Fabrication Of Complex Shapes Research Articles

Development of lightweight and high-strength hollow titanium-plated denture material using three-dimensional printing.

Owing to its desirable ability to fabricate complex shapes, three-dimensional printing is preferred over casting for manufacturing dentures. Furthermore, titanium is widely used in dental implants and dentures because of its high corrosion resistance, biocompatibility, strength, and low density. In this study, we aimed to develop a new metal denture material from three-dimensional-printed (3DP) to achieve lighter weight and greater strength than those of PMMA dentures. Hollow (3DP-H) structure and solid (3DP-S) structure titanium plate specimens of 0.5, 1.0, and 3.0mm in thickness were used. Casted Ti, casted Co-Cr, and PMMA plates were fabricated for comparison. Elastic modulus, density, thermal conductivity, hardness, and proof stress of the specimens were measured and plotted on a radar chart to enable multifaceted evaluation. The results indicated that the density of the 3DP-H plates reduced by 28-36% compared with those of 3DP-S and cast Ti plates. The weight of the metal-denture-equivalent section of the 0.5-mm-thick 3DP-H titanium-plated denture reduced to two-thirds that of the 2.0-mm-thick PMMA denture. The proof stress of the 0.5-mm-thick 3DP-H plate increased to about 3 times that of the 2.0-mm-thick PMMA plate. The total value of the 0.5-mm-thick 3DP-H titanium plates was higher than it of the 1.0-mm-thick PMMA plates. This study suggests that it is possible to produce 3DP-H titanium plate dentures exhibiting not only extremely lightweight compared to conventional PMMA dentures but also sufficient strength.

Self‐Healing Materials for 3D Printing

AbstractAdditive manufacturing/3D printing is praised as revolutionary by many because it enables the decentralized and on‐demand manufacturing of complex shapes. With the ongoing rapid development and increased availability of these technologies, it has become crucial to develop novel materials with unique functionalities for 3D‐printed components. Advances in self‐healing materials have resulted in structures capable of recovering from physical damage through material remendability. By applying self‐healing solutions to 3D printing, researchers are attempting to overcome current barriers such as low mechanical properties, material waste, and printability issues, among others. This review summarizes the current state of research on self‐healing materials used for 3D printing and presents recent progress in the 3D printing of self‐healing components. The particular focus is on the use of intrinsic polymer self‐healing, which is prominent in the published literature. The self‐healing mechanisms of the proposed material systems as well as their composition are highlighted, and their intended application with respect to 3D printing is focused on. The scientific and technological challenges involved in the implementation of self‐healing materials and approaches and the potential functional 3D printing applications of these new materials are also discussed.

Biobased Imine Vitrimers Obtained by Photo and Thermal Curing Procedures-Promising Materials for 3D Printing.

Imine-based vitrimers were prepared from synthesized diimine-dimethacrylate monomer derived from biobased vanillin. First, a methacrylate derivative starting from vanillin was synthesized. The diimine derivative was synthesized by condensation of the aldehyde groups from two vanillin methacrylate units with the amine groups of hexamethylenediamine (HMDA). The synthesized product was used in formulations containing ethylene glycol phenyl ether methacrylate (EGPMA) as a reactive diluent for the customization of final material properties and cured by exposure to ultraviolet (UV)-light using suitable radical photoinitiators or else with temperature using a radical thermal initiator. Materials with glass transition temperatures (Tgs) ranging from 70 to 90 °C were prepared, showing good thermal stability and mechanical and thermomechanical properties. The evaluation of their vitrimeric characteristics revealed that all materials achieved a stress-relaxation factor (σ = 0.37σ0) in less than 130 s at 160 °C, with photocured materials exhibiting faster relaxation rates. The catalytic effect of phosphine oxide groups in imine metathesis has also been evidenced. All prepared materials could be mechanically recycled and completely solubilized in a two-step degradation process, putting evidence of their potential use for carbon fiber-reinforced composites (CFRCs). In addition, they demonstrated promising self-repairing abilities. Finally, as a proof of concept, it was established that these formulations could be effectively processed using a Digital Light Processing three-dimensional (3D) Printer (DLP), resulting in the fabrication of complex shapes with high resolution.

