Characterization of the High-Temperature Oxidation Behavior of Inconel 625® Fabricated by Additive Manufacturing and Conventional Methods

Various types of additive manufacturing (AM) methods (also called 3D printing), and materials have been increasingly studied in the field of additive manufacturing of flexible structures such as fabrics, and flexible electronics. Polymer-based AM processes allow the flexibility, rapid, and low-cost fabrication of complex geometries depending on the types of materials used. The purpose of this review article is to summarize the major AM methods, materials, and their emerging applications to additively manufacture the flexible structures. In the AM methods section, Fused Deposition Modeling (FDM), and Selective Laser Sintering (SLS) are reviewed for fabrics, and Direct Ink Writing (DIW) for electronics. In the Materials section, the manufacturing methods, chemical structures, properties, advantages, and limitations of some of the widely used materials in three-dimensional (3D) printing of polymers are reviewed. Third, the applications of these methods and materials for fabrics, and electronics are covered. Finally, the associated opportunities and challenges in 3D printing process of flexible structures are described. The future research should be related to the exploration of combinations and development of innovative materials, printing process parameters, detail study on improving the properties, and hybrid 3D printing process.

Influence of additive manufacturing method and build angle on the accuracy of 3D-printed palatal plates

This article presents the results of exploratory research on novel methods for the fabrication of functional, metallic, gas flow, bi polar plates (BPP) for use in proton exchange membrane fuel cells (PEMFC). Low cost, high speed, additive manufacturing methods that combine 3D printing (3DP) and thermal spray (TS) technologies are described. Functional flow plates were manufactured by creating 3DP patterns and then depositing, and releasing, dense metals with TS methods. The new method yields dense metal plates, with interesting options for material choices and complex designs. 1.0 Introduction and Prior Art The development of hydrogen fuel cell technology is highly relevant to current U.S. industry, global politics and environmental preservation. Gas flow plates are at the core of proton exchange membrane fuel cell (PEMFC) operation, and they present significant manufacturing and design challenges. The gas flow plate is tasked with delivering reaction gasses to adjacent membrane assemblies of a fuel cell, conducting the generated electricity, removing the H2O byproduct, and influencing stack temperature. There are three main established methods for manufacturing flow plates: (1) subtractive machining of graphite plates, (2) molding graphite or carbon materials, and (3) stamping metals. These three current industrial methods are limited by slow, expensive subtractive manufacturing methods, either directly at the part level or indirectly at the tool creation stage. Investigating high-speed, low-cost, additive PEMFC manufacturing methods may provide a superior path to the deployment of renewable, zero noxious emission energy sources. 1.1 Machined Graphite Plates The first widely used method for creating research-grade gas flow plates, machining them from graphite plates, is only suited for low-volume production. All of the plate’s functional geometry is created via CNC machining. An example of a machined graphite plate can be seen in Figure 4. In order to avoid even higher machining costs, flow plate design has been limited to comparatively simple planar geometry, with uniform features typically on the order of 0.79mm in width and depth. These feature dimensions appear to be dictated by existing machine tool design and are not inherently optimal for PEMFC performance. This perpart machining is very expensive and does not scale well with the eventual, requisite high-production volumes associated with the transportation industry. 1.2 Molded Graphite and Carbon Plates Less expensive techniques for the manufacturing of graphite plates were researched by numerous investigators [10]. Thick graphite mats and chopped carbon

A comparative study of additive and subtractive manufacturing for dental restorations

The low-volume spare parts business is often identified as a potential beneficiary of additive manufacturing (AM) technologies. Currently, high AM unit costs or low AM part reliabilities deem the application of AM economical inferior to conventional manufacturing (CM) methods in most cases. In this paper, we investigate the potential to overcome these deficiencies by combining AM and CM methods. For that purpose, we develop an approach that is tailored toward the unique characteristics of dual sourcing with two production methods. Opposed to the traditional dual sourcing literature, we consider the different failure behavior of parts produced by AM and CM methods. Using numerical experiments and a case study in the aviation industry, we explore under which conditions dual sourcing with AM performs best. Single sourcing with AM methods typically leads to higher purchasing and maintenance costs while single sourcing with CM methods increases backorder and holding costs. Savings of more than 30% compared to the best single sourcing option are possible even if the reliability or unit costs of a part sourced with AM are three times worse than for a CM part. In conclusion, dual sourcing methods may play an important role to exploit the benefits of AM methods while avoiding its drawbacks in the low-volume spare parts business.

