Laser Additive Manufacturing for Aerospace Prototypes

By: Agnes Klucha

Pratt & Whitney

Aerospace prototyping is a way to realize the vision of freeform fabricated metal additive manufactured parts on aerospace production engines, gain acceptance for additive manufacturing and change perceptions of what is possible.  The freeform fabrication of laser additive manufactured metal parts is of prime interest in aerospace prototyping since a functional prototype can be delivered quickly to demonstrate and validate concept designs.

Aerospace prototypes are used for a number of different purposes – everything from show and tell pieces to development engine hardware to flight test engine demo hardware, as well as instrumentation and tooling.  There are needs across the entire engine.  When it comes to development engine or flight test engine components, the parts must be able to withstand extreme environments.  Aircraft engines are run in arctic weather conditions as well as desert environments.  The engines must be able to withstand a hail storm as well as bird strikes.  Components must be able to withstand temperature extremes and major g loads and stresses that challenge the structural integrity of the parts.  The environment that will be encountered in the field is simulated in a test stand environment and the engines are tested to harsher requirements than what is required in the field in order to provide adequate margins for safety.

Prototypes are needed to demonstrate concept feasibility for a new engine development program or for a legacy engine driven by performance improvements or cost reductions.  There are several processes that can be used to make a prototype.  The key is to find the process and vendor that can meet the requirements efficiently.  There are several factors under consideration when making the decision.  This includes technical, schedule, cost, export compliance, development only or downstream production considerations.  For prototypes, the name of the game is speed.  The faster a prototype can be delivered, the faster the design concept feasibility can be proven out.  This will accelerate the product development.  Sometimes the program cost impact of a late part is greater than the individual part cost.

The laser additive manufacturing (LAM) technologies hold great promise.  The direct 3D model to net shape or near net shape technologies include selective laser melting powder bed and selective laser melting deposition.  Making metal prototypes is of prime interest since it provides functional components.  It is not enough to be able to make the part, but ensuring it has the desired mechanical properties to meet the application need is important.

The laser sintering of sand to make molds and cores used in castings is an enabling LAM technology that has helped accelerate development hardware needs.  The beauty here is the ability to combine an additive technology with a conventional technology to deliver a solution that meets requirements without additional material characterization work.

To evolve from prototyping to production systems, an integrated approach is needed.  This means a focus on the relationship between the feedstock morphology, the manufacturing process parameters that includes the build process parameters as well as the post-thermal-mechanical process parameters, the technology platform development (i.e. machine development) and part design.  The greatest benefit will come when designers learn how to design for the new processes to optimize on performance and cost.  These integrated systems will need to deliver on the technical, cost and schedule requirements and be repeatable and reliable.

There is a call to action for the additive manufacturing industry to help OEMs identify the right additive manufacturing process for the application, generate design guidelines for the additive manufacturing processes, and provide integrated solutions to deliver finished parts that meet requirements.  There is a need for parts on demand.  The beauty of the LAM technologies in aerospace are to reduce the buy-to-fly ratio – the amount of raw material needed to final product weight.  LAM technologies can pave the way to a greener way of manufacturing parts for aerospace needs.

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