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This research program investigated the effects of layer thickness (50 and 100 microns) on the microstructure and mechanical properties of electron beam powder bed fusion (EBPBF) additive manufacturing of Inconel 625 alloy. The as-built 50 and 100 micron layer thickness components were also heat treated at temperatures above 1100 oC, which produced a recrystallized grain structure containing annealing twins in the 50 micron layer thickness components, and a duplex grain structure consisting of islands of very small equiaxed grains dispersed in a recrystallized, large-grain structure containing annealing twins. The heat treated component microstructures and mechanical properties were compared with the as-built components in both the build direction (vertical) and perpendicular (horizontal) to the build direction. Vickers microindentation hardness (HV) values for the vertical and horizontal geometries averaged 227 and 220 for the as-built 50 and 100 micron layer components, and 185 and 282 for the corresponding heat treated components. The yield stress values were 387 MPa and 365 MPa for the as-built layer horizontal and vertical 50 micron layer geometries, and 330 MPa and 340 MPa for the as-built 100 micron layer components. For the heat treated 50 micron components, the yield stress values were 340 and 321 MPa for the horizontal and vertical geometries, and 581 and 489 MPa for the 100 micron layer components, respectively. The elongation for the 100 micron layer as-built horizontal components was 28% in contrast to 65% for the corresponding 100 micron heat treated layer components, an increase of 132% for the duplex grain structure. However, the coarse grains containing annealing twins and the equiaxed small grain islands in the duplex structure for the heat treated components contained continuous carbides in the grain boundaries, and this may indicate sensitization and a reduction in corrosion resistance. These findings point to the potential mechanical property advantage for heat treatment of Inconel 625 alloy 100 micron layer thickness components fabricated by EBPBF.

This research program investigated the effects of layer thickness (50 µm and 100 µm) on the microstructure and mechanical properties of electron beam powder bed fusion (EBPBF) additive manufacturing of Inconel 625 alloy. The as-built 50 µm and 100 µm layer thickness components were also heat treated at temperatures above 1100 °C which produced a recrystallized grain structure containing annealing twins in the 50 µm layer thickness components, and a duplex grain structure consisting of islands of very small equiaxed grains dispersed in a recrystallized, large-grain structure containing annealing twins. The heat-treated components of the microstructures and mechanical properties were compared with the as-built components in both the build direction (vertical) and perpendicular (horizontal) to the build direction. Vickers microindentation hardness (HV) values for the vertical and horizontal geometries averaged 227 and 220 for the as-built 50 µm and 100 µm layer components, respectively, and 185 and 282 for the corresponding heat-treated components. The yield stress values were 387 MPa and 365 MPa for the as-built horizontal and vertical 50 µm layer geometries, and 330 MPa and 340 MPa for the as-built 100 µm layer components. For the heat-treated 50 µm components, the yield stress values were 340 and 321 MPa for the horizontal and vertical geometries, and 581 and 489 MPa for the 100 µm layer components, respectively. The elongation for the 100 µm layer as-built horizontal components was 28% in contrast with 65% for the corresponding 100 µm heat-treated layer components, an increase of 132% for the duplex grain structure.

The additive manufacturing of piezoelectric ceramic Lead Zirconate Titanate (PZT) through paste extrusion 3D printing was demonstrated. Different paste compositions with varied water weight content were studied to find a composition suitable for printing. The pastes were evaluated in terms of their viscosities, yield stresses, and stability when aged. Furthermore, the material properties of the ceramics produced through paste extrusion were characterized and compared with those of ceramics fabricated through a conventional die pressing method. Paste extruded PZT with achieved densities as high as 94.9% of the theoretical density after sintering, which nearly matched the 95% density attained by the pressed samples. Upon poling, the paste extruded PZT piezoelectric ceramics attained piezoelectric coefficients and dielectric constants that were close to the values of die pressed samples. As near full density PZT ceramics were successfully fabricated through paste extrusion, this work paves the way for piezoelectric ceramics with application-driven geometry designs for sensors, actuators, and energy harvesters.

In this investigation, the optimization of mechanical properties with thermal post-processing treatments was analyzed across a wide range of variants. A major aspect of additive manufacturing is the correlation between heat treatments and the effects on the mechanical properties and microstructure of the printed materials. Therefore, the present paper describes a comprehensive overview of post-process heat treatments for Laser Powder Bed Fusion fabricated AlSi10Mg alloy consisting of stress relief anneals at 190 C and 285 C for 2 h, hot isostatic pressing at 515 C for 3 h, hot isostatic pressing + T6 treatment for 6 h, and final aging of each of these conditions at 177 C for up to 1000 h. This has resulted in 40 experimental variants: 20 in the vertical and 20 in the horizontal tensile direction. After tensile testing, the resulting mechanical properties (ultimate tensile strength, yield strength, and elongation) and stress–strain curves are analyzed for comparison between all variants. Ultra-fine cellular, micro dendritic structures (0.6–1.2 μm) along with melt-band structures dominated the asbuilt and stress relief anneal conditions. In contrast, hot isostatic pressing and hot isostatic pressing + T6 conditions were dominated by ~10 μm, equiaxed, recrystallized grain structures and pseudo-eutectic silicon particles with varying sizes and size distributions. Microhardness and fractography results also corresponded to their specific heat treatment and microstructure. The comparison and correlation of the heat treatments are presented to help advance the selection of design strategies for high performance applications.

Many factors can influence the thermal history during laser powder bed fusion (L-PBF) that contribute to the microstructure and mechanical performance of produced components. These factors can include process parameters, geometry, feedstock characteristics, and more. In this work, we report on the effect that process interruptions have on the thermal history during L-PBF fabrication of simple geometries made out of three alloys of interest: AlSi10Mg, Inconel 718 and Inconel 625. Systematic experiments were carried out with programmed process interruptions lasting one hour and simulating a stop to refill the system with powder, or an unexpected power outage. Specimens produced through these experiments enabled studying microstructural differences using microscopy techniques, and the evaluation of tensile and hardness properties when compared to uninterrupted controls. The findings from this study indicate that there were no distinguishable microstructural differences from interrupted specimens and uninterrupted controls for all three materials. Also, although Inconel 718 interrupted specimens showed a slight reduction in ultimate tensile strength and elongation, these properties remained essentially unchanged for AlSi10Mg and Inconel 625. Although a more comprehensive study is still required that accounts for the effect of thermal post-processing and other factors, the results described here provide several observations of the potential effects of process interruptions, and the implications towards process validation and quality assurance of L-PBF.

