The manufacturing process of 3D printing, also known as additive manufacturing, is much talked about, but what is it delivering now and where might it have a big influence next? Bernie Baldwin gets some leads from a leading developer of the process.
The development of technology to ‘print’ objects in three dimensions can barely have passed anybody’s attention over the past decade. The potential usefulness of such a process is considerable.
In an aviation context, the ability to simply create a spare part when required – rather than needing to send for one from another part of the world – is likely to change airline support significantly. And the number of parts able to be produced by this method, known as 3D printing or additive manufacturing, is growing.
Progress of the process
It’s almost 10 years since BAE Systems Regional Aircraft achieved European Aviation Safety Agency (EASA) certification for an aircraft part using 3D printing. The part was a plastic window breather pipe for the BAe 146, used as a vent to stop cabin windows misting up. These pipes had been made by injection moulding, but the tooling that the supplier had originally used was no longer available. According to BAE Systems, “new tooling would have cost £14,000 and involved several months lead time”, then there would have been a further two months to actually produce the parts.
One of the leading aerospace companies behind the increased use of this technology is GKN Aerospace. And one of the first things the company’s spokesperson clarifies is the terminology, as many people think of ‘3D printing’ and ‘additive manufacturing’ as one and the same.
“The two terms are often mixed up and they both relate to producing a 3D shape, layer by layer. 3D printing is commonly associated with desktop-scale printers and to rapid prototyping and hobby applications, where the focus is on achieving a 3D shape fast and easy with less emphasis on quality,” the spokesperson begins.
“For industrial use of these technologies, the term additive manufacturing (AM) is used and relates to a range of technologies suitable for various scales and applications, with the focus on quality and reliability. It can involve the use of diverse materials, including metals, ceramics, polymers and composites, allowing for the production of complex and functional end-use parts. Additive manufacturing techniques are used to enable the creation of lightweight structures, intricate geometries, and optimised designs.”
AM/3D – a broad church
As might be expected, there are different methods of manufacturing this way, with some 3D/AM processes suiting certain component types more than others. The GKN spokesperson highlights some key processes from the range available.
“Fused deposition modelling (FDM) is a technique that involves extruding thermoplastic materials through a heated nozzle. This is popular for rapid prototyping and hobby production and is often used in the production of functional prototypes, jigs, fixtures, and tooling. The material quality is not very high and suffers from anisotropy [where a measurable physical property of a material differs along different axes].
“Selective laser sintering (SLS) utilises a high-powered laser to selectively fuse powdered materials, typically polymers or metals, to build parts layer by layer. Again, this is a process suitable for complex geometries, and can use of a wide range of materials,” adds the GKN spokesperson.
“Next comes laser powder bed fusion (LPBF), which is an AM technique that employs a laser to selectively melt and fuse metal powders. It is ideal for producing complex metal components with high precision. Melting and fusing is also used in electron beam melting (EBM), where the beam selectively melts and fuses metal powders. High-quality metal parts, particularly for complex and large-scale components, are often the results of this process.
“Directed energy deposition (DED) is related to a family of different technologies where a metal powder or wire is locally melted layer by layer to form a 3D shape in an unrestricted area, enabling the production of very large metal parts. Different DED technologies discriminate between the feed stock material, powder or wire, and heat source, plasma, electric arc, laser, or electron beam. These processes are used for production end-use parts as well as repair technology.”
Stereolithography is another technique used in additive manufacturing, but this technology is currently used for niche applications like hearing aids and dental aligners. Similarly, binder jetting, which involves depositing layers of powdered material and selectively applying a binding agent to solidify the layers, is most commonly used in industries such as automotive, architecture, and consumer goods.
Thus, according to GKN Aerospace, each AM process has its own strengths and weaknesses, making them suitable for specific component types and applications. Factors that influence the process selection include material compatibility, part size and complexity, surface finish requirements, mechanical properties, production volume, and cost considerations.
Market penetration
As mentioned, ever more parts and components are being made using AM. They are, however, still the minority by some way for certain types of part. How far the processes noted will penetrate the parts manufacturing remains uncertain.
“The design freedom that additive manufacturing offers unleashes new possibilities in customisation, performance improvement and weigh reduction that cannot be achieved using conventional technologies. This requires a shift in mindset by the designers, including new computational design methods and manufacturing process understanding,” the company spokesperson emphasises. “It will always be a trade-off with conventional technologies and additive manufacturing will not replace all.
“In supply chain optimisation and on-demand manufacturing, AM has the potential to transform supply chains by enabling decentralised production and localised manufacturing. Instead of shipping parts across the globe, digital designs can be sent instantly, and parts can be produced locally, reducing lead times, inventory costs, and transportation emissions.”
When it comes to spare parts and obsolescence management, AM can address challenges as it did in the BAE Systems example reported above, and as the GKN spokesperson explains. “With the digital storage of part designs and the ability to produce them on demand, an industry such as aerospace can overcome supply chain disruptions and efficiently manage product lifecycles.”
Furthermore, ongoing advancements in materials designed specifically for additive manufacturing – including metals, composites, and biomaterials – are expanding the capabilities and applications of AM. Then, as these materials continue to improve in terms of strength, durability and performance, more industries are likely to adopt additive processes for end-use part production.
The future looks promising
GKN Aerospace believes that while the use of AM technologies will increase in parts manufacturing in the coming years, traditional manufacturing methods will still play a significant role, particularly for high-volume production of standardised components where economies of scale and efficiency are paramount.
Aviation is always under pressure to reduce its environmental footprint, so the introduction of a new process must be at least as environmentally friendly as existing processes. In the case of additive manufacturing, there are a number of ‘green’ benefits to be accrued, according to GKN Aerospace.
“First, AM allows for the creation of complex geometries and optimised designs, enabling the production of lightweight components,” the spokesperson remarks, noting that reduced weight in aircraft means lower fuel consumption and thus fewer emissions. “In terms of material efficiency, traditional manufacturing processes often result in a significant amount of material waste due to subtractive machining or casting. By contrast, AM adds material only where it is needed, minimising waste and contributing to a more sustainable manufacturing approach.”
AM also aids the consolidation of parts, because with the design freedom the process offers, multiple components or assemblies can be consolidated into a single printed part. A reduction in the number of parts means weight, complexity and assembly time are reduced.
The AM/3D process enables the creation of highly complex and optimised designs that were previously not feasible with traditional manufacturing methods. By utilising these capabilities, engineers can design components with improved aerodynamics and better structural performance, again contributing to reduced energy consumption and environmental impact.
“It’s important to note that while additive manufacturing offer significant environmental benefits, the overall impact will depend on factors such as material selection, energy consumption during the printing process, and end-of-life considerations,” the GKN spokesperson advises. “Continual advancements in sustainable materials, recycling methods, and energy-efficient printing technologies will further enhance the environmental advantages of these manufacturing techniques in the aviation industry and beyond.”
In other words, 3D printed parts not only add up, so do the benefits from the process.
Author: Bernie Baldwin
Published 08 August 2023
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