The first part of this paper shows that the implementation of twin-web (hollow) discs can lead to an 8–30% decrease in mass or to a cyclic life increase of up to 300%, depending on the size of the disc and the operating conditions. The second part of this paper describes the results of the development of approaches for the manufacturing and processing of twin-web discs, both with the help of additive and traditional manufacturing methods. Several hollow discs with a closed cavity and a slot in the hub are made from the heat-resistant nickel alloy EI698P with the help of additive manufacturing (AM) and hot isostatic pressing (HIP), respectively. Various welding methods are considered for the production of the twin-web discs. The effect of post-processing on the characteristics of the materials is investigated in specimens that were produced with AM methods. Special attention is paid to the surface treatment methods that should be used for discs manufactured by AM methods. The “printed” discs were controlled using radiographic, ultrasonic, fluorescent penetrant, and eddy current methods, and they were examined using computed tomography. As a result, this paper shows that different approaches can be used for the manufacturing and processing of twin-web discs.

Performance enhancements in heat exchanger design and manufacturing have been achieved over the past several decades through a combination of improved thermal-hydraulic modeling and experimentation tools, enhancements in material formulations and associated property characterizations, and new manufacturing methods. Most recently, Additive Manufacturing (AM) methods have matured sufficiently that they are now being considered as realizable heat exchanger fabrication methods. More complex, compact, and efficient designs can be achieved with AM methods that could not be easily obtained through more traditional manufacturing techniques. This study expands upon a previous work [1] in which an optimized twisted tube shell and tube stainless steel heat exchanger was designed, analyzed, and fabricated with a Direct Metal Laser Sintering (DLMS) AM method. In that study, the twisted tube heat exchanger performance was a considerable improvement over that of a traditional straight tube shell and tube heat exchanger. In the present study, the AM twisted tube heat exchanger was subjected to thermal-hydraulic tests to measure its performance and to identify any necessary refinements to the previous CFD model. For the conditions used in this study, the experimental data will show how the previous CFD model over-predicted the twisted tube heat exchanger’s heat transfer rate of 2,297 W and under predicted its overall heat transfer coefficient of 1,008 W/m2/K. Interrogation of the CFD model found that this discrepancy was due to the utilization of a k-ε turbulence model. Once this turbulence characterization was replaced with a more suitable shear transport model, the numerical predictions and experimental measurements of total heat transfer rate and overall heat transfer coefficient were in very close (∼10%) agreement. When combined with the previous study, this current work reveals how a complex, twisted tube shell and tube heat exchanger can be designed with existing CFD modeling tools and efficiently manufactured with current AM technologies to significantly improve its performance over a more traditionally manufactured straight tube version of the heat exchanger.

Evaluation of environmental impact of additive and subtractive manufacturing processes for sustainable manufacturing

This article presents economic models for a new hybrid method where additive manufacturing (AM) and subtractive methods (SMs) are integrated through composite process planning. Although AM and SM offer several unique advantages, there are technological limitations such as tolerance and surface finish requirements; tooling and fixturing, etc. that cannot be met by a single type of manufacturing. The intent of this article is not to show a new manufacturing method, but rather to provide economic context to additive and subtractive methods as the best practice provides, and look at the corresponding economics of each of those methods as a function of production batch size, machinability, cost of the material, part geometry and tolerance requirements. Basic models of fixed and variable costs associated with additive, subtractive and hybrid methods to produce parts are also presented. An experimental design is used to study the influence of production volume, material and operating cost, batch size, machinability of the material and impact of reducing AM processing time. A composite response model for the unit cost is computed for the various levels associated with such engineering requirements. The developed models provide insight into how these variables affect the costs associated with engineering a mechanical product that will be produced using AM and SM methods. From the results, it appears that batch size, AM processing time and AM processing cost were the major cost factors. It was shown that the cost of producing ‘near-net’ shape through SM and AM was the decision criteria; which will be critical for tough-to-machine alloys and at multi-batch size.