Laser-assisted gas nitriding of selective Ti-6Al-4 V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen. Systematic variation of processing parameters allowed microdendritic TiN surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns, with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75; and corresponding Vickers microindentation hardness values ranging from ∼ 7.5 GPa–9.5 GPa. Embedded TiN hard layers ranging from 50 μm to 150 μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4 V alloy producing prototype, hybrid, planar composites having alternating, ductile Ti-6Al-4 V layers with a hardness of ∼ 4.5 GPa and a stiff, TiN layer with a hardness of ∼8.5 GPa. The results demonstrate prospects for fabricating novel, additively manufactured components having selective, hard, wear and corrosion resistant coatings along with periodic, planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.

Aluminum nitride (AlN) ceramics have attracted broad interest due to their potential applications in electronics. Additive manufacturing of ceramic components are rapidly advancing, could provide a new way of manufacturing over conventional methods. Non-destructive testing of 3D printed ceramic samples is an important step for quality control in manufacturing. Here we show that AlN ceramics show strong optical second harmonic generation (SHG) signals due to its wurtzite crystal structure. Microscopic SHG imaging can also examine the microscopy domains in AlN ceramics with submicron spatial resolution. This technique has the potential to be applied as a non-destructive testing method for examining 3D printed AlN ceramic components.

In this work, we report on the novel fabrication of aluminum nitride (AlN) components using Binder Jetting (BJT) additive manufacturing (AM). The AlN constructs were subjected to post-fabrication thermal treatment by hot isostatic pressing (HIPing) for 8 hours at a pressure of 206 MPa and temperature of 1900 °C. This treatment resulted in a 60.1% relative density maximum densification for AlN. The BJT printed AlN specimens were analyzed using various characterization techniques. The purity, microstructure, and polycrystallinity of the AlN phase formed were confirmed by techniques that included x-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). Second harmonic generation (SHG) microscopy showed polarization dependence and second harmonic signal at 470 nm, indicating the potential to produce thermal and optical-mechanical devices. Mechanical properties obtained by nanoindentation resulted in an elastic modulus of ~251 GPa when measured in fully dense, contiguous crystalline regions, corresponding to an apparent, porous bulk stiffness of ~90 GPa for the final, 60.1 % dense products. Finally, the laser flash method (LFM) was used to measure the thermal conductivity of the material as a function of temperature resulting in values from 4.82 W/mK to 3.17 W/mK for the temperature range from 23 °C to 500 °C, respectively.

Additive manufacturing (AM) technologies are capable of fabricating custom parts with complex geometrical shapes in a short period of time relative to traditional fabrication processes that require expensive tooling and several post processing steps. Material extrusion AM, known commercially as Fused Filament Fabrication (FFF) technology, is a widely used polymer AM process, however, the effects of inherent porosity on mechanical strength continues to be researched to identify strength improvement solutions. To address the effect of porosity and layer adhesion on mechanical properties (which can sometimes result in 27–35% lower ultimate tensile strength when compared to plastic injection molding), an approach was employed to reinforce 3D printed polycarbonate (PC) parts with continuous carbon fiber (CF) bundles. ASTM D638 Type I specimens were fabricated with printing interruptions to manually place and embed CF bundles. Specimens contained either one, two, or three layers of embedded CF bundles. Results demonstrated a maximum of 77% increase in tensile yield strength when PC was reinforced with three CF bundles and micrographs showed multiple regions with zero porosity due to the CF inclusion. PC with three bundles of CF (modulus of 3.36 GPa) showed 85% higher modulus of elasticity than the neat PC specimens (modulus of 1.82 GPa). The manual placement of CF and its impact on mechanical properties motivated the development of an automated selective deposition method using an ultrasonic embedding apparatus. Substantial technology development towards the embedding process of continuous carbon fiber bundles using ultrasonic energy was achieved in an automated fashion which is complementary of digital manufacturing and novel when compared to other existing processes.

To enable the advancement of large-scale additive manufacturing processes, it is necessary to establish and standardize methodologies to characterize the mechanical properties of printed test coupons. Due to the large size of the print beads, conventional test standards are inadequate. The focus of this study was to determine the feasibility of using Digital image correlation (DIC) technology as a key enabler for robust data collection of strain measurements of large 3D printed parts. To incorporate the DIC measurements, a novel method was developed to prepare large 20% (by wt.) glass filled ABS test coupons for adequate contrast. Through this technique, Poisson's ratio and elastic modulus were measured and stress strain curves were generated. The data produced by DIC correlated well with failure analysis performed on spent test coupons. Additionally, fracture surface analysis of the specimens revealed poor adhesion among the ABS matrix and glass fibers. This matrix/fiber debonding demonstrated the need for improved printing parameters to maximize tensile strength. Finally, critical length analysis of the fibers revealed them to be dimensionally inadequate.

This study examines and compares the microstructures, Vickers microindentation hardness, and mechanical properties for additively manufactured (AM) samples built by a variety of AM processes: wire arc AM (WAAM), electron beam powder bed fusion (EB-PBF), laser wire direct energy deposition (LW-DED), electron beam direct energy deposition (EB-DED), laser-powered direct energy deposition (LP-DED), and laser powder bed fusion (L-PBF). These AM process samples were post-processed and heat-treated by stress relief annealing at 1066 °C, HIP at 1163 °C, and solution annealing treatment at 1177 °C. The resulting microstructures and corresponding microindentation hardnesses were examined and compared with the as-built AM process microstructures and hardnesses. Fully heat-treated AM process samples were mechanically tested to obtain tensile properties and were also evaluated and compared. Principal findings in this study were that high-temperature heat treatment >1100 °C of AM process-built samples was dominant and exhibited recrystallized, equiaxed grains containing fcc {111} annealing twins and second phase particles independent of the AM process, in contrast to as-built columnar/dendritic structures. The corresponding yield stress values ranged from 285 MPa to 371 MPa, and elongations ranged from 52% to 70%, respectively. Vickers microindentation hardnesses (HV) over this range of heat-treated samples varied from HV 190 to HV 220, in contrast to the as-built samples, which varied from HV 191 to HV 304.

