Metal 3D Printing Research Articles

CAD-CAM Workflows for Palatal TAD Anchored Appliances

Mini-implants inserted in the anterior palate are showing the very high success rates of 91.5% - 99%. Compared to other insertion sites, they can be used effectively for molar distalization, space closure, rapid maxillary expansion and protraction, molar intrusion and alignment of impacted upper teeth. In recent years, CAD-CAM techniques such as printed insertions guides and 3D metal printing were integrated into full digital workflows. These new procedures allow mini-implant insertion and appliance fitting in one appointment and may give orthodontists more confidence to insert in the optimum site. Additionally, the CAD/CAM design process may offer the opportunity to further improve orthodontic appliances biomechanically.

Development of a novel V-frame octocopter: design, kinematic analysis and simulation using PID controllers with Ziegler Nichols tuning method

PurposeThe main purpose of the study was mechanical designing, simulation and manufacturing process for a new model of octocopter V-frame and to achieve simple manufacturing with 3D printing technology. Moreover, the octocopter PID controller was simulated on the Simulink environment to get performance on the roll and pitch angle control.Design/methodology/approachOctocopter is one kind of multirotor vehicle (a rotorcraft with more than two rotors), that has lately gained a lot of attention for both the scientific and commercial spheres. With a greater number of rotors, the multirotor is very maneuverable and robust. Multi-copter makes an important contribution to the technological revolution in the military, industry, transportation, mapping and especially agriculture. Nowadays, we are heading to the four-industrial revolutions as well as the new technological application in the agricultural field such as precision agriculture, mapping and surveillance. Due to recently advanced technology about sensors, electronics, 3D printing, battery with high performance, multi-copter can be manufactured at low cost.FindingsThe V-frame octocopter was chosen to design in this paper; it had better performance scores including high redundancy rotors, high payload capability and affordable cost than another multi-copter family. The V-frame octocopter increasing freedom field of view of the camera was considered to place the camera position in the front of the drone.Research limitations/implicationsFor the future aspects, the mechanical structure of the octocopter could be improved by using more advanced metal 3D printing to produce the aluminum or titan alloy materials for lighter and more rigid compared with ABS material, and finally the assembly to the real test.Originality/valueThe study shows the new platform of the V-frame octocopter kinematics analysis, designed on the CAD software, with some important mechanical parts using FEM analysis to find the highest stress and displacement under high load applied, the result of all connecting the joints 3D printing part is completely safe. Mechanical parts were manufactured by using 3D printing technology and CNC milling. Moreover, the study has shown V-frame octocopter simulation based on Simulink using the second method Ziegler- Nichols to find suitable parameters of the PID controller for roll and pitch angle. Using the block simulation is good for implementing and fast checking the new algorithm when building the new platform of the robot.

Design tools for metal additive manufacturing: a critical and perspective overview

Metal Additive Manufacturing is quite expensive and very different from traditional schemes. The possibility of realizing lightweight products with free-form shapes increases the interest in this technology in the industry. The main limitations of the widespread of Metal Additive Manufacturing concern the high cost of materials and 3D printers, and the necessity of post-processing activities. Additive Manufacturing generally claims different design constraints if compared to traditional manufacturing technologies. The improvements in 3D Metal Printing are increasing the design practices in Additive Manufacturing. The design workflow for Additive Manufacturing includes different tools and methods to manage the design complexity. These tools are CAD/CAE software, numerical simulations, database, etc. They mostly are the updated versions of already existing tools. Therefore, these tools are not directly developed to support the phases of Additive Manufacturing. The paper analyzes the main functionalities of Design for Metal Additive Manufacturing tools. The critical analysis suggests the necessity to improve the interactive practices between users and tools along the design workflow. A more interactive approach to design could reduce the gap between the definition of the part geometry and the parameter settings for the additive process.

Formation and Control of Pore Defects in Metal 3D Printing

Formation and Control of Pore Defects in Metal 3D Printing

Evaluating the Effectiveness of Planar and Waveguide 3D-Printed Antennas Manufactured Using Dielectric and Conductive Filaments

3D printing is a technology suitable for creating electronics and electromagnetic devices. However, the manufacturing of both dielectric and conductive parts in the same process still remain a challenging task. This study explores the combination of 3D printing with traditional manufacturing techniques for antenna design and fabrication, giving the designer the advantage of using the additive manufacturing technology only to implement the most critical parts of a certain structure, ensuring a satisfying electromagnetic performance, but limiting the production cost and complexity. In the former part of the study, the focus is on three proximity-coupled patch antennas. It demonstrates how hybrid devices made of metal, dielectric, and 3D-printed (using Fused Filament Fabrication) conductive polymers can be successfully simulated and created for different operating frequency bands. In the latter part, the study compares three prototypes of a 5G-NR, high gain, and wideband waveguide antenna: respectively a fully 3D printed one made of electrifi (which is the most conductive commercial 3D-printable filament), an all-metal one, and a hybrid (3D-printed electrifi & metal) one. The results show a 15% reduction in efficiency when using the all-Electrifi configuration compared to all-metal one, and a 4-5% reduction when using the hybrid version.

