Wire And Arc Additive Manufacturing Research Articles

Wire Arc Additive and High-Temperature Subtractive Manufacturing of Ti-6Al-4V

We investigated the fabrication and finishing of wall-profile machining by wire and arc additive manufacturing (WAAM) employing plasma welding with Ti-6Al-4V wire. We fabricated and integrated a local shield and a cover for the area below the local shield to achieve higher shielding ability. The tensile strength of the fabricated object met the forging standard for Ti-6Al-4V, but elongation was about 7%. We also focused on the possibility of reducing the cutting force and increasing the efficiency of the finishing process by cutting workpieces softened by high temperature immediately after the deposition process. We investigated the cutting force and tool wear of the fabricated objects heated to 300 °C using ceramics tools. Results showed that although the cutting force was reduced at high temperature, the wear rate of the tools was high, and the increase in cutting force due to wear was significant.

Static and dynamic mechanical properties of wire and arc additively manufactured SS316L and ER70S6

The worldwide growing demand for additive manufacturing (AM) has led to the development of wire and arc additive manufacturing (WAAM) technique. In this work, SS316L and ER70S6 thick-walled cylinders were produced, and specimens were extracted in the as fabricated condition. For comparison, bulk SS316L and AISI 1020 specimens were machined from cold drawn (also in as received condition) bars and tested accordingly. Four types of specimens were used: “dog-bone” for tension, cylinder for compression, shear tension specimen (STS) and shear compression specimen (SCS) for both mixed shear tension and shear compression loading, respectively. Experiments were carried out under static (ca. 10−3 1/s) and dynamic conditions (from 102 to 104 1/s). WAAM SS316L SCS under static conditions, and WAAM cylinder under dynamic loading showed a unique stress-strain curvature (hardening) that was not observed for the bulk material. By contrast, WAAM ER70S6 material shows somewhat similar properties to those of AISI 1020, indicating it might be a suitable candidate for repair or even material replacement for AISI 1020 as a material for AM products.

A review on wire and arc additive manufacturing of titanium alloy

Wire and arc additive manufacturing (WAAM) is considered to be an economic and efficient technology that is suitable to produce large-scale metallic components. In the past few decades, it has been widely investigated in different fields such as aerospace, automotive, and marine industries. Due to its relatively high deposition rate, low machinery cost, high material efficiency, and shortened lead time compared to other powder-based additive manufacturing (AM) techniques, WAAM has been significantly noticed and adopted by both academic researchers and industrial engineers. Titanium alloys as valuable metallic materials have been increasingly applied in aeronautics and astronautics fields owing to their excellent comprehensive properties. However, there are many challenges to fabricate large-scale titanium components with traditional manufacturing methods, particularly in consideration of complex component geometries and high Buy-To-Fly (BTF) ratio. Therefore, due to the advantages of relatively low manufacturing cost, good quality, and high efficiency, WAAM is becoming popular to fabricate near-net-shape and large-scale titanium alloy in recent years. This paper provides an overview of the 3D metallic printing of titanium alloy by employing WAAM as the deposition method. At first, the review introduces titanium alloys and WAAM technique, followed by WAAM systems which are used to manufacture titanium, and post-treatment which aims to optimize microstructure, improve mechanical properties, and eliminate residual stress of the WAAM deposited titanium components. Afterward, the economic applicability of applying WAAM on titanium alloys is also discussed. In the end, applications in various fields of WAAM titanium components are displayed.

Investigation of deposition strategy on wire and arc additive manufacturing of aluminium components

Wire and Arc Additive Manufacturing (WAAM) is known for its higher deposition rate and its ability to manufacture medium-large scale components compared to other related techniques. However, the manufacturing of small to large scale structures would require a choice of deposition strategies to implement. Parallel and oscillation deposition is implored for structures with large widths that cannot be attained by a single pass. These strategies are expected to improve the structural geometry, mechanical properties and the product's production time. In this study, Al2319 WAAM block structure was fabricated using an oscillation deposition strategy with Advanced cold metal transfer process. The influence of this strategy on porosity, microstructure, microhardness and mechanical properties of the structure were investigated. Based on the results, the structure deposited by oscillation strategy has more of its micro porosity within 0.5-50um, and its average percentage area porosity was comparable to thin wall fabricated with CMT-Pulse Advanced. Furthermore, the tensile properties of the vertical specimen were superior to the horizontal specimen, and the ultimate tensile strength (223 MPa) and yield strength (127 MPa) attained satisfies that of O-tempered wrought Al2219 alloys.

