Introduction: Robotic arc Directed Energy Deposition (DED) Additive Manufacturing (AM) offers maximum build volume and range of motion for manufacturing large-scale structures and features. Shipbuilders need agile automation technology for robotic welding, cladding, and additive manufacturing to build large structures and/or additively manufacture features on structures. Each shipyard needs to establish metal AM design and manufacturing competencies. Shipyards need experience to develop and implement digital data workflow processes, evaluate process-feature-property requirements for a wide range of arc process consumable combinations, and establish process metrics for their implementation business case. Shipbuilders also need affordable robotic arc DED AM systems for implementation. This National Shipbuilding Research Program (NSRP) project is using an integrated approach to break down these barriers and accelerate the transition and implementation of robotic arc DED AM in shipbuilding. This presentation will describe Year 1 results.
Experimental Approach: A series of tasks were used to mature robotic arc DED AM technology for shipbuilding. A basic training program was developed for Powermill robotic DED AM Computer Aided Modeling (CAM) software. Using Powermill simulation tools, a robotic system model (digital twin) was developed for ABB, Cloos, Fanuc, and Motoman robot systems that range from 6 to 11 axis of coordinated motion. Post-processor software code was developed for each robotic system to compile build simulation solutions into the real system software language. Depending on the robotic system and target application, builds were made using either single-sided or double-sided procedures with either an integrated or non-integrated build platform. DED AM parameter sets were developed using the pulse gas metal arc (P-GMA) DED process for several common shipbuilding materials. Build demonstrations were completed on components of basic complexity. The project also tested DED AM procedure qualification schemes being developed in a separate program. A large-scale gantry test-bed was integrated to provide a unique resource for testing DED processes; developing support processes for thermal, dimensional and quality management; and building prototypes of increasing complexity.
Results and Discussion: The project developed robotic computer aided manufacturing (CAM) competencies for additive manufacturing. Autodesk Powermill Robotic CAM software was selected for the project, and offers robot agnostic tools for digital machining, additive manufacturing, and inspection of structures. A robotic DED AM training program was completed providing detail instructions on how to setup robotic systems as DED AM systems and develop digital data workflow process competencies. The training included methods on how to review and assess CAD geometry for DED AM, modify the design for build (add stock, tabs, supports, etc.), model representative robotic systems (digital twin), and optimize trajectory path planning using multi-axis robotic articulated arm and positioning systems. A range of robot system were modeled in Powermill. These systems were used to build basic components and build standard qualification builds for different applications. The project designed and integrated a large-scale, standardized, robotic gantry DED AM “test-bed” system that can significantly lower system acquisition costs. The 3-axis gantry carries a 6-axis robot for 9-axes of coordinated motion. The gantry system has a 2-axis tilt/turn positioner that can be located at various locations within the system build area. With the positioner, the system offers 11 axes of coordinated motion and capability to maximize productivity. The system is capable of building complex shapes like impellers and valve bodies, and adding features to structures like flanges, bosses, nozzles, and other geometric sections to large structures.
Conclusion: Robotic arc DED AM offers a range of benefits for digital manufacturing of structures, adding feature to structures, and repairing structures in high mix environments. Training programs, robotic test-bed systems, procedure standard qualification builds, and new robotic systems technology were developed to lower implementation barriers for shipbuilders and other large-scale manufacturers.
Acknowledgement: This project was funded by the National Shipbuilding Research Program (NSRP) under contract 2019-375-004, “Robotic Arc Directed Energy Deposition of Additive Manufacturing.”