Design, fabrication and evaluation of periodic metal composite beams constructed using metal 3D printer for aiming at band gap formation

Design, fabrication and evaluation of periodic metal composite beams constructed using metal 3D printer for aiming at band gap formation

Design of a Dual-Polarization All-Metal Vivaldi Array Antenna Using a Metal 3D Printing Method for High-Power Jamming Systems

This paper proposes an all-metal Vivaldi array antenna with a wide-angle impedance matching (WAIM) layer for high-power jamming systems. To reduce fabrication complexity and time, the proposed array antenna is manufactured using a metal 3D printing method. The Vivaldi unit cell, composed of a radiating flare part and an inner cavity, is extended into an 8 × 8 array with a ±45° slant configuration. To further enhance the beam steering angle, the WAIM layer is placed on top of the proposed array antenna. The performances of the proposed array antenna, such as its active reflection coefficients (ARC), gains, and array radiation patterns, are investigated in a full anechoic chamber. At a steering angle of (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 25°), the measured and simulated average ARCs of the center element (Port 36) with the WAIM layer are –13.2 dB and –18.5 dB, respectively. At 4 GHz, the measured and simulated bore-sight gains of the proposed array antenna are 19 dBi and 20.6 dBi, respectively. In addition, the measured and simulated bore-sight gains for the (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0°) steering angle in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">zx</i> -plane are 18 dBi and 21 dBi, respectively. In the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">zy</i> -plane, bore-sight gains for the (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0°) steering angle are 19.3 dBi by measurement and 19.1 dBi by simulation. These results demonstrate that the proposed array antenna is suitable for high-power jamming systems because stable bore-sight gains are observed even at wide steering angles without unwanted grating lobes.

Innovative design of bone quality-targeted intervertebral spacer: accelerated functional fusion guiding oriented collagen and apatite microstructure without autologous bone graft

BACKGROUND CONTEXTAlthough autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting. PURPOSEWe developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure. STUDY DESIGNThis was an in vivo animal study. METHODSIntervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2–L3 or L4–L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests. RESULTSThe spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The push-out load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix. CONCLUSIONSThe developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft. CLINICAL SIGNIFICANCEOur results provide a foundation for designing future spacers for interbody fusion in human.

High-Throughput Metal 3D Printing Pen Enabled by a Continuous Molten Droplet Transfer.

In metal additive manufacturing (AM), arc plasma is attracting attention as an alternative heat source to expensive lasers to enable the use of various metal wire materials with a high deposition efficiency. However, the stepwise material deposition and resulting limited number of degrees of freedom limit their potential for high-throughput and large-scale production for industrial applications. Herein, a high-throughput metal 3D printing pen (M3DPen) strategy is proposed based on an arc plasma heat source by harnessing the surface tension of the molten metal for enabling continuous material deposition without a downward flow by gravity. The proposed approach differs from conventional arc-based metal AM in that it controls the solidification and cooling time between interlayers of a point-by-point deposition path, thereby allowing for continuous metal 3D printing of freestanding and overhanging structures at once. The resulting mechanical properties and unique microstructures by continuous metal deposition that occur due to the difference in the thermal conditions of the molten metal under cooling are also investigated. This technology can be applied to a wide range of alloy systems and industrial manufacturing, thereby providing new possibilities for metal 3D printing.

Development of the Customized Asymmetric Fixation Plate to Resist Postoperative Relapse of Hemifacial Microsomia Following BSSO: Topology Optimization and Biomechanical Testing.

