Additive manufacturing (AM) has been steadily growing in the aerospace manufacturing industry, with new applications being developed on a constant basis. The key areas where AM has made progress is in applications where parts are complex and require expensive tooling and long lead times. This article will examine how AM is growing within aerospace OEMs.
There are various parts currently being manufactured using AM machines. The two cases below serve as typical examples:
GE Fuel Nozzles – These fuel nozzles are being manufactured for the LEAP engine, one of the most popular engines in the commercial aerospace industry. The parts are mass-manufactured in a purpose-built facility and, as of 2018, 30000 of them have been produced. This is a proven application of mass-manufactured aerospace parts using additive manufacturing.
Airbus Satellite Structure – Launching material into space is incredibly costly and the weight of a part needs to be reduced as far as possible without compromising its functionality and structural integrity. AM coupled with optimisation algorithms allow for complex, organically designed parts to be manufactured with reduced weight and optimal strength. Airbus has developed a lightweight antenna mounting bracket for their Eurostar E3000 communications satellite.
Other well-known companies that are embracing additive methods for aerospace manufacturing are Rolls-Royce, and SpaceX.
Some key advantages of AM for aerospace manufacturing are:
Part Consolidation – Limitations of traditional manufacturing techniques have resulted in the design of complex assemblies built with multiple components. Each of these components need to be designed to interlock with the next component which increases design and assembly time. Furthermore, controlling the tolerance and quality of each of these components is critical.This adds time and complexity to the process. AM allows the entire part to be designed, manufactured and tested with far fewer steps.
Flexibility – Parts designed for AM have more flexibility in terms of design and optimisation. With traditional techniques, the functionality of a part is limited by manufacturing capabilities. AM has far fewer limitations and can create parts that are close to their theoretically optimal form.
Advanced Materials – As the demand for different materials for AM has grown, companies have begun to see the benefit of offering more and more variations of materials optimised specifically for AM. These can include powdered materials such as Inconel, copper, stainless steel and even precious metals like gold.
Modify or Repair Existing Parts – Certain AM machines can deposit metal onto existing components to either add additional material onto a new part or to repair an existing component. These DED (directed energy deposition) machines essentially weld material onto existing parts. This is ideal for the repair of expensive and sensitive components like turbine blades for example.
AM is primarily used for components that undergo static or very limited dynamic loading. Parts that experience significant fatigue loading pose a risk. This is partly because of the limited understanding of the effect of fatigue loading on AM-based manufacturing and thus requires rigorous testing and monitoring of real-world applications. The nature of powder-based AM creates a rough surface profile which behaves as multiple stress risers that can initiate cracking. Studies have shown that there is a direct correlation between surface roughness and the fatigue limit of a part. This is not to say that it is impossible to manufacture parts that undergo fatigue loading, but rather that rigorous testing is required to accurately categorise the fatigue life.
Validation is a crucial step in any manufacturing process; all the more with the heavily regulated aerospace manufacturing industry. With AM on the rise, it has become even more critical to standardise the verification of parts made using this technology. Examples of challenges unique to validation in the AM space are listed below:
Dimensional Verification – Due to the often-complex geometries of AM parts, traditional measurement techniques are not always sufficient for dimensional validation. For example, a nozzle guide vane that has been additively manufactured will have complex internal geometries that cannot be reached with typical measurement tools. It is therefore a challenge to determine if the manufactured part meets the tolerances required by the design. There are however techniques that can be used to measure internal geometries using x-rays. This allows accurate measurements of the complex part that can then be compared to the 3D model.
Mechanical Strength Verification – When designing for AM, it is important to remember that the material properties are different from a billet of machined material. Furthermore, if there were any anomalies in the manufacturing process then it is possible that the material may be out of spec. AM material is built up incrementally, and various factors influence the final properties of the part. It is therefore critical to perform both nondestructive and destructive testing on samples to ensure they align with the design assumptions.
As the aerospace manufacturing industry continues to grow in scope and capability, Kingsbury is able to provide you with valuable industry-relevant insights on how best to incorporate AM into your production line. In addition, we offer state-of-the-art AM technology through our partners and our Additure brand to take your manufacturing to the next level.
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