Viable route to the manufacture of short carbon fiber-rich UHTC complex shapes with enhanced toughness

ZrB2 - based pasted, containing 5, 20, 45, 60 vol% short carbon fibers (Cf), were prepared in order to obtain complex shapes via direct ink writing, which were then sintered by hot pressing. The rheological behavior of the pastes indicated that at low Cf concentrations, the fibers act as a lubricant decreasing the paste viscosity. Above 20 vol% Cf, they act also as a binder creating an interconnected network that dominates over the lubrication effect, resulting in a viscosity increase. Complex shapes in the form of a hollow cylinder and a winglet with a functionally graded composition were then extruded and hot pressed, using a versatile powder bed method that enabled full densification with no need to use ad-hoc machined graphite inserts. Bars obtained from the direct ink writing process resulted in high alignment of the short fiber and displayed fracture toughness increase of 54% over that of the unreinforced matrix, while demonstrating a 42% increase with respect to conventionally hot pressed dry mixtures of ZrB2 and short fibers.This work shows the great potential of manufacturing complex shapes in ultra-high temperature ceramics matrices reinforced with short fibers for a plethora of design possibilities, including functional grading with control over layer composition, thickness and even alignment of short fiber.

Lattice concrete: 3D printed periodic cellular structures through selective cement hydration

3D printing of concrete allows fabrication of complex shapes and structures. Among various 3D printing approaches, the particle bed 3D printing technique has gained attention in recent years, especially for its ability to generate complex topologies that are otherwise impossible to make using cement-paste extrusion-based techniques. In this work, we present our trials on 3D printing cellular lattice concrete structures using a powder bed technique by employing selective cement hydration. Specifically, we print two-types of cellular concrete blocks (i) with interconnected spherical voids and (ii) with gyroid structures, each block with uniform edge lengths of 15 cm. We use Ordinary Portland Cement, fine-grained sand, and normal water, without the use of any admixtures or additives. The printing technology used was custom-made and is quite simple and inexpensive involving a syringe based water jetting on to a powder bed of cement and sand mixture. We discuss the quality of the printed specimens obtained as well as their strength characteristics. An inadvertent observation was made, where a compressive strength gain by a factor of more than 2 was obtained in specimens that were exposed to open atmosphere for a long duration after a 28 day curing period compared to those that were tested immediately after curing. The current study demonstrates the feasibility of fabricating cellular lattice concrete structures that can potentially be useful as programmable metamaterials for civil engineering applications.

Experimental Study of a 3D Printing Strategy for Polymer-Based Parts for Drone Equipment Using Bladeless Technology.

The present study focuses on an up-to-date topic regarding flying equipment identified within the category of drones that use, for propulsion and air movements, the power generated by electric motors. In this paper, researchers focus on implementing bladeless technology to calculate, develop, and construct flying equipment known in the literature as drones. The entire structure of the prototype, all the needed parts, is to be obtained using additive manufacturing technologies, which assumes practical realization using 3D-printing equipment. Nowadays, the 3D-printing process has been proven to be a reliable solution when it comes to manufacturing complex shape parts in quite a short time and with reduced costs. The practical study within the present research aims to obtain polymer-based, lightweight parts with complex shapes inside to be implemented in the propulsion of a drone. The complex surface geometry of the parts that this research used is influenced by the ventilation technology offered by the "Air Multiplier" technology. The entire structure of the final drone equipment, all the parts, is to be manufactured using fused filament fabrication (FFF). The main purpose of the fusion is to use the advantages offered by this technology in drones to obtain advantages such as augmented values of thrust, a more agreeable and muffled sound signature, or an increased level of safety.