Hemifacial microsomia (HFM), one of the most common congenital facial anomalies, was usually treated with the bilateral sagittal split osteotomy (BSSO) procedure to correct the asymmetric appearance and malocclusion of the mandible. However, the frequent post-operative relapse incidents would lead to the restoration of the mandibular segment to its preoperative position and failure of the BSSO procedure. In this study, a customized asymmetric fixed plate (CAF plate) was developed to resist relapse due to hemifacial microsomia occlusal forces and the different muscular traction forces on both sides of the mandible. For the actual HFM case in this study, the reconstructed mandibular segmental bone model was fixed using BSSO with a rectangular plate (the original CAF plate appearance) in the topology optimization analysis. With the topology optimization technique, the CAF plate was designed with a lightweight profile and excellent structural strength in consideration of the HFM asymmetrical muscle traction and occlusal force. Using biomechanical simulations, the von-Mises stress and CAF plate mandibular segment displacement and the miniplate were compared to evaluate which had superior relapse resistance. In the in-vitro biomechanical test, a fatigue force of 250,000 cycles and a constant muscle traction force were applied to the HFM mandibular model, which was fixed with the CAF plate fabricated using metal 3D printing (selective laser melting, SLM) to obtain the mandibular segment displacement as a relapse assessment. The topology optimization analysis showed that the CAF plate has the best characteristics, light weight and structural strength with 30% volume retention. The biomechanical analysis showed that the maximum von Mises stress of the mini-plate was 2.71 times higher than that of the CAF plate. The relapse displacement of the mandibular segment fixed with the mini-plate was 1.62 times higher than that fixed with the CAF plate. The CAF plate ability to resist relapse was confirmed by the biomechanical testing results so that only 0.29mm of recurrence displacement was observed in the mandibular segment. The results indicated that the CAF plate structural strength and resistance to relapse was significantly better than that of the mini-plate. This study developed a customized asymmetric fixation plate for hemifacial microsomia, integrating topology optimization, metal 3D printing, and in vitro biomechanical testing to resist occlusal forces and differential muscle traction on both sides of the mandible to reduce relapse and improve fixation stability.

Design of 3D-printed metal micro-truss porous configurations with geometric inhomogeneity

The metal micro-truss porous structures demonstrate industrial application values in lightweight, high specific strength, impact resistance and energy absorption. 3D printing brings a feasible path to design and directly fabricate metal micro-truss parts. Spatially geometrically uniformly distributed and unit-symmetrically arrayed porous structures still need to further improve the structural performance. This work studies the design principles and several design cases of geometrically non-uniform micro-truss porous structures via metal 3D printing method. The high-stress localized micro-regions are filled with denser and more reinforced micro-truss cell arrays that conform to the main loading direction of localized stress.

A Hybrid Model Based on Jensen’s Inequality Theory for 3D Printed Lattice Structures Maximum Stress Prediction

Inherent defects in 3D-printed metal lattice structures are inevitable and significantly affect the structural part’s maximum stress. To solve this problem, a hybrid model based on Jensen’s Inequality Theory to predict the maximum stress of 3D printed lattice structures is proposed in this study. Jensen’s inequality theory means that the average of the model predictions will not be lower than the predictions of the individual prediction models. Therefore, the optimal number of hybrid models is discussed and designed, and the optimal base estimators are trained and selected on the same dataset. A hyperparametric approach is used to optimise the base estimator parameters. The experimental results demonstrate that the hybrid model performs better than a single estimator’s prediction, with an R2 of 0.83. This research offers a novel approach for the prediction of 3D-printed lattice structures using machine learning.

Analysing the Generative Design of Payload Part for the 3D Metal Printing

Additive manufacturing provides the possibility to print complex generative designed bodies. The research deals with redesigning a payload part of a camera holder using generative design for selective laser melting. The possibility of replacing the original polymer component with a metal printed component of a greater strength and the effect of different parameters of generative design were investigated. By comparing the generative design results obtained in several phases, the goal was to find a solution that can be used to replace the previous part and become printable with 3D metal printing. The internal stress values for each case and the amount of weight reduction that can be achieved were determined. With the results obtained, the parts were prepared for printing. It is the key aspect of the industrial application of generative optimization.

Particle Swarm Optimization of Printing Parameters for Open-source TIG-based Metal 3D Printing

Proprietary metal 3D printing is still relegated to relatively expensive systems that have been constructed over years of expensive trial-and-error to obtain optimum 3D printing settings. Low-cost open-source metal 3D printers can potentially democratize metal additive manufacturing; however, significant resources are required to redevelop optimal printing parameters for each metal on new machines. In this study, the particle swam optimization (PSO) experimenter, a free and open-source software package, is utilized to obtain the optimal printing parameters for a tungsten inert gas-based metal open source 3D printer. The software is a graphical user interface implementation of the PSO method and is designed specifically for hardware-in-loop testing. It uses the input of experimental variables and their respective ranges, and then proposes iterations for experiments. A custom fitness function is defined to characterize the experimental results and provide feedback to the algorithm for low-cost metal additive manufacturing. Four separate trials are performed to determine the optimal parameters for 3D printing. First, an experiment is designed to deposit and optimize the parameters for a single line. Second, the parameters for a single-layer plane is optimized experimentally. Third, the optimal printing parameters for a cube is determined experimentally. Fourth, the line optimization experiment is revised and reconducted using different shield gas parameters. The results and limitations are presented and discussed in the context of expanding wire arc additive manufacturing to more systems and material classes for distributed digital manufacturing.

