3D Printing and Additive Manufacturing最新文献

Wire and arc additive manufacturing (WAAM) is becoming a promising technique due to its high deposition rate and low cost. However, WAAM faces challenges of coarse grains. In this study, a novel in situ vibration method was proposed to suppress these imperfections of WAAM. Temperature and vibration distributions were explored first, and the optimized parameters were utilized for manufacturing low-carbon steel parts. The results revealed that after the vibration, the average grain size in fine grain zone was reduced from 9.8 to 7.1 μm, and that in coarse grain zone was declined from 10.6 to 7.4 μm, respectively. No large deformation occurred due to the low temperature. Grain refining was attributed to more dendrite fragments induced by excessive stress at the roots of dendrites. The refined grains enhanced mechanical strength of the parts in both X and Z directions and improved the average hardness. After the vibration, the ultimate tensile strength and yield strength were increased to 522.5 and 395 MPa, which represented an increase of 10% and 13.8%, respectively. The average hardness was improved to 163 HV, which was an increase of 10.1%.

Copper (Cu) nanoparticles are considered a promising alternative to silver (Ag) and gold (Au) for printed electronics applications. Because Cu has higher electrical conductivity, it is significantly cheaper than Ag and Au. To study the applicability of electronic printing, we prepared Ag@Cu conductive ink by using a stepwise feeding method to disperse nano Ag and nano Cu in ethanol and water. The ink has the advantages of nontoxic, low content, and low cost. A three-dimensional (3D) model was designed, and a conductive pattern was printed on the photo paper substrate using extrusion 3D printing technology. The influence of waterborne resin on the adhesion of conductive patterns is discussed. The printed conductive pattern can maintain the stability of conductivity after 100 bending cycles. The conductive pattern has good thermal stability. It can be tested 10 times under 2 conditions of 85°C and room temperature to maintain good conductivity. This shows that Ag@Cu conductive ink printed flexible electronic products are competitive.

Do extrusion temperature, printing speed, and layer time affect mechanical performance of interlayer bonds in material extrusion additive manufacturing (MEAM)? The question is one of the main challenges in 3D printing of polymers. This article aims to analyze the independent effect of printing parameters on interlayer bonding in MEAM. In previous research, printing parameters were unavoidably interrelated, such as printing speed and layer cooling time. Here, original specimen designs allow the effects to be studied independently for the first time to provide new understanding of the effects of a wide range of thermal factors on mechanical properties of 3D-printed polylactide. The experimental approach used direct GCode design to manufacture specially designed single-filament-thick specimens for tensile testing to measure mechanical and thermal properties normal to the interface between layers. In total, five different extrusion temperatures (a range of 60°C), five different printing speeds (a 16-fold change in the magnitude) and four different layer times (an 8-fold change) were independently studied. The results demonstrate interlayer bond strength to be equivalent to that of the bulk material within experimental scatter. This study provides strong evidence about the crucial role of microscale geometry for apparent interlayer bond strength relative to the role of thermal factors. By designing specimens specifically for the MEAM process, this study clearly demonstrates that bulk-material strength can be achieved for interlayer bonds in MEAM even when printing parameters change severalfold. Widespread industrial and academic efforts to improve interlayer bonding should be refocused to study extrusion geometry-the primary cause of anisotropy in MEAM.

In the production of geometries that traditional methods cannot produce, it is seen that additive manufacturing (AM) technology, which has come to the fore, has been used extensively in conformal cooling channel (CCC) applications in recent years. This study, conducted within the scope of CCC's use of applied mold cores in automotive industry plastic part production, aimed to reduce the cycle time in the injection printing process. The v1 geometry, which gives the analysis results for ideal printing quality from the channel geometries developed with three different design approaches, is produced with direct metal laser sintering, which is an AM laser sintering technology, and the injection printing cycle time has been reduced by 38%. CCC applied the study's primary motivation to develop duct geometry to provide balanced cooling in the automotive industry's mold cores produced with AM. It is known that the Computer Numerical Control machining process in traditional mold methods does not allow the processing of the channels in the internal geometries, and the deep areas where the heat is concentrated cannot be cooled sufficiently. In the study, CCC geometries where AM design parameters are used effectively and the balanced cooling performance expected from the die core can be achieved. The effects of different geometries on production are discussed.

We present a generative approach for creating three-dimensional lattice structures optimized for mass and deflection composed of thousands of one-dimensional strut primitives. Our approach draws inspiration from topology optimization principles. The proposed method iteratively determines unnecessary lattice struts through stress analysis, erodes those struts, and then randomly generates new struts across the entire structure. The objects resulting from this distributed optimization technique demonstrate high strength-to-weight ratios that are at par with state-of-the-art topology optimization approaches, but are qualitatively very different. We use a dynamics simulator that allows optimization of structures subject to dynamic load cases, such as vibrating structures and robotic components. Because optimization is performed simultaneously with simulation, the process scales efficiently on massively parallel graphics processing units. The intricate nature of the output lattices contributes to a new class of objects intended specifically for additive manufacturing. Our work contributes a highly parallel simulation method and simultaneous algorithm for analyzing and optimizing lattices with thousands of struts. In this study, we validate multiple versions of our algorithm across sample load cases, to show its potential for creating high-resolution objects with implicit optimized microstructural patterns.

