Additive manufacturing (AM) is a non-conventional manufacturing process that enables the solid physical realization of a given model. Various AM processes and techniques are available that provide flexibility over the material, quality, and cost. Screw extrusion-based additive manufacturing (SEAM) is a novel AM technique that uses a single-screw extruder for continuous extrusion and selective deposition of thermoplastic materials. The process depends heavily on the extruder screw and its geometry in terms of pitch, helix angle, and length; defines the process parameters such as mass flow rate, extrudate size, and metering capacity. In this paper, geometric design optimization of an indigenously fabricated single-screw extruder set-up is performed, for AM applications. The objective is to optimize the helix angle of the extruder screw for maximum output flow rate. It is found that, for the given set of conditions (melt viscosity, extruder screw size, screw speed, nozzle dimensions, flight height, and flow rate), the optimum helix angle is 20.184°. The corresponding flow rate, in terms of extrusion velocity, showed an improvement of almost 1.5 times. The overall size of the set-up is also reduced to almost 50

Electron beam powder bed fusion (EB-PBF) is an integration of electron beam (EB) technology and a powder management system (PMS) with three-axis motion. The EB gun produces a collimated beam, which helps in melting powder materials. The EB is generated by a cathode, confined by the grid, and accelerated by the anode. Further, focusing coil and deflection coils are used to focus the beam and move the beam over the worktable. Considering the requirement of a small beam diameter and circularity of the beam, the design of the focusing coil is crucial. This chapter presents a customized design of the focusing coil that can converge the EB to a very sharp point. An analytical design has been performed for magnetic field calculation and gyro-radius calculations for optimal focusing. Further, the fabricated coil has been tested for focusing and found that it can generate a beam of less than 1 mm average diameter at a distance of 710 mm from its center.

Additive Manufacturing (AM) is an evolving technique that can fabricate any class of material with complex geometrical shape as it is known for selectively controlling the layer-wise deposition of single or multi-materials directly from the CAD model. Multi-Station Multi-Axis—Hybrid Layered Manufacturing (MSMA-HLM) is a hybrid metal AM process that additionally allows for various levels of process hybridization (material addition/removal) and integration of multiple technologies; face milling for surface management, pneumatic hammering, and induction preheating for residual stress management, and optical inspection for crack and surface porosity detection). Functionally gradient material (FGM) is a class of novel material whose properties or functions change gradually in any direction or over volume resulting from variations in its compositions/elements and/or microstructures. FGM has been used in a variety of industries, including aerospace, automotive, biomedical, and defense. In this paper, the mechanical properties of Mild Steel (ER70S-6) such as hardness and tensile strength are gradually improving along the deposited direction of material by MSMA-HLM technique since it involves process hybridization and multiple technologies.

PurposeThis paper aims to investigate the dispenser featuring a slotted rotary metering mechanism and a spiral recoater with a hybrid path combining spiral and linear motions for the laser powder bed fusion (L-PBF) apparatus.Design/methodology/approachAn analytical and experimental study was performed on the proposed apparatus, subsequently comparing it with a dual blade recoater for accuracy, compressive strength and roughness of the specimen produced using the L-PBF apparatus.FindingsThe dispenser ensures powder delivery to the bed's center. The recoater improved layer uniformity by reducing ridge height by 96.30%. Although the heap's bottom-side width and top-side length exhibited minimal deviation, a significant variation was observed in the top-side width, height and bottom-side length. It has led to an oval heap shape instead of the combination of a frustum of a cone and a trapezoidal prism, attributed to the counter-clockwise motion and powder inertia. The experimental study revealed that the spiral path completes its motion 4.82% earlier than anticipated. Furthermore, the authors observed significant improvements in part properties: compressive strength increased by 29.99% and areal surface roughness reduced by 10.78% without affecting dimensional accuracy compared to dual-blade recoaters.Research limitations/implicationsDespite the promising performance, challenges such as ridge formation and heap shape deviations highlight areas for refinement. Future work will focus on optimizing dispenser slot geometry and recoating parameters, broader material compatibility and real-time monitoring.Originality/valueThis study presents the proposed apparatus's analytical modeling, fabrication and experimental validation.