Digital Twin Science of Metal Powder Bed Fusion Additive Manufacturing: A Selective Review of Simulations for Integrated Computational Materials Engineering and Science

A digital twin (DT) is a cyberspace replica of a system, such as manufacturing equipment. A DT consists of statistical models and computer simulations of physical phenomena occurring in the system. The modeling is adjusted to the system based on signals from sensors attached to the system and their temporal changes. In general, a DT is utilized to (i) predict phenomena occurring in the system, (ii) optimize control parameters, and (iii) estimate part replacement schedules. We propose to use a DT to elucidate the unique solidification phenomena occurring in a type of metal 3D printing (i.e., additive manufacturing: AM) process. Thus, we propose that applications of DT that obtain scientific data be referred to as “digital twin science (DTS).” This paper first reviews the fundamental of the AM process, particularly powder bed fusion (PBF) and relevant computer simulations, and then studies on computer simulations conducted to elucidate the relationship between the extreme conditions characteristic of the PBF process and solidification microstructures. The findings achieved by the DTS approach indicate that the combination of experimental and simulation data aid the future development of techniques to obtain required microstructures exhibiting desired properties.

Evaluation of 3D printed PEEK and other 3D printed biocompatible materials as healthcare devices

Introduction and Aim: Additive manufacturing has sought a widespread attention and higher rate of development which can also be modeled by processing of the data acquired by medical Computer Tomography scan. The object is built on a built plate of the printer in layers to form a final required model. Thus, a patient-specific model can be created from imaging data set. Materials available for such printing are elastomers, polymers, metals, or ceramics. The polymer, Polyether ether ketone (PEEK) has been used in health care applications, such as medical devices, and implants due to its high strength, biocompatibility, and light weight. Stainless steel (316L) is commonly used due to its strength, bio-tolerance, corrosion resistance and its formability. The aim of this study was to compare the mechanical strength and biocompatibility of medical grade PEEK and stainless steel. Material and Methods: The test sample of PEEK was prepared using unreinforced PEEK (450G-Victrex Plc., Lancashire, UK) at the Prototyping Lab with a 3D-Printer - INTAMSYS - FUNMAT HT. Samples of stainless steel was printed using the iFusion SF1 Metal 3D Printer using Powder Bed Fusion (PBF) technology. The mechanical tests such as compressive, impact, and tensile tests were performed using an electromechanical universal testing machine (UTM) model- Zwick/Roell Z020 with a 20kN load cell. Biocompatibility tests were done using L929 cells to assess the cytotoxicity of the dental materials. Results: The tensile strength of PEEK polymer was 70+1.6 and the impact strength of PEEK polymer was 289 J/m. Conclusion: The tensile strength of stainless steel was higher compared to that of PEEK polymer, and the impact strength of PEEK polymer higher compared to stainless steel. Thus, it can be concluded that both biomaterial such as 316L stainless steel and PEEK are non-toxic to fibroblast.

Bone marrow stromal cells are sensitive to discrete surface alterations in build and post-build modifications of bioinspired Ti6Al4V 3D-printed in vitro testing constructs.

Current standards in bone-facing implant fabrication by metal 3D (M3D) printing require post-manufacturing modifications to create distinct surface properties and create implant microenvironments that promote osseointegration. However, the biological consequences of build parameters and surface modifications are not well understood. This study evaluated the relative contributions of build parameters and post-manufacturing modification techniques to cell responses that impact osseointegration in vivo. Biomimetic testing constructs were created by using a M3D printer with standard titanium-aluminum-vanadium (Ti6Al4V) print parameters. These constructs were treated by either grit-blasting and acid-etching (GB + AE) or GB + AE followed by hot isostatic pressure (HIP) (GB + AE, HIP). Next, nine constructs were created by using a M3D printer with three build parameters: (1) standard, (2) increased hatch spacing, and (3) no infill, and additional contour trace. Each build type was further processed by either GB + AE, or HIP, or a combination of HIP treatment followed by GB + AE (GB + AE, HIP). Resulting constructs were assessed by SEM, micro-CT, optical profilometry, XPS, and mechanical compression. Cellular response was determined by culturing human bone marrow stromal cells (MSCs) for 7 days. Surface topography differed depending on processing method; HIP created micro-/nano-ridge like structures and GB + AE created micro-pits and nano-scale texture. Micro-CT showed decreases in closed pore number and closed porosity after HIP treatment in the third build parameter constructs. Compressive moduli were similar for all constructs. All constructs exhibited ability to differentiate MSCs into osteoblasts. MSCs responded best to micro-/nano-structures created by final post-processing by GB + AE, increasing OCN, OPG, VEGFA, latent TGFβ1, IL4, and IL10. Collectively these data demonstrate that M3D-printed constructs can be readily manufactured with distinct architectures based on the print parameters and post-build modifications. MSCs are sensitive to discrete surface topographical differences that may not show up in qualitative assessments of surface properties and respond by altering local factor production. These factors are vital for osseointegration after implant insertion, especially in patients with compromised bone qualities.

