Adaptive process control implementation of wire arc additive manufacturing for thin-walled components with overhang features

The ability to fabricate overhang structures in WAAM (wire arc additive manufacturing) is vital in ensuring that a wide variety of designs can be realised. Unlike other additive manufacturing techniques that leverage on the addition of support structures, WAAM utilises a support-free approach for overhang fabrication to ensure components achieve a minimal buy-to-fly ratio. Currently, turntables are employed to achieve features with overhangs, but this does not scale well for large parts, in which the substrate's position is fixed. This paper presents an alternative approach to overcome this limitation by implementing adaptive process control for the fabrication of thin-walled components with overhang features under flat-position deposition conditions. An overhang slicer algorithm was developed to generate the toolpath based on the sliced computer-aided design model and tag the toolpath with overhang angle information. A data-driven interpolation model was then used to determine the torch speed for each path segment based its overhang angle that would result in uniform layer height. A thin-walled part with a complex overhang feature that varies from 0 degrees to 37.5 degrees was fabricated using the proposed approach. The result is a near-net shape part, as verified using an industrial optical three-dimensional digitiser.