Mass casualty incidents such as those that are being experienced during the novel coronavirus disease (COVID-19) pandemic can overwhelm local healthcare systems, where the number of casualties exceeds local resources and capabilities in a short period of time. The influx of patients with lung function deterioration as a result of COVID-19 has strained traditional ventilator supplies. To bridge the gap during ventilator shortages and to help clinicians triage patients, manual resuscitator devices can be used to deliver respirations to a patient requiring breathing support. Bag-valve mask (BVM) devices are ubiquitous in ambulances and healthcare environments, however require a medical professional to be present and constantly applying compression to provide the patient with respirations. We developed an automated manual resuscitator-based emergency ventilator-alternative (AMREV) that provides automated compressions of a BVM in a repetitive manner and is broadly compatible with commercially-available BVM devices approximately 5 inches (128 mm) in diameter. The AMREV device relieves the medical professional from providing manual breathing support and allows for hands-free operation of the BVM. The AMREV supports the following treatment parameters: 1) adjustable tidal volume (V T ), 2) positive end-expiratory pressure (PEEP) (intrinsic and/or external), 3) 1:1 inspiratory: expiratory ratio, and 4) a controllable respiratory rate between 10-30 breaths per minute. The relationship between the inherent resistance and compliance of the lung and the delivered breaths was assessed for the AMREV device. Adjustable V T of 110-700 ml was achieved within the range of simulated lung states. A linear increase in mean airway pressure (P aw ), from 10-40 cmH2O was observed, as the resistance and compliance on the lung model moved from normal to severe simulated disease states. The AMREV functioned continuously for seven days with less than 3.2% variation in delivered V T and P aw . Additionally, the AMREV device was compatible with seven commercially-available BVM setups and delivered consistent V T and P aw within 10% between models. This automated BVM-based emergency-use resuscitator can provide consistent positive pressure, volume-controlled ventilation over an extended duration when a traditional ventilator is not available. True ventilator shortages may lead to manual resuscitators devices such as the AMREV being the only option for some healthcare systems during the COVID-19 pandemic.

This article provides an overview of the implementation of wire embedding with ultrasonic energy and thermal embedding for polymer additive manufacturing, discussing the applications and advantages of the technique. The mechanical and electrical performance of the embedded wires is compared with that of other conductive ink processes in terms of electrical conductivity and mechanical strength.

The purpose of this study was to perform a comparative analysis of powder-bed-based additive manufacturing (AM) technologies during the production of metallic components using Inconel 625 powder material. The AM technologies explored in this study include electron beam powder bed fusion (EPBF), laser powder bed fusion (LPBF), and binder jetting technology. Samples were fabricated in two build directions (X and Z build orientations) for this evaluation process, where all specimens underwent a hot isostatic pressing (HIP) post-process. The comparison was made in terms of microstructure and mechanical properties including ultimate tensile strength (UTS), yield strength (YS), percent elongation, and modulus of elasticity (E). Microstructural characterization showed evidence of equiaxed grain formation for binder jetting and LPBF parts, whereas EPBF parts displayed a more columnar grain formation parallel to the build direction. Six specimens were tested per technology, three built in the X orientation and three built in the Z orientation. All six specimens were built in a single run of each AM machine. Results indicated that all three technologies are capable of meeting the minimum requirements of the ASTM F3056-14 standard for parts produced in the X orientation, with properties that are similar to wrought Inconel 625. In the Z orientation, however, only LPBF was able to meet the minimum standard requirements. Through the comparative analysis of the mechanical properties, this work showed that LPBF outperformed the other technologies in a majority of the evaluated properties, followed by EPBF and binder jetting. An analysis of the fracture surfaces of tensile specimens was also performed, and it indicated ductile fracture (dimple rupture) for the specimens produced with all three of the AM technologies studied. Nevertheless, the characterization also showed certain differences in the fractured surfaces, such as the presence of un-sintered powder particles for the binder jetting processed Inconel 625, or the development of the so called woody structure for the EPBF processed material. This study can be used to determine distinct characteristics between the three powder-bed-based technologies for the fabrication of Inconel 625 that can further include other technologies and materials using similar approaches.

A novel, Ti-6Al-4V (Ti64)/Hydroxyapatite (HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion (EPBF) additive manufacturing (AM): specifically, the commercial electron beam melting (EBM®) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell (model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm3, and corresponding Young’s moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ∼3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography (OM) and scanning electron microscopy (SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha (hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ∼5 μm in the EPBF-fabricated Ti64 to ∼1.1 μm for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 μm. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors’ knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.

This research explores the prospect of fabricating a face-centered cubic (fcc) Ni-base alloy cladding (Inconel 690) on an fcc Fe-base alloy (316 L stainless-steel) having improved mechanical properties and reduced sensitivity to corrosion through grain boundary and microstructure engineering concepts enabled by additive manufacturing (AM) utilizing electron-beam powder bed fusion (EPBF). The unique solidification and associated constitutional supercooling phenomena characteristic of EPBF promotes [100] textured and extended columnar grains having lower energy grain boundaries as opposed to random, high-angle grain boundaries, but no coherent {111} twin boundaries characteristic of conventional thermo-mechanically processed fcc metals and alloys, including Inconel 690 and 316 L stainless-steel. In addition to [100] textured grains, columnar grains were produced by EPBF fabrication of Inconel 690 claddings on 316 L stainless-steel substrates. Also, irregular 2–3 μm diameter, low energy subgrains were formed along with dislocation densities varying from 108 to 109 cm−2, and a homogeneous distribution of Cr23C6 precipitates. Precipitates were formed within the grains (with ∼3 μm interparticle spacing), but not in the subgrain or columnar grain boundaries. These inclusive, hierarchical microstructures produced a tensile yield strength of 0.527 GPa, elongation of 21%, and Vickers microindentation hardness of 2.33 GPa for the Inconel 690 cladding in contrast to a tensile yield strength of 0.327 GPa, elongation of 53%, and Vickers microindentation hardness of 1.78 GPa, respectively for the wrought 316 L stainless-steel substrate. Aging of both the Inconel 690 cladding and the 316 L stainless-steel substrate at 685 °C for 50 h precipitated Cr23C6 carbides in the Inconel 690 columnar grain boundaries, but not in the low-angle (and low energy) subgrain boundaries. In contrast, Cr23C6 carbides precipitated in the 316 L stainless-steel grain boundaries, but not in the low energy coherent {111} twin boundaries. Consequently, the Inconel 690 subgrain boundaries essentially serve as surrogates for coherent twin boundaries with regard to avoiding carbide precipitation and corrosion sensitization.

Fabrication of parts exhibiting multi-functionality has recently been complemented by hybrid polymer extrusion additive manufacturing in combination with wire embedding technology. While much mechanical characterization has been performed on parts produced with fused deposition modeling, limited characterization has been performed when combined electrical and thermal loads are applied to 3D printed multi-material parts. As such, this work describes the design, fabrication, and testing of 3D printed thermoplastic coupons containing embedded copper wires that carried current. An automated fabrication process was used employing a hybrid additive manufacturing machine that dispensed polycarbonate thermoplastic and embedded bare copper wires. Testing included AC and DC hipot testing as well as thermal testing on as-fabricated and heat treated coupons to determine the effect of porosity in the substrate. The heat-treated parts contained reduced amounts of porosity, as corroborated through scanning electron microscopy, which led to 50 % increased breakdown strength and 30 to 40 % increased heat dissipation capabilities. The results of this research are describing a set of design protocol that can be used as a guideline for 3D printed embedded electronics to predict the electrical and thermal behavior.