Effects of cellular crossing paths on mechanical properties of 3D printed continuous fiber reinforced biocomposite honeycomb structures

3D printing continuous fiber reinforced composite (CFRC) has the advantages of manufacturing complex shapes and short production cycles. Due to the anisotropic mechanical properties of continuous fibers, the printing path of the fibers determines the properties of the printed CFRCs. In this paper, a series of novel cellular crossing paths were proposed to print continuous ramie fiber reinforced biocomposite honeycomb structures (CFHSs). The compression, bending, and tensile tests were performed to analyze the effects of cellular crossing paths on the mechanical properties of CFHSs. An assessment method was presented for analyzing the comprehensive mechanical properties of CFHSs printed by different printing paths. The results showed that the CFHSs printed by no-crossing path (Path-1), single-crossing path (Path-3), and double-crossing path (Path-4) exhibited better compression, bending, and tensile properties, respectively. In addition, the samples printed by Path-3 were the most outstanding in the assessments of comprehensive mechanical properties, the comprehensive performance assessment score was 1.5 times that of the single-crossing path (Path-2, minimum score). Thus, an appropriate cellular crossing path could be selected according to the structural load-bearing state, thereby providing higher mechanical properties.

Rapid and selective actuation of 3D-printed shape-memory composites via microwave heating

Three-dimensional (3D) printing allows the fabrication of complex shapes with high resolutions. However, the printed structures typically have fixed shapes and functions. Four-dimensional printing allows the shapes of 3D-printed structures to be transformed in response to external stimuli. Among the external stimuli, light has unique advantages for remote thermal actuation. However, light absorption in opaque structures occurs only near the sample surface; thus, actuation can be slow. Here, we propose and experimentally demonstrate the rapid and selective actuation of 3D-printed shape-memory polymer (SMP) composites using microwave heating. The SMP composite filaments are prepared using different amounts of graphite flakes. Microwave radiation can penetrate the entire printed structures and induce rapid heating. With sufficient graphite contents, the printed SMP composites are heated above their glass transition temperature within a few seconds. This leads to rapid thermal actuation of the 3D-printed SMP structures. Finally, dual-material 3D printing is demonstrated to induce selective microwave heating and control actuation motion. Our experiments and simulations indicate that microwave heating of SMP composites can be an effective method for the rapid and selective actuation of complex structures.

High gravity material extrusion system and extruded polylactic acid performance enhancement

Additive manufacturing (AM) has gained significant attention in recent years owing to its ability to quickly and easily fabricate complex shapes and geometries that are difficult or impossible to achieve with traditional manufacturing methods. This study presents the development of a high-gravity material extrusion (HG-MEX) system, which generates a high-gravity field through centrifugal acceleration. In this process, the material is dissolved by heating the nozzle and subsequently deposited on the construction platform. The primary objective of this research is to evaluate the positive effects of gravity on material extrusion (MEX), which is a key aspect of AM. To accomplish this, a combined machine comprising a MEX unit and centrifuge is constructed. This HG-MEX system is used to analyze and reflect the influence of gravity on the material extrusion. The experimental evaluations demonstrate that the application of high gravity is a promising approach to improve the shape accuracy and performance of the parts fabricated through MEX. Notably, our results confirm the feasibility of utilizing MEX under high gravity to enhance performance in AM processes.

Fabrication of 3D Printed Ceramic Part Using Photo-Polymerization Process.

