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11th China Academic Conference on printing and Packaging, CACPP 2020

作者： Chen, Chen Wang, Lei Wang, Xiaochun Xiong, Taotao Chen, Guangxue State Key Laboratory of Pulp and Paper Engineering South China University of Technology Guangzhou China YUTO R&D Institute Shenzhen YUTO Packaging Technology Co. Ltd Shenzhen China School of Artificial Intelligence Shenzhen Polytechnic Shenzhen China School of Art and Design Shenzhen Polytechnic Shenzhen China

ISBN: (纸本)9789811605024

powder-based 3dP was the first technique to print full color 3d objects with continuous tone. However, limited by the size of the printing platform, large 3d objects can hardly be printed efficiently which has affected the spread of this technology. In consideration of the above issues, this paper discussed the relationship between printing time and model height, and a algorithm for optimizing printing time was presented. Ten typical models had been printed to verify the effectiveness of XYX rotation method. The results showed that the maximum time reduction is 65.7% less than the modeling time before optimizing. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Cutting-bonding frame Large-size 3d printing powder-based 3d printing printing time

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Printability, accuracy and strength of geopolymer made using powder-based 3d printing for construction applications

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AUTOMATION IN CONSTRUCTION 2019年 101卷 179-189页

作者： Xia, Ming Nematollahi, Behzad Sanjayan, Jay Swinburne Univ Technol Fac Sci Engn & Technol Ctr Sustainable Infrastruct Hawthorn Vic Australia

The authors of this study have recently succeeded to develop geopolymer materials using slag only formulations for the requirements and demands of commercially available powder-based 3d printers. In this study, the formulation is extended to fly ash and slag combinations so that to expand the scope of geopolymer materials that can be used in the commercially available powder-based 3d printers for construction applications. The quantitative influence of fly ash content on the printability characteristics (i.e., depositability and wettability) of the geopolymer powder, as well as the linear dimensional accuracy and compressive strength of the printed specimens were investigated. The effect of type of alkaline solution used for post-processing on the linear dimensional accuracy and compressive strength of the post-processed specimens were also evaluated. The results indicated that the increase in fly ash content had no effect on the powder depositability, but adversely affected the powder wettability, linear dimensional accuracy and compressive strength of the printed specimens. The minimum slag content required to prepare fly ash/slag blended geopolymer powder for powder-based 3d concrete printing process is 50 wt%. The post-processing significantly increased the compressive strength. The post-processed specimens printed with 50 wt% slag/50 wt% fly ash powder exhibited a 7-day compressive strength of up to 25 MPa, which is sufficiently high for many construction applications.

关键词： Geopolymer Fly ash Construction powder-based 3d printing Compressive strength Additive manufacturing dimensional accuracy Post-processing

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powder-based 3d printed magnesium phosphate cement: Mechanical isotropy optimization using borax

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CONSTRUCTION ANd BUILdING MATERIALS 2024年 432卷

作者： Liu, Xiongfei Zhao, Xi Wang, Nan Zhang, Yi dai, Ziheng Hebei Univ Technol Sch Civil & Transportat Engn 5340 Xiping Rd Tianjin 300401 Peoples R China

Mechanical isotropy is essential for improving the integrity and application of 3d printed structures. In this paper, based on the high bonding, fast-hardening, and early strengthening characteristics of magnesium phosphate cement (MPC), the exothermic rate of MPC hydration reaction is optimized by controlling the content of borax (0.5%-3%) to improve the adhesive integrity for the interlayer interface of powder-based 3d printed MPC. In addition, the physical phase components, microscopic morphology, degree of hydration, and pore structure of borax-modified powder-based 3d printed MPC are analyzed by using various microscopic characterization methods of XRd, SEM, thermal analysis, and X-CT. Experimental findings demonstrate that borax, through its influence on the hydration environment and encapsulation of the hydration film, reduces the exothermic rate of the MPC reaction, thereby enhancing the structural integrity with improved mechanical isotropy. Printed MPC specimens with 2% borax content reach compressive strengths of 10.45-11.39 MPa at 28d in the X/Y/Z directions, with an optimum mechanical isotropy index of 3.6%. Furthermore, microscopic analysis reveals that the 2% borax-modified MPC displays a denser morphology, with the main hydration product struvite enhanced by 8.53% compared to the 0% specimen. The interlayer interfaces of the printed MPC demonstrate exceptional qualities, being small and homogeneous, with 4.20% less total porosity than the unmodified group.

