Hybrid Additive Manufacturing Research Articles

Embedding and Contacting of Electrical Components for Hybrid Additive Manufacturing

Integrating electrical functionality during additive manufacturing (AM) is a promising new field of application. In this article, different concepts for combining an extrusion-based AM process called 3-D dispensing (3DD) with the embedding of electrical components are developed and compared. Based on criteria, such as resulting surface quality or overall accuracy, the best strategy among six different approaches is identified. To further validate and confirm the choice, long-term reliability tests [humidity and thermal shock testing (TST)] with a particular focus on the electrical contacts between the printed tracks and the embedded electronic components have been conducted. It was shown that the embedding strategy and the cavity design have no influence on the long-term properties of the printed electrical tracks. Finally, an acceleration sensor is embedded in a 3-D housing to prove real use-case applicability and to show the improvements identified in the previous study.

Optimization of Friction Stir Welding Parameters in Hybrid Additive Manufacturing: Weldability of 3D-Printed Poly(methyl methacrylate) Plates

In this work, the expansion of friction stir welding (FSW) in parts made via material extrusion (MEX) 3D printing was investigated. Poly(methyl methacrylate) (PMMA) plates were joined in a full factorial experimental design. The effects of three FSW parameters (weld tool pin geometry, rotating speed, and travel speed) on the weld results were studied. The tensile strength was investigated using statistical modeling tools. A morphological characterization study was also conducted on the weld zone, with microscopy. The state of the material during the FSW process was monitored via real-time temperature measurements. The feasibility of the process was verified. The results show high industrial merit for the process. The highest tensile strength was reported for the sample welded with the frustum tool, at 1400 rpm and a 9 mm/min travel speed (the highest studied), with a welding efficiency > 1. This can be attributed to the reduced porosity of the weld area compared to the 3D printed structure, and indicates a high potential for joining 3D-printed PMMA sheets via the FSW process.

Hybrid additive manufacturing of an electron beam powder bed fused Ti6Al4V by transient liquid phase bonding

Hybrid Additive Manufacturing (HAM) is a production strategy enhancing the flexibility of the already versatile Additive Manufacturing (AM) techniques. AM of Ti6Al4V, on the other hand, has been of great interest to numerous research works, thanks to the unique corrosion, biomedical and mechanical properties of the alloy. Hence, this research marks the first report on the HAM of Ti6Al4V by Transient Liquid Phase (TLP) bonding of an Electron Beam Powder Bed Fused (EB-PBF) sample to a conventional one. A copper interlayer was used for bonding, and the TLP process was performed at 890 °C and 970 °C for 60 min. Shear strength test was carried out and the results showed the highest shear strengths of 579.3 and 662.5 MPa for TLP bonding at 890 °C and 970 °C, respectively. By increasing the bonding temperature to 970 °C, no Cu-rich phases were observed in the microstructure, as opposed to the 890 °C samples, and a complete isothermal solidification without intermetallic phases was achieved. Moreover, the 970 °C TLP sample was featured with a much better microstructural integrity and homogeneity in both the base metals and the bonded zone. TLP bonding at 970 °C resulted in a more ductile fracture surface than that bonded at 890 °C. The strong differences between the two TLP bonds were primarily attributed to the faster diffusion rate of elements along the joint and base metal at higher temperatures.

A review of hybrid additive manufacturing of metal parts

This article provides an overview of the latest developments in the field of hybrid additive manufacturing of metal parts. The concept and various kinds of additive manufacturing are discussed. Special attention is paid to hybridization of additive technologies and various processes of forming: die forging, deep drawing, and others. The background and significance of the technologies, as well as their applicability in production are presented. The combination of additive manufacturing with forming processes is carried out with a dual purpose: to expand the area of application of additive manufacturing and overcome its limitations associated with low productivity, metallurgical defects, surface roughness and lack of dimensional accuracy; new application of traditional forming processes.

