Shaped Metal Deposition Research Articles

Rate-dependent strength and ductility of binder jetting 3D-printed stainless steel 316L: Experiments and modeling

Binder-jetting is an additive manufacturing process for metals which involves the rapid making of a binder bonded metal powder part followed by the removal of the binder and creation of a fully dense part in a subsequent sintering step. This emerging process has the potential of high cost efficiency as compared to selective laser melting (SLM) or shaped metal deposition. Here, we determine the rate-dependent plasticity and fracture properties of binder-jetted stainless steel 316L. Electron Back-Scattered Diffraction (EBSD) analysis and tomography revealed an equi-axed grain structure with an initial porosity of 3%. The latter is due to pores with an average size of 20μm that are clustered in layers perpendicular to the build direction. The observed stress-strain curve of the binder-jetted material always lies below that of wrought stainless steel 316L with a 50% lower initial yield stress and a 30% lower ultimate strength. Both the material anisotropy and strain rate sensitivity may be considered as second order effects in that comparison. The equivalent plastic strain obtained from fracture experiments for different stress states is also always lower for the binder-jetted material. The observations for the binder-jetted material therefore stand in stark contrast to those for SLM-made stainless steel which can provide an even higher yield strength than the wrought material. From a mechanism point of view, the low mechanical properties of the binder-jetted material may be explained by the high initial porosity which is reminiscent of cast metals.

Design, Integrating and Controlling of Mig-Based Shaped Metal Deposition System with Externally Cold Wire Feed in Additive Layered Manufacturing Technology

Cold wire feeding plus MIG-based shaped metal deposition process has been proved to be a promising technology capable of using materials and energies reasonably to manufacture complex large-scale metal components. The shaped metal deposition with cold wire feeding process is suitable as an alternative technique for traditional manufacturing methods, especially for complex and large-scale solid parts and it is especially used for structural components in aerospace and the manufacture and repair of dying/molds. In this paper, a new experimental setup was developed, which consists of a MIG welding source, an external cold wire feed unit and a 3-axis machine. The paper explains the design, implementation, and stages of control programing (CAD-CAM) of the developed system. Furthermore, the paper presents the important design steps from the design database using CAD to the final shape of the part to be configured. The proposed system is capable of producing parts of different shapes in sizes of more than 450 mm directly from the computer-aided design. Several components are fabricated with SS309L components to achieve the capability of the advanced proposed system. The results showed that the integrated system and the program are feasible and flexible and hence can be used to manufacture variously shaped parts.

Metal Inert Gas Welding-Based-Shaped Metal Deposition in Additive Layered Manufacturing: A Review

Shaped Metal Deposition (SMD) in additive layered manufacturing technique is a promising alternative to traditional manufacturing used for manufacturing large, expensive metal components with complex geometry in addition to producing free structures by building materials in a layer by layer technique. The present paper is a comprehensive review of the literature and the latest rapid manufacturing technologies of the SMD technique. The aim of this paper is to comprehensively review the most prominent facts that researchers have dealt with in the SMD techniques especially those associated with the cold wire feed. The intent of this study is to review the literature presented on metal deposition processes and their classifications, including SMD process using Wire + Arc Additive Manufacturing (WAAM) which divides into wire + tungsten inert gas (TIG), metal inert gas (MIG), or plasma. This literary research presented covers extensive details on bead geometry, process parameters and heat input or arc energy resulting from the deposition process in both cases MIG and Tandem-MIG in SMD process. Furthermore, SMD may be done using Single Wire- MIG (SW-MIG) welding and SMD using Double Wire-MIG (DWMIG) welding. The present review shows that the method of deposition of metals when using the DW-MIG process can be considered a distinctive and low-cost method to produce large metal components due to high deposition rates as well as reduce the input of high temperature generated during deposition and reduce the distortions. However, the accuracy and surface finish of the MIGSMD are less as compared to electron and laser beam.