The Electrochemical Society Interface • Spring 2016 • www.electrochem.org 61 A lthough there has been tremendous growth in the capabilities of additive manufacturing in recent years, its roots go back hundreds of years. In many ways, some of the first electrochemists were also the first practitioners of additive manufacturing when they demonstrated that a low cost base metal could be coated with a premium finish in a conformal manner at room temperature in minutes. The first electrodeposition experiments date back over 200 years when Luigi Valentino Brugnatelli first electrodeposited gold upon silver, at first for academic experiments, and then for commercial application. Since that time, scaled commercial applications of electrodeposition have been critical to many aspects of science and engineering. More recently, the emergence of affordable, commercially-available 3D printers capable of depositing electrically insulating media via extrusion printing and additive photocuring methods have offered a wonderful complement to traditional electrodeposition, enabling both rapid prototyping and precise, high-throughput freeform manufacturing. In this issue of Interface we explore some of the benefits and opportunities that modern additive manufacturing methods offer for the practice of electrochemical analysis, engineering, and energy storage. In the first paper of this issue, Robert B. Channon, Maxim B. Joseph and Julie V. Macpherson, demonstrate the use of low cost additive manufacturing based on stereolithography, to create (micro) fluidic flow cells at scales that are either difficult or impossible to achieve with traditional methods. The ability to create high resolution, customized flow cells allows researchers to study fluid transport and electrochemical phenomena, as well as enabling highly accurate electroanalytical sensing with small analyte volumes and high throughput for a wide range of applications. With the methods described in this section, (micro)fluidic analysis systems can go from a sketch to a practical system within an afternoon, and that same device can be effortlessly replicated with slight variations in device geometry to create an array of parallel experiments. Trevor Braun and Dan Schwartz provide an article exploring the intersection of freeform patterning and electrodeposition with the use of software reconfigurable scanning electrodeposition cells. In traditional electrodeposition, the volume of the electrolyte is far larger than that of the deposited materials. This article shows that when the ratio is inverted, the small electrolyte volume can be used to direct growth and structure in exceptional ways without the limitations of traditional maskor stamp-based patterning techniques. Another exciting development that is discussed in this article is the use of bipolar electrochemistry to perform localized freeform electrodeposition without an electrical contact to the substrate, a development that greatly expands the utility and throughput of electrodeposition-based additive manufacturing. The final paper by Corrie Cobb and Christine Ho demonstrates how additive manufacturing and rapid prototyping methods can improve the performance and the range of applications of electrochemical energy storage. Given the particle/composite structure of most secondary storage devices, the materials selection available is largely the same as those for traditional batteries. A device designer, using the methods described here, can embed a battery optimized not only between power and energy density, but also between conformable, flexible, and stretchable factors. Critical to this new paradigm in product design is a deep level of interaction between the design of the battery, powertrain, and the device itself. With modern rapid prototyping methods, all three components can be iteratively edited and optimized with unprecedented speed. Beyond device integration, these new manufacturing methods for batteries may improve batteries for traditional applications: Rational integration of separator and electrode can allow for thicker electrodes at a given power density, improving cost per unit energy and energy density at a system level. Taken together, these three pieces provide an excellent overview of how recent advances in electrochemical engineering and electroanalytical tools can be merged with modern prototyping tools to create new opportunities for sensing, device production, and electrochemical energy storage. However, we believe that these examples are only the tip of the iceberg, and that the integration of electrochemical engineering and additive manufacturing will only accelerate in the years to come. While these articles are not meant to be comprehensive reviews of additive manufacturing, we hope that they inspire Interface readers to learn more about these powerful new tools and invent novel ways that additive manufacturing can advance electrochemistry, and that electrochemistry can advance additive manufacturing. Electrochemical engineering, the first in additive manufacturing and rapid prototyping, still has much to contribute to this growing field. In the spirit of access knowledge sharing, DS has recently created a website (echem.io) where users can share (via GitHub) 3D cad design files and other open source hardware and software tools that were generated as a part of electrochemistry-focused research and development efforts. We hope you check it out!