Ceramics are high-strength and high-temperature resistant materials that are used in various functional parts. However, due to the high strength and brittleness properties, there are many difficulties in the fabrication of complex shapes. Therefore, there are many studies related to the fabrication of ceramic parts using 3D printing technology optimized for complex shapes. Among them, studies using photo-polymerization (PP) 3D printing technology with excellent dimensional accuracy and surface quality have received the most widespread attention. To secure the physical properties of sintered ceramic, the content and distribution of materials are important. This study suggests a novel 3D printing process based on a high-viscosity composite resin that maximizes the content of zirconia ceramics. For reliable printing, the developed 3D printers that can adjust the process environment were used. To minimize warpage and delamination, the divided micro square pattern images were irradiated in two separate intervals of 1.6 s each while maintaining the internal chamber temperature at 40 °C. This contributed to improved stability and density of the sintered structures. Ultimately, the ceramic parts with a Vickers hardness of 12.2 GPa and a relative density of over 95% were able to be fabricated based on a high-viscosity resin with 25,000 cps.

Two-phase topology optimization for metamaterials with negative Poisson’s ratio

Although recent developments in 3D printing technology have made it possible to fabricate metamaterials with characteristic mechanical properties, it is not easy to fabricate complex shapes containing cavities. In this study, a composite structure comprising two types of materials without a cavity was optimized. Moreover, a mechanical metamaterial with a negative Poisson’s ratio that can be fabricated using an additive manufacturing method was developed. First, a homogenization method that characterizes the properties of composite structures was briefly described. Then, an optimization problem to realize a negative Poisson’s ratio was formulated, and a level set-based topology optimization method was proposed to solve the abovementioned problem. Next, three-dimensional numerical examples are presented to confirm the effectiveness of the proposed method, and the deformation behaviors of the optimized designs are numerically examined. Furthermore, a sample containing the optimized design with negative Poisson’s ratio for the tensile test was fabricated using a 3D printer. We conducted some experiments to evaluate its mechanical performance.

Computationally Guided DIW Technology to Enable Robust Printing of Inks with Evolving Rheological Properties

AbstractSoft multifunctional materials allow for mechanical sensing or actuation as a response to multiple physical stimuli, while providing material stiffness that mimic soft biological tissues (≈1–10 kPa). One of the main bottlenecks in the state of the art relates to the difficulty for manufacturing complex shapes when using inks whose properties significantly change over the printing time. To overcome this issue, the implementation of a hybrid (theoretical‐experimental) framework that allows optimal printability of time‐dependent viscosity inks by using the direct ink writing technology. Although the rheological properties of the ink vary during printing time, a combination of theoretical and experimental methods provides evolving printing conditions that ensure efficient and robust printability over the process. The method removes the need of introducing additives to the ink. To enable this technology, an in‐house printer that provides flexibility to modulate the extrusion pressure over printing time is developed. The method is validated by manufacturing magnetorheological elastomers and conductive soft materials for specific bioengineering and soft electronics applications.

Special Issue: Design for Advanced Manufacturing

Abstract Design and manufacturing are intimately coupled in the conceptualization and realization of products. Engineering design is regularly a key component of innovation and successful product development, yet promising designs that are very costly or challenging to manufacture may never be realized in practice. Advancement of manufacturing technologies tends to lower barriers to realization and expands design freedom but may also introduce unique restrictions on the design space. A clear example of this connection is the maturation of additive manufacturing technologies, which has created immense design freedom for both researchers and practitioners to explore. New capabilities, such as the ability to fabricate complex shapes, tailor materials and properties, and provide complex functionalities, present a whole new paradigm and a wider range of opportunities for intricately design, highly functional, cost-effective, high-value products. However, additive manufacturing technologies also bring new types of constraints to be carefully considered in design. New design methods and tools are therefore needed to help engineers navigate both the novel design space created by advanced manufacturing and the new manufacturing constraints. This special issue aims to consolidates some of the most recent design research in support of advanced manufacturing.

Methods for biomaterials printing: A short review and perspective.

