Additive manufacturing processes have been successfully used within a wide spectrum of industries spanning aerospace, automotive, biomedical, energy conversion, consumer products, and sporting goods. The additive manufacturing field can best be represented by the tree model shown in Figure 1.17, the development of which led to a Roadmap for Additive Manufacturing (RAM) workshop being held in 2009.110 The base of the tree consists of the various feasible additive manufacturing processes. The trunk is representative of the research and development efforts that often result from use of these processes. The branches clearly represent the direct outcomes and benefits culminating from these efforts. With time, in synergism with a rapid pace of research and development, both new and emerging applications and their benefits are expected to gradually grow and attract greater
Aerospace Architecture
Jewelry
Aeronautical Art Automotive
Energy Entertainment Electronics Education
Food
Consumer Products
Footwear
Clothing
Repair Tooling
Visualization
3-D Printing Stereolithography
Selective Laser Sintering Fused Deposition Modeling
Powder Metal Deposition
Tissue Engineering Nanotechnologies Medical
Implant Orthopedic
Research and Development
Other
fIgure 1.17 A simple overview of the field of additive manufacturing and the many domains for research.110
attention. In recent years, the use of additive manufacturing for a variety of purposes has expanded as more advanced additive manufacturing techniques are being developed and getting approved. An early application of additive manufacturing was the production of tools that had specific channels to facilitate plastic injection molding. Today, additive manufacturing has been put to effective use to make a variety of products, including (1) medical implants, (2) orthopedic and dental parts, (3) hearing aids, (4) forming tools, (5) aerospace components, (6) military and automotive components, (7) electronics, (8) art, (9) jewelry, (10) commercial lighting, (11) videogame avatars, and (12) engi- neered foods. Much of the current and ongoing research that is actively being pursued is focused on biomedical applications, particularly the generation of living tissues.111
Several of the aerospace components are noted for their complex geometries and are often made from advanced materials such as alloys of titanium, nickel-based superalloys, specialty steels, ultra-high-temperature ceramics, and even metal–matrix composites. Several of these materials are often difficult to work with and it can be time consuming to manufacture an intri- cate part using conventional manufacturing techniques. Further, production runs for the aero- space industry are usually small and limited to a maximum of a few thousand parts. This makes the technology of additive manufacturing both suitable and appropriate. Following tests on addi- tive manufactured parts, BAE Systems approved a replacement part that was made entirely by additive manufacturing. The part was a plastic window breather pipe for the 146 regional jets of BAE. Around the same time, Optomec, Inc. (Albuquerque, NM) used the LENS process to fab- ricate complex metal components for use in satellites, helicopters, and jet engines.112 Arup, Inc.
(London), another rapidly growing small business venture, developed a 3D printing technique for creating structural steel elements that can be used in construction. Although laser sintering has traditionally been used, researchers at Arup believe that the prudent use of 3D printing to create steel elements will eventually reduce the usage of energy and the overall costs and waste so often involved with construction
In the commercial sector, research performed at General Electric Aviation’s Additive Manufacturing Technology Center based in Cincinnati, OH, led to novel breakthroughs in design that encouraged additional investments in additive ma nufacturing technologies. This successful research into building fuel nozzles using additive manufacturing techniques led to the construction of a high-volume additive manufacturing factory in Auburn, AL.
