Among the different additive manufacturing (AM) processes, hybrid-layered manufacturing (HLM) is the AM process of metals which combines the best features of additive and subtractive manufacturing techniques. In HLM process, the metal is deposited by a cladding process and after the deposition of near-net shape, a machining operation is used for achieving dimensional accuracy. In this work, TIG cladding-based HLM process has been studied and stabilized by retrofitting a TIG cladding unit on an existing CNC machine. The behavior of TIG-HLM process has been studied for a mild steel cladding wire ER70S-6 of 1.2 mm diameter by performing the three types of experiments: single-bead, multi-bead and multilayer experiments. The single-bead experiments are performed along with Taguchi and ANOVA to find out the contribution of process parameters such as cladding current, torch speed, wire feed rate and standoff distance on the bead width, height and penetration. The multi-bead experiments are performed to find out the optimal height of a layer where bead width is the input parameter. The multilayer experiments are required for the characterization of the process and consist of hardness test by nano-indentation testing, microstructure analysis by electron backscattered diffraction, and interlayer fusion test by X-ray analysis. A case study has been done by manufacturing a cylindrical object of 50 mm height using this process. Keywords Additive manufacturing (AM) Á Hybridlayered manufacturing (HLM) Á Tungsten inert gas (TIG) Á Taguchi Á ANOVA Á Electron backscattered diffraction (EBSD)

Purpose In additive manufacturing (AM) process, the physical properties of the products made by fractal toolpaths are better as compared to those made by conventional toolpaths. Also, it is desirable to minimize the number of tool retractions. The purpose of this study is to describe three different methods to generate fractal-based computer numerical control (CNC) toolpath for area filling of a closed curve with minimum or zero tool retractions. Design/methodology/approach This work describes three different methods to generate fractal-based CNC toolpath for area filling of a closed curve with minimum or zero tool retractions. In the first method, a large fractal square is placed over the outer boundary and then rest of the unwanted curve is trimmed out. To reduce the number of retractions, ends of the trimmed toolpath are connected in such a way that overlapping within the existing toolpath is avoided. In the second method, the trimming of the fractal is similar to the first method but the ends of trimmed toolpath are connected such that the overlapping is found at the boundaries only. The toolpath in the third method is a combination of fractal and zigzag curves. This toolpath is capable of filling a given connected area in a single pass without any tool retraction and toolpath overlap within a tolerance value equal to stepover of the toolpath. Findings The generated toolpath has several applications in AM and constant Z-height surface finishing. Experiments have been performed to verify the toolpath by depositing material by hybrid layered manufacturing process. Research limitations/implications Third toolpath method is suitable for the hybrid layered manufacturing process only because the toolpath overlapping tolerance may not be enough for other AM processes. Originality/value Development of a CNC toolpath for AM specifically hybrid layered manufacturing which can completely fill any arbitrary connected area in single pass while maintaining a constant stepover.

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Purpose The support structures of sacrificial material are built in deposition-based additive manufacturing (AM), which are later removed either by breaking or dissolving. Such a sacrificial material is not feasible in metal AM. The purpose of this study is to find a suitable method for eliminating the need of support mechanism. In this work, the authors use the tilting of the substrate to alleviate the need for the support mechanism altogether. Design/methodology/approach As in the traditional AM, the object is grown in horizontal layers. However, wherever undercuts are encountered, the substrate is tilted appropriately to capture the droplets. Such a tilt involves two rotary axes invariably. To conform to the slice geometry, these two tilts are accompanied by the three linear movements. Thus, the object with undercuts is grown in planar layers using five-axis deposition without any support structure. Each pair of the corresponding top and bottom contours of any slice defines a ruled surface. The axis of the deposition head will be aligned with the rules of this surface. Findings The need for the support mechanism was eliminated using five-axis deposition. This was experimentally demonstrated by building an aluminum impeller using a metal inert gas cladding head. Research limitations/implications In the proposed methodology, the objects with an abrupt change in the geometry are not possible to realize. Originality/value This manuscript proposed a novel method of eliminating the support mechanism through continuous five-axis deposition.

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