An approach to improve the microstructure and mechanical properties: A hybrid manufacturing of laser directed energy deposition and shot peening

As one of the most popular additive manufacturing technologies, laser directed energy deposition (LDED) has been extensively and deeply studied to improve the microstructure and properties of formed materials. Hybrid additive manufacturing(HAM) of LDED and shot peening is an innovative technology that combines the principle of surface strengthening and additive manufacturing. It can improve the mechanical properties and optimize the microstructure of the formed materials by strengthening the surface layer-by-layer. In this paper, the phase, oxygen content, microstructure, tensile properties, hardness and fracture morphology of the samples formed by LDED and HAM are compared. It is found that the mechanical properties of the forming samples are significantly improved by HAM, and the yield strength, ultimate tensile strength and average hardness are increased by 53%, 12% and 7%, respectively. Meanwhile, the microstructure of the sample is improved, some of the coarse columnar grains are refined, the heterogeneity of grain size is reduced, and the fibrous microstructure between layers is reduced. The hybrid additive manufacturing of LDED and shot peening can achieve high efficiency and high quality integrated manufacturing of forming parts, which is expected to promote its efficiency and applicability in practical cases in the future.

Microstructural evolution and tensile property enhancement of remanufactured Ti6Al4V using hybrid manufacturing of laser directed energy deposition with laser shock peening

Laser-directed energy deposition (LDED) provides an attractive and cost-effective way to remanufacture high-value engineering components. However, the LDED manufactured (LDEDed) components are usually characterized by large columnar grains along the deposition direction, leading to mechanical anisotropy. Meanwhile, higher performance is usually required in the damaged regions. In this paper, the effects of interlayer laser shock peening (LSP) treatment, namely, an innovative laser hybrid additive manufacturing technology combined LDED with LSP, on microstructural evolution and mechanical performance of Ti6Al4V alloy were investigated. Particularly, the microstructural features between adjacent deposited layers were clarified using scanning electron microscope (SEM) and transmission electron microscopy (TEM) observations. The results indicated that the epitaxial growth of columnar grains caused by LDED was inhibited, and fine equiaxed grains were formed between deposited layers due to the recrystallization behavior. Besides, the microhardness and tensile property of the LDEDed specimen were significantly improved by the interlayer LSP treatment. Consequently, the laser hybrid additive manufacturing -generated dominant mechanism of the microstructural evolution and tensile property enhancement was revealed. • LSP was combined with LDED to realize the laser hybrid remanufacturing. • Epitaxial growth of columnar grains in the LDEDed specimen was inhibited by LSP. • The micro-hardness of the LDEDed specimen was significantly improved by LSP. • A good combination of UTS and ductility was achieved in the LDED-LSPed specimen. • The mechanism of the tensile property enhancement by LHAM was revealed.

Friction Stir Welding Optimization of 3D-Printed Acrylonitrile Butadiene Styrene in Hybrid Additive Manufacturing.

The feasibility of joining material extrusion (MEX) 3D-printed acrylonitrile butadiene styrene (ABS) plates with the friction stir welding (FSW) process was investigated herein as a promising topic of hybrid additive manufacturing (HAM). The influence of three process parameters on the mechanical strength of the joints was thoroughly examined and analyzed with a full factorial experimental design and statistical modeling. Hereto, the welding tool pin geometry, travel speed, and rotational speed were investigated. The joint’s efficiency and quality are evaluated through tensile tests and morphological characterization. More specifically, specimens’ areas of particular interest were investigated with stereoscopic, optical, and scanning electron microscopy. Throughout the FSW experimental course, the welding temperature was monitored to evaluate the state of the ABS material during the process. The majority of the welded specimens exhibited increased mechanical strength compared with the respective ones of non-welded 3D printed specimens of the same geometry. Statistical modeling proved that all processing parameters were significant. The feasibility of the FSW process in 3D printed ABS workpieces was confirmed, making the FSW a cost-effective process for joining 3D printing parts, further expanding the industrial merit of the approach.

Hybrid Additive Manufacturing of Fused Filament Fabrication and Ultrasonic Consolidation.