Most recently, a joint research effort by researchers at NASA’s Jet Propulsion Laboratory, the California Institute of Technology, and Pennsylvania State University resulted in the development of a valuable method to build gradient metal objects that will allow for the design and production of parts in which the metal within a single part changes based on specific requirements.113
Within the realm of space exploration, a custom 3D printer that enables the fabrication of all necessary tools and components required for a space mission will be sent to the International Space Station. The printer was developed by Made-in-Space (Mountain View, CA). The new printer suc- cessfully completed all flight certification and acceptance testing in 2014, and engineers at NASA are hoping to demonstrate that a 3D printer can function as expected in space to print components of similar quality to those fabricated on Earth.114,115
Optomec, Inc., successfully leveraged the advantages of LENS 3D printing and the expertise of the world’s leading aerospace companies and industry organizations to advance a reliable and cost- effective approach to replace conventional repair processes, such as manual welding. Optomec’s LENS process can add metal onto any existing substrate of almost any 3D shape, making it well suited for repair operations.112 The European Space Agency, working with a cross-section of indus- trial partners, demonstrated in 2013 that 3D printing using lunar material was feasible, at least in principle. The shielding against radiation provided by a 3D printed block of simulated lunar rego- lith was evaluated and provided important input for future designs. The agency is also planning to investigate another lunar 3D printing method involving the harnessing of concentrated sunlight to melt the regolith rather than use a binding liquid. Each small step put forward in research makes the possibility of future lunar colonization a little more imaginable.111,115
Within the automotive industry, additive manufacturing has been explored as a viable tool in the design and development of automotive components primarily because it can shorten the devel- opment cycle while reducing not only manufacturing costs but also product costs. Additive man- ufacturing processes have also been used to make small quantities of structural and functional components, such as engine exhausts, braking systems, drive shafts, and gear box components for luxury and low-volume vehicles. Unlike widely used passenger cars, vehicles used in motor sports require lightweight alloys (such as alloys of titanium and aluminum) that often have complex structures and low production volumes. Additive manufacturing has been successfully applied to manufacture components that are functional for use in racing vehicles, and the technology has been put to effective use to replace the time-consuming and often expensive sand-casting and die-casting processes that have been traditionally used to make large metal components.111,114
Local Motors (Phoenix, AZ) has 3D printed a fully working car called the Strati. The car was printed at the International Manufacturing Technology Show held in 2014. The entire printing pro- cess took 44 hours. The Strati was the outcome of a 3D printed car design challenge that attracted more than 200 entrants from more than 30 countries. The company claims that it is the first time the main portion of a car has been printed in one piece using direct digital manufacturing. In addition to the 44 hours to print it, the car required 1 day to mill and 2 days to assemble, resulting in a 5-day build event.116 Local Motors is a growing company in the 3D printed car arena.
German electric vehicle manufacturer Street Scooter recently completed the prototype of its C16, the exterior components of which were created using the Stratasys Object1000 3D production system.
The 3D printed parts of the car include (1) its front and back panels, (2) door panels, (3) bumper sys- tems, (4) side skirts, (5) wheel arches and lamp masks, and (6) some smaller interior items. Although many parts of the production version of the C16 will be built using more conventional methods, the 3D printing approach allowed for the prototype to be constructed inexpensively and within a time frame of 12 months.117 The resultant 3D printed car was able to perform in strenuous testing environ- ments at the same level as a vehicle that was made using traditionally manufactured parts.
In the biomedical field, several recent applications have enabled the use of additive manufactur- ing for the fabrication of (1) custom-shaped orthopedic prostheses and implants, (2) medical devices, (3) biological chips, (4) skull and jaw implants, (5) custom-molded mouthpieces for individuals suffering from sleep apnea, (6) tissue scaffolds, (7) living constructs, (8) drug-screening models, (9) surgical planning and training apparatus, and (10) 3D printed spine cages. The potential of 3D printing within the domain of spinal fusion surgery lies in its ability to be tailored to a particular patient’s anatomy.111 Recently, an orthopedic implant manufacturer (Medicrea; Neyron, France) was able to use custom software and imaging techniques to produce a spine cage made out of polymeric material and customized to perfectly fit to the patient’s vertebral plates.118 The process is patent pending, but Medicrea is hopeful that a breakthrough will pave the way for further development of implantable devices that either replace or reinforce damaged parts of the spine. The ambitious vision to devise a developmental biology-enabled, scaffoldless technique to fabricate living tissues and organs by printing living cells was realized in 2013, the 15th year of printing cells. A typical cell printing process consists of the following three distinct steps:
1. Preprocessing—Creating tissue-specific or organ-specific CAD models for each patient using CT scan data
2. Processing—Using any of the viable additive manufacturing processes to deposit living cells onto 3D biological constructs
3. Postprocessing—Incubating printed tissues or organs to encourage both tissue fusion and maturation
In recent years, additive manufacturing has been successfully applied in the prosthetics industry to design and fabricate lightweight and low-cost robotic parts, such as hands and wrists, thus mak- ing it possible to consolidate complex assemblies into a single unit that is functional.111 In 2013,
Brightwake Limited (Nottinghamshire, U.K.) developed a blood recycling machine called Hemosep using the Stratasys Dimension 1200es 3D printer. The Hemosep can recover the blood that is lost following open-heart or major trauma surgery so it can be transfused back into the patient. This process, referred to as autotransfusion, reduces the volume of donor blood that is required and the problems associated with transfusion reactions.119 The prototype device has some Stratasys 3D printed parts, including the main filtration and cooling systems. Clinical trials of well over 100 open-heart surgeries in Turkey confirmed the ability of Hemosep to significantly reduce the need for blood transfusions.119 Medicine is certainly a field where 3D printing has made a splash.