In this work, a three-dimensional printable multilayer phased array system was designed to demonstrate the applicability of additive manufacturing for radio frequency (RF) systems. A hybrid process incorporating a thermal wire-mesh embedding method for conductors and thermoplastic material extrusion for dielectrics is employed. The designed phased array, operating at 3.5 GHz, consists of three functional layers: a 1-to-4 Wilkinson divider at the bottom, embedded voltage-controlled phase shifters at the center, and patch antennas on the top. Standalone parts of the proposed multilayer phased array were printed to verify the integrated dielectric-conductor printing process as well as the incorporation of active semiconductor devices at room temperature.

The chemistry and physics of surfaces is an increasingly important subject. The study of surfaces is the key of many important nanotechnological applications due to the understanding of phase transitions, electronic structure, and chemical bonding. In later years, exotic phenomena that jointly involve the magnetic and electrical conductivity properties have been discovered in oxides that contain magnetic ions. Moreover, the uses of magnetic oxides in electronic technology have become so important due to the miniaturization of devices and magnetic materials with dielectric properties or vice versa being required for inductors, information storage, thin films for high-density computer memories, microwave antireflection coatings, and permanent magnets for automobile ignitions among others. On the contrary, nanotechnology developments over 10 years or so have provided intensive studies in trying to combine properties such as ferroelectric, ferromagnetic, and optics in one single-phase nanoparticles or in composite thin films; this last effort has been recently known as multiferroic. Because of this, the resurgence of nanomaterials with multiferroic and optical properties is presented in this work of one single phase in lanthanum lithium niobate (La0.05Li0.85NbO3) and lithium niobate (LiNbO3) with ferromagnetic, ferroelectric, relaxor ferroelectricity, second harmonic generation, high-temperature ferromagnetic, and magnetoelectric properties.

During solidification of many so-called high-performance engineering alloys, such as 6000 and 7000 series aluminum alloys, which are also unweldable autogenously, volumetric solidification shrinkage and thermal contraction produces voids and cracks. During additive manufacturing processing, these defects can span the length of columnar grains, as well as intergranular regions. In this research, laser powder bed fusion (LPBF) of aluminum alloy (AA) 6061 used powder bed heating at 500 °C in combination with other experimentally determined processing parameters to produce crack-free components. In addition, melt-pool banding, which is a normal solidification feature in LPBF, was eliminated, illustrating solidification process modification as a consequence of powder bed heating. Corresponding microindentation hardness and tensile testing of the as-fabricated AA6061 components indicated an average Vickers hardness of HV 54, and tensile yield, ultimate strength, and elongation values of 60 MPa, 130 MPa, and 15%, respectively. These mechanical properties and those of heat treated parts showed values comparable to annealed and T6 heat treated wrought products, respectively. X-ray diffraction and optical microscopy revealed columnar grain growth in the build direction with the as-fabricated, powder-bed heated product microstructure characterized by [100] textured, elongated grains (∼ 25 μm wide by 400 μm in length), and both intragranular and intergranular, noncoherent Al-Si-O precipitates which did not contribute significantly to the mechanical properties. The results of this study are indicative that powder bed heating may be used to assist with successful fabrication of AA6061 and other alloy systems susceptible to additive manufacturing solidification cracking.

In this work, a 3D printed patch antenna is fabricated within a complex dielectric structure relevant to the construction of satellites – an isogrid panel. The antenna was fabricated via a multi-process, hybrid, additive manufacturing system that included polymer material extrusion enhanced with complementary manufacturing capabilities of foil placement and patterning, wire integration and component placement. The antenna design targeted the commercial frequency of Bluetooth communication at 2.4 GHz by introducing a rectangular conductor of precise width, height and thickness from ground plane for the specific resonance. The measured reflection and gain coefficients were reasonable, however, two challenges were identified with the fabrication related to (1) imperfections typical of material extrusion additive manufacturing processes including unintentional porosity and (2) the insecure mechanical bonding between the output connector and substrate. Porosity impacted the dielectric features (permittivity) of the substrate and consequently introduced error in final antenna resonance (2.13 GHz versus the target of 2.4 GHz). The bonding affected mechanical reliability and caused changes in input impedance which affected signal quality for some orientations depending on cable flexing. Several remediations were identified, all of which included reinforcing the connector during embedding with a bonding agent. In the end, the antenna was compared to a commercial dipole antenna and the signal-to-noise ratios were within 6%.

Build defects, such as nozzle clogging and thermal substrate deformation, are common in material extrusion additive manufacturing technologies, and are difficult to detect because of the high-temperature environment of fused deposition modeling (FDM) machines that do not accommodate internal sensors. To overcome this difficulty, this paper integrated an external sensor to monitor the supply current of the motor that fed filament into an extrusion head. This paper describes the investigation of the relationship between the deposition status and the reaction torque on the filament-feed motor. A dynamic model of the internal operation of the FDM extrusion head was developed and used to infer printing defects. The change in reaction force opposing extrusion was indirectly measured by monitoring the current delivered to the filament-feed motor, and consequently, the use of other sensors in the high-temperature chamber was avoided. An analysis of the supply current, in both time and frequency domains, enabled the detection of defects during material deposition.

The ability to fabricate or join components of 316 L austenitic stainless steel using additive manufacturing (AM) processes such as laser and electron beam melting (EBM®) offers several advantages including enhanced part complexity, narrow or absent heat affected zones, increased part precision, avoidance of filler materials (such as traditional welds), and the ability to create metallurgically sound bonds. These attributes can contribute to improved mechanical properties of the fabricated components and component repair in nuclear, aerospace, and chemical industries. In the present work, we report that austenitic 316 L stainless steel additively manufactured by EBM exhibits a 76% increase in the yield strength and a corresponding increase of 29% in the ultimate tensile strength in contrast to the wrought substrate and commercial forged 316 L stainless steel. The EBM clad 316 L stainless steel elongation was 36%. The wrought substrate equiaxed grain size was ∼30 μm in contrast to elongated, columnar grains ∼0.1 mm wide and >1 mm in length for the EBM cladding. Transmission Electron Microscopy (TEM) analysis revealed that these columnar grains, which exhibited very straight, and presumably special grain boundaries having a very high (100) texture, contained a variety of sub-grain microstructures consisting of low-angle sub-grain boundaries containing dislocation tangles and stacking-fault arrays, and homogeneously distributed Cr23C6 carbide precipitates, with no preferential carbide precipitation on either the straight, special columnar grain boundaries, or the very low-angle sub-grain boundaries. This observation and the formation of hierarchical microstructures which produce high strength and possibly corrosion resistance as a consequence of the absence of grain boundary carbide precipitation, illustrate the prospects for AM as a novel concept for achieving grain boundary engineering to promote high-strength and corrosion resistant alloys for high-temperature, corrosive environments, including elevated temperature nuclear reactor applications.