Powder-based (inkjet) three-dimensional printing (3DP) technology presents great promise in the construction industry. The capacity to build complex geometries is one of the most appealing features of the process without formwork. This article focuses on the vital aspect of using a modified powder (CP) instead of commercial powder (ZP 151). It also discusses the effects of the size of specimens and the curing process of 3DP specimens. This article presents not only the improved mechanical properties of the mortar that are revealed through a heat-curing procedure but also the properties of the reinforced mortar with chopped glass fibers. Experiments are conducted on cubic printed mortar specimens and cured in an oven at different temperature regimes. Tests show that 80°C is the optimum heat-curing temperature to attain the highest compressive and flexural strength of the specimens. The orientation angle has a significant effect on the mechanical behavior of printed specimens. Therefore, specimens are prepared by printing at different orientation angles to compare the mechanical properties of common construction materials. Powder-based 3DP has three planes (XY, XZ, and YZ) along which a load can be applied to the specimen. The mechanical strength in each direction across each plane is different, making it an anisotropic material. For CP specimens, the highest compressive strength was obtained using a 0° rotation in the printing orientation of the XY plane. For shear strength, a 45° orientation gave the optimum result, while for tensile and flexural strength, a 0° orientation provided the highest values. The optimum strength for ZP 151 specimens in compression, shear, tension, and bending was obtained by printing with orientation angles of 0°, 30°, 0°, and 0°, respectively. Finally, laser scanning of the printed specimens has been conducted so the surface roughness profiles for the 3DP specimens of ZP 151 and CP can be compared and presented.

In this article, four new semi-auxetic structures are designed by changing the way of interface connection and adding external frames. These structures were fabricated by fused deposition modeling, which is an additive manufacturing technology. The effects of interface design and external frame on deformation mode and energy absorption performance of semi-auxetic structure under quasi-static compression are studied. It was found that the deformation modes of framed and frameless structures are different. The specific energy absorption of the semi-auxetic structure is increased by ∼52% compared with the frameless hexagonal honeycomb structure. In addition, Abaqus was used to establish finite element models of the four new semi-auxetic structures and the frameless hexagonal honeycomb structure. It can be found that the simulation results were consistent with the experimental results.

The injection molding process is only economical with large batch sizes due to expensive tools that cannot be used variably. Additively manufactured tools made of plastic could reduce manufacturing costs and represent an alternative to conventionally manufactured tools for prototype applications as well as enabling small series with the injection molding process. The aim of this article was to examine additively manufactured injection molding tools; to determine their potential in terms of service life, surface quality, and production time; and to link them with the production costs so that the profitability can be assessed. Therefore, a reference component and an injection mold have been designed. To test the capabilities of different 3D printing techniques and materials, three molds have been produced by fused filament fabrication (FFF), one by PolyJet process, one by digital light processing, and for a direct comparison to conventional methods, one mold has been milled from aluminum. All molds have been tested in two series. First, they were used under the same conditions over a period of 100 injection molding cycles. Based on the knowledge obtained and an additional profitability analysis, three forms could be identified as promising. Two of these forms could be further investigated in a second series of tests. Based on all experiments, the technical feasibility of additively manufactured injection molds for small batch production could be confirmed. It could be evaluated that each manufacturing process and every material has some advantages and disadvantages. On the one hand, temperature-resistant thermoplastics can be processed with FFF, which can withstand service lives of more than 150 cycles without any signs of wear and are therefore suitable for small series. On the other hand, the PolyJet process achieves good surface qualities and short production times, which means that it can be used for prototype applications.

This study addresses the influence of build orientation and loading direction on the static and dynamic mechanical properties of three-dimensional-printed thermoplastic polyurethane-based lattice structures (with different cell shape). Specimens were printed in horizontal, 45° angle, and vertical orientations. Three-point bending tests showed that the investigated specimens are characterized by a strong anisotropy of the mechanical properties, which depends on the loading direction. In this regard, the influence of the loading direction is much stronger for the specimens printed vertically or at an angle of 45°, whereas the properties of the lattice structures printed horizontally are almost isotropic. The best set of mechanical properties (regardless of the loading direction) is shown by the samples of lattice materials, with square cells obtained by horizontal orientation of the polymer layers. The possibility of significant (one order of magnitude) increase in strength properties with satisfactory ductility is shown by using an epoxy polymer as a filler. A mathematical model of the bending of a mesostructured beam was established, which made it possible to describe qualitatively the various mechanisms of its destruction, such as: the breaking of the bonds between the polymer layers due to their mutual sliding and flaking, and the rapture of the layers themselves. The findings presented here provide new insights into the development of lattice structures with unique mechanical properties for a wide range of applications.

Additive manufacturing-oriented topology optimization features in the extreme geometric complexity that magnifies the product functional performance. However, the increased geometric complexity makes postprocessing of the designs technically nontrivial and sometimes inefficient because of too many structural details. To address this issue, this article presents a novel printing-ready topology optimization method whereby the topological designs can be directly exported in the format of a printing-ready G-code, which saves the postprocessing efforts of stereo lithograph (STL) model generation, model slicing, and tool path planning. More importantly, the slicing and tool path information can be tracked all the time during optimization to facilitate the evaluation of the tool path-related material constitutive model, for example, the fiber-reinforced composites, so as to improve the numerical analysis accuracy and the design result optimality. Finally, three case studies are performed to test the postprocessing efficiency of the printing-ready approach and the multi-scale design case, which demonstrates the outstanding high efficiency characteristic of the proposed approach.