Multiaxis wire and arc additive manufacturing for overhangs based on conical substrates

PurposeThis paper aims to present a series of approaches for three-related issues in multiaxis in wire and arc additive manufacturing (WAAM) as follows: how to achieve a stable and robust deposition process and maintain uniform growth of the part; how to maintain consistent formation of a melt pool on the surface of the workpiece; and how to fabricate an overhanging structure without supports.Design/methodology/approachThe principal component analysis-based path planning approach is proposed to compute the best scanning directions of slicing contours for the generation of filling paths, including zigzag paths and parallel skeleton paths. These printing paths have been experimented with in WAAM. To maintain consistent formation of a melt pool at overhanging regions, the authors introduce definitions for the overhanging point, overhanging distance and overhanging vector, with which the authors can compute and optimize the multiaxis motion. A novel fabricating strategy of depositing the overhanging segments as a support for the deposition of filling paths is presented.FindingsThe second principal component of a planar contour is a reasonable scanning direction to generate zigzag filling paths and parallel skeleton filling paths. The overhanging regions of a printing layer can be supported by pre-deposition of overhanging segments. Large overhangs can be successfully fabricated by the multiaxis WAAM process without supporting structures.Originality/valueAn intelligent approach of generating zigzag printing paths and parallel skeleton printing paths. Optimizations of depositing zigzag paths and parallel skeleton paths. Applications of overhanging point overhanging distance and overhanging vector for multiaxis motion planning. A novel fabricating strategy of depositing the overhanging segments as a support for the deposition of filling paths.

Control of forming process of truss structure based on cold metal transition technology

PurposeThe purpose of this paper is to study the wire and arc additive manufacturing (WAAM) method and path planning algorithm of truss structure parts, to realize the collision-free rapid prototyping of truss structures with complex characteristics.Design/methodology/approachFirst, a point-by-point stacking strategy is proposed based on the spot-welding mode of cold metal transfer welding technology. A force analysis model of the droplet is established, which can be used to adjust the posture of the welding torch and solve the collapse problem in the WAAM process of the truss structure. The collision detection model is developed to calculate the interference size between the truss structure and the welding torch, which is used to control the offset of the welding torch. Finally, the ant colony algorithm has been used to optimize the moving path of welding torch between truss with considering the algorithm efficiency and collision avoiding and the efficiency of the algorithm is improved by discretizing the three-dimensional workspace.FindingsA series of experiments were conducted to prove the validity of the proposed methods. The results show that the wire feeding speed, welding speed are the important parameters for controlling the WAAM process of truss parts. The inclination angle of the welding torch has an important influence on the forming quality of the truss.Originality/valueThe force analysis model of truss structure in the WAAM process is established to ensure the forming quality and a collision-free path planning algorithm is proposed to improve forming efficiency.

Experimental behaviour of Wire‐and‐Arc Additively Manufactured stainless steel rods

AbstractRecently, metal Additive Manufacturing has gained great importance in many industrial sectors with first pioneering applications in also in the Construction field. In particular, a weld‐based technique called Wire‐and‐Arc Additive Manufacturing (WAAM) allows to build real‐scale structural elements of complex geometry thanks to 6‐axes robotic arms and off‐the‐shelf welding equipment able to print at higher speed thus overcoming the geometrical constraints typical of other 3D printing technologies such as Powder Bed Fusion. Nonetheless, the printing outcomes need to be properly characterized both in terms of their specific material properties, which substantially differ from the feedstock, and the geometrical imperfections proper of the printing process. Among possible deposition strategy for WAAM the dot‐by‐dot printing results to be particularly suitable to realize metal 3D lattice structures made by straight rods. This novel dot‐by‐dot printing could bring to different mechanical parameters with respect to the layer‐by‐layer deposition (widely known and studied in the literature and already adopted for first practical applications). This work presents the first results of a wide experimental investigation carried out at University of Bologna to study the geometrical imperfections and the main mechanical properties (through tensile and compression tests) of WAAM‐produced stainless steel rods of different lengths. First indications are given on the influence of the rods length on the compression capacity Future work is aimed at quantifying the influence of geometrical irregularities (initial crookedness and cross‐section variation) and non‐linear material behavior in the compression response of 3D‐printed rods through numerical studies to calibrate a set of ad‐hoc buckling curves.

