Abstract
Wire Arc Additive Manufacturing (WAAM) is a relatively low-cost, high throughput additive manufacturing technology that uses arc welding to deposit metal beads in a layer-wise fashion to produce large-scale, complex parts. Oscillatory deposition strategies in WAAM are known for increasing deposition rate, obtaining more uniform layer surfaces, and their ability to reduce thermal cycling. In addition, small changes to the oscillatory path planning can result in a wide variety of bead shapes, which can be used to enable adaptive layer height throughout the build. The ability to build part regions at different layer heights could further mitigate process constraints (e.g. thermal input) during fabrication, compensate for build defects to enable manufacture of unique geometries, and ultimately increase throughput. However, to enable adaptive build height in WAAM, both predictive bead geometry models and in-situ control must be used to manage the interface between varying deposition regions and obtain consistent geometries.
This study compares a bead geometry prediction model to enable adaptive layer height via oscillatory toolpathing with an in-situ 3D scanning strategy. The bead geometry prediction model incorporates multiple processing parameters, including arc voltage, arc current, mass flow rate, travel speed, along with intrinsic material properties. This model, in concert with oscillatory path frequency and amplitude, can be used to predict bead geometry (width and height). During manufacturing, in-situ top-down 3D scans are collected at every layer to gather depth information of as-built geometries. This depth information is used to evaluate the efficacy of the oscillatory deposition with respect to each deposition type/region. This comparison is demonstrated with the manufacture of large-scale, functional metal parts.