Fused filament fabrication (FFF) additive manufacturing technology has the advantages of being low cost, having a simple operation, using wide types of molding materials, and producing less pollution during the printing process. However, the mechanical properties of the molded sample are unsatisfactory due to the limited bonding force between the filaments during the forming process, which limits its further development and application in the engineering field. Herein, the hybrid additive manufacturing technology for heterogeneous materials based on the ultrasonic-assisted enhanced fused filament fabrication technology was proposed. The mechanism of ultrasonic vibration on the strengthening of FFF samples was explored. The influence mechanisms of bonding time and ultrasonic strengthening times, ultrasonic strengthening and static load compression on the strengthening of mechanical properties of the sample were investigated. The effects of the thickness and printing angle of the FFF samples on the ultrasonic-enhanced mechanical properties were explored. The tensile strength of the one-time ultrasonic-strengthened sample is up to 43.43 MPa, which is 16.12% higher than that of the original. The maximum bending strength of the four-time ultrasonic-strengthened sample is 73.38 MPa, which is 78.98% higher than that of the original. Ultrasonic strengthening not only re-fused the pores inside the sample, but also improved the bond strength between the rasters. With the increase in the thickness of the sample, the increase rate of ultrasonic to the strength of the sample decreased significantly. The effects of ultrasound on the interlayer adhesion of samples with various printing angles were different. Based on the systematic research on the influence mechanism of ultrasonic process parameters and molding process parameters on the strengthening of FFF, a molding method for additively manufacturing heterogeneous material parts while strengthening the mechanical properties of FFF samples was proposed, and the influence mechanisms of the molding process on the mechanical properties and shape memory properties of the sample were explored, which can broaden the application of FFF technology in the engineering field.

Cracking suppression in additive manufacturing of hard-to-weld nickel-based superalloy through layer-wise ultrasonic impact peening

Fusion-based additive manufacturing (AM) techniques that use high energy beams, such as laser and electron beam, to layer-wise fuse and form materials, are quickly becoming mainstream in the fabrication of performance-critical metal parts. However, the vast majority of alloys currently used in industry are not compatible with fusion-based AM. One major reason is the occurrence of high thermal stress and solidification cracking resulting from the far-from-equilibrium thermal history. In this research, a novel hybrid AM process that combines directed energy deposition (DED) and layer-wise ultrasonic impact peening (UIP) is used to mitigate residual stress formation and to suppress the occurrence of solidification cracking in a hard-to-weld Inconel 100 superalloy. A series of materials characterization techniques, including 3D topography, optical microscopy, electron backscattered diffraction, and X-ray residual stress analysis, is carried out to investigate the effect of layer-wise UIP on the additively manufactured products. Three levels of UIP force, i.e., 25 N, 50 N, and 75 N, are investigated. The results indicate that there is an inverse relationship between the crack density and applied UIP force. At the highest level of UIP force, the crack density reduces to near-zero with significantly improved surface quality. To successfully suppress detrimental residual stress, the depth of the peening-affected-zone (PAZ) must be larger than the heat-affect-zone (HAZ) of laser melting.

Selectively Metalizable Low-Temperature Cofired Ceramic for Three-Dimensional Electronics via Hybrid Additive Manufacturing.

With increasing interest in the rapid development of customized ceramic electronics, hybrid additive manufacturing (HAM) technology has become a competent alternative to traditional solutions such as printed circuit boards and cofired ceramic technology. Herein, the novel HAM technology is proposed by combining a dispensing three-dimensional (3D) printing process and selectively laser-activated electroless plating for fabricating 3D fully functional ceramic electronic products. An appropriative 3D-printable and metalizable low-temperature cofired ceramic slurry is developed to build the green body of ceramic electronics. After the debinding and sintering process, the 3D ceramic structure can be selectively laser-activated and then electrolessly plated to achieve electronic functionality. The thickness of the plated copper layer approaches 10 μm after 4 h of plating, and the electrical conductivity is 5.5 × 107 S m-1, which is close to pure copper (5.8 × 107 S m-1). To reduce the surface roughness of the laser-activated ceramic surface and thereby enhance the conductivity of the copper layer, the laser parameters are optimized as a 1250 mm s-1 scan speed, a 0.4 W laser power, and a 20 kHz laser-spot frequency. A high-power 3D light-emitting diode circuit board with an internal cooling channel is successfully developed to prove the feasibility of this HAM technology for customizing fully functional 3D conformal ceramic electronics.

