Additive manufacturing letters最新文献

Effect of raster orientation on large-scale robotic 3D printing of short carbon fiber-reinforced PLA composites

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-18 DOI: 10.1016/j.addlet.2025.100276

E. Baharlou , J. Ma

Additive manufacturing in building construction can be extended for mass customization of building components or even complex mold making. This study examines the process parameters of raster orientation of short carbon fiber-reinforced polylactic acid (SCF-PLA) and neat PLA in large-scale 3D printing. Three raster orientations—unidirectional, cross-ply, and quasi-isotropic layups—were printed using a pellet extruder assembled on an industrial robotic arm. Tensile and flexural tests were conducted to characterize the differences between SCF-PLA and neat PLA across all raster orientations. This study shows that neat PLA has higher tensile strength compared to SCF-PLA, and quasi-isotropic orientation can improve the week mechanical properties of both SCF-PLA and PLA. This research highlights the interface bonding challenges encountered with larger 3D printed filaments, which result in more significant pores. Furthermore, any factor that modifies rheological properties of the filament, such as carbon filling, can lead to a higher likelihood of material defects. To understand this discrepancy, microstructure analyses were conducted on intact and fractured 3D printed samples, including the analysis of micro voids, interlayer voids, and bonding between SCF and the PLA matrix. This suggests that the effects of quasi-isotropic layups can be applied to enhance 3D print large-scale polymer-based building components.

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引用次数: 0

Process screening in additive manufacturing: Detection of keyhole mode using surface topography and machine learning

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-17 DOI: 10.1016/j.addlet.2025.100275

Mingzhang Yang, Ali Rezaei, Mihaela Vlasea

Screening of defective additive manufactured (AM) parts is crucial for ensuring process consistency and part reliability, yet common microstructural inspection methods can be time-consuming or destructive. This study explores how surface analysis combined with machine learning (ML) algorithms can effectively infer the microstructure of laser powder bed fusion (LPBF) parts. As a case study, non-spherical ZrH₂ nanoparticle-enhanced AA7075 aluminum powders was fabricated using 60 different LPBF recipes. ML classification models were then employed to link side-surface topographical features to keyhole melting occurring within the parts. Among the tested ML models, random forest (RF) achieving a testing accuracy of 95 % and an F1-score of 0.98, outperforming both the neural network (NN) and support vector machine (SVM) models. To enhance the interpretability of the ML model, the RF model was leveraged to identify the hierarchical importance of surface features associated with keyhole melting mode. This resulted in the development of keyhole-probability maps based on superficial surface parameters, providing engineers with an effective and easy-to-use tool for screening keyhole mode parts. While further validation is needed, the proposed strategy lays a foundation for leveraging surface topography to infer microstructural features and adapting the method to different material systems.

筛查有缺陷的增材制造（AM）零件对于确保工艺一致性和零件可靠性至关重要，但常见的微观结构检测方法可能会耗费大量时间或具有破坏性。本研究探讨了表面分析与机器学习（ML）算法相结合如何有效地推断激光粉末床熔融（LPBF）零件的微观结构。作为案例研究，使用 60 种不同的 LPBF 配方制造了非球形 ZrH₂ 纳米粒子增强 AA7075 铝粉。然后采用 ML 分类模型将侧面表面地形特征与零件内部发生的锁孔熔化联系起来。在测试的 ML 模型中，随机森林（RF）的测试准确率达到 95%，F1 分数为 0.98，优于神经网络（NN）和支持向量机（SVM）模型。为了提高 ML 模型的可解释性，利用 RF 模型识别了与钥匙孔熔化模式相关的表面特征的层次重要性。这样就开发出了基于表面参数的锁孔概率图，为工程师筛选锁孔模式零件提供了有效且易于使用的工具。虽然还需要进一步验证，但所提出的策略为利用表面形貌推断微观结构特征以及将该方法适用于不同材料系统奠定了基础。

