From the standpoint of technological innovations and advancements, additive manufacturing pro- vides useful control over the composition, shape, and functionality of the fabricated end products while facilitating a high degree of personalization. Referred to as the “third industrial revolu- tion,”86 additive manufacturing has the potential to realize cost-effective mass customization and production of complex products that could not be easily manufactured using any one of the con- ventionally available techniques. With the aid of additive manufacturing, products can be easily manufactured
1. In a broad range of sizes (from nanometer to micrometer scale to tens of meters)
2. From a variety of materials (metals, polymers, ceramics, composites, and even biological materials)
3. With numerous functionalities (such as load-carrying brackets, energy conversion struc- tures, and tissue-growing scaffolds)
The science and technological capabilities of additive manufacturing have made possible its use in a wide spectrum of applications, including the following:
Cellular machines Custom medications Flexible electronics
High-strength, lightweight aerospace structures having material gradients High-power, high-energy-density microbatteries
Human organs
Multifunctional houses
Products having embedded multi-material sensors and actuators Turbine blades having internal cavities
These applications represent only a few of the opportunities offered by the technological capability and power of additive manufacturing to print complex shapes that have a controlled composition and functionality.85,86
Additive manufacturing has the potential to produce complex parts using functionally graded materials (FGMs). The ability to deliver different materials to building areas is necessary to build components using FGMs. This is an advantages of additive manufacturing that cannot be easily realized using any of the conventional manufacturing methods.87 Furthermore, additive manufac- turing offers the intrinsic flexibility to control the composition of a part or component to provide multiple functionality. Two noticeable examples are88
1. Grading tungsten carbide for the primary purpose of enhancing its erosion resistance 2. Grading cobalt for the purpose of enhancing its ductility
Additive manufacturing processes can control and optimize the properties of the part being built.
A practical example of this is a pulley that contains more carbide near the hub and rim to make it harder and more wear resistant. It contains less carbide in other areas for enhanced compliance.87 One other notable example is the nose of a metallic missile cone made using ultra-high-temperature ceramic graded to a refractory metal from the outside to inside surface of the cone so it can sustain extreme external temperatures and still be attached easily to the metallic missile cone.88,89
The rapidly evolving capabilities of additive manufacturing include several functions related to printing by careful programming of the behavior of the active materials. This allows the manufac- tured part (1) to both sense and react and (2) to compute and behave as expected. Active systems can be manufactured that are comprised of both active and passive substructures, an ability that has applications within the biomedical field. Additive manufacturing has been put to both effective and efficient use to fabricate tissue scaffolds that are bioabsorbable, biocompatible, and biodegradable and for in vitro biological constructs containing living cells and biological compounds.
Many of the advancements in both consumer and engineering manufacturing have been related to the following:
Technological intersections of low-cost computer-based computational capability The ease of using CAD software
Low-cost, high-precision platforms and controllers
Availability of a variety of technologically viable additive manufacturing techniques
Much of the technological progress that is being made, in both methods and materials, is a direct consequence of ongoing research in industry, government laboratories, and academia and is now being expanded to develop a consumer base. Low-cost additive manufacturing technology is becom- ing more feasible and will be able to satisfy the needs of a diverse end-user community. Additive manufacturing is leading to new developments in the fields of materials science, materials engineer- ing, and manufacturing technology, as well as in the design and development processes specific to the needs of end users.88,89
Despite the many advantages additive manufacturing has to offer, it will not replace conventional manufacturing methods within the near future, but it is bringing about revolutionary changes to the manufacturing industry through its integration with conventional manufacturing technologies. A good example is the integration of laser metal deposition with computer numerical control (CNC) machining to form a hybrid process.89 For the high-volume production of parts, additive manufac- turing offers the promise and capability of providing technological support, such as the fabrication and repair of dies and molds used in various manufacturing processes (e.g., injection molding).
Currently, at least 63 companies worldwide are offering more than 66,000 professional-grade additive manufacturing systems for eight industrial sectors.90 The largest sector is the production of consumer products and electronics at 21.8%, followed by the fabrication of parts for motor vehicles at 18.6%, medical and dental uses at 16.4%, industrial and business machines at 13.54%, and aero- space at 10.2%. An overview of the dominant products resulting from use of this technology is pro- vided in Figure 1.16. Additive manufacturing products have transitioned from industrial prototypes to actual parts used in engineering applications, leading to the development of new and broader engineering standards in the additive manufacturing industry. The sale of additive manufacturing machines for metal manufacturing in 2013 increased by 76% over the previous year, and overall the market for 3D printing products and services grew to more than $3 billion in 2013, representing a growth of 35% over 2012.
Inspired and driven by the promise of inexpensive, highly customizable manufacturing, growth in 3D printer manufacturing has surged over the last several years. This growth has been made pos- sible by rapid technological developments, falling costs, and new and improved applications for 3D printing technology. The 3D printing industry grew at a very rapid pace, reaching about $2 billion worldwide in 2012 and $3 billion in 2013.91 In the United States alone, the 3D printer market in the year 2014 was estimated to be close to $4 billion with a compound annual growth rate (CAGR) of 22.8% over the period from 2009 to 2014.91 The primary buyers of 3D printing machines come from the medical/dental and aerospace industries, and they are being used for both prototype and manufacturing purposes. The aerospace companies are using 3D printers for testing and even certi- fication as they gear up for manufacturing on a noticeably large scale.91,92
0 20 40
Functional parts (29%) Tooling components (5.6 %) Patterns for metal castings (9.5%) Patterns for prototype (10.9%) Fit and assembly (19.5 %) Presentation models (8.7 %) Visual aids (8.7%) Other (2%) Education/research (6.1%)
3D Printing and Additive Manufacturing State of the Industry,
Annual Worldwide Progress Report
fIgure 1.16 Bar graph showing the uses of the additive manufacturing systems in 2013. (From Wohlers, T.T., 3D Printing and Additive Manufacturing State of the Industry, Annual Worldwide Progress Report, Wohlers Associates, Inc., Fort Collins, CO, 2014.)
With regard to its overall impact on the economy and continued sustainability, additive man- ufacturing offers several advantages over conventional manufacturing techniques, including (1) fabrication of structures not possible using the conventional techniques, (2) just-in-time manufac- turing, (3) reduced material waste and energy consumption, and (4) shortened time to market. Most importantly, the intrinsic capability of adding materials layer by layer to create 3D objects reduces material wastage. The traditional manufacturing of aerospace components made from an alloy of titanium that are machined down to size from a large block generates up to 90% waste material, which cannot be put to use or reused immediately. The various additive manufacturing processes can reduce such waste generation, thereby reducing the energy required for the production of tita- nium materials and parts made from titanium alloys.93 Complex shapes can be easily produced without tools, dies, or molds, which shortens the fabrication time and cuts production costs. A new era of digital additive manufacturing (DAM) will allow manufacturers to adapt new product designs without the limitations imposed by investing in new physical tools associated with conventional manufacturing processes.