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Additive manufacturing was invented more than 30 years ago and, from small beginnings in prototyping, has developed and grown into a $6 billion industry. While additive manufacturing for aerospace and defense has seen slower adoption than some other industries, the velocity is now visibly increasing. This has been enabled by the ongoing development of additive technologies that apply more increasingly to aerospace and defense -namely better plastics materials, faster 3D printing technologies, focused development of metals materials, and resulting technologies and processes that are increasingly easier to get qualified.

Additive Manufacturing (AM) has many advantages to manufacturers of every type. As additive processes, materials and technologies have improved, the reality of those advantages is coming to the fore. They include:

  • Design Freedom: AM opens new possibilities for every manufacturing process. Traditional constraints such as irregular profiles, internal structures and channels on the part, or draft angles and undercuts, are no longer relevant when creating parts.

  • Part Weight Reduction: Design for weight reduction by engineering optimized shapes and adding lightweight internal structures where appropriate is now becoming highly feasible. Good structural analysis will indicate where materials can be removed without compromising tensile strength and strength-to-weight ratios. On occasion, strong plastics used in 3D printing can replace conventional metal, providing another weight reduction advantage.

  • Reduced Machining: AM can often eliminate machining traditionally required to get a part or tool to the right dimensional tolerance. When the most demanding tolerances are required, 3D printed parts can still be machined to a fine finish.

  • Reduced Assembly Processes: Design for AM allows the consolidation of several parts in an assembly into a single-build part, reducing assembly time, errors and typically having a lighter-weight part that doesn't need glue, screws and fixings.

  • On-Demand Production: Many times the need for a short production run can kill a project, simply because the costs are too high for small batches and return on investment is thereby non-existent. 3D printing is ideally suited for short production runs. The digital file is always available, and the printing can be done on an as-needed and ‘lights-out’ basis at any time.

  • Design Clarity with Rapid Prototyping: This original use of AM remains highly relevant, enabling very rapid production of prototypes, at lower costs, to remove any ambiguity about form, fit and function at an early stage.

To stay competitive, manufacturers must find ways to stimulate the product development and production process, and AM is starting to play a very big role in agile manufacturing and improving product time-to-market. This need is no different in aerospace and defense.

One great example of that type of approach is the invention of ‘microvanes’ by Metro Aerospace. Eschewing traditional manufacturing processes, the Texas-based team turned to 3D Systems On Demand Manufacturing Services to rapidly prototype, qualify and then produce production parts using additive manufacturing. The microvanes are a drag-reduction and performance-enhancement technology recently commercialized by minority-owned business Metro Aerospace. Developed for the C-130/L-100 aircraft, the microvanes are adhesively fastened on both sides of an aircraft's fuselage and are designed to reduce drag by reshaping airflow around the aft cargo door, saving fuel at a rate of 25-30 gallons per hour.

In partnership with 3D Systems, the company used Selective Laser Sintering (SLS) with DuraForm ® glass-filled nylon materials to first prototype, deliver first article inspection reports for qualification, and then deliver the production parts. The vanes are delivered in sets of 20 and each vane is slightly different in size and shape, which, in traditional manufacturing would have required 20 different sets of tools. Instead, the 3D CAD data is arranged into a virtual build space for batch printing on the SLS platforms and takes just a few hours. Post-processing is minimal and after a 3D inspection report, the kits are sent to the customer.

Developing Metal Additive for A&D

Metro Aerospace delivers uniquely-designed drag-reduction microvanes for cargo aircraft that are 3D printed using Selective Laser Sintering (SLS) and DuraForm GF glass-filled nylon material, enable a 4% fuel savings, and achieved regulatory requirements within a few months, saving time and money.

Some additive machine vendors such as EOS entered the aerospace market roughly a decade ago with metal 3D printing. Others, including 3D Systems, GE, and others entered more recently. These entries into the market have not just validated the opportunity at hand but have increased the velocity of adoption, qualification and use. This year has seen the announcement of ever-bigger laser powder-bed metal AM machines from GE, Arconic and 3D Systems, and that won't simply stop there. A growing range of carefully focused metal powder materials, known parameters and monitoring devices inside the platforms is also starting to accelerate the qualification process. In due course we will see more and more metal printed structural and non-structural parts in aircraft.

