheet which is not contained within the final part is sliced into cubes of material using a crosshatch cutting operation. A schematic of the LOM process can be seen in Fig. 9.1.

Ian Gibson, David Rosen, Brent Stucker

10. Directed Energy Deposition Processes

Abstract

Directed energy deposition (DED) processes enable the creation of parts by melting material as it is being deposited. Although this basic approach can work for polymers, ceramics, and metal matrix composites, it is predominantly used for metal powders. Thus, this technology is often referred to as “metal deposition” technology.

Ian Gibson, David Rosen, Brent Stucker

11. Direct Write Technologies

Abstract

The term “Direct Write” (DW) in its broadest sense can mean any technology which can create two- or three-dimensional functional structures directly onto flat or conformal surfaces in complex shapes, without any tooling or masks [1]. Although directed energy deposition, material jetting, material extrusion, and other AM processes fit this definition; for the purposes of distinguishing between the technologies discussed in this chapter and the technologies discussed elsewhere in this book, we will limit our definition of DW to those technologies which are designed to build freeform structures or electronics with feature resolution in one or more dimensions below 50 μm. This “small-scale” interpretation is how the term direct write is typically understood in the additive manufacturing community. Thus, for the purposes of this chapter, DW technologies are those processes which create meso-, micro-, and nanoscale structures using a freeform deposition tool.

Ian Gibson, David Rosen, Brent Stucker

12. The Impact of Low-Cost AM Systems

Abstract

Media attention over additive manufacturing is at an all-time high. Much of this is to do with the vast increase in the availability of the technology due to massive reductions in the technology costs. By making it possible for individuals to afford them for their own personal use, the true potential has been, to some extent, uncovered. This chapter will discuss some of the issues surrounding the low-cost technologies, including machine developments due to patent expiry, the rise of the Maker movement and some of the new business models that have resulted.

Ian Gibson, David Rosen, Brent Stucker

13. Guidelines for Process Selection

Abstract

AM processes, like all materials processing, are constrained by material properties, speed, cost, and accuracy. The performance capabilities of materials and machines lag behind conventional manufacturing technology (e.g., injection molding machinery), although the lag is decreasing. Speed and cost, in terms of time to market, are where AM technology contributes, particularly for complex or customized geometries.

Ian Gibson, David Rosen, Brent Stucker

14. Post-processing

Abstract

Most AM processes require post-processing after part building to prepare the part for its intended form, fit and/or function. Depending upon the AM technique, the reason for post-processing varies. For purposes of simplicity, this chapter will focus on post-processing techniques which are used to enhance components or overcome AM limitations. These include:

Ian Gibson, David Rosen, Brent Stucker

15. Software Issues for Additive Manufacturing

Abstract

This chapter deals with the software that is commonly used for additive manufacturing technology. In particular we will discuss the STL file format that is commonly used by many of the machines to describe the model input data. These files are manipulated in a number of machine-specific ways to create slice data and for support generation and the basic principles are covered here including some discussion on common errors and other software that can assist with STL files. Finally, we consider some of the limitations of the STL format and how it may be replaced by something more suitable in the future like the newly developed Additive Manufacturing File format.

Ian Gibson, David Rosen, Brent Stucker

16. Direct Digital Manufacturing

Abstract

Direct digital manufacturing (DDM) is a term that describes the usage of additive manufacturing technologies for production or manufacturing of end-use components. Although it may seem that DDM is a natural extension of rapid prototyping, in practice this is not usually the case. Many additional considerations and requirements come into play for production manufacturing that are not important for prototyping. In this chapter, we explore these considerations through an examination of several DDM examples, distinctions between prototyping and production, and advantages of additive manufacturing for custom and low-volume production.

