Additive Manufacturing Of Metallic Components Research Articles

The Potential of Additive Manufacturing of Metal Components to Reduce Environmental Impacts

The Potential of Additive Manufacturing of Metal Components to Reduce Environmental Impacts

A Design Strategy for Removing the Debinding and Sintering Gas in Additive Manufactured Samples of a Bronze/Polylactic Acid Filament

To lower the cost of additive manufacturing of metallic components, the goal of this work is to investigate and optimize a multi‐step process by material extrusion (MEX) of a polylactide filament loaded with bronze to remove the gas produced during the debinding and sintering steps. First, by adjusting the infill (10%, 50%, and 100%), and then by designing and constructing internal passages to aid in the expulsion of gases that occur during the debinding, a calibration cube is created. Additionally, the impact of the cooling period during the debinding is examined. To assess how the technique changes shape, sizes, and internal structure, all the samples are ultimately weighed, scanned, and cut. In order to reduce deformation occurred during the debinding and sintering gases, a new design method has been developed. The method consists of the generation of internal channels which connect the voids of the infill and allow gases to flow out through a central channel. As seen, samples with ejection channels and an intermediate infill (i.e., 50%) both exhibit better attributes.

Segmentation-based closed-loop layer height control for enhancing stability and dimensional accuracy in wire-based laser metal deposition

Laser metal deposition (LMD) with wire is a versatile additive manufacturing process used for the production of near-net-shape metal components as well as for modification and repair applications. Major advantages of using wire as the feedstock material as opposed to powder include the elimination of hazardous metal dust in the process environment and the lower costs. However, the process is highly sensitive to disturbances and requires a significant effort for parameter tuning. Thus, in order to achieve a stable process as well as defined geometric properties over many layers, dedicated approaches for monitoring and control are essential. In particular, maintaining a constant distance between the workpiece surface and the deposition head is an important prerequisite for process stability. Therefore, in this work, a layer height control system for wire-based LMD was implemented. The objective was to ensure a constant layer height corresponding to the specified height increment even in case of disturbances. Using a laser line scanner, the height profile of the part was obtained after each deposited layer. The weld beads were then divided into small segments to obtain a fully discrete height profile, and the wire feed rate for the next layer was set by an individual controller within each segment. The implemented control system was tested for its effectiveness under different disturbances, whereby significant height differences could be fully compensated within few layers. The developed segmentation approach was found to be an effective method to ensure the dimensional accuracy of LMD components. This work thus constitutes a major contribution to the advancement of fully automated additive manufacturing of metallic components.

Modeling the process behavior in laser additive manufacturing of metallic materials—A tribute to professor Jyoti Mazumder

This paper provides an overview of Professor Jyoti Mazumder's contribution in modeling of laser-matter interaction during materials processing over the past four decades, particularly in the area of laser-based metal additive manufacturing of metallic components, followed by the work at The University of Manchester in modeling and simulation of powder/wire-feeding laser additive manufacturing, in-space laser additive manufacturing, high deposition rate laser metal deposition, and multiple-material laser powder bed fusion additive manufacturing processes. Future challenges and opportunities in this field are discussed.

Modeling the thermomechanical processes and residual stresses in additive manufacturing of metallic components

AbstractIn additive manufacturing of metallic components and fusion welding, undesirable deformations and residual stresses are common drawbacks, which directly influence the performance and functionality of the manufactured components. In this work, a thermomechanical continuum model is developed by using the phase‐field method to track the evolution of the melting/remelting‐solidification occurring due to the incident of localized heat input sources, e.g, by means of a laser heat source. The result of the thermal analysis is then employed for the mechanical analysis to predict the residual stresses. In the thermal and mechanical analysis, the thermomechanical properties are considered to evolve with the phase‐field variable. In addition, a scalar‐valued history variable is introduced to distinguish between consolidated and loose powder materials. This enables single‐track additive manufacturing simulations with a possible extension to multi‐layer and multi‐track simulations. To verify and validate the modeling approach, the coupled system of equations is implemented in the open‐source FEniCS project and a numerical example for additive manufacturing is solved and compared qualitatively and quantitatively with reference results from the literature.

Development of Fused Deposition Modeling of Multiple Materials (FD3M) Through Dynamic Coaxial Extrusion.

Multimaterial additive manufacturing is expanding the design space realizable with 3D printing, yet is largely constrained to sequential deposition of each individual material. The ability to coextrude two materials and change the ratio of materials while printing would enable custom-tailored polymer composites. Here, the evolution of a dynamic material coextrusion process for additive manufacturing capable of printing any ratio between and including two neat input materials is described across 3 hot-end generations and 14 implemented design iterations. The designs evolved with increased understanding of manufacturing constraints associated with the additive manufacturing of metal components with internal flow bore diameters on the order of 2 mm and typical bore length around 50 mm. The second generation overcame this issue by partitioning the design into two pieces to locate the flow channel geometry at the interface between the components so that the details could be easily printed on the components' external surfaces. The third concept generation then focused on minimizing flow channel volume to reduce the average length when transitioning between materials by 92%. The third-generation design was also used to investigate the improvements in dimensional stability during annealing of acrylonitrile butadiene styrene (ABS) made possible by coextruding ABS with a polycarbonate (PC) core. The standard deviation of part shrinkage after annealing was 7.08% for the neat ABS but reduced to 0.24% for the coextruded ABS/PC components.