Heat Transfer Performance of 3D-Printed Aluminium Flat-Plate Oscillating Heat Pipes for the Thermal Management of LEDs

With the rapid development of electronic technologies towards high integration, high power and miniaturization, thermal management has become an increasingly important issue to guarantee the reliability and service life of electronic devices. The oscillating heat pipe (OHP), which was governed by thermally excited oscillating motion, was considered as a promising technology to dissipate high-density heat and had excellent application prospects in many important industrial processes. A flat-plate OHP, however, was fabricated by traditional welding methods, which were difficult and inefficient, resulting in increasing the cost and wasting the production time. In this work, we adopted a new metal 3D printing technology to develop an aluminum flat-plate OHP, which made it facile to build complex inner channels with high-precision molding at one time. AlSi10Mg powders, as raw materials, were selectively melted and solidified to form the container of the flat-plate OHP. The sintered inner surface presented excellent wettability to the working fluid, which facilitated the evaporation of the working fluid. Acetone was chosen as the working fluid, and the filling ratios with a range of 40-70% were loaded into the flat-plate oscillating heat pipe to analyze its effect on heat transfer performance. It was found that the 3D-printed flat-plate OHP with a 60% filling ratio had a better heat transfer performance and a lower thermal resistance, and it was able to work properly in both vertical and horizontal operation modes. The 3D-printed flat-plate OHP had been successfully applied for the thermal management of high-power LEDs, and the results showed that the temperature of LEDs was maintained within 60 °C, and its service life was prolonged.

Ultrahigh-temperature melt printing of multi-principal element alloys

Multi-principal element alloys (MPEA) demonstrate superior synergetic properties compared to single-element predominated traditional alloys. However, the rapid melting and uniform mixing of multi-elements for the fabrication of MPEA structural materials by metallic 3D printing is challenging as it is difficult to achieve both a high temperature and uniform temperature distribution in a sufficient heating source simultaneously. Herein, we report an ultrahigh-temperature melt printing method that can achieve rapid multi-elemental melting and uniform mixing for MPEA fabrication. In a typical fabrication process, multi-elemental metal powders are loaded into a high-temperature column zone that can be heated up to 3000 K via Joule heating, followed by melting on the order of milliseconds and mixing into homogenous alloys, which we attribute to the sufficiently uniform high-temperature heating zone. As proof-of-concept, we successfully fabricated single-phase bulk NiFeCrCo MPEA with uniform grain size. This ultrahigh-temperature rapid melt printing process provides excellent potential toward MPEA 3D printing.

A comprehensive investigation on application of machine learning for optimization of process parameters of laser powder bed fusion-processed 316L stainless steel

Metal 3D printing has gained a lot of attention among industries since it offers a practical solution to problems rising during the manufacturing of parts and components with complex geometry. This is an additive technology that eliminated several fabrication steps and at the same time reduces material waste during the manufacturing process. However, in all additive manufacturing technologies, the final properties of the parts are determined by the operational process parameters. In this study, several machine learning algorithms were examined to characterize the effects of the printing process parameters on relative density, hardness, yield strength, and tensile strength in manufactured parts. It was possible by using “Big Data” collected from a large number of previously published articles on the application of laser powder bed fusion (LPBF) for the 3D printing of 316L stainless steel samples. Among different process parameters, laser power, laser energy density, and scanning speed were proven to have the largest effects directly on the physical and mechanical properties of LPBF-processed parts. Six different classification models and five support vector machine regression-based models were tested to find the most accurate prediction algorithm. To validate the obtained results from the applied machine learning models, a set of 316L specimens were produced using LPBF technology using a random set of process parameters. The physical and mechanical properties of 3D printed samples were tested and compared to the ones predicted from the optimum models from machine learning analysis. The results were in great agreement, which shows the high accuracy of the developed machine learning algorithms in this study.