The last 3-4 years has seen the space industry critically advancing qualification of structural metal components using additive manufacturing processes to reduce weight, reduce size, and maintain tensile strength of parts.

In 2016, Thales Alenia Space collaborated with 3D Systems to develop a new antenna bracket for a geostationary telecommunications satellite. Using design for additive manufacturing processes to combine several parts into one component, and then software to topologically optimize the part, the titanium-printed part was reduced in weight by 25% while maintaining required tensile strength. In addition, production costs have been considerably reduced and production time reduced by more than 50%.

Design for additive software such as 3DXpert enables the completion of designs of metal parts that are tuned for additive printing, including custom and optimized support structures, ‘lightweighting’ of parts to reduce weight and material cost, and build simulation to anticipate and avoid stresses on the parts as they are built.

In November 2017, DLR Institute of Structures and Design advanced its SMILE (SMall Innovative Launcher for Europe) project with the first successful testing of a LOX/kerosene rocket engine using a metal 3D printed injector. The project aims to design and produce a cost-effective launch vehicle for the delivery of small satellites into Sun-Synchronous Orbits (SSO). To achieve this, 3D Systems’ ProX DMP 320 metal 3D printer was used to build the very complex injector head component, which combined several parts into a compact single-build piece.

While adoption like this is slower in commercial aviation, the same process has already begun to happen. However, due to higher volumes and more stringent qualification requirements, this will take some time to develop.

Developing Plastic Additive for A&D

Developing structural parts that are optimized for minimum material use and reduced weight while maintaining weight to strength ratios becomes straightforward in additive processes, such as this satellite antenna bracket developed with Thales Alenia.

Plastic additive is also growing in usage in the industry and, although ideal for commercial aviation, adoption has been slower to gain momentum. Over the next five years, we will see a big expansion in interior cabin plastics as a key surge. This is due to the high demand for customization and the inherent limitations of using injection molded parts (i.e., tooling costs, inventory, time to market, design). Major airlines and OEM's are now getting into a position to be able to develop industry-wide practices that enable the adoption of plastic AM and key vendors such as 3D Systems are developing fire retardant materials for in-cabin parts. Our FR1200 SLS material complies with U.S. Federal Aviation Regulation 25.853 and falls within Airbus Industries Test Method (AITM) guidelines for smoke density and toxicity.

In 2017, Emirates Airlines and 3D Systems collaborated to address supply chain delays for in-cabin parts using 3D scanning to 3D printing to replace parts faster and more efficiently. Using 3D Systems scanning and engineering software and SLS 3D nylon printing, the first cabin part to be reproduced was a video shroud. Now in-flight, the shroud can be easily and quickly replaced, is 15% lighter than alternative materials, is compliant to fire retardant standards and can be produced within several hours. The airline is looking to expand this work to reduce time and cost of Aircraft On Ground.

Accelerating Qualification of Additive Processes

3D Systems is also working closely with the Department of Defense (DoD) to automate qualification of metal 3D printing for the defense/aerospace industries. Currently, according to the DoD, qualification of new manufacturing processes and materials can take anywhere between 5-15 years and millions of dollars to complete. 3D Systems’ Defense Research Team has been developing and implementing in-process sensors, machine-learning, and innovative software, with an aim of reducing that qualification process time down to months.

This will save key resources and will also increase the velocity of adoption for additive manufacturing, especially metal, and we will see defense and aviation not just ‘catch up’ to other industries, but take it to new levels.

The Future

In addition to the progress being made with current metal and plastic additive, new technologies coming on line in the next couple of years will also address another perceived barrier to additive manufacturing -slow production. The Figure 4™ platform being made available by 3D Systems in 2018 promises to address much faster production of plastic parts with a highly-scalable, tool-free environment. While it will not come near to injection-molded throughput as yet, it provides that ability to produce thousands of plastic parts every day with lower cost of operation than the alternatives.

This article was written by Bryan Newbrite, Aerospace Applications Leader, Advanced Aerospace Applications, 3D Systems (Rock Hill, SC). For more information, visit here.