Department of Mechanical engineering
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Item Additive Manufacturing of Complex Shapes Through Weld-Deposition and Feature Based Slicing(ASME, 2016-04) Sharma, Panchagnula JayaprakashFabricating fully dense and functional metallic components is one of the important challenges in Additive Manufacturing (AM). Additive Manufacturing is a technology in which functional components can be fabricated rapidly and efficiently from their CAD models. It is also referred as Layered Manufacturing (LM) as the object is created by slicing the CAD model into layers and realizing each layer at a time. These layers are thin and stacked or glued together to get the physical shape of the CAD model. However, realizing overhanging features is a difficult task due to deficiency of support mechanism for metals. A separate support structure has to be deposited to build overhanging structures. Although, use of a distinct support material is quite common in non-metallic AM processes, such as Fused Deposition Modelling (FDM), and the same for metals is not yet available. The various techniques in AM process for fabricating metal parts can be mainly classified as laser based, electron beam based and arc based processes. While some Additive Manufacturing processes like Selective Laser Sintering (SLS) employ easily-breakable-scaffolds made of same material to realize the overhanging features, the same approach cannot be extended to deposition processes like laser or arc based direct energy deposition processes.Item Inclined slicing and weld-deposition for additive manufacturing of metallic objects with large overhangs using higher order kinematics(Taylor & Francis, 2016-04) Sharma, Panchagnula JayaprakashThis paper presents an automated tool path planning for deposition of overhanging features using GMAW-based weld-deposition. Overhanging features, although possible to a certain extent in power-bed process like SLS, remain a challenge in deposition-based processes. Deposition processes like weld-deposition-based AM realised smaller overhangs by exploiting the inherent overhang capability of the weld bead; but the same cannot be applicable for complex geometries with large overhangs. This paper explains an efficient way of depositing the overhanging features through weld-deposition, without use of supports, based on inclined slicing and deposition. This approach uses higher order kinematics, that is, adding extra degrees of mobility to workpiece. The methodology used for realising these inclined slices based on an in-house MATLAB code has also been presented. While this concept is implemented in the context of weld-deposition, it can be extended for any other metallic deposition processes as well.Item Feature based Weld-Deposition for Additive Manufacturing of Complex Shapes(Springer, 2016-08) Sharma, Panchagnula JayaprakashFabricating functional metal parts using Additive Manufacturing (AM) is a leading trend. However, realizing overhanging features has been a challenge due to the lack of support mechanism for metals. Powder-bed fusion techniques like, Selective Laser Sintering (SLS) employ easily-breakable-scaffolds made of the same material to realize the overhangs. However, the same approach is not extendible to deposition processes like laser or arc based direct energy deposition processes. Although it is possible to realize small overhangs by exploiting the inherent overhanging capability of the process or by blinding some small features like holes, the same cannot be extended for more complex geometries. The current work presents a novel approach for realizing complex overhanging features without the need of support structures. This is possible by using higher order kinematics and suitably aligning the overhang with the deposition direction. Feature based non-uniform slicing and non-uniform area-filling are some vital concepts required in realizing the same and are briefly discussed here. This method can be used to fabricate and/or repair fully dense and functional components for various engineering applications. Although this approach has been implemented for weld-deposition based system, the same can be extended to any other direct energy deposition processes also.Item Influence of Various Tool Path Patterns on Hardness Used in Weld Deposition-Based Additive Manufacturing(Springer, 2019-10) Sharma, Panchagnula JayaprakashIdentification of optimal tool path is critical for successful fabrication of bulk metallic parts using weld deposition-based additive manufacturing (AM). The various features of tool path, i.e., the number of starts and stops, convolutions, and continuity, have a significant effect on the geometric as well as physical properties of manufactured parts. Ideally, an optimised tool path is a continuous path with no self-intersecting pattern, with a minimum of starts and stops and minimum convoluted patterns. The tool paths available in the literature are unable to achieve all the listed requirements. Further, there are no one-to-one comparisons of these tool paths in detail in the literature. The present work aims in comparing various tool path techniques based on flatness achievable by minimum material skinned out during face milling (thickness of the deposited layer) and the hardness achieved. Experiments are performed using the in-house developed weld-based metallic AM workstation (weld deposition torch is retrofitted with a CNC).Item A Complete Study on Various Area Filling Strategies Used in Weld Deposition-Based Additive Manufacturing(Springer, 2021-06) Sharma, Panchagnula JayaprakashAchieving the optimal toolpath as well as obtaining the desired physical and geometrical properties for bulk metallic parts through weld deposition-based additive manufacturing (AM) is a challenging task. The current work aims in identifying the suitable toolpath for bulk weld deposition-based AM applications by comparing the various toolpath (eleven types) techniques. These toolpaths were evaluated based on the final layer thickness attained after face milling (skinning) operation, minimum amount material machined during the face milling, average hardness achieved, length of the heat-affected zone (HAZ) and the microstructural behaviour. Amongst the various toolpath patterns considered, hybrid toolpath (Single Contour Out with Hilbert In) is ideal for bulk deposition-based AM owing to its maximum final layer thickness and the minimum amount of material removed in skinning operation. On the other hand, it has been observed that Spiral Out to In toolpath pattern is inferior for bulk deposition-based AM. Additionally, the average grain size is presented for some of the toolpath patterns in the current article.Item A novel methodology to manufacture complex metallic sudden overhangs in weld-deposition based additive manufacturing(Emerald, 2023-01) Sharma, Panchagnula JayaprakashAmongst various additive manufacturing (AM) techniques for realizing the complex metallic objects, weld-deposition (arc)-based directed energy AM technique is attaining more focus over commercially available powder bed fusion techniques. This is because of the capability of high deposition rates, high power and material utilization, simpler setup and less initial investment of arc-based AM. Nevertheless, realization of sudden overhanging features through arc-based weld-deposition techniques is still a challenging task because of the necessity of support structures. This paper aims to describe a novel methodology for producing complex metallic objects with sudden overhangs without using supports.