Fine structures (ferroelectric domains), ferroelectricity and Second Harmonic Generation results were found and studied as a function of laser linearly and circularly polarization dependent polarized excitations in ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material. Scanning Electron Microscope images are taken as a comparison to Second Harmonic Generation intensity profiles revealed fine structures. By using laser polar measured response we are able to find the angle orientation from 0° to 90° angles of ferroelectric domains with highly good definition contrast obtained in blue/gray colors. It shows ferroelectric hysteresis loops at room temperature with a polarization saturation of (0.247 μC/cm 2 ), remnant polarization of (0.15 μC/cm 2 ) and coercitivity field of (1.31 kV/cm). X-ray Diffraction, Atomic Force Microscope, Raman spectroscopy and X-ray Photoelectron Spectroscopy, revealed well formed of ferroelectric ABO 3 perovskite crystal structure, piezoelectric image response indicate ferroelectric pattern domain structure, new vibrations modes on LaO 6 , LiO 6 and NbO 6 octahedral sites and binding energies of electronic structure of La 57 , Nb 41 , O 8 , Li 3 from the surface of the ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material, respectively.

Several reports have studied the mechanical properties of the material extrusion additive manufacturing process, specifically referred to as fusion deposition modeling (FDM) developed by Stratasys. As the applications for 3D printed parts continue to grow in diversity (e.g., gears, propellers, and bearings), the loading conditions applied to printed parts have become more complex, and the need for thorough characterization is now paramount for increased adoption of 3D printing. To broaden the understanding of torsional properties, this study focused on the shear strength of specimens to observe the impact from additive manufacturing. A full factorial (42) design of experiments was used, considering the orientation and the raster angle as factors. XYZ, YXZ, ZXY, and XZY levels were considered for the orientation parameter, as well as 0°, 45°, 90°, and 45°/45° for the raster angle parameter. Ultimate shear strength, 0.2% yield strength, shear modulus, and fracture strain were used as response variables to identify the most optimal build parameters. Additionally, stress-strain diagrams are presented to contrast elastic and plastic regions with traditional injection molding. Results demonstrated an interaction of factors in all mechanical measured variables whenever an orientation and a raster angle were applied. Compared to injection molding, FDM specimens were similar for all measured torsion variables except for the fracture strain; this led to the conclusion that the FDM process can fabricate components with similar elastic properties but with less ductility than injection molding. The orientation in YXZ with the raster angle at 00 resulted in the most suitable combination identified in the response optimization analysis.

The ability to access individual layers of a part as they are being printed has allowed additive manufacturing (AM) researchers to experiment with the in situ placement of components, thereby creating multi-process parts with additional functionality, such as customized printed electronics. As AM has evolved to become an established method for creating end-use parts, this interest in multi-process printing has increased. Although progress has been made in developing multi-process hardware, which can combine AM with other technologies, holistic design software, capable of readily integrating these processes, is developing at a slower rate. In this paper, an integrated software solution capable of supporting multi-process 3D printing from design through manufacture is described, featuring the integration of electronic components and circuits interconnected by copper wires. This solution features automated generation of the cavities that accommodate electronic components as well as toolpath generation for a multi-process 3D printer capable of automated wire embedding. As a case study of the developed technology, a hexagonal 3D printed body, which included a microcontroller, four LEDs, a USB connector, two resistors, and a Zener diode, all interconnected by embedded copper wires, was fabricated within a short cycle time: 5.75 h from design to fabricated part. Short cycle times allow multiple design iterations to be realized and printed within the same day.

Radiation thermometry methods used in powder bed fusion (PBF) additive manufacturing for in situ monitoring and control and quality assurance are increasing in importance. Arguably, the most significant challenge associated with radiation thermometry methods is the limited understanding of the emissivity, that is the emissive behavior of the entire region being measured. This work describes a new approach for measuring the emissive behaviors of PBF materials during processing using a multi-wavelength (MW) or Spectropyrometer operating in the spectral range from 1000 to 1650 nm. The approach was implemented in an electron beam (EB) PBF machine, using the electron beam as a heat source, allowing for (1) measuring spectral emissive behavior of the surface in a fixed small region (~2.65 mm) throughout a variety of dynamic processing conditions including heating, melting, and cooling; (2) controlling the scanning (heating) profile during processing while rejecting radiative interference in the measurements due to heating lasers (~1070 nm) commonly used in laser PBF; and (3) processing in an evacuated environment to assist with reduction of additional environmental effects that could impact the measurements. The experimental setup included a sight tube that prevented both metallization of the viewport and resultant signal decay, which enabled near-continuous measurements throughout processing. Measurements from the MW pyrometer were compared against those of a type K thermocouple that was placed in the vicinity of the measurement area. Prior to the powder bed preheating experiment, the MW pyrometer was calibrated against a NIST traceable blackbody source. The utility of the approach was demonstrated by acquiring measurements from the surface of a copper (d50~75 µm) powder bed that was progressively heated in a series of nine steps inside an Arcam A2 EB-PBF system through scanning with the electron beam. Following the preheat steps, seven consecutive melt steps were implemented enabling measurements of the emissive behavior for copper during its multiple solid-liquid-solid transitions. The unique capabilities of the MW pyrometer provided measured values of emissivity of copper that exhibited temporal, spectral (1080–1640 nm) and thermal dependence, verifying the non-graybody behavior for copper. Ongoing work will demonstrate the applicability of this technique across multiple powder metal alloy systems and PBF technologies.