Finite element analysis of the surface finishing of additively manufactured 316L stainless steel by ball burnishing

As additive manufacturing of metal components is becoming increasingly significant due to high levels of design freedom yet features insufficient surface quality, finishing processes need to be further developed. As an alternative to machining, investigating the ball burnishing of powder bed fusion (PBF) workpieces provides opportunities to advance fundamental research. Studying this method's capabilities, finite element analyses (FEA) were conducted based on a flow stress model parameterized with Split-Hopkinson Pressure Bar (SHPB) tests. The roughness smoothing and a macroscopic approach mapping residual stress distributions was modelled and validated. Improvements in surface integrity were confirmed in both the FEA and experimentally.

Spatio-temporal LPV model of 2D workpiece temperature for Direct Laser Deposition

Additive manufacturing of metallic components presents challenges regarding quality assurance and consistency, owing to the workpiece's complex spatially-dependent temperature history and a lack of suitable models for closed-loop temperature control of the fabrication process. The selected case study is the laying of cladding material (workpiece) through Direct Laser Deposition. The paper proposes identifying a linear spatio-temporal parameter-varying model for the workpiece temperature for control-oriented applications. For this, the temperature distribution is reconstructed from data measured by an infrared camera. The model structure is derived from the inhomogeneous heat equation. Finally, the model parameters are identified using a nonlinear least-squares solver. The relationships between theoretical and estimated model parameters are presented.

Bulk-like ductility of cold spray additively manufactured copper in the as-sprayed state

• As-sprayed CSAM Cu can exhibit a simultaneous high ductility and strength. • This is triggered by a specific topology of bimodal grain size. • The deposits have a high thermal conductivity comparable to bulk. • They are perfectly gas-tight with He leakage rate of less than 1 × 10 −7 mbar•l/s. • All these were achieved with 99% efficiency using inexpensive nitrogen. In recent years, cold spray process is increasingly used for additive manufacturing of metallic components, referred to as cold spray additive manufacturing (CSAM). Unlike the fusion-based AM processes, CSAM is achieved in a solid-state, bringing several advantages such as the absence of severe oxidation or phase composition changes. At the moment, the main limitation of CSAM is the generally low ductility of the as-sprayed deposits. In this paper, using Cu as a model material, we demonstrate a way to overcome this limitation. Importantly, a high ductility of the deposits in their as-sprayed state is achieved without a trade-off in mechanical strength. Furthermore, we show that without any post-heat treatment, the properties of CSAM Cu are comparable to bulk, non-AM Cu.

A Study on Additive Manufacturing of Metal Components for Mobility in the Area of After-Sales with Spare and Performance Parts

Mobility is undergoing changes. Increasingly strict legislation regarding pollutant emissions and the protection of the environment are more important than ever. The change to electric mobility is also presenting the mobile world with new challenges and opportunities. Vehicles are becoming more and more efficient with higher power densities and better performance. Application-adapted components are being developed and used as a matter of preference. New production technologies can help to realise the change in mobility reliably. Additive manufacturing is one way of producing functionally integrated and performance-optimised components. AM offers the possibility to produce application-specific performance parts. Electric vehicles often have a problem with the thermal load of the components during power output and charging. Additively manufactured components with optimised topology and integrated cooling strive to achieve higher power density, enhanced cooling performance, and improved mechanical properties. AM not only makes it possible to produce functionally integrated and application-adapted components but also to reduce CO2 emissions and conserve resources. The potential of additive manufacturing for mobility is particularly interesting for the spare and performance parts sector. Components can be improved in performance and manufactured directly on-site. The higher power density and the elimination of transport routes can make an additional significant contribution to environmental protection. This paper presents an overview of the current state of additive manufacturing in the field of electromobility with regard to replacement and performance parts using 3D metal printing. Based on an extensive literature research, a market overview is given. This serves as the basis for the further procedure and, building on this, the advantages of additive manufacturing are demonstrated using the example of an electric motor. The selected electric motor is an example of a defective component in a vehicle that needs to be replaced and whose performance can be improved by additive manufacturing and which can be produced on-site in a quantity of one. The motor is verified by means of a FEM simulation in order to determine the selection of an optimal water jacket topology and to demonstrate further potential for the future.