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引用次数: 0

Influence of the laser strategy on bi-metallic interfaces printed via multi-material laser-based powder bed fusion

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-10 DOI: 10.1016/j.addlet.2025.100274

Isabel B. Prestes, Eric A. Jägle

Metallic Multi-material Additive Manufacturing (MMAM) is an emerging research topic, with potential applications in heat exchangers, metamaterials and satellite components. In recent years, new multi-material laser powder bed fusion (PBF-LB) techniques have been developed. However, processing challenges may arise, since materials with dissimilar properties are mixed at the interfaces, which might lead to defects such as cracks. This work aims to investigate the influence of different laser scan strategies to achieve sound interfaces with different material mixing gradients. The samples, made of Inconel 718 and Invar were deposited by the patterning drums technique and were analyzed by means of optical microscopy and energy-dispersive X-ray spectroscopy (EDS) mappings and line scans. The orientation in which melt pools cross the material interface plays an important role in mixing the materials. Different orientations in subsequent layers create a certain “jagged” pattern of mixing at the interface. Sigmoid functions of Boltzmann fitted to the line scans show a significant slope steepness increase – up to 75 % – in the element count from double scan to single scan, suggesting a stronger material mixing. The double scan strategy leads to porosity at the interface and thus should be avoided. The remelt at the interface partially healed defects such as cracks but does not seem to influence the mixing width at the interface. These findings give general guidance for selecting scan strategies in MMAM depending on the desired mixing pattern at the material interface.

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引用次数: 0

Impact of a typical scanner delay processing parameter on local microstructure in metallic laser-based powder bed fusion

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-09 DOI: 10.1016/j.addlet.2025.100273

Brenda Leticia Valadez Mesta , Pascal Thome , Marcus C. Lam , Sammy Tin , Jorge Mireles , Ryan B. Wicker

In laser-based powder bed fusion of metals (PBF-LB/M), variations in laser scanner movements, particularly lesser-studied parameters like scanner delays that control laser directional changes, can influence the microstructure in a part during fabrication as each of typically millions of individual laser vectors impact part thermal history and resulting microstructure. While the impact of commonly researched parameters such as laser power, scan speed, hatch spacing, and layer thickness on part microstructure have been well studied, considerably less attention has been given to scanner delays such as the polygon delay. This study uses electron backscatter diffraction to investigate the microstructural variations caused by polygon delay values ranging from 0 to 450 microseconds, beginning with individual scan tracks. The study then extends single tracks to a simple three-dimensional part to examine if microstructure differences due to polygon delays may be influenced by localized heating and cooling caused by nearby hatch vectors and successive layers. The results reveal that varying polygon delay clearly affects grain morphology during individual scan tracks, although these effects are less clear during a three-dimensional build. Future PBF-LB/M studies should focus more on understanding time-resolved laser beam processing effects to better reduce inconsistencies and improve part quality.

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引用次数: 0

Comparative analysis of machining and electropolishing for surface quality improvement of shape memory nitinol samples additively manufactured by laser powder bed fusion

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100261

Rodrigo Zapata Martínez , Shohom Bose-Bandyopadhyay , Alan Burl , Óscar Contreras-Almengor , Carlos Aguilar Vega , Kyle Saleeby , Thomas Kurfess , Andrés Díaz Lantada , Jon Molina-Aldareguia

Nickel-titanium (NiTi) or nitinol alloys exhibit high corrosion resistance, mechanical strength, biocompatibility, and smart properties, rendering them ideal materials for active biomedical devices. Traditional manufacturing techniques struggle with these alloys, prompting the adoption of Laser Powder Bed Fusion (L-PBF) as a viable alternative for producing geometrically challenging features. However, L-PBF inherently introduces geometric inconsistencies and surface defects, necessitating post-processing. Electropolishing and chemical etching, while effective for surface smoothing, result in non-conformal material removal, potentially altering the designed geometry. This study examines the use of machining as a post-processing method to achieve uniform material removal and maintain geometric fidelity. Planar spring-shaped actuators were fabricated via L-PBF and subsequently machined to their final geometry using a Computer Numerical Controlled (CNC) system. The actuators were assessed for geometric accuracy and shape memory properties. Machining of the actuators lead to a near homogeneous thickness of 300 µm in all cases, whereas the electropolished + chemically etched samples varied dramatically from <50 µm to over 400 µm in thickness. The findings demonstrate that CNC machining effectively enhances the geometric precision of L-PBF-manufactured NiTi components, while preserving shape memory characteristics. This research underscores the potential of integrating L-PBF with CNC machining to improve the precision and functionality of NiTi-based biomedical devices.