Laser powder bed fusion (L-PBF) has emerged as one of the mainstream additive manufacturing approaches for fabricating metal parts with complex geometries and intricate internal structures. However, large deformation associated with rapid heating and cooling can lead to build failure and requires post-processing which may increase manufacturing cost and prolong the production period. In this work, an island scanning pattern design method is proposed to optimize the scanning direction of each island in order to reduce part deformation after cutting off the build platform. The objective of this optimization is to minimize the upward bending of the part after sectioning, which allows the part deformation to satisfy the tolerance requirement or reduce the post heat treatment time. Inherent strain method is employed in the sequential finite element analysis consisting of layer-by-layer activations and sectioning for fast residual distortion prediction. Full sequential sensitivity analysis for the formulated optimization is provided to update the island scanning directions. To show the feasibility and effectiveness of the proposed method, the scanning patterns of a block structure and a connecting rod were designed and parts were fabricated using an open architecture L-PBF machine. The fabrication experiments demonstrated that the residual deformation of both parts fabricated by optimized scanning pattern can be reduced by over 50% compared to the initial scanning patterns, which demonstrate the effectiveness of the proposed method.

The final functionality of parts produced by Additive Manufacturing (AM) can, in part, be improved by the inclusion of multi-material capabilities. The Multi3D Manufacturing System uses material extrusion printing (fused deposition modeling technology from Stratasys), solid conductor wire embedding, direct-write, component placement, and micromachining to enable the fabrication of multi-functional products. The material handling methodology, implemented by the Multi3D System, transports a workpiece between manufacturing stations via a six-axis robot, portable build platform, and a controlled temperature environment or chamber that travels to each manufacturing station. Also discussed in this work, is the investigation and improvement of registration parameters between the two material extrusion printers within this system. The registration was ultimately quantified to have minimal errors: 69 μm along the x-axis, 183 μm along the y-axis, and 215 μm along the z-axis. The fabrication of a multi-colored part demonstrated the automated transfer of the workpiece, which offers early promise for an automated solution for multi-material fabrication using commercially-available fused deposition modeling machines.

To facilitate adoption of Ti-6Al-4V (Ti64) parts produced via additive manufacturing (AM), the ability to ensure part quality is critical. Measuring temperatures is an important component of part quality monitoring in all direct metal AM processes. In this work, surface temperatures were monitored using a custom infrared camera system attached to an Arcam electron beam melting (EBM®) machine. These temperatures were analyzed to understand their possible effect on solidification microstructure based on solidification cooling rates extracted from finite element simulations. Complicated thermal histories were seen during part builds, and temperature changes occurring during typical Ti64 builds may be large enough to affect solidification microstructure. There is, however, enough time between fusion of individual layers for spatial temperature variations (i.e., hot spots) to dissipate. This means that an effective thermal control strategy for EBM® can be based on average measured surface temperatures, ignoring temperature variability.

Polymer extrusion three dimensional (3D) printing, such as fused deposition modeling (FDM), has recently garnered attention due to its inherent process flexibility and rapid prototyping capability. Specifically, the addition of electrical components and interconnects into a 3D printing build sequence has received heavy interest for space applications. However, the addition of these components, along with the thermal load associated with space-based applications, may prove problematic for typical thermally insulating 3D printed polymer structures. The work presented here addresses thermally conductive polymer matrix composites (specifically, graphite, carbon fiber, and silver in an acrylonitrile butadiene styrene polymer matrix) to identify the effect of composite geometry and print direction on thermal anisotropic properties. The work also examines the effect of these composites on print quality, mechanical tensile properties, fracture plane analysis, micrograph imaging, and cube satellite thermal analysis. The thermal conductivity of 3D printed material systems in this work may enable the production of thermally stable 3D printed structures, supports, and devices. Key results of this work include anisotropic thermal conductivity for 3D printed structures related to print direction and filler morphology meaning that thermal conductivity can be controlled through a combination of print raster direction and material design. When the materials analyzed in this work are incorporated with other active cooling systems, space-based 3D printed applications can then be designed to incorporate increasing thermal loads, opening a new door to producing space-ready 3D printed structures.

The article presents an exploration of design and prototyping of oxy-fuel injectors with integrated temperature sensing capabilities using powder bed fusion additive manufacturing (AM) technologies. A primary focus of this work was to develop powder removal techniques to completely remove sintered powders from internal cavities, which facilitated the implementation of complex injector geometries as well as sensor placements within the parts. It was found that submerging the part in liquid nitrogen, in combination with exposure to ultrasonic vibration, provided effective powder removal. Mechanical testing of fabricated components and test coupons showed no significant change in the mechanical strength of the part due to the addition of liquid nitrogen which creates a thermal shock. Metallography and powder characterization through the use of SEM and EDS showed no change in metallurgical properties of the parts due to the use of liquid nitrogen and ultrasonic energy. The injectors were then test fired in both atmospheric and high-pressure conditions at different firing inputs (55–275 kW).

Test artifacts have been used to evaluate additive manufacturing (AM) systems since the early 1990s with over 65 artifacts published to date. Due to the system agnostic approach to artifact design, principally focused on geometric accuracy, there has yet to be a widely adopted artifact for laser powder bed fusion (LPBF). To speed qualification of LPBF, a rapid method that quantifies impacts of process variables on part structure, properties, and performance is required. Using a list of design requirements developed from literature, build experience, and needs from several major roadmapping efforts, a test artifact was designed to evaluate geometry-specific microstructure, dimensional accuracy, residual stress, chemistry, surface integrity, powder removal, and distortion. The LPBF artifact includes: four sides for geometric feature accuracy and surface integrity analysis, indication marks for accurate sectioning for metallography, and additional features specifically designed to evaluate residual stress, powder removal, mechanical properties and distortion. The artifact is compact and designed to fit within a standard 50 mm metallographic mount with indication marks used to improve measurement repeatability and accuracy. Microstructure and anomaly population are quantifiable on features including overhangs, islands, thin features, channels, lattice structures and bulk areas representing different thermal histories. It is believed that this single test artifact can be used for many purposes, including optimization of LPBF input variables, qualification and more. Ongoing work is continuing to improve the artifact design, testing its implementation across LPBF platforms, and using the artifact to concretely define process sensitivity currently limiting standardization and adoption of LPBF due to costs associated with defining process windows in terms of qualification and certification. As part of this effort, the artifact described here forms the basis of the Global Test Artifact Data Exchange Program – a program designed and managed by the authors for the benefit of research to advance LPBF qualification efforts and help lead to more widespread adoption of LPBF (described in more detail at keck.utep.edu/GTADExP).