Additive Manufacturing of Metal Components by Thermal Spray Deposition on 3D-Printed Polymer Parts

Additive Manufacturing of Metal Components by Thermal Spray Deposition on 3D-Printed Polymer Parts

Additive Manufacturing of Metallic Components for Hard Coatings

Metals additive manufacturing is a new concept of fabrication that consists of depositing material layer-by-layer in a very precise and automatized way [...]

A Coaxial Wire-Feed Additive Manufacturing of Metal Components Using a Profile Electron Beam in Space Application

Despite the variety of different methods of metal 3D printing on Earth, only a few of them can be realized in space. Processes that employ electron beam as a heat source and wire as a consumable material is among the most promising methods for these applications. But to date, such processes still have not been implemented in actual space operation, mainly due to the low accuracy and resolution of these 3D printed products that require significant post-processing for their intended use. Large and heavy hardware employed in these processes is another significant problem. xBeam 3D Metal Printing is the electron beam DED-wire additive manufacturing technology that has already demonstrated the capability to produce high-quality parts with high productivity on terrestrial relatively lightweight and compact hardware. xBeam process employs a profile electron beam generated by low-voltage gas-discharge electron beam guns combined with the coaxial wire feed to provide excellent control of metallurgy processes in the melt pool and around it during deposition. Realized metallurgy conditions are the crucial factor in providing the combination of high accuracy and resolution with good metal structure and properties. Moreover, maintaining such metallurgy conditions does not require gravity—only cohesion/adhesion forces and surface tension forces are involved. This fact suggests good prospects for using the xBeam 3D Metal Printing in space applications. In addition, the method opens several unique technological opportunities that are important in space exploration, including the nonstick deposition technique allowing the production of "ready-to-use" parts, surface glazing able to substitute machining, recycling of the metal waste directly into wire for 3D printing, and others. The article presents technical solutions for implementing 3D printing and related processes in space conditions and analyzes the metallurgical aspects of the technology using titanium alloy Ti-6Al-4V as an example.

Fundamental mechanics problems in metal additive manufacturing: A state-of-art review

Metal additive manufacturing (AM) is a kind of disruptive manufacturing technology that considers the needs of complex geometry fabrication and high-performance part fabrication. Hence, it has broad applications and extensive development space in aviation, aerospace, transportation, nuclear power, to name a few. However, its large-scale applications suffer from the challenge, including improving manufacturing efficiency and achieving the geometry and mechanical property as desired, which is a cross-cutting problem involving multi-discipline such as mechanics, optics, material science, mechanical engineering, control science. In the viewpoint of mechanics associated with the challenge, this paper critically reviews the recent research progress of AM-oriented structure topology optimization design, numerical simulation of the metal AM process, as-built defects characterization, and mechanical performance evaluation of the fabricated metal materials and components, which are referred to as structure design-process modelling-performance evaluation for metal AM. Finally, research topics that are required to address the fundamental mechanical problems in terms of structure design-process modelling-performance evaluation in AM of metallic components are provided.

Tangent stiffness for nonlinear heat transfer and its application to additive manufacturing

Prediction-correction method is commonly employed in the solution of nonlinear heat transfer equation with temperature dependent thermophysical parameters arising in various engineering problems such as additive manufacturing of metal components. However, the stiffness of such conventional method is secant rather than tangent and thus it only results in suboptimal rate of convergence in Newton's iteration. In this paper, tangent stiffness for nonlinear heat transfer is proposed through the linearization of the weak form and an additional term presents which disappears in the conventional prediction-correction method. Numerical results show that the solution with the proposed tangent stiffness converges much faster than that with secant stiffness and approximately only half of the iteration steps are needed. Especially, in the case that the thermal conductivity varies dramatically with the temperature, the conventional method diverges whereas the tangent stiffness still shows quite good convergence. Application of the proposed method to the modeling of heat transfer in additive manufacturing (AM) process is presented and the obtained temperature results agree quite well with the existing experimental studies. It is worth mentioning that almost half of CPU time is saved due to the application of the proposed tangent stiffness. This saving is of great significance for modeling the AM process of complicated components, which is usually very time-consuming.

Conjugate Thermal Optimization With Unsupervised Machine Learning

Abstract With advances in additive manufacturing of metal components, commercial production of complex turbine components is becoming feasible. Thus, designers are not constrained to the limitations of conventional manufacturing methods. A new conjugate optimization technique is proposed, which is not computationally demanding and can be used when several heat transfer modes are working simultaneously. For this study, film cooling holes in the leading edge of a gas turbine airfoil are optimized without trial and error simulations. Since the machine learning technique is not dependent on thermal analysis, the optimization technique can be applied to any nonlinear problem. Film hole sizes are optimized to minimize coolant flow rate while reducing the temperature variations in the stationary vane. The technique used a transfer function based iterative optimization process with unsupervised machine learning that has been termed nonlinear optimization with replacement strategy (NORS). It uses a grading metric to replace the worst performing hole combinations with one that has been optimized with a given objective and several constraints. Optimized results show significant reductions in vertical temperature variations along the leading edge while minimizing coolant flow rate. Reduced temperature variation results in reduced thermal stresses. The finite element (FE) model and the associated correlations are not part of the unsupervised machine learning technique; therefore, the proposed optimization model can be generalized for any engineering design with multiple inputs for learning and multiple outputs for grading.