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引用次数: 0

Resin-dependent mechanical anisotropy in laser vat photopolymerization correlates to the initial rate of polymerization and critical energy

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100264

Dagoberto Torres-Alvarez, Angel Celis-Guzman, Alan Aguirre-Soto

The degree of mechanical anisotropy in objects printed with laser vat photopolymerization (VPP) remains controversial. It has been stated that objects with a higher degree of mechanical isotropy are produced with VPP as compared to other polymer-based additive manufacturing techniques, such as fused filament fabrication (FFF). However, reports on the evaluation of resin-dependency of the mechanical anisotropy obtained with VPP are scarce. Furthermore, the degree of anisotropy (DA) was quantified using different procedures. Here, six commercial resins were selected to evaluate how the DA correlates to the initial rate of polymerization (R_P0), critical energy (E_C), and penetration depth (D_P) for materials with a broader range of properties. State-of-the-art procedures to calculate the degree of mechanical anisotropy are discussed, and an ideal method is proposed, namely, the ratio of the standard deviations related to the inter- and intra-layer forces: DA=(sd_inter/sd_intra). The elastic modulus (E) was confirmed isotropic with the three resins that were previously reported. However, objects printed with the additional resins that polymerize at higher initial rates (R_P0 =72.1 mM/s) and with lower critical energies (E_C = 0.36 mJ/cm²) appear more anisotropic. A linear trend was obtained for the scaling of the mechanical DA with R_P0. Moreover, a logarithmic correlation between E_C and the DA in E was found, which appears inappropriate for E_C as a function of the DA in the maximum stress (σ_Max). This study aims to spur research on the mechanisms underlying the dependence of the mechanical DA on the resin-curing behavior for objects fabricated by VPP.

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引用次数: 0

Micro-X-ray-CT for analysis of particle size segregation during powder spreading in Binder Jet Printing

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100266

Julia G. Behnsen , Joseph W. Roberts , Oliver J. Rogan , James M. McArdle , Kate Black

The uniformity of the powder bed in Binder Jet Printing can impact the final properties of additively manufactured components. Granular flow phenomena, such as particle size segregation can influence the uniformity of the powder bed. Due to the 3D nature of the powder bed and the standard requirement for sintering parts following printing, direct experimental observation of the particle distribution and packing density can be difficult. The use of Micro-X-ray-CT however, enables the high-resolution imaging of components manufactured by binder jetting and allows quantification of particle size distribution and packing density throughout the powder bed. This study analyses the periodicity of effects such as in-layer particles size segregation and packing density. The results presented here show that particles segregate by size within each layer of the binder jet printed sample, which resulted in a periodic density change within each layer. The particle size distribution changes over the length of the power-bed, with the volume fraction of smaller particles increased near the front of the powder bed, and the volume fraction of larger particles increased near the back. The insights gained from the Micro-X-ray-CT characterisation approach allow for an enhanced understanding of the powder spreading process in additive manufacturing, paving the way forward for possible part optimisation.

