Wire + Arc Additive Manufacturing

Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed

Wire + Arc Additive Manufacturing

Additive manufacturing is a rapidly developing technology which promises to drastically reduce the cost and waste associated with manufacturing parts. However, current systems of additive manufacturing used for creating metal parts which are suitable for use in the aerospace, automotive, and defense industries are complex, expensive, and not robust enough to produce a wide range of part features and geometries. A relatively new method, called wire arc additive manufacturing(WAAM) is a low cost option that can create parts which have a near-net shape, and only require a small amount of post processing before they are ready for use. This system, when attached to a 6 degree of freedom robotic arm, can be effectively used to create a system that offers a very high level of design flexibility to an engineer. Parts produced by this system also have nearly zero material waste, when compared to up to 90% material waste on parts produced by a conventional subtractive, computer controlled, machine. As part complexity increases, the manufacturing costs associated with that part rise at a much faster, non-linear, rate. With WAAM, the complexity increase would only correspond to a slightly higher manufacturing cost, if any increase at all. The principles behind WAAM are simple. A welder, with an automatic wire feed attachment is used to deposit metal onto a metal substrate. The deposition of metal on the base layer would resemble the bottom of the part. Additional layers are added one by one in a very similar method that 3D printing uses. Because each layer is, on average, only .070 thick, it allows for complex or curved surfaces to be formed during the build process with relative ease. These surfaces are cleaned up during the final post processing of the part so that they are exactly what is represented by the part model. The WAAM system is also capable of creating a single part that is made from more than one type of material, something that is impossible with subtractive manufacturing. Additionally, a small robotic arm, weighing only 60 lbs, can build parts in a work envelope of over 8 cubic feet, whereas a subtractive machine with a similar work volume could weigh upwards of 7,000 lbs, occupy a much larger floor space, require significantly more power, and cost 2 to 3 times as much as a robotic WAAM system to implement. The welder, wire feed, and robot are controlled through an offline-programming software. With the software, the part can be visualized as it is built, layer by layer, and the motion of the robot is simulated. In addition to the programming of motion of the robot, the material science behind the deposition of the welded metal is under investigation in order to give favorable parameters to the software for controlling the welding current, wire feeding speed, wire current, and robotic arm movement rates

Residual stress of as-deposited and rolled Wire + Arc Additive Manufacturing Ti–6Al–4V components

Wire + arc additive manufacturing components contain significant residual stresses, which manifest in distortion. High-pressure rolling was applied to each layer of a linear Ti–6Al–4V wire + arc additive manufacturing component in between deposition passes. In rolled specimens, out-of-plane distortion was more than halved; a change in the deposits' geometry due to plastic deformation was observed and process repeatability was increased. The Contour method of residual stresses measurements showed that although the specimens still exhibited tensile stresses (up to 500 MPa), their magnitude was reduced by 60%, particularly at the interface between deposit and substrate. The results were validated with neutron diffraction measurements, which were in good agreement away from the baseplate

Wire+Arc Additive Manufacturing of Aluminum

Wire+Arc Additive Manufacturing is very suitable for the production of large scale aluminium parts. However implementation is currently limited by issues such as porosity and low mechanical properties. We have studied the utilization of new deposition processes such as pulsed advanced cold metal transfer which allows modification of the thermal profile resulting in refined equiaxed microstructure and elimination of porosity. Standard and new feedstock compositions are being evaluated and developed with ultimate tensile strengths of up to 260 MPa with 17% elongation being obtained in the as-deposited condition. Post build heat treatments compositional changes and high-pressure inter-pass rolling are being investigated in order to increase the strength further.Mechanical Engineerin

MECHANICAL SYSTEM FOR WIRE ARC ADDITIVE MANUFACTURING

This article discusses the reassembly of a mechanical system for 3D printing plastic parts to be used for plasma arc additive manufacturing. The main issues in converting an existing 3D printer designed for plastic additive to used for producing metal parts are: control of the welding power source; installation and realization of the movement with the welding torch; set the height of the zero layer; setting up the program software to generate the control file

Process planning for robotic wire ARC additive manufacturing

Robotic Wire Arc Additive Manufacturing (WAAM) refers to a class of additive manufacturing processes that builds parts from 3D CAD models by joining materials layerupon- layer, as opposed to conventional subtractive manufacturing technologies. Over the past half century, a significant amount of work has been done to develop the capability to produce parts from weld deposits through the additive approach. However, a fully automated CAD-topart additive manufacturing (AM) system that incorporates an arc welding process has yet to be developed. The missing link is an automated process planning methodology that can generate robotic welding paths directly from CAD models based on various process models. The development of such a highly integrated process planning method for WAAM is the focus of this thesis

A THERMAL MODEL FOR WIRE ARC ADDITIVE MANUFACTURING

Layer-by-layer detailing processes, which used wire and electric arc - wire arc additive manufacturing (WAAM), are among the most productive in 3D metal printing technologies. From this point of view, the solution of the thermal task, and subsequently of the deformation problem, are particularly relevant. It is natural that these simulation modelling processes are closely related to welding, but at the same time it is necessary to take into account particularities that are crucial for WAAM and are not always relevant in welding. In this research, one such model is proposed, which takes into account the gradual filling of the working space with the deposited metal. The specific issues related to the construction of the model, the definition of the heat source and the first layer formation in the conditions of WAAM are considered. The obtained numerical results enable the prediction of the layer dimensions

The current state of research of wire arc additive manufacturing (WAAM): a 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

Microstructure of interpass rolled wire + arc additive manufacturing Ti-6Al-4V components

Mechanical property anisotropy is one of the issues that are limiting the industrial adoption of additive manufacturing (AM) Ti-6Al-4V components. To improve the deposits’ microstructure, the effect of high-pressure interpass rolling was evaluated, and a flat and a profiled roller were compared. The microstructure was changed from large columnar prior beta grains that traversed the component to equiaxed grains that were between 56 and 139 μm in size. The repetitive variation in Widmanstätten alpha lamellae size was retained; however, with rolling, the overall size was reduced. A “fundamental study” was used to gain insight into the microstructural changes that occurred due to the combination of deformation and deposition. High-pressure interpass rolling can overcome many of the shortcomings of AM, potentially aiding industrial implementation of the process.EPSRC, AirBu