3D‐Printing with Steel: Additive Manufacturing of a Bridge in situ

AbstractAdditive manufacturing (AM) plays an increasing role in the production of complex structures in steel construction. Robot‐guided Gas Shielded Metal Arc Welding (GMAW), known as Wire and Arc Additive Manufacturing (WAAM), is suitable for this purpose. At TU Darmstadt, a small pedestrian bridge in shell form was designed. It was completely additively manufactured on site with a welding robot over a creek. This paper presents selected aspects of this project. The focus is particularly on the preliminary strength investigations carried out and the process sequences required for homogenous manufacturing. The paper concludes with a consideration of the implementation on site.

3D‐Printing with steel of a bolted connection

AbstractAdditive Manufacturing seems promising for the steel construction industry, especially for small components with complex shapes. With Wire‐and‐Arc‐Additive‐Manufacturing (WAAM) a process was found which is fast and cheap compared to other Additive Manufacturing processes for metals. Furthermore, arc‐welding is well known in steel construction industry.Bolted head plates are a common connection. Although they are relatively easy to produce, they are uneconomical in load transfer due to straining of the plates which are subject to bending. This type of connection is predestined for Additive Manufacturing. Rethinking the structure by taking into account the potentials of Additive Manufacturing brings a clear advantage compared to the conventional production. Thus, with a material saving of 60 % the same load capacity of the original flat head plate can be achieved.The paper shows how the new production process WAAM can significantly change the shape of structures on the example of a bolted head plate. Therefore, all steps from the original design to the manufactured structure are demonstrated, including the structure finding by using topology optimization, the manufacturing with different parameters and a first testing of the manufactured structures.

On the topological optimization of horizontal links in eccentrically braced frames

This paper presents an implementation of structural optimization algorithms for the design of horizontal links of Eccentrically Braced Frames (EBFs) when subjected to monotonic shear loading. The objective is to study optimized geometries that open new design paths for these types of elements. With the advent of new additive manufacturing techniques such as WAAM (wire and arc additive manufacturing), energy dissipators may become one of the strategic applications for 3D printing of steel structures. For this purpose, an optimization procedure based on a displacement-controlled lateral load (push-over) applied to a single-storey EBF has been created using Abaqus FEA and Abaqus Optimization Module (ATOM). The performance of the optimized links has been compared with the performance of original links in terms of initial stiffness, yield strength, maximum strength and energy dissipation. The results show a set of promising geometrical configurations for horizontal links. Further research lines related to cyclic loading, anisotropic behaviour and advanced loading protocols are suggested.

A Literature Review on the Wire and Arc Additive Manufacturing—Welding Systems and Software

Wire and arc additive manufacturing (WAAM) is considered to be an economic and efficient technology that is suitable to produce large-scale and ultra-large-scale metallic components. In the past two decades, it has been widely investigated in different fields, such as aerospace, automotive and marine industries. Due to its relatively high deposition rate, material efficiency, and shortened lead time compared to other powder-based additive manufacturing (AM) techniques, wire and arc additive manufacturing (WAAM) has been significantly noticed and adopted by both academic researchers and industrial engineers. In order to summarize the development achievements of wire and arc additive manufacturing (WAAM) in the past few years and outlook the development direction in the coming days, this paper provides an overview of 3D metallic printing by applying it as a deposition method. The review mainly focuses on the current welding systems, software for tool path design, generation, and planning used in wire and arc additive manufacturing (WAAM). In the end, the state of the art and future research on wire and arc additive manufacturing (WAAM) have been prospected.

Welding parameters effect and optimization on bead geometry during arc additive manufacturing

This paper discusses the effect of parameters in MIG based wire and arc additive manufacturing (WAAM) using stainless-steel wire and Q235 as substrate. The response surface methodology (RSM) and ANOVA were used to determine the effects of current, voltage, and welding velocity on the responses of bead height and width. It was found that voltage had the largest effect on the bead width, followed by welding velocity and current. But on the bead height, welding velocity is the most significant parameter, followed by current and voltage. The genetic algorithm (GA) was utilized to optimize the parameters to obtain the maximum ratio of weld bead width to height for multi-layer single-pass arc additive deposition.

Influence of Interlayer Forced Air Cooling on Microstructure and Mechanical Properties of Wire Arc Additively Manufactured 304L Austenitic Stainless Steel

Wire‐and‐arc additive manufacturing (WAAM) is an innovative technology that involves deposition of subsequent layers of molten materials. Due to the high deposition rates, this technology is suitable for the production of large‐scale complex structures. Further enhancement in the productivity can be achieved by an interlayer cooling strategy that reduces idle time between depositions. However, the effect of the interlayer cooling on microstructure and mechanical properties has to be addressed. In this view, the present work compares microstructural features and mechanical properties of WAAM‐produced plates of austenitic AISI 304 L, focusing on the effect of both active interlayer air cooling and possible anisotropy induced by the additive process. Microstructural and mechanical characterization was conducted on samples extracted along the longitudinal, transverse, and diagonal directions to the deposition layers of WAAM plates, processed with and without interlayer active cooling. Results showed no remarkable influence of cooling conditions on the microstructure and mechanical properties of WAAM plates, which are indeed affected by the anisotropy induced by the additive process. The observed anisotropy in the elastic modulus, independent from different cooling conditions, was related to the crystallographic texture consequent to the highly oriented microstructure typically induced by the process.