The 3D printing techniques have allowed companies to move from an idea to a product concept design to a functional prototype much more quickly and more accurately than previous traditional prototyping methods allowed.119 Stratasys has introduced a new 3D printer for dental applications.
The printer will become the standard for prototyping and developing dental products and devices.
The same company is now working with suppliers to develop integral scanners that will allow for the production of crowns, bridges, and even veneers. The Stratasys 3D printing technology prom- ises to reduce patient time in the dental chair while making the experience of getting dental surgery more pleasant and more cost effective.
In 2014, a group of researchers at Harvard University (Boston, MA) solved one of the most dif- ficult problems with growing artificial human organs. The team used a 3D printer to make human tissue that included rudimentary blood cells. The success of their preliminary project inspired the researchers to undertake an ambitious project to make fully functional kidneys. The researchers made significant progress by fabricating the rudimentary versions of structures in kidneys called nephrons. These artificial nephrons will help drug companies to quickly screen potential medica- tions and will help scientists to understand kidneys at a more detailed level.120
At around the same time, 3D-printed syringe pumps were being produced at Michigan Technological University (Houghton) and made available to the public at a cost as low as $50 apiece.
These pumps can be used in laboratories to administer small amounts of liquid for the purpose of drug delivery or chemistry-related research. Scientists can customize the design of a pump to suit their study needs just by making minor modifications in the control software.121
When a medication is consumed, it eventually enters the bloodstream and ends up being concen- trated in the liver, whose primary function is to cleanse the blood. This means that if a drug is going to have an adverse effect on any part of the body, chances are it will be the liver. Therefore, should a pharmaceutical company want to test the safety of its products, it would be convenient to have some miniature human livers on which to experiment. The biotech firm Organovo (San Diego, CA) has begun selling such a device.122 Known as Vive3D, the three-dimensional liver model measures just a few millimeters across and is created using a 3D bioprinter. The device incorporates two print heads; one deposits a support matrix while the other precisely places human liver cells in the matrix.
The resulting models are composed of living human liver tissue and incorporate hepatocytes, stel- late cells, and endothelial cells, just like an actual, full-sized liver. It is also possible to produce liver proteins such as albumin, fibrinogen, and transferrin and to synthesize cholesterol. Additionally, the cells are arranged in a 3D orientation relative to one another, as would occur naturally. By con- trast, the liver cell cultures currently used to test pharmaceuticals are two dimensional and may not always function in the same manner as the actual organ.122
No industry is as poised to benefit from this burgeoning technology as the field of medicine.
Replacing cancerous vertebrae, delivering cancer-fighting drugs, and even assisting in spinal fusion surgery are just a few of the recent advances being made. A recent groundbreaking application involved a cancer patient whose entire upper jaw was replaced with the help of 3D printing.123 OSTEO 3D (Bangalore, India) used a CT scan to create a 3D reconstruction of the patient’s face.
A replica of the patient’s mouth, complete with lower jaw, upper jaw, and teeth, was printed. Using the 3D printed replica as a template, a wax model was produced and adjusted for proper fit. The jaw assembly was subsequently hardened and fitted with teeth.123 Harvard Apparatus Regenerative Technology (HART) is a biotechnology company that develops regenerative organs for the purpose
of transplantation, with an initial focus on the trachea. In collaboration with academia, HART originally developed equipment that could produce hollow organs such as the trachea and gradually expanded into the regeneration of all types of hollow organs using bioreactive technology.124
In the industry sector, medium and large quantities of polymer-based components are being manufactured using injection molding. It is quite difficult for the techniques of additive manufac- turing to compete with injection molding in producing these components; however, the additive manufacturing processes can be used to manufacture injection molds (i.e., rapid tooling) to reduce the time and costs involved in the development of new tools. Similarly, metallic parts can be eas- ily cast from molds or dies made using additive manufacturing. An example of a company that has embraced the use of additive manufacturing in the United States is Direct Manufacturing, Inc.