Additive manufacturing (AM) is a disruptive technology that enables the fabrication of intricate geometries layer-by-layer by discretizing the given geometry into multiple slices. Overhangs are regions of these slices where the surface projection exceeds the underlying horizontal support. AM techniques, like material extrusion (MEX), require explicit support structures, which are added to ensure proper printability and dimensional stability. Although supports provide part balancing to avoid material sagging, they should be minimised as they increase the overall material usage, print time and associated costs. Limited studies have been done on the self-supporting capacity of thin-walled AM structures. This research presents a novel analytical model based on the beam bending principle to determine the material’s limit to self-sustain overhangs. The model determines this limit in terms of an overhang angle (from the vertical) using part geometry, process parameters and material properties. It is found that the overhang angle has an inverse square root relation with an apparent number of layers, which can be linearly approximated as a function of the number of layers. The model is further extended to incorporate buckling effects in the extruder fibres. Analytical results showed that overhangs as high as 75o are possible without any external supports, as against the conventional 45° limit. The presented model can alleviate the AM process by increasing the printing efficiency and reducing material wastage.

Powder recoating is a critical aspect of powder-based Additive Manufacturing (AM) techniques. The creation of a uniform powder layer is a top priority due to the dependence of the mechanical and microstructural properties of the specimen. Several recoaters, including blade and roller, are reported in the literature to distribute and level uniform powder layers to fulfill the layerwise AM approach. However, the literature fails to report a framework for selecting the optimal blade recoater. This study proposes a framework based on four parameters: deep-dipping approach, layer thickness, recoating time, and powder wastage. The authors tailored the deep-dipping approach from the Stereolithography (SLA) AM process and applied it to the powder-based AM processes. The framework is applied to seven-blade recoater combinations based on the blade count (one or two) and directionality (unidirectional or bidirectional). The analytical and experimental study resulted in the selection of the dual-blade bidirectional recoater. The selected recoater fulfilled the deep-dipping approach and achieved the required layer thickness (ta=tr) in minimum recoating time (T = Tmin) and powder wastage (Vw=2 V). Subsequently, the selected recoater is physically realized with a proof-of-concept (POC) followed by full-scale model installation in a self-developed laser-powder bed fusion (L-PBF) apparatus. The experimental study resulted in the production of a uniform sand layer and multiple specimens. The analysis revealed that the deviation in average specimen dimension along the build direction was < 3.23

A vacuum system is one of the crucial components of the Electron Beam-Powder Bed Fusion Process (EB-PBF). It ensures the generation of a high-intensity electron beam. This paper presents a vacuum system design for the EBPBF process. The work chamber and EB gun chamber have been designed and verified using ANSYS workbench for stress, strain, and deformation limits and found satisfactory. The analytical calculations have been performed for all the pumps, considering the various gas loads during the process. After the design, the vacuum system has been fabricated and tested for its stability, ultimate vacuum, and leak rate. The helium leak test results show that all the joints have a leak rate better than 1 x 10- 8 mbar l/s. Further, the analytical results of each pump have been compared with experimental results and found almost in line with the theoretical results. The results show that a pressure lower than 1 x 10-5 mbar and 5 x 10-6 mbar can be achieved in the work chamber and EB gun chamber in less than 23 min and 10 min respectively. The chamber was evacuated multiple times and found that the chamber could still hold pressure better than 1 x 10- 2 mbar after 48 h.

Existing Additive Manufacturing (AM) processes offer great details in small and difficult-to-produce parts, but they are limited in small parts, slow, and expensive. Wire-based Additive Manufacturing (WAM) processes offer more advantages in terms of simplicity, higher deposition rate, and large-scale part production. Apart from several benefits of WAM processes, it is still far behind conventional manufacturing processes in terms of manufacturing time and cost. Furthermore, omnidirectionality is one major bottleneck in most WAM processes, creating inhomogeneity in the material property. This paper presents a novel Multi-Wire Feeding (MWF) system, which can enhance the capabilities of the existing WAM processes by increasing the deposition rate up to four times (up to 50 kg/h) compared to commercially available WAM processes and is capable of producing omnidirectional products with high dimensional accuracy. It consists of a compact four-wire feeding arrangement where four wires of the same/different materials can be used simultaneously, with different feed rates of up to 15 m/min, for manufacturing different heterogeneous materials. To achieve omnidirectionality, the MWF system will oscillate with an oscillation frequency of 10 Hz. A retraction system has also been added for space optimization where the multiwire setup can be retracted, and the allocated space can be used for other purposes. The MWF system is primarily designed for EB/laser-based WAM processes but can also be used for TIG-based WAM processes with minor modifications. The proposed design has been validated for its structural rigidity using Ansys simulation.