Machinability of wire and arc additive manufactured components

Wire and Arc Additive Manufacturing (WAAM) aims to be a cost-effective and material-efficient process to produce medium and large-scale metal parts. Nevertheless, post-processing is still required due to the low quality of the as-deposited surface. With the objective to divulge the complex interaction between the welding and machining phenomena, which determines the final surface quality, this paper focuses on the machinability of WAAM parts through a comprehensive investigation on the key parameters of both additive and subtractive processes. The effect of the WAAM parameters on the as-deposited part characteristics (i.e., hardness, flatness deviation, wall thickness, and initial surface waviness) and machining process has been analyzed. Consequently, the first of its kind, a non-linear function that can predict the effect of welding and milling parameters on the final surface roughness, is presented. The complex interaction between the local (e.g., surface irregularities and hardness) and global (e.g., wall thickness) effects of welding heat input and the resulting impact on the machining stability is analyzed. For example, slow welding speed results in a soft and irregular surface that is not easy to machine. Still, at the same time, the slow speed increases the wall width that provides the essential damping to reduce the chatter during machining. The obtained results help understand the interactions between the WAAM and milling processes and further determine the optimal machining allowances and optimal process conditions.

Influence of Post-Deposition Heat Treatments on the Microstructure and Tensile Properties of Ti-6Al-4V Parts Manufactured by CMT-WAAM

Cold metal transfer (CMT)-based wire and arc additive manufacturing (WAAM) of Ti-6Al-4V alloy has been investigated to manufacture walls with two different building strategies. This study focuses on the influence of the application of thermal treatments on the resulting microstructure and mechanical properties. Deep microstructural analysis revealed different grades of growth of lamellae α phase after several thermal treatments at different temperatures, which lead to different tensile mechanical properties and better strength and ductility balance compared to the as-built condition. Results are compared with equivalent forged and casting standards and the state of the art for WAAM of Ti-6Al-4V alloy. At temperatures of 920 °C, anisotropy was maintained and elongation increased by 70% while yield strength and UTS was slightly decreased by 8%.

Bimetallic structure of Ti6Al4V and Al6.21Cu fabricated by cold metal transfer additive manufacturing via Nb interlayer added by TIG

In this study, a method of introducing an Nb intermediate layer added by tungsten inert gas welding was proposed and used in the fabrication of a crack-free Ti6Al4V/Al6.21Cu bimetallic structure by wire and arc additive manufacturing (WAAM) based on cold metal transfer (CMT) technique. The results showed that the addition of an Nb interlayer between Ti6Al4V and Al6.21Cu could effectively impede the diffusion of Ti and Al elements, thereby inhibiting the formation of Ti-Al brittle intermetallic compounds. The reaction layer composed of Al3Nb was formed at the Al6.21Cu/Nb interface. The average ultimate tensile strength of the Ti6Al4V/Al6.21Cu bimetallic structure with and without Nb interlayer were 120.9 MPa and 94.5 MPa respectively, indicating that the addition of Nb interlayer can significantly improve the mechanical properties of the Ti6Al4V/Al6.21Cu bimetallic structure.

Fatigue crack growth behaviour of wire and arc additively manufactured ER70S-6 low carbon steel components

The new emerging Wire and Arc Additive Manufacturing (WAAM) technology has significant potential to improve material design and efficiency for structural components as well as reducing manufacturing costs. Due to repeated and periodic melting, solidification and reheating of the layers, the WAAM deposition technique results in some elastic, plastic and viscous deformations that can affect material degradation and crack propagation behaviour in additively manufactured components. Therefore, it is crucial to characterise the cracking behaviour in WAAM built components for structural design and integrity assessment purposes. In this work, fatigue crack growth tests have been conducted on compact tension specimens extracted from ER70S-6 steel WAAM built components. The crack propagation behaviour of the specimens extracted with different orientations (i.e. horizontal and vertical with respect to the deposition direction) has been characterised under two different cyclic load levels. The obtained fatigue crack growth rate data have been correlated with the linear elastic fracture mechanics parameter varDelta K and the results are compared with the literature data available for corresponding wrought structural steels and the recommended fatigue crack growth trends in the BS7910 standard. The obtained results have been found to fall below the recommended trends in the BS7910 standard and above the data points obtained from S355 wrought material. The obtained fatigue growth trends and Paris law constants from this study contribute to the overall understanding of the design requirements for the new optimised functionally graded structures fabricated using the WAAM technique.