关键词： powder-based 3d printing Magnesium phosphate cement Mechanical isotropy Borax

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Binder jetting 3d printing rock analogs using magnesium phosphate cement

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CONSTRUCTION ANd BUILdING MATERIALS 2024年 420卷

作者： Ma, Guowei Hu, Tingyu Li, Zhijian Hebei Univ Technol Sch Civil & Transportat Engn Tianjin 300401 Peoples R China

Fractures in rocks have significant effects on the stability of rock mass structures. Physical model testing is an effective approach for investigating the failure mechanisms of fractured rocks. In this paper, a new binder jetting (BJ) 3d printing technology using magnesium phosphate cement (MPC) is proposed to fabricate rock models with isotropic and brittle matrices and complex fractures. A self-developed BJ 3d printer is used to perform the printing and investigate the effects of different layer thicknesses, molar ratios of magnesium oxide to phosphate (M/P), and borax retarder contents on dimensional accuracy, mechanical anisotropy, and brittleness. The test results show that the layer thickness and M/P exert significant influences on the dimensional accuracy and mechanical anisotropy by regulating the binder's diffusion and penetration into the powders. The degree of hydration, and thus the brittleness of the specimens, is also influenced by different M/P values. The borax retarder prolongs the setting time, and thus provides a longer hydration time, resulting in better interlayer bonding and lower mechanical anisotropy. The optimized specimens exhibit a much lower anisotropy index in compressive strength compared to that of the counterpart commercial sand and gypsum BJ printed specimens, and the high brittleness index of the 3d printed specimens indicates it can achieve the rating of brittle rocks. The crack initiation angles and failure patterns of printed specimens with single and double fractures are consistent with those of practical rock specimens, which demonstrates that the proposed BJ 3d printing method using MPC is promising for reproducing highly accurate rock-like models with complex fractures.

关键词： Binder jetting 3d printing powder-based 3d printing Magnesium phosphate cement 3d printed fractured rock Mechanical anisotropy

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Topology optimization based channel design for powder-bed additive manufacturing

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AddITIVE MANUFACTURING 2022年 54卷

作者： Wang, Weiming Xia, Yi Dalian Univ Technol Sch Math Sci Key Lab Computat Math & Data Intelligence Liaoning Dalian 116024 Peoples R China Chongqing Univ Key Lab New Technol Construct Cities Mt Area Minist Educ Chongqing 400045 Peoples R China Chongqing Univ Sch Civil Engn Chongqing 400045 Peoples R China

Additive manufacturing (AM) technology allows us to manufacture 3d models with arbitrarily complex shapes. Among different AM technologies, powder-based 3d printing techniques, such as laser-based powder bed fusion of metals and polymers (PBF-LB/M and PBF-LB/P), are common tools favored by engineers and have been widely used in the industrial field. In order to reduce the cost of printing materials, a large variety of lightweight infill structures have been proposed, such as skin-frame structures, lattice structures, honeycomb structures and porous structures. Currently, most of the proposed methods lead to a large number of closed voids in the printed models. These closed voids are particularly detrimental to structures printed using powder-based 3d printing techniques. A large amount of powder remains in the closed voids and cannot be discharged, which will reduce the performance of the printed structure. This problem limits the application of powder-based 3d printing techniques for printing complex structures. To the best of our knowledge, very few investigations have been conducted to address this problem. In this paper, a method based on topology optimization (TO) is proposed to automatically generate channels between closed voids and outlets, by which the remaining powder of the powder-based printing structures can be discharged. The proposed method consists of three main steps: 1) topology optimization, 2) topology extraction, 3) channel generation. Six standard structures with a large number of closed voids are investigated to demonstrate the applicability of the proposed method. In addition, experimental tests are conducted to validate the effectiveness of the generated channels.

关键词： Additive manufacturing powder-based 3d printing Channel design Topology optimization Topology extraction Light-weight structure

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The printability of three water based polymeric binders and their effects on the properties of 3d printed hydroxyapatite bone scaffold

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CERAMICS INTERNATIONAL 2020年第5期46卷 6663-6671页

作者： Chai, Weihong Wei, Qinghua Yang, Mingming Ji, Kang Guo, Yuhong Wei, Shengmin Wang, Yanen Northwestern Polytech Univ Sch Mech Engn Xian 710072 Peoples R China Northwestern Polytech Univ Inst Med Res Xian 710072 Peoples R China

As the basic material of 3d printing, the binder is the key factor to a successful 3d printing process as it determines the property and structure of the printed bone scaffolds, as well as the reliability of the entire printing system. In this study, three commonly used polymeric binders (PVA, PVP and PAM) were applied to fabricate HA embryonic scaffolds by powder-based 3d printing technology. The suitable printing concentrations of three binders were screened by investigating their printability and drop penetration. Following, based on the printable binders, different scaffold samples were fabricated and characterized. And the effects of different binders on the properties of scaffolds were investigated in terms of mechanical properties and cell attachment. Results show that the binder of 1.0 wt% PVA and its scaffolds possess the best the printing resolution, solidification ability and compressive strength, while the binder of 1.5 wt% PVP and its scaffolds possess the shortest penetration time and the largest compressive modulus. Additionally, the cell culture experimental results demonstrate that the scaffolds printed with 1.0 wt% PVA process the best cytocompatibility and are most conducive to cell attachment among three binders. Therefore, comprehensive considering the current results of three binders we conclude that among three binders the binder of 1.0 wt% PVA is most suitable for fabricating HA bone scaffolds by 3d printing technology.

