Additive Manufacturing of Small Tactical Munitions

May 1, 2014

Raytheon
Fullerton, CA
714-446-2315
www.raytheon.com

Solid Concepts Inc.
Valencia, CA
661-295-4400
www.solidconcepts.com

Raytheon is addressing the need for smaller tactical weapons that still incorporate all fundamental features for small tactical manned or unmanned aerial platforms with some help from additive manufacturing (a.k.a. 3D printing). Their newest tactical munition, named Pyros, is light, precise, and a serious weapon.

“Right now with Pyros we’re looking at transitioning into full fledged production within the next year,” says J.R. Smith, Senior Manager of Business Development at Raytheon, “and this is certainly one of the first times we’ve used additive manufacturing to go directly from prototyping to actually using additive manufactured parts on a production component.”

Pyros utilized multiple additive manufacturing technologies during prototyping and into final production, including Fused Deposition Modeling (FDM) and Selective Laser Sintering (SLS). Both FDM and SLS offer high quality materials resistant to chemical and heat environments. FDM works via a heated nozzle which extrudes material layer by layer while SLS works via a bed of powdered nylon and a CO2 laser which sinters material layer by layer. Both processes grow parts from the ground up, which affords part complexity that subtracting technologies like machining find difficult to emulate.

Smith, familiar with traditional precision machining, views additive manufacturing as a solution to the inhibitions of machining. His team has even experienced better tolerances from additive manufacturing than from machining. He says that the drilling and milling of computerized CNC machining centers is very costly. For complex parts, contends Smith, it’s quicker and cheaper—especially with small tactical munitions like Pyros or even standard missiles— to use additive manufacturing to achieve good, tight tolerances.

The Raytheon engineering team worked hard to design Pyros for manufacturability and affordability, and that translated into using additive manufacturing early on in the project. For Pyros it was important to keep in mind the feasibility of assembling it fast. Additive manufacturing helps reduce manual labor by integrating features directly into the geometry (such as attachment features and fittings, mounting brackets, control surfaces), a difficult or impossible task to achieve in one simultaneous build when using machining. Additive manufacturing allows the team to consolidate multiple features into one part, and gives them full control over incremental changes in control surfaces and tolerances.

Pyros is built with fins upon its frame. These fins steer it toward its target via two frames of reference, a GPS and a semiactive laser seeker. “With 3-dimensional coordinates for its GPS, Pyros knows exactly where it’s at, allowing us to direct Pyros within 3 meters of where we want to be,” says Smith. “For moving targets, or targets within buildings, Pyros is equipped with a semi-active laser guidance system with demonstrated accuracy within one meter. A laser designator’s energy reflected off the target is used by the seeker to guide Pyros. All this direction and information is processed simultaneously, making accurate fin movement in accordance with the GPS and laser information quite crucial to the success of its mission.”

Raytheon worked with custom manufacturing company Solid Concepts on different components and iterations of Pyros, utilizing the prototyping and production capabilities of additive manufacturing. Smith says his team is looking to rework Pyros’ guiding fins using additive manufacturing. As the control fins are imperative to guiding Pyros, experimenting with their control surfaces is on the forefront of future iterations.

Additive manufacturing has also played a role in weight reduction. Pyros is ideal for small UAS that have payloads ranging from 5 – 100 lbs or for manned attack and armed surveillance platforms. With the majority of Pyros’ weight coming from its warhead, weight must be subtracted elsewhere. Material compositions of nylon, used in conjunction with Selective Laser Sintering (SLS), yield parts that are light but still strong and highly resistant to harsh environments while incorporating more features than machining could feasibly achieve in a single manufacturing instance.

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