Printing technologies have opened larger windows of innovation and creativity to biomaterials engineers by providing them with the ability to fabricate complex shapes in a reasonable time, cost, and weight. However, there has always been a trouble with function adjusting in printing technologies in view of the multiplicity of materials and apparatus parameters. 3D printing, also known as additive manufacturing, revolutionized biomaterials engineering by the conversion of a digital subject into a printed object (implants, scaffolds, or diagnostics and drug delivery devices/systems).Inspired by the lessons learned from 3D printing, the concept of 4D printing (better called shape-morphing fabrication) was conceptualized and put into practice to reply on the need for responsiveness of the printed platforms to a stimulus (light, pH, temperature, voltage, humidity, etc.) in a programmable manner. Later, the next milestone in printing technology was reached by 5D printing, by which the desired objects could be printed from five axes compared to the upward one-point printing by 3D printers. 5D printers use ≈20-30% fewer materials comparatively, enabling the printing of curved surfaces. Nevertheless, all bioprinters need a bio-ink with qualified characteristics for the biomedical applications. Thus, we discussed briefly the cell viability, scaffold biomimicry, scaffold biodegradation and affordability.

Experimental Investigation of Technological Indicators and Surface Roughness of Hastelloy C-22 after Electrical Discharge Machining Using POCO Graphite Electrodes.

Modern industry is focused on looking for new and effective technologies to manufacture complex shapes from alloys based on nickel and chromium. One of the materials widely used in the chemical and aerospace industry is Hastelloy C-22. This material is difficult to machine by conventional methods, and in many cases, unconventional methods are used to manufacture it, such as electrical discharge machining (EDM). In the EDM process, the material is removed by electrical discharges between a workpiece and a tool electrode. The physical and mechanical properties of the tool electrodes have a direct impact on the process efficiency, machining accuracy, and surface roughness. Currently, there has been a significant increase in the use of graphite as a material for tool electrodes due to the low purchase cost of the raw material, good machinability, and high sublimation temperature. In this work, an experimental investigation of the influence of the grain size of the graphite tool electrode on material removal rate (MRR), tool wear rate (TWR), and surface roughness (Ra) of Hastelloy C-22 was carried out. Two POCO graphite tool electrodes with a grain size of 1 µm (AF-5) and 10 µm (S-180) were used. Based on the experimental studies, empirical models describing the influence of machining parameters on technological indicators and the condition of the surface texture were determined. The research indicates that graphite with a larger grain provides higher process efficiency with high relative wear of the tool electrode. The lowest surface roughness was obtained for graphite with a smaller grain size (AF-5). The analysis of the machining parameters proves that the discharge current and pulse duration are the main factors determining the MRR and Ra values for both AF-5 and S-180 graphite. The time interval is the dominant parameter with regard to the relative wear of the graphite electrode.

Monitoring of the powder bed quality in metal additive manufacturing using deep transfer learning

Laser Powder Bed Fusion can be used to additively manufacture complex shapes directly from metal powder. Achieving reproducible component quality requires a homogenous powder bed. In this research, a recoater-based line sensor is used to acquire images of the powder bed with 6 µm/pixel resolution under coaxial, darkfield, and diffuse lighting conditions. Strategies for the provocation of various inhomogeneities are derived and used to compile datasets comprising the classes balling, incomplete spreading, groove, ridge, spatters, protruding part, scattered powder, and homogenous. A data pipeline is designed to extract image patches ranging up to6 × 6 mm2 in size and from 6 µm/pixel to 96 µm/pixel in geometrical resolution. The resulting 45 data sets are used to train convolutional neuronal networks using the Xception architecture pretrained on ImageNet.The highest classification accuracy of 99.15 % is achieved for 6 × 6 mm2 patch size and 6 µm/px using the dark field lighting. Seven classes are classified with F1-scores between 97.85 % and 99.71 %. A gradual improvement of the geometrical resolution from 96 µm/pixel to 6 µm/pixel increases the classification performance while requiring smaller patches. This demonstrates the advantage of imaging systems with increased resolution compared to presently utilized camera systems.

