Page 32 - 3D Metal Printing Fall 2018

3D AM INSIGHTS
Designing for Additive Manufacturing
Brings with It Design Freedom
By Rutuja Samant
In conventional manufacturing, well- established practices such as design for manufacturability (DFM) and design for assembly (DFA)—design parts for ease of fabrication, reduce total number of parts in an assembly, design multi-functional parts, avoid tooling, etc.—are easier said than done. Each principle has its own manufacturability limitations when it comes to complex part designs.
Today, however, additive manufactur- ing (AM) enables industry to overcome manufacturing limitations that curtail design freedom using AM processes to build complex, optimized geometries one layer at a time, without having to think about fabrication.
New Design Possibilities
AM has enabled a paradigm shift in design practices. Designers can base their designs purely on functional requirements of the application without worrying about process constraints. To leverage the potential of AM technolo- gies, designers must think beyond the
Rutuja Samant (rsamant@ewi.org) is responsible for managing EWI’s AM portfolio at its Buffalo (NY) Manufacturing Works. She serves as interim director of the Additive Manufacturing Consortium (AMC), a collaborative group of industry, academia and national labs advancing metal-AM technology adoption and deployment. In addition, She represents EWI as the R&D lead for the ASTM Additive Manufacturing Center of Excellence, which aims to create a global innovation hub for advancing AM technical standards, related R&D, education and training. Samant has experience in various metal- and polymer-based AM processes. Her area of specialty at EWI is metal AM with a primary focus on electron-beam-melting technology. Her project portfolio includes work for aerospace, medical, defense and nuclear-industry clients, as well as AM material qualification research for multiple metal-powder producers.
Fig. 1—These AM aerospace brackets demonstrate the advantages of topology optimization.
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conventional and constrained possibili- ties that traditional CAD tools enabled. One could categorize the design enable- ment of AM processes into these groups:
• Topology-optimized design. Topolo- gy optimization identifies the minimal material requirement in a design space to satisfy the defined boundary condi- tions. AM processes make it possible to build topology-optimized components. Many conventionally designed parts, now being topology-optimized and redesigned to reduce weight and materi- al consumption (Fig. 1), point to the growing popularity of topology opti- mization. As a result, many CAD-soft- ware companies are launching commer- cial topology-optimization software packages.
• Part consolidation. Designing con- solidated parts by eliminating the need for large, multicomponent assemblies leads to faster overall turnaround times by eliminating individual-part lead times as well as their logistics and assembly costs. Multiple studies have discussed that fasteners needed for component assembly account for 5 per-
cent of material costs, yet contribute to 70 percent of labor costs. AM enables new designs that potentially eliminate these costs. One of the best-known applications of this concept is General Electric’s fuel-nozzle test case for the next-generation LEAP jet engine, in which 18 parts are combined into a sin- gle assembly. Utilizing design strategies that harness the benefits of consolida- tion is just one way to justify the transi- tion from traditional manufacturing techniques to AM.
• Functionally graded part design. The ability to build functionally graded component designs is another outcome of AM design not possible through any other manufacturing process. This can be achieved by designing a part made of dissimilar materials with varying strength properties for different sections of the part, but printed through one continuous AM process. The other method to achieve similar functionally graded material properties would be to design a part using lattice structures of varying thicknesses in different loca- tions that control the varying strength