Additive Manufacturing (AM) is a disruptive technique that enables solid physical realization of a given 3D model, via layer-by-layer deposition in a rapid manner. Various AM techniques have been developed to suit different material, geometric, and property needs. Motion systems are crucial for any advanced manufacturing technique, as they define the kinematic capabilities of the overall system, such as range of travel, feed speed, acceleration, and working volume. While the majority of the machine tools and AM systems are based on serial kinematic motion systems, parallel machines are also gaining popularity because of their precision and design. The scissor mechanism is a parallel kinematic system that offers a compact design with an extensive motion range and distributed loading. Although they are extensively used in material handling and lifting operations, limited research has been done on the incorporation of scissor-based motion systems for advanced manufacturing. This research presents a novel arrangement of scissor kinematics, retrofitted with a rotary table, to provide an overall tri-axial hybrid motion system, suitable for machine tools or AM applications. The system achieves two Parallel Translations (2PT) along Y and Z directions and a rotation about the Z-axis using a Serial Rotary table (1SR). Analytical design and computational models are prepared to validate the proposed design. A design case study is presented to demonstrate the potential application of the triaxial scissor system in sheet-based Electron Beam Additive Manufacturing (EBAM).

Recently, the metal Additive Manufacturing (AM) process has seen a substantial surge in its usage than other processes, especially indirect routes to obtain metal parts, including Rapid Sand Casting (RSC) using Selective Laser Sintering (SLS) and Binder Jetting (BJ). Further, it is observed that the SLS process has lost importance due to the dominance of the BJ. Thus, literature and commercial AM systems are investigated to determine the causes. This study comprises a Systematic Literature Review (SLR) and Bibliometrix using the Biblioshiny web application for patternless sand mold and core production using RSC. This article aims to obtain research articles via SLR for the SLS and BJ AM process, followed by the Bibliometrix using the Biblioshiny web application. The SLR divided the RSC domain into the AM and the Sand Casting (SC). The authors considered three databases, Scopus, Web of Science (WoS), and EBSCO, and applied the SLR, resulting in 148 articles. Subsequently, the authors analyzed 131 relevant articles via Biblioshiny, which led to valuable insights for future research. The bibliometrix and content analysis revealed seven clusters: RSC processes, its optimization, comparison, multi-material compatibility, environmental impact, mold coating, and applications. The RSC via BJ exhibited dominance in the research and commercial market over SLS, one reason SLS lost its importance. The authors proposed the revival of the SLS AM process by employing affordable CO2 laser and linear motor flying optics coupled with recent advancements, including incorporating a hybrid AM approach, adaptive slicing, and mold design for AM (DfAM).

Kinematics plays a crucial role in additive manufacturing (AM), including the synergic movements and relative positioning of different machine components to create the final three-dimensional (3D) model. Therefore, it is essential to understand the underlying kinematics of the machine set-up in use to produce high-quality prints, including complex geometries, intricate shapes, and difficult-to-reach overhangs and underlying supports. Achieving the desired efficiency and required accuracy while printing significantly measures the machine’s capabilities and kinematic limits. The overall machine kinematics includes not only the coordinated movements of the print head and the build platform but also the material feeding and curing mechanisms. Factors such as the machine type, material choice and form, and the desired resolution of the printed part also contribute to the overall kinematic requirements. The kinematic analysis of an AM machine system also includes the properties of printer components, motion control algorithms, and the software used for process control. In this research, various state-of-the-art AM set-ups have been described with dedicated applications for metals (multi-station multi-axis hybrid layered manufacturing (MSMA-HLM), electron beam hybrid manufacturing (EBHM)), thermoplastics (plastic additive manufacturing (PAM), foam additive manufacturing (FAM)), ceramics (sand 3D printing (Sand-3DP)), composites (optimal laminated additive manufacturing (Opti-LAM)), and jettable liquids (sub-zero additive manufacturing (SAM)). Fabricated sample parts are also described. Investigating the various kinematic set-ups can help in enhancing the capabilities and efficiency of additive manufacturing techniques, leading to advancements in the field of rapid manufacturing.

