No abstract

Purpose Electron beam-based additive manufacturing (EBAM) is an emerging technology to produce metal parts layer-by-layer. The purpose of this paper is to systematically address the research and development carried out for this technology, up till now. Design/methodology/approach This paper identifies several aspects of research and development in EBAM. Findings Electron beam has several unique advantages such as high scanning speed, energy efficiency, versatility for several materials and better part integrity because of a vacuum working environment. Originality/value This paper provides information on different aspects of EBAM with the current status and future scope.

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)

In this work, the finite-element method (FEM) is used to develop the governing equation of motion of the working roll of a four-high rolling mill and to study its vibration due to different process parameters. The working roll is modeled as an Euler Bernoulli beam by taking beam elements with vertical displacement and slope as the nodal degrees-of-freedom in the finite-element formulation. The bearings at the ends of the working rolls are modeled using spring elements. To calculate the forces acting on the working roll, the interaction between the working roll and the backup roll is modeled by using the work roll submodel, and the interaction between the working roll and the sheet is modeled by using the roll bite submodel (Lin et al., 2003, “On Characteristics and Mechanism of Rolling Instability and Chatter,” ASME J. Manuf. Sci. Eng., 125(4), pp. 778–786). Nodal displacements and velocities are obtained by using the Newmark Beta method after solving the governing equation of motion of the working roll. The transient and steady-state variation of roll gap, exit thickness profile, exit stress, and sheet force along the length of the strip have been found for different bearing stiffnesses and widths of the strip. By using this model, one can predict the shape of the outcoming strip profile and exit stress variation which will be useful to avoid many defects, such as edge buckling or center buckling in rolling processes.

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.

Induction heating (IH), a clean energy source, is potentially used to develop wire additive manufacturing (AM) system. The optimised parameters that simultaneously melt the mild steel wire and raise the substrate temperature is established. A fully coupled thermal-electromagnetic model of AM system is developed to perform numerical experiments on temperature development. The proposed hybrid helical-pancake coil with circular cross-section melt the metallic wire and raise the substrate temperature to 1490 K. The hybrid coil provides rapid heating to the wire (2819 K) and substrate together by enhancing magnetic field strength. The experiments using high-frequency IH system (550 A and 353 kHz) with a 3-turn helical coil is validated with model results for 2 mm mild steel wire.

In this study, the effect of process parameter and various post-processing techniques on surface roughness of PLA object produced by fused deposition method is investigated. The economical and versatile method with the proper design of the experiments to reduce the surface roughness is our objective. The PLA is selected as the workpiece material, a biodegradable material which is vastly used in medical implants, where surface roughness is a major issue. The various post-processing technique is analyzed, and the parameter optimization is taken into consideration. Post-processing technique like chemical treatment, vapour smoothing, sanding and polishing is carried out. Taguchi design of the experiment is also used to optimize the parameter that affects the targeted surface roughness. Taguchi L 9 orthogonal array is used to organize the different parameters, and Minitab software is used to determine the optimum parameter setting. The dichloromethane chemical is found to be the best chemical for dissolving the PLA material and reducing the layer lines so that the surface roughness can be reduced. The final results confirmed that the chemical vapour treatment using dichloromethane and the Taguchi method sufficient to improve the surface roughness.

In this work, a four high cold rolling mill is modeled as a spring-mass-damper system considering horizontally and vertically applied time-dependent forces due to the interac tion between the strip and the working rolls. The effect of vibration of the moving strip on the work roll vibration is also considered for developing the governing equation of motion o f the system which is found to be that of a nonlinear parametrically excited sys tem. The governing equation of motion is solved by using the method of multiple scales to find the instability regions and frequency-response curves of the system. The critical am plitude of horizontal load in roll bite is calculated and the frequency-response is studied in detail considering the effect of various process parameters, such as velocity, thickness of strip, time delay, amplitude, arid frequency of horizontal load in roll bite. This work can find application in the design and development of high speed and chatter free rolling mills.