Aerospace and defense firms are at the forefront in the adoption of 3-D printing processes that promise significant improvements in production flexibility and reductions in overall manufacturing costs. According to John Schmidt, managing director for the North American arm of consulting group Accenture, the technology, also known as additive manufacturing, will be a major theme of this year’s Paris Air Show, with companies gaining a clearer understanding of what it will take to reap the full benefits.
“3-D printing enables airplane parts to be made in various locations, and this simplifies supply chains and creates more economical warehousing of parts,” Schmidt told AIN. “Using this customizable technology, manufacturers can be more innovative in designing products. If you currently have a supply chain measured in 14 to 18 months, this can go down to weeks and that gives you real benefits in terms of saving working capital. And manufacturers can produce a part where they need it, when they need it.”
Companies are having to make significant investments in 3-D printing equipment and processes, resulting in higher direct costs than many traditional manufacturing techniques, countered by the promise of eventually reduce total costs resulting from the increased flexibility they are already delivering. For instance, supply chains stand to be rationalized significantly through the ability to produce parts in multiple locations closer to customers. In some cases, parts can be made lighter, contributing to aircraft fuel savings, while not being compromised in terms of strength.
At the same time, the potential applications for additive manufacturing are set to increase as technology improvements allow more materials to be “printable.” In addition to the plastics and photosensitive resins that have been used to date, ceramics, glass, metals and metal alloys are now being introduced to the mix, as are thermoplastic composites infused with carbon nanotubes and filters.
GE Aviation has made a strong commitment to additive manufacturing and the progress it has made was highlighted by the recent first flight of a GE90 engine fitted with additive manufactured housing for the T25 temperature/pressure sensor (located in the inlet to the high pressure compressor, it is being retrofitted into more than 400 GE90-94B engines). However, the U.S.-based group is implementing the technology one step at a time and takes the view that the full benefits might take some time to materialize.
According to Greg Morris, GE Aviation’s general manager for additive technologies, additive manufacturing is reducing the weight, number of parts and overall complexity of assemblies, as well as delivering improvements in their durability. “As we move forward, we continue to explore where additive manufacturing makes sense and cost plays a central role,” he told AIN. “We trying not to look at this purely in terms of want we can achieve today, but what we might be able to leverage in five, 10 or 20 years from now.”
Engineers Must Think Different
A lot of work is going into improving the 3-D printing machines so that they can deliver increased output rates. But Morris explained that companies have to retrain engineers to more effectively design products using additives. “It can be very difficult for engineers to think in terms of the layered additive approach [to producing parts], rather the traditional subtractive technologies [involving materials being removed from an existing block of material], and the best guide is to look at how nature does it,” he explained.
“It’s a moving target, but for now it mainly makes sense to use additives for fairly small components,” he said. “The limiting factors are the size of the part that we can make in our powder-bed system, and also the complexity of developing the right materials to use. We’ve had to develop a detailed database of materials and how they can be used to design components, taking account of factors such as their tensile strength.”
This year, GE began operations at its new high-volume additive manufacturing facility in Auburn, Alabama, and eventually this facility will be filled with banks of machines “printing” parts around the clock. For now, the engine maker intends to keep additive manufacturing in-house, but eventually it expects to help its vendors to produce parts remotely.
Additive manufacturing is by no means a flawless process and human intervention and monitoring is still essential for quality control. “For some time to come, we will have to have a very strict inspection regime,” said Morris. “Additives are great in terms of the geometric freedom they give, but their surface finish can be a drawback and we’ve had to come up with techniques to deal with rough surfaces.”
Relatively slow production rates are another limitation. “With the limited throughput of today’s machines, we have to focus on components that have fairly high value propositions, but the rate of production could be five to 10 times faster in the future,” said Morris.
Eventually, GE expects to be able to use 3-D printing to produce around 45,000 examples of the same part annually. Ultimately, it estimates that this may reduce the cost of producing an item such as a fuel nozzle by as much as three-quarters, partly because it will be made in one piece, rather than by having to assemble as many as two dozen pieces.
UTC Aerospace Systems recently opened a new materials research laboratory in Windsor Locks, Connecticut, and this is a focal point for the aerostructures and systems manufacturer’s efforts to advance additive manufacturing. “There is a lot of hype around this and there are some significant limitations,” cautioned Dave Carter, the company’s senior vice president for engineering and quality.
The U.S-based group has defined a list of around 100 part numbers that it could produce with 3-D printing, including items such as brackets, impellers, rotors, fuel injectors and heat exchangers. In its view, advanced metals, such as nickel and titanium, offer greater potential with the manufacturing process than plastics. For instance, some parts can be built up from titanium wire, rather than having to machine it out from a larger block of titanium.
“As we look at the capability of the machines, the main limiting factor is their size [typically around one cubic foot],” said Carter. “The production rate still seems pretty slow and what we really need are multiple laser and optical systems in a single machine. We need second- or third-generation equipment. The long-term benefit will be in taking a design-for-additive approach, using tailor-made materials and we could be starting this later this year or in early 2016.”
According to Accenture’s Schmidt, 3-D printing should bring significant benefits to spares and service provision by optimizing supply chain. But for now this might have limited impact in that most of the existing fleet of aircraft do not have parts made from additive manufacturing. He also flagged up the challenges posed by having to ensure that exactly the right 3-D model is used for additive manufacturing, meeting airworthiness requirements and protecting intellectual property.
“Where the industry is making progress today is in the materials technology and the fact that the cost [of additive manufacturing has come to the point that leveraging it finally makes sense, and there is now the ability to print somewhat larger parts,” said Schmidt. “We expect 3-D printing to take the same route [in aerospace manufacturing] that robotics did, and with that the first concerns were safety issues.”
In his view, for Western manufacturers the technology “will change the equation in terms of whether to build or buy [a part] because there won’t be a labor rate issue and so it changes the calculus in terms of time and money.” Accenture has extensive experience of helping companies to manage many aspects of digital design, production and support of products through their full life cycle.
Lockheed Martin is now working with the U.S. defense department, Cincinnati Tool Steel and Oak Ridge National Laboratory on plans to 3-D print the endo- and exto-skeletons for F35 fighters, including bodies, wings, internal structural panels, embedded wiring and antennas. Making larger parts like these will involve large gantries with computerized controls to move the printers.
As of last month, additive manufacturing specialist Stratasys had produced more than 1,000 3-D printed parts for the Airbus A350XWB. The airframer started working with Stratasys back in 2013 as part of a strategy to maximize flexibility in the program’s supply chain and avoid delays.