In-process process sensing and monitoring is being incorporated across additive manufacturing technologies due to the need for part qualification. Implementation of additively manufactured end-use parts has been hindered by the inherent process variability and anisotropy that adversely affect part performance. Process monitoring methods have the potential to ensure fabrication integrity is achieved and part isotropy is maintained across the entirety of a part. This manuscript compares two methods (pyrometer and infrared thermography) that have the potential to monitor layerwise surfaces of a powder bed fusion process. Measurement of surface temperatures during fabrication can be useful for parameter development of novel materials, prediction of resulting microstructural architectures, and ultimately as feedback used in a closed-loop control system to allow full spatial and temporal control of melting and microstructure. A multi-wavelength pyrometer was externally mounted atop an electron beam melting (EBM) additive manufacturing system to observe and record surface temperatures during the fabrication process. The multi-wavelength pyrometer used in this study was a non-contact device that was emissivity independent and capable of taking fixed spot sized measurements. An infrared camera was also installed atop an EBM system to monitor the fabrication surface and was used to measure temperature variations across the entire build area. Although the IR camera produces spatial measurements of an entire part, temperature data is emissivity dependent. Parts with variations in processing were fabricated and monitored using each instrument. Thermal variations between parts were identified with each instrument and related to microstructure. The advantages and disadvantages of each monitoring device were documented and are discussed in this manuscript.

Binder jetting additive manufacturing is an emerging technology with capability of processing a wide range of commercial materials, including metals and ceramics (316 SS, 420 SS, Inconel 625, Iron, Silica). In this project, aluminum oxide (Al2O3) powder was used for part fabrication. Various build parameters (e.g. layer thickness, saturation, particle size) were modified and different sintering profiles were investigated to achieve nearly full-density parts (~96%). The material's microstructure and physical properties were characterized. Full XRD, compression testing, and dielectric testing were conducted on all parts. Sintered alumina parts were achieved with an average compressive strength of 131.86 MPa (16 h sintering profile) and a dielectric constant of 9.47–5.65 for a frequency range of 20 Hz to 1 MHz. The complexity offered by additive processing aluminum oxide can be extended to the manufacturing of high value energy and environmental components for environmental systems (e.g. filters and membranes) or biomedical implants with integrated reticulated structures for improved osseointegration.

This work describes the design, fabrication, and testing of an Archimedean spiral or spiral antenna using polymer extrusion 3D printing of polycarbonate base material. The spiral antenna design was simulated using CST Microwave Studio (R), and the resulting 3D printed antenna characterized in terms of return loss, directivity, and polarization. The antenna design was embedded into a 3D printed structure using a unique ultrasonic method while a ground plane was inserted through a thermal embedding process. These fabrication methods provide process flexibility, which allows multiple conductive antenna layers to be additively constructed in a single build sequence. The method described can be used to create unique electromagnetic structures such as waveguides directly in a 3D printed dielectric part. The spiral antenna was tested with three variations of microstrip feed line used to match 50 impedance and introduce a 180 degrees phase shift between the two arms of the spiral. These include a Duroid balun attached to feed of the antenna after fabrication, a Duroid balun embedded into the polycarbonate during fabrication, and the same microstrip design fabricated out of copper mesh and embedded into the structure using the polycarbonate as a dielectric substrate. The results of these three approaches will be discussed. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1662-1666, 2016

This paper presents an efficient GPU-based part-scale thermal process simulator for laser powder bed fusion ( L -PBF) additive manufacturing (AM). To take full advantage of modern GPU computing, a matrix-free preconditioned conjugate gradient (PCG) finite element algorithm with voxel mesh is proposed to solve the transient heat transfer problem involved in the L -PBF process. The accuracy of the developed simulator is demonstrated by comparing with a commercial software (ANSYS) using representative L -PBF process parameters and temperature-dependent thermal properties for Ti6Al4V. For efficiency, it is found that the process simulation has a significant speedup going from a single CPU to a single GPU implementation. A speedup is also observed with the matrix-free method compared to a linear solver using a sparse matrix, both on a single GPU. In addition, several schemes devised to gain higher efficiency are discussed in details, which include exclusion of inactive elements from the memory, adaptive meshing in the build direction, preconditioner, and layer lumping. Using these schemes, the adaptability and scalability of the developed simulator are demonstrated on a complex geometry. A calibration of the model is also performed in realistic conditions with a thermocouple measurement coming from experimental data.

While additive manufacturing (AM), commonly known as 3D printing, has been in existence commercially for ∼30 years, desktop 3D printers are a relatively new and rapidly growing market segment. Both well-established AM companies and an increasing number of new enterprises are designing and retailing desktop systems of various sizes, capabilities, and prices. With the abundance of desktop systems now on the market, a consumer may benefit from determining which system best serves their needs. This research highlights differences amongst 45 desktop 3D printers and suggests a method by which to evaluate such differences. For this, a standard part consisting of various geometric features was designed and printed using each system. An updated version of a previously developed quantitative ranking model was utilized to rate the build precision of each system as well as other features, including build volume, size, cost, weight, and layer resolution. In addition, the research team observed part aesthetics and quantified mechanical properties. The criteria evaluated in this ranking model may be modified by each user, to extend this methodology to other desktop AM systems, including professional-grade machines. The results from the model presented in this research were compared with other commonly used ranking methods to help evaluate each technique. These included a simple ascending order rank based model adjusted for ties (1-best and 45-worst), a percentile value based model evaluating the factor contribution values presented in this paper; and the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) which evaluated separation measures from ideal and worst solutions. As expected, the comparisons demonstrated that each model had slightly different rankings as compared to the model presented in this paper, with some outliers. Consequently, it was observed that percentile value based models (such as one presented in this paper) provide rankings different from separation value based models (from ideal and worst solutions) such as TOPSIS.

In the context of the large format additive manufacturing in ambient conditions, extrusion materials need to be thermally stable, thus short fiber-reinforced composites have been developed to tailor the thermal behavior. However, lack of public knowledge in material properties and dataset lead to improper processing; yielding degradation of materials during trial & error operations which not only increase cost but also reduce the quality of printed parts. This research investigated neat and composite ABS filled with short carbon fiber (ABS/CF) and glass fiber (ABS/GF) using thermophysical and thermomechanical characterization techniques to generate dataset and knowledge that can be used to process materials without degrading the properties as well as achieving the quality parts in future. Thermogravimetric analysis was performed to study the degradation behavior. Differential scanning calorimetry (DSC) analyzed the glass transition temperature ( T g ) and specific heat to understand the heat dissipation of neat and composite materials. While the T g measured in DSC was not significantly different, the dynamic mechanical analysis showed that T g in ABS/CF was increased due to the impeded polymer chain mobility. In addition, both ABS/CF and ABS/GF showed that mechanical stiffness increased by 272 % and 84 % respectively compared to the neat ABS. The thermomechanical analysis described the deformation behavior before and after the transition temperature which suggested that ABS/CF has the highest thermal stability to retain the shape at elevated temperature followed by ABS/GF and neat ABS. The findings of this article can be used during the modeling of pellet-fed large format AM and developing empirical process parameters.