粘合剂喷射印刷中粉末床的均匀性会影响快速成型部件的最终性能。粒度偏析等颗粒流动现象会影响粉末床的均匀性。由于粉末床的三维性质和打印后部件烧结的标准要求，很难对颗粒分布和堆积密度进行直接实验观察。然而，使用 Micro-X 射线-计算机断层扫描可以对通过粘合剂喷射制造的部件进行高分辨率成像，并对整个粉末床的粒度分布和堆积密度进行量化。本研究分析了层内颗粒尺寸偏析和堆积密度等效应的周期性。研究结果表明，在粘合剂喷射打印的样品中，每层内的颗粒都会发生尺寸偏析，从而导致每层内的密度发生周期性变化。颗粒尺寸分布在粉末床的长度方向上发生变化，较小颗粒的体积分数在靠近粉末床前部的位置增加，而较大颗粒的体积分数在靠近粉末床后部的位置增加。从显微 X 射线-计算机断层扫描表征方法中获得的启示有助于加深对增材制造中粉末铺展过程的理解，为可能的零件优化铺平道路。

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引用次数: 0

Calibration and compensation of 5-axis 3D-printers for printed electronics 校准和补偿用于印刷电子产品的 5 轴 3D 打印机

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100265

Daniel Ahlers, Tom Schmolzi, German Junca, Jianwei Zhang, Florens Wasserfall

5-axis 3D printing presents a promising approach to overcome the limitations of traditional 3-axis methods, particularly in the domain of printed electronics where conformal conductive connections are printed onto the surface of freeform objects. However, this additional freedom comes with a demand for high positioning accuracy, as the rotary movements amplify small axis deviations through the lever effect. This paper presents an approach for an automatically self-calibrating low-cost 5-axis printing system using a built-in 3D touch probe. The calibration data is used to generate a precise kinematic printer model in the Unified Robot Description Format (URDF). Our inverse kinematic solver uses this model in our pathplanning software to generate fully compensated G-code trajectories, maintaining the correct position without needing an expensive high-precision motion system. First results are presented as evaluation which were printed on our low-cost 5-axis system with 3D-printed rotary axes, demonstrating the capability to reliably print circuits on imprecise hardware. The calibration process can be executed quickly and automatically every time the printer is restarted. This approach makes multi-axis 3D printing more accessible and increases potential uses, leading to more precise and cost-effective manufacturing solutions.

五轴三维打印技术为克服传统三轴方法的局限性提供了一种前景广阔的方法，尤其是在将保形导电连接打印到自由形态物体表面的打印电子领域。然而，这种额外的自由度对高定位精度提出了要求，因为旋转运动会通过杠杆效应放大小的轴偏差。本文介绍了一种利用内置 3D 触摸探头自动自校准低成本 5 轴打印系统的方法。校准数据用于在统一机器人描述格式（URDF）中生成精确的运动学打印机模型。我们的逆运动学求解器在路径规划软件中使用该模型生成完全补偿的 G 代码轨迹，无需昂贵的高精度运动系统即可保持正确的位置。首批评估结果在我们的低成本五轴系统上打印出来，并带有三维打印的旋转轴，证明了在不精确的硬件上可靠打印电路的能力。每次重新启动打印机时，校准过程都能快速自动执行。这种方法使多轴三维打印更容易获得，并增加了潜在用途，从而带来了更精确、更具成本效益的制造解决方案。

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引用次数: 0

Thermo-mechanical response of aluminum alloy in the additive friction-stir deposition process