Heterogeneous random medium plasticity and fracture model of additively-manufactured Ti-6Al-4V

The large deformation response of Ti-6Al-4V structures made through shaped metal deposition is heavily affected by the prior-beta grain structure induced by the manufacturing process. Based on more than 25 tension and shear experiments on individual prior-beta grains, the statistical distribution of the isotropic hardening response of prior-beta grains is identified. In close analogy with Crystal Plasticity Finite Element (CPFE) analysis, Voronoi tesselation is used to generate finite element models of additively-manufactured structures containing multiple prior-beta grains. For each prior-beta grain, a different hardening curve is assigned using a random pull from the truncated Gaussian distribution of Hockett-Sherby type of hardening curves. Similarly, the parameters of the Hosford-Coulomb fracture initiation model are assigned. The comparison of the CPFE simulation results with the experimental results on tension specimens containing multiple prior-beta grains, shows good qualitative and quantitative agreement with regards to the force-displacement response, the surface strain fields, and fracture occurrences. The results demonstrate that the failure of additively-manufactured Ti-6Al-4V components through ductile fracture requires a heterogeneous random medium modeling approach. While the present study focuses on strength and hardening variations, it is noted that further improvements are expected when considering the known texture mismatch between prior-beta grains along with detailed models of the prior-beta grain boundaries.

Deposition-Path Generation of SS308 Components Manufactured by TIG Welding-Based Shaped Metal Deposition Process

Wire plus arc-based shaped metal deposition is a metal rapid manufacturing technique whereby 3D complex parts are produced by building up metallic parts in layer by layer. In the present work, a type of shaped metal deposition using tungsten inert gas welding plus SS308LSi Wire technique was developed and integrated it with a new computer-aided metal deposition machine (CAMDM). The intent of this paper is to investigate the CAMDM system capabilities about the part modeling and slicing, deposition-path planning, and the part depositing processes. Additionally, this paper highlights the capabilities and limitations of the developed system. The results show that the current manufacturing system is capable to produce various features for metal components with accepted surface quality and free internal defects. The most suitable deposition-path strategy for depositing the solid and hollow components is the combined pattern method, which comprises of the spiral/contour path pattern for the outside/inside boundaries of the part and either spiral or zigzag/raster path pattern for the interior spaces. The controlling system of the present setup allows tuning the deposition parameters during deposition process which usually contributes with selecting of the proper path pattern to manufacture a free defects deposited parts.

Development of a cold wire-feed additive layer manufacturing system using shaped metal deposition method

Shaped metal deposition (SMD) method would be an alternative way to traditional manufacturing methods, especially for complex featured and large scale solid parts and it is particularly used for aerospace structural components, manufacturing and repairing of die/molds and middle-sized dense parts. This method is implemented by depositing continuous cold or hot-water melted via welding arc plasma heat. This paper presents the designing, constructing, and controlling of an additive manufacturing system using TIG plus wire based Shaped metal deposition (TW-SMD) method. The aim of the current study is to design and develop an integrated system which is able to reduce time consuming and boring task of deposition process. The developed additive system is capable of producing near net shaped components of sizes not exceed 400 mm in 3 directions directly from CAD drawing. The results showed that the developed system succeeded to produce near net geometries and error-free depositions for various features of SS308LSi components. Additionally, workshop tests have been conducted in order to verify the capability and reliability of the developed AM system.

Microstructural characterisation of a nickel alloy processed via blown powder direct laser deposition (DLD)

A three dimensional structure of varying wall thickness has been manufactured from an alloy similar to 718 and subjected to metallographic characterisation. The technique is evaluated as a process capable of generating complex geometries. This can be used to add features or as a free form fabrication method. However, in order to allow for comparison to structures developed through more traditional techniques, detailed microstructural characterisation has been undertaken to attempt to understand the potential effect of variation on resultant mechanical properties.Samples were extracted from six locations with different wall thicknesses, intricate features and intersecting ligament geometry. A γ″ linearly arrayed structure within a γ matrix was consistent throughout the component. Micro-porosity was restricted to isolated, spherical pores <1μm in diameter. Electron back-scatter diffraction and X-ray computed microtomography quantitative microstructural analysis techniques have been utilized to assess the influence of layering upon microporosity, patternation and grain structure.A detailed comparison is also made between blown powder Direct Layer Deposition (DLD) and a similar deposition technique, shaped metal deposition (SMD). Blown powder DLD produces a smaller weld pool and results in a more consistent microstructure than SMD, with less evidence of unfavourable phases brought about by prolonged exposure to high temperatures. The improved microstructure, however, must be measured against the different process economics of the blown powder DLD technique.

