Abstract Scope |
Introduction:
Arc directed energy deposition (DED) is an emerging process that is beginning to be implemented in the heavy industry sector. The industry is still in the early stage of additive manufacturing (AM) adoption, where AM is used mostly for rapid prototyping. AM and arc DED have the potential to build parts on demand, reducing the need for spare parts as well as decentralize the manufacturing process. This allows for parts to be made either on or near site. Komatsu Mining Corp. has allowed EWI to fabricate one of their components to demonstrate feasibility of arc DED for a large-scale part. To adequately replace other manufacturing process, such as castings, arc DED must demonstrate its ability to fabricate high-quality parts that are near net shape and require minimal final machining.
Experimental Approach:
Arc DED is being evaluated as a feasible replacement to casting for critical, large-scale components. All welding work was completed using a Fronius power supply interfaced with a Motoman welding robot along with tailstock positioner table. AM builds were completed on 4140 base material using 0.045-in. 4130 GMAW wire. Argon shielding gas with 0.5% CO2 added was used for all builds fabricated for this project.
Build quality was verified along every step of the development process. Preliminary block parameters were validated by sectioning, polishing, and etching the samples so fusion quality could be verified. Subsize build parameters were verified through tensile and bend tests after a heat treat was completed. Chemistry and hardness tests were also completed to ensure that the subsize test build met property requirements.
With property requirements verified, a full-size build was fabricated. To control distortion the build was welded from two sides, employing the robotic tailstock to flip the build plate. The robotic path used to fabricate the build was planned using Autodesk’s AM path planning software, PowerMillŪ. PowerMill allows for robotic path planning based on a given 3D model. The software outputs robot code used to produce the part. The full-size build was 3D scanned at EWI to ensure that the part met size requirements set by Komatsu.
Results and Discussion:
The objective of this project was to develop parameters and build strategies to fabricate a breakout wrench for the Komatsu Mining Corp. using Arc DED. Initial testing displayed the need for weld puddle control of the ER4130 wire. The weld puddle was highly fluid due to the minimum preheat and inter-pass temperature requirement of 400 °F. This required the implementation of both torch oscillation and dwells to allow for precise control of the puddle.
It was found that separate parameters were not needed for specific layers or sections of the build (sidewalls or center sections). A quality weld bead for arc DED applications minimizes the weld cap while wetting out at the toes, allowing for complete melting and re-fusion of the weld material at weld toes.
The results of this project show that arc DED has the potential to replace castings and other manufacturing techniques in the heavy machinery sector. High quality parts can be achieved with short lead times, increasing manufacturing efficiency and adding flexibility to the supply chain.
Conclusions:
Arc DED has shown itself to be a competent replacement of traditional manufacturing methods for this designated application. Even with an alloy that requires stringent preheat and inter-pass requirements, along with a complex heat treatment, it is possible to achieve satisfactory results using arc DED.
Key Words:
Additive Manufacturing, Arc Directed Energy Deposition
Acknowledgement:
This project was funded by EWI and completed in association with Komatsu Mining Corp. |