关键词： Polymeric binders Hydroxyapatite powder-based 3d printing Printability

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Post-processing Methods to Improve Strength of Particle-Bed 3d Printed Geopolymer for digital Construction Applications

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FRONTIERS IN MATERIALS 2019年 6卷

作者： Nematollahi, Behzad Xia, Ming Sanjayan, Jay Swinburne Univ Technol Fac Sci Engn & Technol Ctr Smart Infrastruct & Digital Construct Hawthorn Vic Australia

The strength of powder-based 3d printed geopolymer samples immediately after the de-powdering process ("green" strength) is inherently very low. Therefore, different post-processing techniques have been explored in the previous study of the authors to enhance the "green" strength of the printed geopolymer. The highest strength of around 30 MPa was achieved for the printed slag-based geopolymer sample cured in an alkaline solution for 7 days at 60 degrees C. Although this strength is sufficient for a wide range of construction applications, the necessity for the heat curing procedure, which requires a significant amount of energy, can compromise the sustainability credentials of the developed powder-based 3d printed geopolymer and limit its commercial viability and large-scale applications in the construction industry. To tackle this issue, this study aims to develop a new post-processing method which eliminates the necessity for the heat curing. The influences of type of curing medium, duration and temperature of curing, and testing direction on the compressive strength of the printed geopolymer were investigated. The "green" printed geopolymer samples were immersed in four different curing mediums, including two sodium (Na)-based, and two potassium (K)-based activators with different alkali modulus (SiO2/M2O where M = Na or K), and cured at two different curing temperatures (ambient temperature (23 degrees C) vs. 60 degrees C) for 7 and 28 days. The compressive strength of the "post-processed" printed geopolymer specimens was measured in two different testing directions, namely the binder jetting direction and layer stacking direction. The results showed that the 28-day compressive strength of the ambient temperature cured printed geopolymer sample was comparable to the 7-day compressive strength of the corresponding heat cured sample. Therefore, the feasibility of enhancing the strength of printed geopolymer by curing in an alkaline solution at ambient temperature

关键词： geopolymer 3d concrete printing digital construction post-processing powder-based 3d printing

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Method of formulating geopolymer for 3d printing for construction applications

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MATERIALS & dESIGN 2016年 110卷 382-390页

作者： Xia, Ming Sanjayan, Jay Swinburne Univ Technol Dept Civil & Construct Engn Ctr Sustainable Infrastruct Fac Sci Engn & Technol Hawthorn Vic 3122 Australia

An innovative methodology is presented for formulating geopolymer-based material for the requirements and demands of commercially available powder-based 3d printers. different key powder parameters such as particle size distribution, powder bed surface quality, powder true/bulk densities, powder bed porosity, and binder droplet penetration behavior were used to quantitatively evaluate the printability of prepared geopolymer-based material. Results indicated the prepared geopolymer-based material achieved sufficient printability to be used in a powder-based 3d printer. 3d printed specimens from the geopolymer were assessed for printing accuracy, apparent porosity and mechanical property. All printed cubic specimens exhibited an anisotropic phenomenon in dimensional accuracies and mechanical properties. Before further post-processing, the printed cubic structure gained compressive strength of up to 0.9 MPa with an acceptable low dimensional expansion of <4%. Post processing by immersion in saturated anhydrous sodium metasilicate solution at 60 degrees C gained compressive strength of up to 16.5 MPa. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Additive manufacturing powder-based 3d printing Construction Geopolymer

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Compressive Assemblies: Bottom-Up Performance for a New Form of Construction

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ARCHITECTURAL dESIGN 2017年第4期87卷 104-109页

作者： Block, Philippe Rippmann, Matthias Van Mele, Tom ETH Inst Technol Architecture Zurich Switzerland ETH BRG Zurich Switzerland Swiss Natl Ctr Competence Res NCCR Digital Fabric Zurich Switzerland ETH NCCR Digital Fabricat Zurich Switzerland Behnisch Architekten Stuttgart Germany LAVA Stuttgart Germany Inst Lightweight Struct & Conceptual Design Stuttgart Germany Werner Sobek Engineers Stuttgart Germany

From Inuit igloos to Roman arches to Gothic cathedrals, builders have long used friction and balance to make structures hold together. The Block Research Group at ETH Zurich is involved in ongoing research that investigates historical techniques and fuses them with the latest technologies, including robotics and 3d printing, to establish new methods of architectural assembly. Group founder Philippe Block, co-director Tom Van Mele and team member Matthias Rippmann explain.

关键词： Roman arch Block Research Group Institute of Technology in Architecture ETH Zurich Armadillo Vault "Beyond Bending' exhibition Ochsendorf deJong & Block Engineering The Escobedo Group Venice Architecture Biennale discrete structural systems igloo Gothic builders Autonomous Systems and Robotic Systems Labs Sports Palace in Tbilisi Georgia "pre-cracking' Robert Maillart Salginatobel Bridge Schiers Switzerland Pantheon Rome microcracks unreinforced concrete funicular floor powder-based 3d printing self-supporting stay-in-place formworks "masonry model'

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