3D Plotting of Calcium Phosphate Cement and Melt Electrowriting of Polycaprolactone Microfibers in One Scaffold: A Hybrid Additive Manufacturing Process.

The fabrication of patient-specific scaffolds for bone substitutes is possible through extrusion-based 3D printing of calcium phosphate cements (CPC) which allows the generation of structures with a high degree of customization and interconnected porosity. Given the brittleness of this clinically approved material, the stability of open-porous scaffolds cannot always be secured. Herein, a multi-technological approach allowed the simultaneous combination of CPC printing with melt electrowriting (MEW) of polycaprolactone (PCL) microfibers in an alternating, tunable design in one automated fabrication process. The hybrid CPC+PCL scaffolds with varying CPC strand distance (800–2000 µm) and integrated PCL fibers featured a strong CPC to PCL interface. While no adverse effect on mechanical stiffness was detected by the PCL-supported scaffold design; the microfiber integration led to an improved integrity. The pore distance between CPC strands was gradually increased to identify at which critical CPC porosity the microfibers would have a significant impact on pore bridging behavior and growth of seeded cells. At a CPC strand distance of 1600 µm, after 2 weeks of cultivation, the incorporation of PCL fibers led to pore coverage by a human mesenchymal stem cell line and an elevated proliferation level of murine pre-osteoblasts. The integrated fabrication approach allows versatile design adjustments on different levels.

Influence of Heat Treatment on Stainless Steel 316L Alloy Manufactured by Hybrid Additive Manufacturing Using Powder Bed Fusion and Directed Energy Deposition

Influence of Heat Treatment on Stainless Steel 316L Alloy Manufactured by Hybrid Additive Manufacturing Using Powder Bed Fusion and Directed Energy Deposition

Hybrid additive manufacturing for the fabrication of freeform transparent silica glass components

Additive manufacturing of ceramic and glass materials has been developed extensively over the past years, revealing strengths and limitations of the various technologies. In this work, a hybrid extrusion-photopolymerization process is developed to exploit the benefits of both approaches. Their combination allows for more complex geometries with less rheological constraints and no influence of scattering and/or absorption. With this method, transparent silica glass 3D honeycomb-like structures are fabricated starting from a suspension that combines silica particles and a silicon alkoxide. The rheological behavior and reactivity of the ink are tailored with an appropriate blend of acrylates as well as with the alkoxide addition. The latter also contributes to the final ceramic yield, allowing for faster thermal treatments despite a low particle loading. The final components closely match the shape provided by the CAD model; their physical properties confirm the formation of a fully dense silica glass after the heat treatment.

In-situ and off-line deformations of cylindrical walls manufactured by directed energy deposition with different dwell times

Deformation of directed energy deposition (DED) is an index to reflect the relationship among fabricating quality, parameters and process method. In the present work, Inconel 718 cylindrical walls are manufactured by hybrid additive and subtractive manufacturing (HASM) to investigate the deformation. In-situ and off-line measurements are used to detect the deformation of the cylindrical walls with laser displacement measurement sensor and precision contact probe. The finite element simulation is used to analyze the relationship among the temperature, stress and deformation. The effect of different interlayer dwell times (from 0 to 45 s) on residual stress and deformation are compared. The deformations of different positions and processing parameters are analyzed.