An essentially fully acicular alpha-prime martensite within an equiaxed grain structure was produced in an Electron Beam Melting (EBM)-fabricated Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy using two different Arcam EBM machines: An A2X system employing tungsten filament thermionic electron emission, and a Q20 system employing LaB6 thermionic electron emission. Post-process Hot Isostatic Pressing (HIP) treatment for 2 h at 850, 950, and 1050 &deg, C resulted in grain refinement and equiaxed grain growth along with alpha-prime martensite decomposition to form an intragranular mixture of acicular martensite and alpha at 850 &deg, C, and acicular alpha phase at 950 and 150 &deg, C, often exhibiting a Widmanst&auml, tten (basketweave) structure. The corresponding tensile yield stress and ultimate tensile strength (UTS) associated with the grain growth and acicular alpha evolution decreased from ~1 and ~1.1 GPa, respectively, for the as-fabricated Ti6242 alloy to ~0.8 and 0.9 GPa, respectively, for HIP at 1050 &deg, C. The optimum elongation of ~15&ndash, 16% occurred for HIP at 850 &deg, C, for both EBM systems. Because of the interactive role played by equiaxed grain growth and the intragrain, acicular alpha microstructures, the hardness varied only by ~7% between 41 and 38 HRC.

In large area pellet extrusion additive manufacturing, the temperature of the substrate just before the deposition of a new subsequent layer affects the overall structure of the part. Warping and cracking occur if the substrate temperature is below a material-specific threshold, and deformation and deposition adhesion failure occur if the substrate temperature is above a different threshold. Currently, Big Area Additive Manufacturing (BAAM) machine users mitigate this problem by trial and error, which is costly and may result in decreased mechanical properties, monetary losses and time inefficiencies. Through thermal imaging, the range of temperatures present during the printing of a 20 wt. % carbon fiber reinforced acrylonitrile butadiene styrene (ABS-20CF) single-bead vertical wall via the BAAM machine was measured. Compression tests were performed to understand the material behavior at those temperatures. Optical imaging was performed to identify a relationship between porosity in the printed bead and plateau regions in the compression curves at temperatures of 170 °C and below. From the thermal imaging and compressive testing, it was concluded that if the substrate temperature is above 200 °C, it will not be able to withstand the load exerted by the deposition of a new layer without experiencing deformation. This behavior was attributed to the experimentally obtained low compressive strength of ABS-20CF observed at temperatures above 200 °C.

Machine vision is widely used in industry for monitoring and inspection. In additive manufacturing technology (AM), it is especially important in that it can cover an entire 2-dimensional printed surface area instantly. Additionally, AM technologies can also be used to make a mechanical part for a machine vision system such as mount or illumination devices on a 3D printer. For the industrial 3D printer, the camera mount requires to have temperature control capabilities for the vision system. This research aims to develop a method to build a mount with cooling capability with AM technology. This paper introduces a 3D printed camera cooling housing and proposes a temperature feed-back control method based on the image sensor itself without adding a thermal sensor to increase the user friendliness and simplicity. In the demonstration, a camera cooling housing that was developed enabled a camera module to operate at 200C in an industrial Fortus 400 (Stratasys, MN).

Mechanical properties of additive manufactured metal components can be affected by the orientation of the layer deposition. In this investigation, Ti–6Al–4V cylindrical specimens were fabricated by electron beam melting (EBM) at four different build angles (0 deg, 30 deg, 60 deg, and 90 deg) and tested as per ASTM E8 Standard Test Methods for Tension Testing of Metallic Materials. With the layer-by-layer fabrication suggesting granting anisotropic properties to the builds, strain fields were recorded by digital image correlation (DIC) in the search for shear effects under uniaxial loads. For the validation of this measuring method, axial strains were measured with a clip extensometer and a virtual extensometer, simultaneously. Failure analysis of the specimens at different orientations was conducted to evidence the recording of shear strain fields. The failure analysis included fractography, optical micrographs of the microstructure distribution, and failure profiles displaying different failure features associated with the layering orientation. Additionally, an experimental study case of how the failure mode of components can potentially be designed from the fabrication process is presented. At the end, remarks about the shear effects found, and an insight of the possibility of designing components by failure for safer structures are discussed.

In the last decade, research has focused on 3D printing for not only creating conceptual models but functional end-use products as well. As patents for 3D printing expire, new low cost desktop systems are being adopted more widely. This trend is leading to products being fabricated locally and improving supply chain logistics. However, currently low cost 3D printing is limited in the number of materials used simultaneously in fabrication and consequently is confined to fabricating enclosures and conceptual models. For additively manufactured end-use products to be useful, supplementary features and functionalities will need to be incorporated in to the final structures in terms of electronic, electromechanical, electromagnetic, thermodynamic, and optical content. The University of Texas at El Paso has recently been reporting on embedding electronic components and electrical interconnect into 3D printed structures either by interrupting the process or by inserting the additional content after the structure has been built. However, only until recently and with an investment from the presidential initiative on Additive Manufacturing “America Makes” has there been a concentrated research focus on developing technology that produces multi-functionality. This presentation will describe a project in which copper wires were used to supply a short burst of energy at high voltages in order to activate electro-propulsion. Pulsed Plasma Thursters provided by Busek were demonstrated where one joule of energy was supplied at 2000 volts in order to ablate the thruster in a vacuum and provide precise micro-newton-levels of force - as required for attitude control in small and nano satellites.

Izod impact test specimens were fabricated via a desktop grade material extrusion 3D printer process using ABS in four build orientations. The 3D printed impact test specimens were examined in order to compare the effect of stress concentrator fabrication on impact test data where two methods were used to fabricate the stress concentrating notch: (1) printing the stress concentrator; and (2) machining the stress concentrator where the dimensions of the notch matched those specified in the ASTM standard D256-10. In both test cases, sensitivity to build orientation was also observed. The sample sets with printed stress concentrators were found to be statistically similar to their counterparts with milled stress concentrators. The experiment was repeated again on a commercial grade material extrusion 3D printer using ABS, PC, PC-ABS, and Ultem 9085 and differences in impact test results were observed most notably when Ultem 9085 was tested. Scanning electron microscopy was utilized to perform fractograpy on impact test specimens to explore the effect of stress concentrator fabrication on the fracture surface morphology of the failed specimens. The work here demonstrates the need for materials testing standards that are specific to additive manufacturing technologies; as well as concluding that all-printed impact test specimens may offer the best representation of the impact characteristics of 3D printed structures.