Correlation between pore characteristics and tensile bond strength of additive manufactured mortar using X-ray computed tomography

Additive manufacturing has gained considerable attention for building biomedical scaffolds due to its presumed ability to provide porous structures adequate for inflow and ingrowth of blood and tissues that facilitate bone regeneration. Various paste designs, consisting of mixtures of polymers with various ceramic or glass particles were proposed as additive manufacturing inks. However, proper paste design is still an open research subject as the link between the paste performance and various properties such as solids loading ability, homogenization, jellification, or particle morphology needs further characterization. This chapter explores the possibilities of using starch gels in combination with various bioceramics for producing biomedical scaffolds for bone regeneration using either additive manufacturing methods or more cost-effective alternative methods. Next, an integrated technological solution for manufacturing biomimetic implants for filling large bone defects is presented in the chapter, as a practical alternative to the current additive manufacturing attempts. This solution aims to solve the challenges related to tissue vascularization and mechanical stability associated with bone scaffolds by creatively using low-cost, natural, and biocompatible sintering additives such as starch. Various three-dimensional test samples prepared with bioceramics and starch gels by applying this technology are evaluated, with good perspectives for clinical application.

The advantages of individuality and complexity for free are commonly known in the field of additive manufacturing, but, nevertheless, they compete with advantages of conventional manufacturing methods. On the one hand, a small size production can be economically viable through additive manufacturing. On the other hand, conventional manufacturing methods are well known and optimized, so that they have low cost per unit. Therefore, to evaluate the economic efficiency various criteria are needed to compare additive and conventional manufacturing methods. In the following part comparative criteria and influence factors for economic efficiency are identified and described. Besides general aspects personal reasons may influence a manufacturing decision. Therefore, the identified criteria are used to build a method which helps the user to decide on a manufacturing method depending on personal preferences. The structure and use of this method is described in the second part. After this, an outlook and conclusion is given.

PurposeIn industry applications, polymer hybrid bearings have become widespread in recent years owing to the lack of lubricant requirements, particularly in areas requiring hygiene. The additive manufacturing method gives significant advantages to have complex machinery parts, and it has become popular in the industry in recent years. However, it has some inherent disadvantages caused by layered deposition/addition of the materials, and the probability of the localized defect is much higher than in the conventional manufacturing methods. This study aims to investigate the effect of the outer race defect on the characteristics of vibration and service lifetime of hybrid polymer ball bearings produced with the stereolithography (SLA) additive manufacturing method.Design/methodology/approachIn this study, polymer bearings’ races were produced with the additive manufacturing SLA method, and the outer race defect was analyzed with measured vibrations.FindingsThe results show that the additive manufacturing method suggests a practical solution for producing a polymer hybrid ball bearing. On the other hand, the hybrid three-dimensional-printed bearing, which has an outer race defect, worked for approximately 8 h without any problems under a 1 kg load and a shaft speed of around 1,000 rpm. In addition, when there is a defect in the outer and/or inner race of the ball bearing, the crest factor and kurtosis of the vibration are higher than faultless ball bearing, as expected.Originality/valueThis paper provides valuable information on the lifetime and vibration characteristics of polymer hybrid ball bearing produced by means of additive manufacturing.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2023-0183/

Additive manufacturing method and different welding applications