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100263

Chowdhury Sadid Alam , Vahid Karami , Shengmin Guo , M Shafiqur Rahman

Additive Friction Stir Deposition (AFSD) is an emerging solid-state additive manufacturing (AM) technique that creates fully dense metallic structures with equiaxed fine microstructures. The feedstock material is plasticized via frictional heating and deposited in the solid state. Due to the complex multi-physics nature of the process, an in-depth understanding of the interplay between material flow, temperature variations, and stress distribution within the deposited layers under various process parameters is crucial for achieving desired outcomes. This study focuses on the development of a plasticity-based computational model that employs a coupled Eulerian-Lagrangian (CEL) finite element methodology to analyze the thermo-mechanical response of the AA6061-T6 alloy in the AFSD process. By incorporating essential AFSD process variables namely, tool rotation speed, tool traverse speed, and material deposition rate, the model can accurately forecast the flow of material, temperature fluctuations, and stress distribution across different operational settings. For instance, an optimal solid-state deposition of AA 6061-T6 alloy is achieved with 380 RPM tool rotation speed, 0.9 mm/s tool traverse speed, and 0.3 mm/s material deposition rate for the geometry reported in this study. The CEL model is validated by comparing its results (e.g., peak temperature) with the experimental data and published computational results for the same combination of process parameters, giving the maximum errors of 8 % and 2.8 %, respectively. Through the utilization of this proposed model, a practical and efficient means of predicting process results is established, enabling a rapid and cost-effective optimization of the AFSD process parameters for different scale of the feed material, tool, and substrate. Ultimately, this advancement contributes to the progression of solid-state AM techniques and development of digital twins by streamlining the process with scalability, multifunctionality, and a variety of material selections.

增材摩擦搅拌沉积（AFSD）是一种新兴的固态增材制造（AM）技术，可制造出具有等轴细微结构的全致密金属结构。原料通过摩擦加热塑化，然后在固态下沉积。由于该工艺具有复杂的多物理特性，深入了解各种工艺参数下沉积层内材料流动、温度变化和应力分布之间的相互作用对于实现预期结果至关重要。本研究的重点是开发基于塑性的计算模型，该模型采用欧拉-拉格朗日（CEL）耦合有限元方法来分析 AA6061-T6 合金在 AFSD 工艺中的热机械响应。该模型结合了重要的 AFSD 工艺变量，即工具旋转速度、工具移动速度和材料沉积速率，可以准确预测不同操作设置下的材料流动、温度波动和应力分布。例如，对于本研究中报告的几何形状，在 380 RPM 的工具旋转速度、0.9 mm/s 的工具移动速度和 0.3 mm/s 的材料沉积速率下，AA 6061-T6 合金实现了最佳固态沉积。通过将 CEL 模型的结果（如峰值温度）与相同工艺参数组合下的实验数据和已公布的计算结果进行比较，验证了该模型的有效性，得出的最大误差分别为 8 % 和 2.8 %。通过使用该模型，建立了一种实用、高效的工艺结果预测方法，可针对不同规模的进料、工具和基体，快速、经济地优化 AFSD 工艺参数。最终，通过简化工艺流程，使其具有可扩展性、多功能性和多种材料选择性，这一进展有助于固态 AM 技术的进步和数字双胞胎的开发。

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引用次数: 0

Liquid-induced heat treatment strategy for eliminating anisotropy of IN718 fabricated by laser powder bed fusion

IF 4.2 Q2 ENGINEERING, MANUFACTURING

Additive manufacturing letters

Pub Date : 2025-02-01 DOI: 10.1016/j.addlet.2024.100262

Zhuoyu Li , Xiaogang Hu , Fan Zhou , Zhifang Shi , Zhiwei Lyu , Zhen Xu , Yu Li , Xin Zhao , Hongxing Lu , Qiang Zhu

The laser-based additive manufacturing process often results in highly textured columnar grain structures along the build direction, leading to undesirable anisotropic mechanical properties in most industrial applications. Tailored heat treatments are currently the predominant approach to address anisotropy issues. However, the lack of driving force for recrystallization during the post-heat treatment within laser powder bed fusion (LPBF) makes this method inapplicable to the process. Here, we develop a novel liquid-induced heat treatment (LIHT) post-processing. The intergranular liquid film is introduced to facilitate the columnar-to-equiaxed transition of grains in IN718 alloy fabricated by LPBF. Microstructures and mechanical properties parallel and perpendicular to the build direction have been analyzed. The degree of anisotropy in ultimate strength was reduced from 21.1% to 3.5%. The anisotropy in creep performance also decreased from 52.1% to 11.3%. LIHT is anticipated to be a typical process for eliminating the anisotropy in the mechanical properties of metallic components.

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引用次数: 0