A-axis support redesign for a 5-axis waterjet-cutting CNC: Lightweighting via topology optimisation and wire-fed AM

Additive Manufacturing (AM) has emerged as a technology that allows the development of complex and customized components. Recently, its capabilities have been explored for the repair, remanufacturing, and functional upgrading of existing and ageing machinery. Beyond restoring damaged components, AM enables the redesign of conventional parts into lightweight, topology-optimized structures, allowing significant mass reduction while maintaining or even improving mechanical and functional performance. This provides an opportunity to extend the service life of existing machines and to enhance their overall performance. In the present context, AM was implemented to upgrade the A-axis support of a five-axis computer numerical control (CNC) waterjet-cutting machine, which provides the structural interface between the swivel head motor/gearbox and the abrasive waterjet tool. The current component is produced by welding and machining Al5083, and its mass adversely affects kinematic performance. This work presents an ongoing industrial case study aimed at introducing metal AM within the machine builder by redesigning the A-axis support for Wire Arc Additive Manufacturing (WAAM). A process development campaign was carried out on a robotic WAAM platform (using Fronius Cold Metal Transfer (CMT)) using SuperGlaze® 5183 Plus wire to identify stable deposition conditions with adequate geometric resolution and surface quality. The parameter study focused on deposition strategy, bead overlap, travel speed, torch inclination, and welding mode, using rapid screening based on bead geometry, dimensional fidelity, and visible defect formation. In parallel, a Topology Optimisation (TO) workflow was applied to minimise mass while limiting static nozzle-tip deflection under the waterjet reaction load and incorporating symmetry, keep-in regions, minimum member size, and WAAM overhang constraints. The optimized design achieved a 29% reduction in component mass while maintaining adequate structural performance under the evaluated static load cases. The WAAM process presented stable deposition conditions and established key manufacturability constraints, including a minimum feature thickness of 7 mm and a maximum self-supporting overhang angle of approximately 45°. Tomographic and corrosion analyses confirmed the importance of controlling process-induced porosity and interpass defects in WAAM-produced aluminium components. The results demonstrate the potential of combining topology optimisation and WAAM for lightweighting and upgrading industrial machine-tool components, while highlighting the need for further prototype validation and life-cycle assessment to quantify the resulting performance and environmental benefits.