Lightweighting Parts Using 3D Metal Printing
Metal additive manufacturing (3D printing), also known as Direct Metal Laser Sintering (DMLS) or Powder Bed Fusion (PBF), is changing the way metal parts are designed and produced. New software, processes and materials are redefining manufacturing value equations for specific types of parts, which can lead to improvements on existing products, new business models and new markets.
Metal additive manufacturing enables the production of high quality, complex metal parts from 3D CAD data. In the metal printing process, a high-precision laser is directed on metal powder particles to selectively build up horizontal metal layers one after the other.
While there are several applications for this technology, we will take a look at the potential offered by lightweighting parts, which has started to evolve during the last few years. The quest for lightweighting (making parts lighter) is prompting a whole new way to think about the manufacturing of metal products and is often a result of efforts to reduce part count on an assembly.
The recent rush to send smaller and lighter objects into space has caused aerospace companies and agencies to focus their critical research on finding new ways to reduce part size, part count and part weight. Every ounce reduced from the weight of an air- or spacecraft equates to a reduction in required fuel. Additionally, while reducing part size for satellites does not shrink the physical size of the satellite, it does open more space to add battery power, thus increasing the amount of time the satellite can remain in space.
As a result, most of the significant advancements being seen in the lightweighting of parts are in the aerospace industries, but researchers know that these advancements will ultimately benefit other industries including automotive, energy, transportation and consumer goods.
Software Is Key
Although metal additive manufacturing has been available for about two decades, not much progress had been made in the lightweighting of parts until recent new software products started to tackle the challenge. Software from Altair, 3D Systems, Siemens PLM, and Materialise, among others, are increasingly delivering software tools that enable features and strategies such as topological optimization, lattice structures, finite element analysis, and zoning strategies. These tools take engineers to a new level of ‘design for additive’ that is not reflected within the standard MCAD systems and are feeding an increased level of ingenuity in the drive for lighter parts.
Topological Optimization of Parts
One of the first key areas of part lightweighting to emerge is in topological optimization of a part or assembly. A few years ago, Thales Alenia Space started research with 3D Systems’ metal experts at its facility in Leuven, Belgium, to qualify metal additive printing for aerospace. The first major project was the design and production of antenna brackets for geostationary communications satellites. By consolidating the various heavy parts of the bracket, and working with software such as Solid Thinking from Altair, the bracket was radically redesigned into a single part that maintains stiffness-to-weight ratios, while reducing weight by 25 percent. Ultimately part production time was also reduced by 50 percent using 3D Systems ProX® DMP 320 printer.
Strut and Lattice Work for Lighter Weights
Research underway between the European Space Agency and 3D Systems has enabled clarity into how strut and lattice work in metal additive parts can be refined to deliver improved performance and lighter weights in rocket parts. In a study on injectors, combustion chambers and expansion nozzles for bi-propellant satellite engines, the teams engineered functional, separated design alternatives to traditional design methods that reduced weight, simplified assembly, sped manufacturing and improved part performance. A great example of this is a consolidated combustion chamber design incorporating a thin wall pressure vessel with a supporting external structural scaffold which could not be produced using traditional methods.
Where combustion chamber functions can be separated between operational and non-operational load cases, crude strut work can be translated into combined low-density mesh supporting the thin combustor wall and the weld flange. As its volumetric density is at 12 percent, this method potentially yields major weight reduction and improvement of structural integrity.
Moving Away from Solid Metal
Because of the restrictions delivered by traditional machining and casting methods, engineers often take for granted that a metal part – even additively manufactured – will be a solid block of metal. It is time to think past that restriction and look at how some metal parts do not need to be solid to achieve performance requirements and even improvements.
In a piston head, for example, engineers deviated away from solid blocks of metal, because it wasn't needed. By using 3D Systems’ 3DXpert™ software to add internal lattice design work into the void areas, and also partially sintering the powder trapped inside the void, the part can have a weight reduction of 30-35 percent while potentially meeting all requirements for the part.
The same methodology was applied to an example of a connecting rod where a partial volume replacement with lattice work reduced the total weight by 30-35 percent.
Part Count Reduction to Reduce Weight
While part count reduction is a clear advantage for improved assembly and reduced part size for metal additive, if properly designed it can also reduce part weight. In 2017, Airbus Defence and Space, in partnership with 3D Systems, developed the first air-worthy metal printed Radio Frequency (RF) filter, tested and validated for use in commercial telecommunication satellites.
RF filters are traditionally designed using standard elements such as rectangular cavities and waveguide cross-sections with perpendicular bends, with shapes and connections dictated by standard processes such as milling and spark eroding. Typically, cavities for RF filters are produced by machining two halves that are bolted together, increasing weight, adding assembly steps and extra quality checks.
Using CST MWS software, a 3D electromagnetic simulation tool, the 3D Systems team developed a depressed super-ellipsoidal cavity to channel RF currents and reject out-of-band signals. The design was driven by pure functionality, and not dictated by manufacturability and resulted in a single-build part that was faster to produce, reduced production costs and reduced weight by 50%.
The Future of Metal Part Lightweighting
These are just some examples of new methodologies to lightweight metal parts, but we believe that current research, design and engineering in Direct Metal Printing has barely scratched the surface of what is possible. What more can be done to lighten parts with hollows and voids? How can materials evolve to meet even more demanding requirements? How can the software evolve to match the innovation required? Although we have seen hints of what's to come, we are about to witness a dramatic rewriting of possibilities as design and manufacturing innovation become the new norm.
This article was written by Bryan Newbrite, Aerospace Applications Leader, 3D Systems (Rock Hill, SC). For more information, visit here .
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