Development and control of shaped metal deposition process using tungsten inert gas arc heat source in additive layered manufacturing

Tungsten inert gas arc welding–based shaped metal deposition is a novel additive manufacturing technology which can be used for fabricating solid dense parts by melting a cold wire on a substrate in a layer-by-layer manner via continuous DC arc heat. The shaped metal deposition method would be an alternative way to traditional manufacturing methods, especially for complex featured and large-scale solid parts manufacturing, and it is particularly used for aerospace structural components, manufacturing, and repairing of die/molds and middle-sized dense parts. This article presents the designing, constructing, and controlling of an additive manufacturing system using tungsten inert gas plus wire–based shaped metal deposition method. The aim of this work is to design and develop tungsten inert gas plus wire–based shaped metal deposition system to be used for fabricating different components directly from computer-aided design data with minimum time consumed in programming and less boring task compared to conventional robotic systems. So, this article covers the important design steps from computer-aided design data to the final deposited part. The developed additive system is capable of producing near-net-shaped components of sizes not exceeding 400 mm in three-dimensional directly from computer-aided design drawing. The results showed that the developed system succeeded to produce near-net-shaped parts for various features of SS308LSi components. Additionally, workshop tests have been conducted in order to verify the capability and reliability of the developed additive manufacturing system. The developed system is also capable of reducing the buy-to-fly ratio from 5 to 2 by reducing waste material from 1717 to 268 g for the sample components.

Shaped metal deposition technique in additive manufacturing: A review

Shaped metal deposition is a relatively new additive layered manufacturing method. It is a novel technique to build net-shaped or near-net-shaped metal components in a layer-by-layer manner via applying metal wire and selection of a heat source such as laser beam, electron beam, or electric arc. It is a manufacturing method used for production of complex featured and large-scaled parts, especially in aerospace and metal-die industries. This method can lower the cost of fabricated parts by reducing further machining and finishing processes and shortening lead time. This article presents a comprehensive literature review on shaped metal deposition, and it mainly aims to highlight some of the areas which were reported by the researchers in this field to give an extensive overview of shaped metal deposition processes, classification of its methods, and their applications. The presented literature review covers extensive details on microstructure, mechanical properties, and residual stresses induced in the metallic parts produced by various shaped metal deposition techniques as well as fabrication of dual-material parts. Additionally, grain refinement of the deposition morphologies using various techniques, especially the arc pulsation process, was mentioned. This study demonstrates that shaped metal deposition method using wire can be considered as a distinctive low-cost method for fabricating large-scaled components due to high deposition rates, high efficiencies, and dense part production capabilities. However, the accuracy and surface finish are less compared to laser and electron beam melting methods.

Microstructure characterization of SS308LSi components manufactured by GTAW-based additive manufacturing: shaped metal deposition using pulsed current arc

Shaped metal deposition method using gas tungsten arc welding is a novel manufacturing technology that can be used for fabricating solid dense parts in layered manufacturing. This paper reports for the first time using the pulsed current shaped metal deposition technique for fabricating components using cold wire of AISI 308LSi stainless steel. The aim of this work was to investigate and compare the effect of pulse frequency and other deposition process parameters on the morphology aspects and microstructure characteristics of the manufactured components using pulsed and continuous current processes. The obtained results reveal that the structure of the deposited specimens produced via pulsed arc current is generally having finer grains, high residual ferrite, and absence of columnar grains. Pulse frequency and current ratio have a significant influence on the surface morphology and microstructure of the manufactured parts. Good metallurgical bonding with no sensitization effects can be seen in all tested specimens. The presented additive layered manufacturing method can be recommended for near net-shaped processing of austenitic stainless steel components, and it can be used as an alternative manufacturing method for fabricating metal components with free defects, higher corrosion resistance, and superior mechanical properties.

Additive Manufacturing of Sn63Pb37 Component by Micro-coating

Micro-coating is a novel technology to build near-net component layer by layer, which uses a crucible and nozzle instead of a weld head and wire feeder to supply material compared with shaped metal deposition. A pneumatic system is adopted to adjust liquid metal flow rate and the layer height is controlled by the distance between nozzle and substrate. Height and width of a single channel are measured by confocal microscopy, it is found that the error between numerical results and experiment are 5.5% and 1.1%. Tensile stress vertically to the deposition layers reaches to 40.89Mpa, while tensile stress parallel to the deposition layers gives a value of 43.14Mpa. Yield stress of vertically and parallel to the layer are respectively 34.28Mpa and 35.23Mpa. Specimens exhibit better mechanical properties than casting component, whose tensile stress and yield stress are respectively 36.51Mpa and 29.25Mpa.