Electron Beam Powder Bed Fusion (EB-PBF) process has various advantages over competing processes, such as high scanning speed, high energy efficiency, better part quality, etc. Furthermore, the EB-PBF process can produce fully dense metallic parts. Despite the various advantages of EB-PBF, smoking is one of the major limitations of this process, which restricts the adoption of this technology. Electrons accumulate on the powder surfaces during EB-particle interaction, causing powder particles to repel each other. The high repulsion forces cause the powder to fly all over the chamber, leading to process termination. This paper presents a comprehensive review of various prediction, monitoring, and mitigation methods adopted by various researchers to analyze, understand, and prevent the smoking phenomenon in the EB-PBF process. Various prediction models, such as electrostatic charging, electromagnetic charging, and momentum transfer models, have been discussed. Furthermore, monitoring methods such as high-speed cameras, ELO imaging, and infrared radiation have been reviewed in detail. Finally, mitigation methods such as preheating, process parameters, powder characteristics, built plate modification, gas purging, and charge neutralization methods have been summarised.

Conventional metal (sand) casting requires solid patterns consisting of two halves (cope and drag) prepared to remove the pattern. The approach is simple but leads to numerous steps and mismatch errors. Also, sand, a porous material, is very sensitive to vibration and susceptible to cracks and breakage. This research presents a novel approach for investment metal casting, where a water-soluble material is used for pattern generation using material extrusion additive manufacturing (AM). As a proof of concept, a semi-complex non-prismatic geometry with various dimensional features is physically realized using this soluble pattern casting (SPC) technique. The pattern is designed and 3D printed out of a water-soluble acrylonitrile butadiene styrene (ABS) thermoplastic using an indigenously fabricated screw extrusion–based AM setup. A ceramic mould is created from plaster of Paris (PoP) around the soluble pattern, generating the mould cavity on further dissolution. A heated water bath with added turbulence via solid vibrations assisted the dissolution process. The final geometry is realized by firing the mould cavity followed by metal pouring. Various geometrical features and intricate details, such as layer lines, are satisfactorily replicated from the 3D-printed pattern to the final metal casting. The dimensional accuracy and surface finish are analysed along the process, starting from the printed pattern to the ceramic mould cavity and the final metal cast part. The presented method has applications in investment casting (IC) industries as it can help significantly reduce the lead time and provide excellent dimensional conformance and geometrical replication from the pattern to cast.

Purpose Integrating additive manufacturing (AM) tools in traditional mold-making provides complex yet affordable sand molds and cores. AM processes such as selective laser sintering (SLS) and Binder jetting three-dimensional printing (BJ3DP) are widely used for patternless sand mold and core production. This study aims to perform an in-depth literature review to understand the current status, determine research gaps and propose future research directions. In addition, obtain valuable insights into authors, organizations, countries, keywords, documents, sources and cited references, sources and authors. Design/methodology/approach This study followed the systematic literature review (SLR) to gather relevant rapid sand casting (RSC) documents via Scopus, Web of Science and EBSCO databases. Furthermore, bibliometrics was performed via the Visualization of Similarities (VOSviewer) software. Findings An evaluation of 116 documents focused primarily on commercial AM setups and process optimization of the SLS. Process optimization studies the effects of AM processes, their input parameters, scanning approaches, sand types and the integration of computer-aided design in AM on the properties of sample. The authors performed detailed bibliometrics of 80 out of 120 documents via VOSviewer software. Research limitations/implications This review focuses primarily on the SLS AM process. Originality/value A SLR and bibliometrics using VOSviewer software for patternless sand mold and core production via the AM process.

Purpose Additive manufacturing (AM) is a layer-by-layer technique that helps to create physical objects from a three-dimensional data set. Fused deposition modeling is a widely used material extrusion (MEX)-based AM technique that melts thermoplastic filaments and selectively deposits them over a build platform. Despite its simplicity and affordability, it suffers from various printing defects, with partial warping being a prevalent issue. Warpage is a physical deformation caused by thermal strain incompatibility that results in the bending of the printed part away from the build platform. This study aims to investigate the warpage characteristics of printed parts based on geometrical parameters and build orientations to reduce the warpage extent. Design/methodology/approach Cuboidal samples of thermoplastic acrylonitrile butadiene styrene ranging from 5 to 80 mm were printed using a commercial MEX system. A Taguchi method-based design of experiment trial was performed to optimize the placement and orientation of the part for minimal warpage. Findings It was found that a lower value of the “in-plane” aspect ratio and a more prominent part thickness are favorable for minimal warpage. The part should always be placed near the region with the highest temperature (least thermal gradient) to minimize the warpage. Originality/value A novel dimensionless parameter (Y) is proposed that should be set to a minimum value to achieve minimal warpage. The results of this study can help improve the design and part placement for the MEX technique, thus elevating the print quality.