3D 프린팅과 구조해석을 이용한 자동용접용 캐리지 레일 설계 및 제작

Recently, 3D printing technology has been used in various industrial production fields such as architecture, automobiles, aviation, medicine, and fashion. 3D printing technology has the advantage of reducing the initial cost of product production and reducing lead time because it can manufacture complex shapes, reduce product weight, and reduce production methods and cutting raw materials through molds. In this study, an integrated manufacturing of standard automatic welding carriage rails used in shipbuilding process that could not be supported by the existing process method using 3D printing technology was attempted. The structure was manufactured using polyamide made of nylon rather than the steel used in the existing welding carriage rails to reduce the weight of the structure and reduce economic costs. Tensile tests and three-point bending tests were performed on specimens and structures made of polyamide to examine the mechanical properties of the material. Thereafter, structural stability was evaluated through structural analysis of the load of the welding robot. Through the experimental results, it was confirmed that the existing automatic welding carriage rail can be replaced with a structure manufactured with 3D printing technology.

Application of Protein in Extrusion-Based 3D Food Printing: Current Status and Prospectus.

Extrusion-based 3D food printing is one of the most common ways to manufacture complex shapes and personalized food. A wide variety of food raw materials have been documented in the last two decades for the fabrication of personalized food for various groups of people. This review aims to highlight the most relevant and current information on the use of protein raw materials as functional 3D food printing ink. The functional properties of protein raw materials, influencing factors, and application of different types of protein in 3D food printing were also discussed. This article also clarified that the effective and reasonable utilization of protein is a vital part of the future 3D food printing ink development process. The challenges of achieving comprehensive nutrition and customization, enhancing printing precision and accuracy, and paying attention to product appearance, texture, and shelf life remain significant.

Selective laser melting of Al–Si–10Mg alloy: microstructural studies and mechanical properties assessment

Additive Manufacturing (AM) technique is widely recognized by aerospace sectors for its potential to fabricate complex shape components directly from a Computer-Aided Model data (CAM). Selective Laser Melting (SLM) is an innovative method high degree of adaptability among different AM techniques. SLM is one of the AM techniques adopted to produce the three-dimensional complex shape components. Current research work focuses on fabricating an Al–Si–10Mg aluminium alloy by SLM process which is studied for the influence of scanning speed and build orientation on the mechanical strength and surface finish of the as built component compared with as casted specimen. The importance of the sample studied for the scanning speed and built direction is relatively essential exclusively for dynamic applications. The as-built samples surface micrographs was surprisingly refined with a progressively reduced grain size diameter from 7.2 μm to 5.5 μm by increasing scanning speed compared to that of AlSi10Mg parts (∼9.1 μm). The mean layer thickness increased from 20 μm to 30 μm by decreasing the scanning speed from 500 mm/s to 200 mm/s. Attractive advantage of the Orowan mechanism, fine grain strengthening, and the graded interfacial layer, a considerably-high microhardness (135 ± 3.1HV), and enhanced mechanical properties were achieved.

Research on energy absorption of gradient porosity structural materials

Different from traditional subtractive manufacturing, additive manufacturing is a layer by layer process which is easier to manufacture complex shape. Among the commonly used metal additive manufactured materials, Ti-6Al-4 V (Ti64) exhibits the characteristics such as low density, good mechanical properties, and lightweight. According to the characteristics mentioned above, Ti64 is a good candidate for structural materials. In this study, porous structures/bionic structures were introduced to evaluate the capacity of energy absorption, namely orthogonal, as shown in. Meanwhile, the porous Ti64 materials were designed with gradient porosity from 50 % to 90 %. All the samples were manufactured using selective laser melting (SLM) technology and tested by compression testing. Through compression testing, the energy absorption capacity of these gradient porosity materials with different porous structures and changes in porosity can be evaluated according to the yield stress, strain at failure, and Young's modulus, meanwhile, toughness and specific energy absorption can also be calculated. The porous structures and changes in porosity induced energy absorption variations are discussed in detail in this study.