Wire and arc additive manufacturing of metal components: a review of recent research developments

Wire arc additive manufacturing (WAAM) is an important metal 3D printing method, which has many advantages, such as rapid deposition rate, low cost, and suitability for large complex metal components manufacturing, and it has received extensive attention. This paper summarizes the research developments of WAAM in recent years, including the WAAM-suitable metal materials and processing technology, deposition strategy optimization including slicing and path planning algorithm, multi-sensor monitoring and intelligent control, and the large complex metal components manufacturing technology. The promising development directions of WAAM are prospected, including the research of new materials and new technology, composite manufacturing, multi-sensor and real-time monitoring, algorithmic optimization of metal filling strategy, and the application of artificial intelligence technology in WAAM, etc.

WAAM system with interpass temperature control and forced cooling for near-net-shape printing of small metal components

In an attempt to find a solution similar to the FDM 3D printers which would allow cost-effective and reliable additive manufacturing of metal components, this paper proposes a three-axis WAAM system capable of reliably printing small, near-net-shape metal objects. The system consists of gas metal arc (GMA) process equipment, a three-axis CNC positioning system, the interpass temperature control and forced cooling of the base plate and the deposit. The main challenge addressed is the minimisation of shape distortions caused by excessive heat accumulation when printing small objects. The interpass temperature control uses an IR pyrometer to remotely measure the last deposited layer and a control system to keep the interpass temperature below the predefined value by stopping the deposition after each layer in order to allow the deposit to cool. This results in a stable and more repeatable shape of the deposit, even when the heat transfer conditions are changing during the build-up process. The combination of adaptive interlayer dwell time and forced cooling significantly improves system productivity. Open-source NC control and path generation software is used, which enables fast and easy creation of the control code. Different control methods are evaluated through the printing of simple walls, and the printing accuracy is evaluated by printing small shell objects. As the results show, the interpass temperature control allows small objects to be printed at near-net shape with a deviation of 2%, which means that successful printing of 3D shapes can be achieved without trial and error approach.

Scanning strategies effect on temperature, residual stress and deformation by multi-laser beam powder bed fusion manufacturing

Laser beam Powder Bed Fusion (PBF-LB) is an increasingly attractive technology due to its capability of manufacturing complex and customised metal parts. However, the build cycle time and resulting residual stress profiles are limiting a wider uptake of PBF-LB manufacturing. The incorporation of additional laser beams in a single build chamber, i.e. multi-laser beam Powder Bed Fusion (PBF-MLB) technology, has been proposed as the next generation of PBF-LB technology. A series of computational process simulations of PBF-MLB was carried out using a 3D coupled thermomechanical model to investigate optimum multi-laser scanning strategies. The influences of twelve different scanning strategies on temperature, the final residual stresses, the z- (build) direction deflections by dual Gaussian profile laser beams PBF-MLB were investigated. It was found that the 90° layer rotation is necessary to reduce the residual stress, and a ‘dual-laser following but time-delayed’ scanning strategy had the lowest final residual stress. Another scanning strategy (45° rotation approaching beam scanning) resulted in the lowest z-direction deflection for the dual laser beams PBF-MLB manufacturing. These findings provide insight and application of PBF-MLB finite element process simulation in improving industrial additive manufacturing of metal components.

Effect of atomization on surface oxide composition in 316L stainless steel powders for additive manufacturing

The initial oxide state of powder is essential to the robust additive manufacturing of metal components using powder bed fusion processes. However, the variation of the powder surface oxide composition as a function of the atomizing medium is not clear. This work summarizes a detailed surface characterization of three 316L powders, produced using water atomization (WA), vacuum melting inert gas atomization (VIGA), and nitrogen atomization (GA). X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy analyses were combined to characterize the surface state of the powders. The results showed that the surface oxides consisted of a thin (~4 nm) iron oxide (Fe2O3) layer with particulate oxide phases rich in Cr, Mn, and Si, with a varying composition. XPS analysis combined with depth‐profiling showed that the VIGA powder had the lowest surface coverage of particulate compounds, followed by the GA powder, whereas the WA powder had the largest fraction of particulate surface oxides. The composition of the oxides was evaluated based on the XPS analysis of the oxide standards. Effects of Ar sputtering on the peak positions of the oxide standards were evaluated with the aim of providing an accurate analysis of the oxide characteristics at different etch depths.