Many times, DDM applications have taken advantage of the geometric complexity capabilities of AM technologies to produce parts with customized geometries. In these instances, DDM is not a replacement for mass production applications, as customized geometry cannot be mass produced using traditional manufacturing technologies. In addition, since the economics of AM technologies do not enable economically competitive high-volume production for most geometries and applications, DDM is often most economical for low-volume production applications. Two major individual-specific medical applications of DDM will be discussed, from Align Technology and Siemens/Phonak, as well as several other applications that make use of the unique design freedom afforded by AM techniques. This will be followed by a discussion of the unique characteristics of AM technologies that lead to DDM.

Ian Gibson, David Rosen, Brent Stucker

17. Design for Additive Manufacturing

Abstract

Design for manufacture and assembly (DFM) has typically meant that designers should tailor their designs to eliminate manufacturing difficulties and minimize manufacturing, assembly, and logistics costs. However, the capabilities of additive manufacturing technologies provide an opportunity to rethink DFM to take advantage of the unique capabilities of these technologies. As mentioned in Chap. 16, several companies are now using AM technologies for production manufacturing. For example, Siemens, Phonak, Widex, and the other hearing aid manufacturers use selective laser sintering and stereolithography machines to produce hearing aid shells; Align Technology uses stereolithography to fabricate molds for producing clear dental braces (“aligners”); and Boeing and its suppliers use polymer powder bed fusion (PBF) to produce ducts and similar parts for F-17 fighter jets. For hearing aids and dental aligners, AM machines enable manufacturing of tens to hundreds of thousands of parts, where each part is uniquely customized based upon person-specific geometric data. In the case of aircraft components, AM technology enables low-volume manufacturing, easy integration of design changes and, at least as importantly, piece part reductions to greatly simplify product assembly.

The unique capabilities of AM include: shape complexity, in that it is possible to build virtually any shape; hierarchical complexity, in that hierarchical multiscale structures can be designed and fabricated from the microstructure through geometric mesostructure (sizes in the millimeter range) to the part-scale macrostructure; material complexity, in that material can be processed one point, or one layer, at a time; and functional complexity, in that fully functional assemblies and mechanisms can be fabricated directly using AM processes. These unique capabilities enable new opportunities for customization, very significant improvements in product performance, multifunctionality, and lower overall manufacturing costs. These capabilities will be expanded upon in Sects. 17.3 and 17.4.

Ian Gibson, David Rosen, Brent Stucker

18. Rapid Tooling

Abstract

This chapter discusses how additive manufacturing can be used to develop tooling solutions. Although AM is not well suited to high-volume production in a direct digital manufacturing sense, it does have some benefit when producing volume production tools. This can be from the perspective of using AM to create patterns for parts that are required using materials or properties not currently available using AM or for longer run tooling where AM may be able to simplify the process chain. Commonly referred to as rapid tooling, we discuss here how AM can contribute to the product manufacturing processes.

Ian Gibson, David Rosen, Brent Stucker

19. Applications for Additive Manufacture

Abstract

Additive manufacturing is coming into its third decade of commercial technological development. During that period, we have experienced a number of significant changes that has led to improvements in accuracy, better mechanical properties, a broader range of applications, and reductions in costs of machines and the parts made by them. In this chapter we explore the evolution of the field and how these developments have impacted a variety of applications over time. We note also that different applications benefit from different aspects of AM, highlighting the versatility of this technology.

Ian Gibson, David Rosen, Brent Stucker

20. Business Opportunities and Future Directions

Abstract

The current approach for many manufacturing enterprises is to centralize product development, product production, and product distribution in a relatively few physical locations. These locations can decrease even further when companies off-shore product development, production, and/or distribution to other countries/companies to take advantage of lower resource, labor or overhead costs. The resulting concentration of employment leads to regions of disproportionately high underemployment and/or unemployment. As a result, nations can have regions of underpopulation with consequent national problems such as infrastructure being underutilized, and long-term territorial integrity being compromised (Beale, Rural Cond Trends 11(2):27–31, 2000).

Ian Gibson, David Rosen, Brent Stucker

Erratum to: Business Opportunities and Future Directions

Ian Gibson, David Rosen, Brent Stucker

Backmatter