J. Mech. Des. 136(9), 090301 (September, 2014) (2 pages)
Paper No: MD-14-1348; doi: 10.1115/1.4028073
The additive manufacturing (AM) field—or 3D printing or rapid prototyping—is an exciting arena of innovations. AM has received a lot of popular press attention in recent years largely, I believe, since the technology has improved tremendously and has become very simple and inexpensive which, in turn, makes the technology accessible by many people. In this brief editorial, I will explain some of the unique capabilities of AM and highlight some of the research opportunities that they afford.
Due to its additive nature, AM possesses several unique capabilities that enable products to have significantly improved performance, to perform multiple functions, to be customized, and to be manufactured at lower overall costs. These unique capabilities include:
- virtually any shape can be fabricated
- features can be fabricated at several hierarchical scales
- material can be deposited and/or processed differently at different points or layers to enable multimaterial devices
- working mechanisms, including with embedded actuators and sensors, can be fabricated directly in some AM machines
Based on these unique capabilities, an overall design for AM (DFAM) objective can be stated and several core DFAM concepts can be articulated. Whereas conventional design-for-manufacturing focuses on understanding the effects of manufacturing constraints, the objective of DFAM should be to:
- Maximize product performance through the synthesis of shapes, sizes, hierarchical structures, and material compositions, subject to the capabilities of AM technologies.
From the unique capabilities and DFAM objective, I offer some example guidelines to designers:
- Utilize complex geometries to achieve design goals to integrate more features into a single part, consolidate several parts into one, or achieve a distribution of effective mechanical properties; doing so is often possible without time or cost penalties compared with conventional manufacturing and assembly processes.
- Utilize customized geometries and parts by direct production from 3D data when such customization adds significant value to the customer.
- Exploit and explore multifunctional part designs with complex material compositions and mechanical property distributions.
- Ignore constraints imposed by conventional manufacturing processes, but be aware that each AM process will have its own capabilities and limitations.
In terms of design methods and tools to support DFAM, the challenge is that new design spaces need to be formulated and explored, requiring significant creativity and innovation to first develop new design concepts and then pursue them into practice. Some researchers have formulated a general design method that takes into account product functionality and manufacturing constraints for AM. However, most researchers and technologists have pursued a specific niche in the creative space and developed specific methods and tools for that niche. In this area, a tremendous opportunity exists for combining industrial design practices with engineering design methods for improved concept generation and exploration. Perhaps bio-inspired design methods also have a role to play here. The often complex and multiscale structures that are inspired by biological systems can be fabricated more easily using AM than conventional manufacturing processes.
The topic of topology optimization has received a lot of research attention, but not as much emphasis has been placed on AM fabrication as is warranted. For a typical structural design problem, part volume or compliance is minimized, subject to constraints on, for example, volume, compliance, stress, strain energy, and possibly additional considerations. Commercial software systems, such as Abaqus andOptiStruct, provide a fairly general topology optimization capability for problems where the structural and system behavior can be simulated by finite element and/or multibody dynamics analyses. Some initial work on automated structure synthesis for AM has investigated different optimization algorithms and, although preliminary, impressive results have been achieved. Many research issues remain, including ensuring connectivity of regions in the resulting structures, improving the computational efficiency by introducing the concept of a topological sensitivity, incorporating concepts of risk or reliability, and exploring alternative solution approaches such as level sets and evolutionary structural optimization.
Cellular materials include foams, honeycombs, and lattice structures, and are representative of approaches that take advantage of AM’s geometric complexity capability. From a mechanical engineering viewpoint, a key advantage offered by cellular materials is high strength accompanied by a relatively low mass. These materials can provide good energy absorption characteristics and good thermal and acoustic insulation properties as well. In the past 15 yr, the area of lattice materials has received considerable attention due to their inherent advantages over foams in providing light, stiff, and strong materials. Some commercial software systems support lattice structure design, e.g., from NetFabb, Within Technologies, and Materialise. Research issues include Cad representations for thousands (or millions) of geometric entities, design methods capable of configuring all of these geometric entities, synthesis methods for designing them, and even finite element analysis methods capable of analyzing cellular structures, taking into consideration their as-manufactured form and property variations.
AM can enable innovative designs of complex 2D and 3D mechanisms. In contrast to multipart mechanisms, compliant mechanisms cause relative movement between the input and the output through designed bending patterns. The simplest types of compliant mechanisms simply replace pin joints with thin plates that act as compliant hinges. More sophisticated compliant mechanisms consist of beams with different widths, and possibly varying thicknesses. An interesting variation of a compliant mechanism is a deployable structure, such as a bridge or an aircraft wing design that could be fabricated using AM and deployed, for example, via air inflation. More generally, new design methods are needed for highly integrated, multimaterial, multitechnology (think embedded sensors, actuators, power sources, etc.) devices that are fully functional after AM fabrication.
Since most AM technologies require little process planning expertise, they enable a “design anywhere, build anywhere” model of product development. This, in turn, opens up many research issues in collaborative design, customer codesign, crowd-sourcing methods, and cloud-based design and manufacturing, as well as information technology infrastructures to support “design anywhere, build anywhere” approaches. New business models are emerging. One needs only to observe the virtual “store front” approach of sites like shapeways.com and ponoko.com to imagine how individuals with creative ideas could offer novel products, while preconfigured complex supply chains support manufacturing and logistics. Could home improvement stores evolve from stocking thousands of manufactured parts to become AM fabrication centers with stocks of raw materials?
Finally, it is important to highlight the exciting opportunities enabled by AM to effect change in science, technology, engineering, and mathematics (STEM) education. Maker spaces are proliferating throughout many engineering departments and in middle and high schools across the U.S. and much of the world. At the university level, maker spaces serve as modern day “machine shops” for students to fabricate parts for capstone and other design courses. But they also serve as interesting venues to engage students in rich “hands on/minds on” engineering activities that virtually any course could use to advantage. Student clubs are forming around these spaces to engage students socially and culturally. In middle and high schools, these maker spaces serve modern day technical education purposes, but also support extracurricular activities, such as FIRST Robotics clubs. Furthermore, math, science, and even history teachers are discovering how to utilize 3D printing in their subjects to enhance student engagement. AM affords tremendous opportunities for novel engineering education and informal learning research.
In summary, AM has uniqueness that is enabling changes in engineering practice and are opening new research directions, particularly in engineering design. In this editorial, I tried to identify some promising research issues, as well as opportunities in the education area. For further reading, I suggest the reports on two recent workshops, the NSF/ONR sponsored Roadmap for AM workshop (http://wohlersassociates.com/roadmap2009.pdf) and the forthcoming report from the NSF sponsored AM Education & Training workshop that was held in April 2014 (organized by Tim Simpson (Penn State) and Chris Williams (Virginia Tech)). Additionally, the America Makes organization has an AM roadmapping activity and is a good source for technology and workshop development activities.
Professor and Associate Chair for Administration,
The George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332-0405
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