Additive manufacturing of steel–bronze bimetal by shaped metal deposition: interface characteristics and tensile properties

In this paper, mild steel–silicon bronze bimetal based on the single-pass multi-layer model was fabricated by shaped metal deposition utilizing gas metal arc welding technology. Suitable deposition parameters of silicon bronze were chosen to match the specific size of mild steel wall. Then the characteristics of interface were analyzed. The results show that Cu element did not exist on the steel side, but Fe element entered the bronze side in the forms of particles and big chunks. Meanwhile, owing to the physical and chemical reasons, the silicon element concentrated in the intermixing zone and on the bronze side where Fe element appeared. The interface between steel and bronze had good adhesion without cracks or pores, and metallurgical bonding was achieved. The tensile strength of the bimetal reached 305 MPa and fracture occurred near the middle of bronze side, implying a firm connection between steel and bronze was obtained.

Finite-element modelling of heat transfer in shaped metal deposition and experimental validation

Shaped metal deposition (SMD) is a novel technology for building near-net-shaped components by successive layer deposition using a welding machine. The SMD rig consists of a robot with a tungsten inert gas welding torch and manipulator, both of which are housed inside a sealed chamber. A series of walls were made from Ti–6Al–4V alloy by SMD and the heat transfer problem during layer deposition was analysed in all cases. The specimens were built using a wide range of process parameters (number of layers, layer height, wire feed rate, travel speed, heat input, etc.) and wall dimensions. During the fabrication process, the SMD built part is subjected repeatedly to high temperature gradients and high heating and cooling rates, resulting in a unique morphology and microstructures usually not observed in conventional fabrication techniques. A finite-element model for the thermal analysis of this deposition process was constructed. The aims of this study are, firstly, to correlate the predicted temperature field to experimental observations to validate the numerical model of this complex process; and secondly, to explain on the basis of the computed temperature and temperature rate the appearance of characteristic microstructures on the top of the walls, and in the substrate and intermediate region.

Closed Loop Welding Controller for Manufacturing Process

The aim of this paper is to investigate on the closed loop welding controller of a rapid manufacturing Shaped Metal Deposition (SMD) process. SMD was developed and patented by Rolls-Royce in order to produce mechanical parts directly from a CAD model. A simplified SMD plant has been set up in order to investigate the welding dynamics and parameters and to develop a SMD automatic controller. On the basis of the experience acquired, some basic control laws have been developed, and a closed loop controller has been implemented. This controller permits to find and to maintain the process stability condition, so that the final process results totally automatic. The control is performed adjusting the welding conditions on the basis of arc voltage information obtained from the welding machine during the deposition. The experimental results reported confirm the validity of the proposed strategy.

Manufacturing Ti-6Al-4V Components by Shaped Metal Deposition: Microstructure and Mechanical Properties

The urge in aeronautics to reduce cost and time to flight of components without compromising safety and performance stimulates the investigation of novel manufacturing routes. Shaped Metal Deposition (SMD) is an innovative time-compression technology, which creates near-net shaped components layer by layer by weld deposition. Especially for Ti alloys, which are difficult to shape by traditional methods such as forging, machining and casting and for which the loss of material during the shaping process is also very expensive, SMD promises great advantages. Applying preliminary SMD parameter, four different tubular components with a square cross section and wall thicknesses of about 9 mm were built. The microstructure of the Ti-6Al-4V components consists of large prior β grains, elongated along the temperature gradient during welding, which transform into a lamellar α/β substructure at room temperature. The ultimate tensile strength was between 880 and 1054 MPa. The strain at failure was between 3.0 and 11.3 % for tensile testing parallel to the deposition plane and between 9.1 and 16.4 % perpendicular to the deposition plane. The micro-hardness (3.1 - 3.4 GPa), the Young's modulus (117 - 121 GPa) and the oxygen and nitrogen content are comparable to cast Ti-6Al-4V material.

