This paper starts from the early developments and working principles of the additive manufacturing of polymers, continues with a glimpse on the extension to metals with identification and characterization of the two most widespread technologies, and ends with an overview of the recent developments in hybrid metal additive manufacturing. Earlier classifications of hybrid manufacturing with roots on the utilization of primarily processed raw materials in the form of ingots, sheets, rods, tubes, profiles, powders and pellets are revisited in the light of the emergence of a new type of hybridization resulting from the combination of additive manufacturing with traditional manufacturing processes. Special emphasis is given to the combination of additive manufacturing with forming processes with the two-fold objective of (i) increasing the applicability domain of metal additive manufacturing and overcoming its limitations related to low productivity, metallurgical defects, rough surface quality and lack of dimensional precision, and (ii) adding flexibility and fostering new applications of traditional forming processes.

Hybrid metal additive manufacturing: A state–of–the-art review

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review.

The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review

Wire arc additive manufacturing (WAAM) outstandingly features in lower cost and higher efficiency than other metal additive manufacturing technologies, which has a great potential in large-scale industrial production. The paper gives a detailed review, which involves WAAM hardware system, physical process, monitoring, property characterization, application and future prospects, to facilitate quick and easy understanding of current status and future prospects of WAAM. WAAM hardware systems are of primary importance and mainly based on four types of arc welding machine. The paper summarized the features of different hardware systems, displayed their suitability for different raw materials, and discussed their respective advantages. There is complex physical phenomenon in WAAM, and many technological parameters, such as heat input, current, wire feeding speed and so on, are investigated to understand the physical mechanism. Monitoring is essential for the additive process, in which optical inspection, spectral sensing, acoustic sensing, thermal sensing, electrical sensing and multi-sensor monitoring system all have been applied. Property characterization is always done to evaluate the quality of additive parts, and typical defects such as high residual stress, deformation, porosity, crack and delamination are reported. Examples of industrial products fabricated by WAAM are introduced. Finally, the paper concluded six possible research directions in future. It is necessary to establish detailed databases about additive parts for sorted hardware systems and metals with suitable operating conditions. Hybrid additive and subtractive technology, additional rolling or temperature control process, multi-scale and multi-physics research, multi-variable monitoring system, and artificial intelligence would help to improve the manufacturing level. 

Comprehensive review of wire arc additive manufacturing: Hardware system, physical process, monitoring, property characterization, application and future prospects

Wire-arc additive manufacturing (WAAM) technology integrates the characteristics of additive manufacturing and traditional welding technology. It has been found to be capable of forming large-scale metal components with low cost and higher deposition rates. However, it also has potential issues in morphological accuracy, microstructure, and properties due to the arc-based metallurgy mechanisms with complex thermal cycles. This article intends to give a detailed overview of the quality diagnosis and control of the WAAM process, including the formation mechanisms of typical defects, detection approaches, and detection challenges that remain in the WAAM industrial environments. Subsequently, a multisensor data fusion-based closed-loop quality control model is proposed. This model could provide a feasible solution to ensure the quality and deposition efficiency of WAAM parts in complex manufacturing conditions. Based on this model, a novel process named hybrid deposition and micro-rolling (HDMR) is introduced as the green transformation of traditional manufacturing approaches with higher energy efficiency and better quality.

A review on wire-arc additive manufacturing: typical defects, detection approaches, and multisensor data fusion-based model

Laser and cold metal transfer (laser-CMT) hybrid additive manufacturing is a novel process that allows the manufacturing of parts with high deposition rates. Residual stress and distortion caused by high heat input hinder the widespread use of this technology in producing large-scale components. This paper studies the effect of the path strategy on residual stress and distortion in laser-CMT hybrid additive manufacturing. Three path strategies viz. same direction motion (SDM), reciprocating motion (RM), and segmental reciprocating motion (SRM) are chosen. A finite element model is built to predict the residual stress and distortion of the thin-walled part with arc and line features. The adequacy of the model is proven by validation experiments. The thermal cycles are obtained by infrared thermography, the residual stress on the beads is measured by X-ray diffraction, and the distortions of the substrate are scanned by the structure light vision sensor. The temperature gradient, residual stress, and distortion of the samples deposited in different path strategies are analyzed using the validated model. The distortion of the substrate in depositing process by the SRM path strategy is smaller than that of the other path strategies. Finally, a manufacturing case for a commercial aircraft load-carrying frame demonstrates that industries can adopt Finite element (FE) analysis as a tool to optimize the path strategy for laser-CMT hybrid additive manufacturing.

Effect of path strategy on residual stress and distortion in laser and cold metal transfer hybrid additive manufacturing

Modeling and control of bead geometry in wire and arc additive manufacturing is significant as it affects the whole manufacturing process. The purpose of this paper is to establish an efficient model to control the bead geometry with fewer experiments in wire and arc additive manufacturing (WAAM).,A multi-sensor system is established to monitor the process parameters and measure the bead geometry information. A dynamic parameters experimental method is proposed for rapid modeling without dozens of experiments. A deep learning method is used for bead modeling and control. To adaptively control the bead geometry in real-time, a closed-loop control system was developed based on the bead model and in situ monitoring.,A series of experiments were conducted to train, test and verify the feasibility of the method and system, and the results showed that the proposed method can build the bead model rapidly with high precision, and the closed-loop system can control the forming geometry adaptively.,The proposed modeling method is novel as the experiment number is reduced. The dynamic parameters experimental method is effective with high precision. The closed-loop control system can control the bead geometry in real-time. The forming accuracy is elevated.

A novel method of bead modeling and control for wire and arc additive manufacturing

Wire-feed additive manufacturing has great potential for building large-scale aerospace parts that commonly contain many grid-stiffened panel structures. The buildup of intersections in the grid tends to generate issues such as porosity, cracks, and surface unevenness. A solution to this problem, end lateral extension (ELE), was proposed in our previous work, in which the weld track was extended along the crossing section and provided moderate benefits. This paper continues to optimize the ELE path strategy. Single beads and intersections are deposited by laser and cold metal transfer (CMT) hybrid additive manufacturing. First, a surface quality metric for intersection builds is proposed based on the volume deviation between the given ideal CAD model and the scanned point cloud of the builds. This metric is used to optimize a set of parameters including start and end dwell times, weld current, travel speed, parallel path offset distance, extension and parallel path offset distance, and extension path length in the crossing. The experiments are designed using the response surface method (RSM). Quadratic models are developed to build relationships between the parameters and response variables, and the effects of the parameters on the response are analyzed. Then, variable optimization is performed to obtain the optimal settings. The validation test with the optimal settings exhibits a significantly improved profile quality, which is acceptable in industrial practices.

Optimization of the geometry for the end lateral extension path strategy to fabricate intersections using laser and cold metal transfer hybrid additive manufacturing

Hao Song

Papers

Effect of path strategy on residual stress and distortion in laser and cold metal transfer hybrid additive manufacturing

A novel method of bead modeling and control for wire and arc additive manufacturing

Optimization of the geometry for the end lateral extension path strategy to fabricate intersections using laser and cold metal transfer hybrid additive manufacturing

Rapid Surface Defects Detection in Wire and Arc Additive Manufacturing Based on Laser Profilometer

Additive manufacturing of Ti-6Al-4V alloy by hybrid plasma-arc deposition and microrolling: Grain morphology, microstructure, and tensile properties