Additive Manufacturing ( AM) is a novel manufacturing process that enables the physical realization of a given 3D model via layered deposition. Material extrusion (MEX) is one of the most widely used forms of the various AM techniques, in which the screw extrusion- based AM (SEAM) processing offers the most versatile characteristics, in terms of material handling and flow rate capacities. It involves continuous extrusion of the semi-solid material via an extruder screw. Ironing is a common practice in MEX techniques, to maintain z- height and improve the surface morphologies while deposition. Most commercially used nozzles for MEX are thin-walled, such that the ratio of the nozzle width to the diameter ( w/d) is close to 1. In this research, investigations on the ironing effect during screw extrusion-based material deposition are explored using a set of wider nozzles (w/d as high as 40). Special emphasis is laid on the deposited surface finish, interlayer strength, and geometrical conformance of the extrusion. The nozzle diameter and the stand-off distance (SOD) are also independently varied. It is found that the best dimensional stability is achieved when the SOD is set between 75 % to 100 % of the nozzle diameter. Ironing improved the surface finish and the interlayer strength in all instances, with an average improvement of 50 % and 200 %, respectively.

Purpose This study aims to improve the acceleration in the additive manufacturing (AM) process. AM tools, such as extrusion heads, jets, electric arcs, lasers and electron beams (EB), experience negligible forces. However, their speeds are limited by the positioning systems. In addition, a thin tool must travel several kilometers in tiny motions with several turns while realizing the AM part. Hence, acceleration is a more significant limiting factor than the velocity or precision for all except EB. Design/methodology/approach The sawtooth (ST) scanning strategy presented in this paper minimizes the time by combining three motion features: zigzag scan, 45º or 135º rotation for successive layers in G00 to avoid the CNC interpolation, and modifying these movements along 45º or 135º into sawtooth to halve the turns. Findings Sawtooth effectiveness is tested using an in-house developed Sand AM (SaAM) apparatus based on the laser–powder bed fusion AM technique. For a simple rectangle layer, the sawtooth achieved a path length reduction of 0.19%–1.49% and reduced the overall time by 3.508–4.889 times, proving that sawtooth uses increased acceleration more effectively than the other three scans. The complex layer study reduced calculated time by 69.80%–139.96% and manufacturing time by 47.35%–86.85%. Sawtooth samples also exhibited less dimensional variation (0.88%) than zigzag 45° (12.94%) along the build direction. Research limitations/implications Sawtooth is limited to flying optics AM process. Originality/value Development of scanning strategy for flying optics AM process to reduce the warpage by improving the acceleration.

In this study, a unique Multi-Station Multi-Axis Hybrid Layered Manufacturing (MSMA-HLM) system that can perform 5-axis deposition utilizing both arc and laser processes is designed, put into practice, and validated. The 5-axis deposition method enables accurate and detailed material deposition using a sophisticated transformation methodology. The revolutionary double slicing approach, which enables smooth integration of the 5-axis deposition and machining processes, is the subject of a thorough investigation of component slicing techniques. To determine the fidelity of the MSMA-HLM, the attained dimensional correctness of the produced components is carefully assessed and compared with CAD data. A thorough case study concerning the fabrication of a gas bottle serves as an example of the suggested methodology's applicability. The MSMA-HLM's simultaneous 5-axis kinematics are used to fabricate and then machine the gas bottle, demonstrating the system's adaptability and power. To demonstrate the significant efficiency benefits inherent to 5-axis deposition, a comparison of material waste between the hybrid layered manufacturing technique and conventional material block machining is presented in this paper. This work represents a substantial leap in advanced manufacturing by demonstrating the effective creation and use of a cutting-edge MSMA-HLM. The ability to do complicated multi-axis deposition and concurrent machining not only increases the precision and complexity of manufactured components, but it also provides a strong case for the better resource utilization that 5-axis deposition methods naturally possess. The results of this study highlight the MSMA-HLM's crucial contribution to the development of additive manufacturing's future landscape as well as its ability to transform conventional ideas about industrial production.