Preliminary Empirical Models for Predicting Shrinkage, Part Geometry and Metallurgical Aspects of Ti-6Al-4V Shaped Metal Deposition Builds

Shaped Metal Deposition (SMD) is an additive manufacturing process which creates parts layer by layer by weld depositions. In this work, empirical models that predict part geometry (wall thickness and outer diameter) and some metallurgical aspects (i.e. surface texture, portion of finer Widmanstätten microstructure) for the SMD process were developed. The models are based on an orthogonal fractional factorial design of experiments with four factors at two levels. The factors considered were energy level (a relationship between heat source power and the rate of raw material input.), step size, programmed diameter and travel speed. The models were validated using previous builds; the prediction error for part geometry was under 11%. Several relationships between the factors and responses were identified. Current had a significant effect on wall thickness; thickness increases with increasing current. Programmed diameter had a significant effect on percentage of shrinkage; this decreased with increasing component size. Surface finish decreased with decreasing step size and current.

Robotic manufacturing by shaped metal deposition: state of the art

PurposeThe purpose of this paper is to provide an overview of shaped metal deposition (SMD). SMD is an additive manufacturing process which uses a robotic cell to create fully dense, near‐net shape, metallic parts directly from computer‐aided design files.Design/methodology/approachResearch into optimising the SMD process was carried out as part of the 6th Framework RAPOLAC project. This included developing both robotic and weld models, creating a weld controller, and using a design of experiments approach to optimise parameters based on the resultant component microstructure and material properties. Extensive metallurgical analysis and mechanical testing was carried out.FindingsA mechatronic model of the robot was produced and integrated with a novel controller to allow parts to be manufactured with little or no operator intervention. Computational models of the temperature field, microstructure, strain and stresses that occur during deposition were also developed. Variation in weld parameters was linked to part microstructure and mechanical properties.Research limitations/implicationsThis research focussed on a common titanium aerospace alloy (Ti‐6Al‐4V).Practical implicationsThe SMD process is applicable to a variety of parts in a range of industrial sectors. It is cost‐effective for low‐volume parts and prototypes, but it is envisaged that its main use will be to add material to previously forged or cast components and therefore SMD will allow companies to reduce both the size of forgings and material waste. SMD as a repair technique is also being investigated.Originality/valueThe paper provides a summary of the latest advances in robotic manufacturing by SMD.

Effect of deposition parameters on mechanical properties of shaped metal deposition parts

The mechanical properties of Ti-6Al-4V parts fabricated by shaped metal deposition, an additive layer manufacturing technique applying wire-based tungsten inert gas welding, have been measured, with the emphasis of comparing the effect of two different deposition rates. Similar part geometries were obtained for two parts fabricated with deposition rates of 0.1 and 0.3 m/min by adjusting the energy input and the wire feed rate accordingly. This affected the thermal history of the parts, and consequently the morphology, microstructure and mechanical performance. The ultimate tensile strength was between 880 and 1000 MPa, where the strength and hardness were lower for the slower deposition rate. The strain at failure was significantly better for tensile testing perpendicular rather than parallel to the base plate, and considerably larger for the part fabricated with the lower deposition rate. The Young’s modulus was comparable for both deposition rates, and independent of the orientation.

Mechanical Properties of INCONEL 718 Parts Manufactured by Shaped Metal Deposition (SMD)

INCONEL 718 parts have been manufactured by shaped metal deposition (SMD), an additive layer manufacturing technique applying wire-based tungsten inert gas welding. This technique is aimed toward mass customization of parts, omitting time- and scrap-intensive, subtractive fabrication routes. SMD results in dense, “near net-shaped” parts without pores, cracks, or fissures. The microstructure of the SMD parts exhibit large, columnar grains with a fine dendritic microstructure. The interdendritic boundaries are decorated by small Laves phase precipitates and by MC carbides. Tensile tests were performed with different strain rates (10−4, 10−3, and 2 × 10−3 1/s), but no dependency on strength or strain at failure was observed. The ultimate tensile strength was 828 ± 8 MPa, the true plastic strain at failure 28 ± 2%, the micro Vickers hardness 266 ± 21 HV200, and the dynamically measured Young’s module was 154 ± 1 GPa.

An Arc Welding Robot Control for a Shaped Metal Deposition Plant: Modular Software Interface and Sensors

This paper is focused on the study and the control of a process of robotic arc welding. The system developed has been used to study the whole process and to develop an automatic controller for the arc process of deposition. The process consists of a shaped metal deposition (SMD) system that is an innovative method for the manufacturing of metal objects, which uses a layer-by-layer deposition technique. A useful software interface has been implemented in a Labview environment to study the system and to develop and tune the parameters of an automatic controller.