**1.2 Wire Arc Additive Manufacturing (WAAM) technology**

The WAAM is a typical AM technology under DED technologies. Generally, in DED, the energy sources such as laser, electric arc, and electron beam are used to melt the feed material in the form of either powder or solid metal wire. Making use of the welding process would enable the heat energy of the process to focus on the metal to be melted directly. This kind of welding based melting and depositing the metal layers additively in order to achieve the final shape and size of the component is known as Wire Arc Additive Manufacturing (WAAM). Therefore, this WAAM particularly falls as one of a DED technique. This WAAM uses an appropriate welding process for melting the metal wire electrode and depositing the melted metal layers over another as in the case of Additive Manufacturing (AM) for the fabrication of metallic components and this is now being one of the fastest and growing research and development field among the almost entire area of engineering fabrication. WAAM generally uses any of the arc welding process power sources along with manipulators for automation to deposit 3D shaped metal components. Manipulations are familiarly being done by CAD/CAM based softwares. Robotic welding equipment is well suited for WAAM because it is easy to get required shape automation/manipulations. The shape of the component being manufactured is achieved by planning the path of the depositions well. This process most normally uses solid wire as a feed material. This solid wire gets melted by an electric arc and moves according to the well-preplanned paths to deposit the metal component in the desired shape. Therefore, the melted metal is deposited layer over a layer to create the required component [5]. **Figure 2** shows a welding based WAAM process for the fabrication of stainless steel plate components in which the arc generated in any

of the arc welding process is directed to the metal wire coming out from the feeder and the arc melts the metal wire thus deposition will be made over a substrate. Thus, the number of required deposition layers would be allowed up to attaining the required shape and size of the component [6].

WAAM illustration may look very simple but in nature, it is not a simple process to carry out. For a WAAM process, the process parameters of the welding process are considered to control to yield desired deposition weld bead geometry there by the final shape of the component is achieved as a single component by arranging weld bead/layer over weld beads/layers. Much care should be given to the welding parameters selected more than the welding operation as these parameters are capable of affecting the quality and shape of the component being fabricated [7]. Therefore, WAAM needs a skilled operator for successful fabrication.