Investigation of the in-situ gas cooling of carbon steel during wire and arc additive manufacturing

Wire and arc additive manufacturing (WAAM) is a promising technology for fabricating large-sized metal parts. However, to use this method efficiently, it is necessary to overcome the problem of severe heat accumulation that reduces manufacturing efficiency and deteriorates material properties. This paper proposes a new method using the in-situ gas cooling (ISGC) for reducing heat accumulation. Three parts were manufactured via the proposed method utilising CO 2 , N 2 , and air as cooling gases, respectively. A fourth part was fabricated with natural cooling (NC), without cooling gas. The temperature data measured by thermocouples and infrared pyrometers indicated that compared with NC, ISGC considerably reduced the temperature of the whole part and CO 2 had the best cooling effect. ISGC efficiently mitigated heat accumulation, due to the large heat transfer coefficient and the great temperature difference between the high-temperature region behind the torch and the cooling gas. Numerical simulations verified by the experimental data further denoted that in ISGC, high-temperature areas near the molten pool shrank sharply and heat dissipation conditions in the molten pool were improved markedly. ISGC not only improved the surface quality of the parts, but also strengthened the mechanical properties of the parts by obtained fine grains. The maximum ultimate tensile strength (UTS) and yield strength (YS) increased to 483 MPa and 358 MPa, respectively, which represented an increase of 4.1 % and 4.7 % respectively. The average hardness was enhanced to 161.3 HV, representing an improvement of 3.7 %.

A model of bead size based on the dynamic response of CMT-based wire and arc additive manufacturing process parameters

PurposeThis paper aims at fabricating large metallic components with high deposition rates, low equipment costs through wire and wire and arc additive manufacturing (WAAM) method, in order to achieve the morphology and mechanical properties of manufacturing process, a bead morphology prediction model with high precision for ideal deposition of every pass was established.Design/methodology/approachThe dynamic response of the process parameters on the bead width and bead height of cold metal transfer (CMT)-based AM was analyzed. A laser profile scanner was used to continuously capture the morphology variation. A prediction model of the deposition bead morphology was established using response surface optimization. Moreover, the validity of the model was examined using 15 groups of quadratic regression analyzes.FindingsThe relative errors of the predicted bead width and height were all less than 5% compared with the experimental measurements. The model was then preliminarily used with necessary modifications, such as further considering the interlayer process parameters, to guide the fabrication of complex three-dimensional components.Originality/valueThe morphology prediction of WAAMed bead is a critical issue. Most research has focused on the formability and defects in CMT-based WAAM and little research on the effect of process parameters on the morphology of the deposited layer in CMT-based WAAM has been conducted. To test the sensitivities of the processing parameters to bead size, the dynamic response of key parameters was investigated. A regression model was established to guide the process parameter optimization for subsequent multi-layer or component deposition.

AA5083 (Al\u2013Mg) plates produced by wire-and-arc additive manufacturing: effect of specimen orientation on microstructure and tensile properties

Among various additive manufacturing (AM) technologies, wire-and-arc additive manufacturing (WAAM) is one of the most suitable for the production of large-scale metallic components, also suggesting possible applications in the construction field. Several research activities have been devoted to the WAAM of steels and titanium alloys and, recently, the application of WAAM to aluminum alloys has also been explored. This paper presents the microstructural and mechanical characterization of WAAM plates produced using a commercial ER 5183 aluminum welding wire. The aim is to evaluate the possible anisotropic behavior under tensile stress of planar elements, considering three different extraction directions in relation to the deposition layer: longitudinal (L), transversal (T) and diagonal (D). Compositional, morphological, microstructural and fractographic analyses were carried out to relate the specific microstructural features induced by WAAM to the tensile properties. An anisotropic behavior was found in regard to the specimen orientation, with the lowest strength and ductility found on T specimens. Reasoning to this was found in the presence of microstructural discontinuities unfavorably oriented with regard to the tensile direction. The results of tensile tests also highlighted an overall good mechanical behavior, comparable to that of conventional AA5083-O sheets, suggesting future use in the realization of very complex geometries and optimized shapes for lightweight structural applications.