Influence of post processing on the micro-machinability of selective laser melted AlSi10Mg: an experimental investigation

ABSTRACT In the present era, machinability studies of selective laser melted (SLM) samples are immensely significant due to the rapid development in hybrid additive manufacturing. In such hybrid process material removal is also performed along with the 3D fabrication of near-net shaped products. Therefore, this work is an effort to compare the machinability characteristics of various samples, namely, cast and SLM produced AlSi10 Mg along with their effect when subjected to T6 solution heat treatment. In the cutting force analysis, it is found that there is an increase in the thrust force (114.8%) and cutting force (33.25%) for SLM manufactured samples in comparison with cast samples. On the other hand, heat treatment on the SLM fabricated samples resulted in the decrease of thrust force (6.94%) and cutting force (13.29%). In addition, the heat treated SLM produced sample showed a steep reduction in Sa by 86.5% compared to as-printed sample. Moreover, lengthier chips were observed in both cast and SLM fabricated specimens, whereas shorter and curlier chips were observed in both heat treated specimen.

Laser-arc hybrid additive manufactured Al[sbnd]Cu alloy for T-shaped structure: Microstructure evaluation and molten pool behavior

T-shaped structure is widely used in the aeronautic and aerospace industries for the development of lightweight applications. However, poor metallurgical bonding and thermal defects by remelting at the intersection is prone to occur in the additive manufacturing of the structure. In this study, T-shaped structure of AlCu alloy was fabricated by laser-arc hybrid additive manufacturing (LAHAM), and the molten pool behavior of the process was analyzed. According to the remelting of intersection, it was divided into the top layer and the remaining layers. The remelting zone of intersection (RZI) was obvious in the top layer. During the solidification of molten pool from the boundary to the center, the ratio of temperature gradient G to solidification rate R (G/R) at the S/L interface decreased from 2.57 × 108 (K·s)/m2 to 9.27 × 107 (K·s)/m2, and promoted the transformation of equiaxed dendrites. In the remaining layers, the recoil pressure, much smaller G/R and larger G∙R made the grains as fine equiaxed along the z direction in the laser zone (LZ), while coarse columnar were observed in the arc zone (AZ). Due to the microstructure changes, the deposited T-shaped structure exhibited a yield strength of 146.5 ± 2.2 MPa and an ultimate tensile strength of 290.3 ± 5.9 MPa.

Vacuum-Formed 3D Printed Electronics: Fabrication of Thin, Rigid and Free-Form Interactive Surfaces

Vacuum-forming is a common manufacturing technique for constructing thin plastic shell products by pressing heated plastic sheets onto a mold using atmospheric pressure. Vacuum-forming is ubiquitous in packaging and casing products in the industry, spanning fast moving consumer goods to connected devices. Integrating advanced functionality, which may include sensing, computation and communication, within thin structures is desirable for various next-generation interactive devices. Hybrid additive manufacturing techniques like thermoforming are becoming popular for prototyping freeform surfaces owing to their design flexibility, speed and cost-effectiveness. This paper presents a new hybrid method for constructing thin, rigid and free-form interconnected surfaces via fused deposition modelling (FDM) 3D printing and vacuum-forming that builds on recent advances in thermoforming circuits. 3D printing the sheet material allows for the embedding of conductive traces within thin layers of the substrate, which can be vacuum-formed but remain conductive and insulated. This is an unexplored fabrication technique within the context of designing and manufacturing connected things. In addition to explaining the method, this paper characterizes the behavior of vacuum-formed 3D printed sheets, analyses the electrical performance of printed traces after vacuum-forming, and showcases a range of sample artefacts constructed using the technique. In addition, the paper describes a new design interface for designing conformal interconnects that allows designers to draw conductive patterns in 3D and export pre-distorted sheet models ready to be printed.

Processing and characterization of tailorable 3D-printed acrylonitrile butadiene styrene composites with hybrid buckypapers

In this work, a hybrid additive manufacturing process was used to incorporate hybrid buckypapers into an acrylonitrile butadiene styrene matrix. The buckypapers were made onsite during manufacturing from a suspension containing carbon nanotubes, short carbon fibres, and polymer binders. The 3D-printed composites were post-processed by vacuum bagging. The composites reinforced with hybrid buckypapers showed a higher tensile strength by 18% and a tensile modulus by 20% than neat ABS. Further improvement in tensile properties (up to 39%) was observed after the modification of hybrid buckypapers with epoxy or thermoplastic polyurethane binders. The porosity was reduced from 4.8% to 0.5% after the post-treatment of ABS. The microstructure of the hybrid buckypapers and the resulting mechanical properties of the composites depended on the weight fraction (1, 5, or 10 wt%) of binders. The composites without binders were the most porous and experienced a 64% reduction in interlaminar shear strength. The thermoplastic polyurethane had a negligible impact on interlaminar shear strength, while the epoxy binder fully recovered it. The results showed that the mechanical properties and morphology of composites containing hybrid reinforcement can be tailored by selecting the type and weight fraction of the polymer binder system.

