A practical path planning methodology for wire and arc additive manufacturing of thin-walled structures

This paper presents a novel methodology to generate deposition paths for wire and arc additive manufacturing (WAAM). The medial axis transformation (MAT), which represents the skeleton of a given geometry, is firstly extracted to understand the geometry. Then a deposition path that is based on the MAT is efficiently generated. The resulting MAT-based path is able to entirely fill any given cross-sectional geometry without gaps. With the variation of step-over distance, material efficiency alters accordingly for both solid and thin-walled structures. It is found that thin-walled structures are more sensitive to step-over distance in terms of material efficiency. The optimal step-over distance corresponding to the maximum material efficiency can be achieved for various geometries, allowing the optimization of the deposition parameters. Five case studies of complex models including solid and thin-walled structures are used to test the developed methodology. Experimental comparison between the proposed MAT-based path patterns and the traditional contour path patterns demonstrate significant improved performance in terms of gap-free cross-sections. The proposed path planning strategy is shown to be particularly beneficial for WAAM of thin-walled structures

A multi-bead overlapping model for robotic wire and arc additive manufacturing (WAAM)

Wire and arc additive manufacturing (WAAM) is a promising alternative to traditional subtractive manufacturing for fabricating large aerospace components that feature high buy-to-fly ratio. Since the WAAM process builds up a part with complex geometry through the deposition of weld beads on a layer-by-layer basis, it is important to model the geometry of a single weld bead as well as the multi-bead overlapping process in order to achieve high surface quality and dimensional accuracy of the fabricated parts. This study firstly builds models for a single weld bead through various curve fitting methods. The experimental results show that both parabola and cosine functions accurately represent the bead profile. The overlapping principle is then detailed to model the geometry of multiple beads overlapping together. The tangent overlapping model (TOM) is established and the concept of the critical centre distance for stable multi-bead overlapping processes is presented. The proposed TOM is shown to provide a much better approximation to the experimental measurements when compared with the traditional flat-top overlapping model (FOM). This is critical in process planning to achieve better geometry accuracy and material efficiency in additive manufacturing

A tool-path generation strategy for wire and arc additive manufacturing

This paper presents an algorithm to automatically generate optimal tool-paths for the wire and arc additive manufacturing (WAAM) process for a large class of geometries. The algorithm firstly decomposes 2D geometries into a set of convex polygons based on a divide-and-conquer strategy. Then, for each convex polygon, an optimal scan direction is identified and a continuous tool-path is generated using a combination of zigzag and contour pattern strategies. Finally, all individual sub-paths are connected to form a closed curve. This tool-path generation strategy fulfils the design requirements of WAAM, including simple implementation, a minimized number of starting-stopping points, and high surface accuracy. Compared with the existing hybrid method, the proposed path planning strategy shows better surface accuracy through experiments on a general 3D component

Advanced Design for Additive Manufacturing: 3D Slicing and 2D Path Planning

Commercial 3D printers have been increasingly implemented in a variety of fields due to their quick production, simplicity of use, and cheap manufacturing. Software installed in these machines allows automatic production of components from computer-aided design (CAD) models with minimal human intervention. However, there are fewer options provided, with a limited range of materials, limited path patterns, and layer thicknesses. For fabricating metal functional parts, such as laser-based, electron beam-based, and arc-welding-based additive manufacturing (AM) machines, usually more careful process design requires in order to obtain components with the desired mechanical and material properties. Therefore, advanced design for additive manufacturing, particularly slicing and path planning, is necessary for AM experts. This chapter introduces recent achievements in slicing and path planning for AM process

Investigation into feasibility of hybrid laser-GMAW process for welding high strength quenched and tempered steel

In this study, the feasibility of hybrid laser-gas metal arc welding process for replacement of conventional flux-cored arc welding procedure for welding high strength quenched and tempered steel was investigated. Experimental work focused on optimisation of process parameters to produce joint with desired properties. Hardness of the weld heat affected zone produced by both processes has been measured. Productivity and cost effectiveness of both processes were compared. It was concluded that hybrid laser-gas metal arc welding process is suitable for welding high strength quenched and tempered steel

Fabricating superior NiAl bronze components through wire arc additive manufacturing

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production

Model-free adaptive iterative learning control of melt pool width in wire arc additive manufacturing

© 2020, Springer-Verlag London Ltd., part of Springer Nature. Wire arc additive manufacturing (WAAM) is a Direct Energy Deposition (DED) technology, which utilize electrical arc as heat source to deposit metal material bead by bead to make up the final component. However, issues like the lack of assurance in accuracy, repeatability and stability hinder the further application in industry. Therefore, a Model Free Adaptive Iterative Learning Control (MFAILC) algorithm was developed to be applied in WAAM process in this study. The dynamic process of WAAM is modelled by adaptive neuro fuzzy inference system (ANFIS). Based on this ANFIS model, simulations are performed to demonstrate the effectiveness of MFAILC algorithm. Furthermore, experiments are conducted to investigate the tracking performance and robustness of the MFAILC controller. This work will help to improve the forming accuracy and automatic level of WAAM

Effect of chemical composition on microstructure, strength and wear resistance of wire deposited Ni-Cu alloys

Two Ni-Cu alloys (Monel K500 and FM 60) having various Mn, Fe, Al, Ti and C contents were deposited on a Monel K500 plate at three different speeds using wire arc additive manufacturing technique. Microstructure characterisation, in particular a detailed study of precipitates, was carried out using optical and scanning electron microscopy. Mechanical properties were assessed using hardness, tensile and wear testing. For similar deposition conditions, Monel K500 has exhibited smaller secondary dendrite arm spacing and higher number density of Ti-rich particles, although the Ti concentration in FM 60 was higher. Finer microstructure and Ti precipitation led to superior hardness, tensile and wear resistance of Monel K500 compared to FM 60. The variation in microstructure-properties relationship with alloy composition is discussed