(Austin, TX). The company has added more machines to its shop floor as many of its customers have gradually moved toward the use of additive manufacturing and away from traditional castings, forgings, assembly of multicomponents, and subtractive manufacturing or machining. Although some machining may still be required for complex parts, the technique of additive manufacturing is considerably faster and noticeably more economical when compared to the other manufacturing methods currently being used. LENS-based 3D metal printing has been used to develop a reliable and cost-effective method to replace conventional repair processes such as welding which required the following:
Precise definition of powder feedstock characteristics Improvements in process monitoring and control Recommendations for repair of the part or component
The potential benefits resulting from the use of any one of the emerging additive manufacturing techniques to repair high-value metal components include lower costs, higher quality, longer life, and quicker return to service.125
The Stratasys Objet500 Connex 3D printer was used in connection with an 85-ton injection molding press to create a 3D injection molding machine. This machine allowed for 3D printing of the injection molds to manufacture small quantities of final prototypes using the same materials, components, and even capabilities as traditional 3D molding.126 Molds can be printed in a couple of hours with 3D printing, and tens and even hundreds of prototypes can be produced within a few days. The two biggest constraints to extensive use of the process are (1) print speeds and (2) the type of materials used. The machine must be able to print at speeds 50 to 100 times their current rates to allow for the printing of actual medical devices. Importantly, such printing could eliminate most logistics, switching, labor, and even assembly costs.118
Another field that can reap the benefits of implementing additive manufacturing is high-perfor- mance ceramics. The widespread or extensive use of parts made from ceramics is often limited by high costs and the tedious and laborious procedures involved in the fabrication of both prototypes and test parts. The primary factor within this process chain is fabrication of the mold. Some of the technologies of additive manufacturing offer numerous advantages that will have a positive impact on the fabrication of parts made from high-performance ceramics. With particular reference to ceramic injection molding (CIM), after giving due consideration to the observed lead times and costly tooling involved, additive manufacturing can serve as a capable complement to this means of production.
The opportunity to produce both accurate and cost-efficient prototypes is of some benefit to ceramic injection molding. Once the given design has been chosen and the prototypes have been evaluated by the end user, the respective part can be fabricated and the means of production changed to ceramic injection molding so as to ensure a high throughput. With the use of additive manufacturing technol- ogy, each part costs approximately the same in production; however, in ceramic injection molding, the cost depends significantly on the size of the lot. This relationship is shown in Figure 1.18. The fabrication of ceramic parts by ceramic injection molding requires a mold, which is a significant expense, particularly if that expense is spread out over the production of only a few components.
Thus, from an economical perspective, ceramic injection molding is not favorable for the production of a few parts or even individual parts. The only prerequisite for additive manufacturing is a CAD drawing, which can be applied to any number of parts. When there exists a need to produce a small number of parts, ceramic injection molding is not the optimum choice.111,127
Three-dimensional printers offered by Aurora Laboratories (Palm Beach, FL) can print multiple metals at the same time, including 316 and 420 stainless steel, Inconel 625 and Inconel 718 alloys, HASTELLOY© C, brass, bronze, and mild steel, along with ceramics and plastics. These machines are a result of innovative breakthroughs in technology and design. Aurora Laboratories claims that one day a 10,000-pound thrust rocket motor could be built. The control system for the printer feeds power to a motor at a controlled speed, and the powder is propelled onto a high-energy beam. It is then melted and fused with the substrate (i.e., base material). The build area often requires an inert gas. Depending on the materials chosen for the part being built, either nitrogen or argon can be used.125
The military has put the many advantages offered by additive manufacturing to good use for a multitude of purposes, including turbine engine blades, heat exchangers, repairs to blades and dies, cooling ducts, and wing brackets for commercial airplanes. However, additive manufacturing must undergo the tedious, expensive, and often time-consuming process of being certified for use in the aerospace, military, and medical fields, which have emerged as markets with demanding structural applications and high-dollar-value components.111,118
Within the domain of consumer goods such as jewelry, precious metal designs raise unique challenges when compared to the more common alloys used in additive manufacturing due to the highly polished surfaces often desired by customers. Additive manufacturing, however, allows for the creation of designs that have never before been achievable, providing both artists and designers insight into new levels of geometrical detail. The art and industry sectors have been able to produce components that are no longer available by entering the appropriate data into an additive manufac- turing machine and building the part new.
A 3D scanner and printer have been used to produce busts of individuals. In 2014, the Smithsonian Institution scanned President Barack Obama and generated a 3D bust of him that was subsequently added to the National Portrait Gallery.128 Bakeries can print figures of the bride and groom as
Injection Molding More Economical Additive Manufacturing
More Economical
Additive Manufacturing
Number of Parts
Cost per Piece
fIgure 1.18 Comparison of the overall cost effectiveness of additive manufacturing to ceramic injection molding.111,118