TPU/CNTs flexible strain sensor with auxetic structure via a novel hybrid manufacturing process of fused deposition modeling 3D printing and ultrasonic cavitation-enabled treatment

The broad technological concept as so-called "hybrid additive manufacturing" is introduced into the fabrication of flexible strain sensing structure, employing the combination process of fused deposition modeling (FDM) 3D printing technique and ultrasonic cavitation-enabled treatment. We customize the FDM settings to print auxetic structures with a negative Poisson's ratio (NPR), using the flexible thermoplastic polyurethane (TPU) material. Then, we employ the ultrasonic cavitation-enabled treatment conducted towards the flexible auxetic structure immersing in carbon nanotubes (CNTs) liquid, aiming to embed the CNTs into the surface layer of the auxetic structures. It is equivalent to two additive manufacturing steps, proving effective in designing and fabricating flexible strain sensors. Instead of 3D printing after the hybridization of the TPU matrix material, this manufacturing procedure can ensure that the intrinsic excellent mechanical properties of TPU are not weakened due to the internally mixed conductive materials but able to exhibit usable sensing performances. The Poisson's ratio of the sensor structure is - 0.8. The sensor achieves over 300% strain. The sensitivity within the initial strain range is 2.661. The reliability of signal acquisition during the cyclic deformations is proved. Its response-recovery duration under 5% strain at 500 mm/min deformation rate is 130 ms(response)− 250 ms(recovery). It gives accurate feedback to external stimuli at different frequencies. It can maintain stable output signals during 3000 cycles of stretching. It also can sense 1% minor-strain stimuli. The strain sensing behavior of the fabricated flexible sensor with the auxetic structure is detailed. The CNTs are combined tightly with the TPU surface layer to form a conductive network with variable resistance during recoverable deformation of the auxetic structure. The macro and micro-mechanisms of sensing are dissected, considering the tunneling effect of discontinuous CNTs. The hybrid additive manufacturing process is verified to be feasible, credible, and low-cost for easy fabrication of flexible strain sensors with complex geometry configurations.

Application of hybrid additive manufacturing technology for performance improvement of martensitic stainless steel

Additive manufacturing (AM) is considered to be an attractive technology that offers tremendous advantages in rapidly producing complex-shaped components close to their final/net shape. However, uncontrolled metallurgical defects (pores, cracks, and inclusions), deleterious tensile residual stresses (RS), as well as scattered and unsatisfactory material performance have hindered its applications. In this study, layer-by-layer ultrasonic micro-forging treatment (UMT) was combined with directed energy deposition (DED) to substantially improve the mechanical performance (e.g., strength-ductility synergy, and fatigue behavior) and corrosion resistance of as-built 15–5PH stainless steel (SS). The surface RS distribution, mechanical properties, corrosion resistance, and microstructural properties of the non-UMT and UMT specimens were analyzed. In particular, focused ion beam (FIB) was employed to prepare the specimen for transmission electron microscopy (TEM) observations of the surface severe plastic deformation (SSPD) zone after UMT. The results indicated that the process with UMT resulted in higher surface compressive stress (~−750 MPa), reduced oxide inclusions, and refined martensite blocks (23.8% finer than that of the non-UMT specimen). The improvement of these characteristics induced by UMT further led to a comprehensive increase in the strength, elongation, fatigue resistance, corrosion resistance, and surface hardness of the DED fabricated parts. This work demonstrated the tremendous potential of integrated DED technology for tailoring the microstructure, controlling the quality, and producing martensitic SS with excellent mechanical performance and corrosion resistance.