The Effects of Overhang Forming Direction on Thermal Behaviors during Additive Manufacturing Ti-6Al-4V Alloy

Wu, Fan; Sun, Zhonggang; Chen, Wei; Liang, Zulei

doi:10.3390/ma14133749

Cited by 9 publications

(3 citation statements)

References 36 publications

(39 reference statements)

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“…The increasement of the highest temperature point tends to be the same among all points, and the temperature change from point R to point S is not as obvious as that between point H and I. This is also because the laser heating rate is much higher than the cooling rate in the LPBF process of the overhang structure [34].Therefore, the in uence of thermal conductivity on the molten pool and temperature eld is more obvious.…”

Section: The Temperature Eld and Dross Formationmentioning

confidence: 94%

Research on warping and dross formation of overhang structure manufactured by Laser Powder Bed Fusion

Lin¹,

Wang²,

Vyacheslav³

et al. 2022

Preprint

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Warping and dross formation are the main defects of overhang structure formed by Laser Powder Bed Fusion. In order to study the process of warping and dross formation, the “7” shape overhang structure with different lengths and heights of overhang was printed. The influence of temperature field and stress field on the forming quality of overhang structure was analysed by numerical simulation. The results of experiment and simulation showed that there were significant differences in the forming process of temperature field between solid support zone and powder support zone. Due to the poor thermal conductivity of powder, the molten pool in the powder support zone was much larger than that in the solid support zone. On one hand, the molten pool sank due to the action of gravity and capillary force, which lead to the melting of the powder outside its original shape and contour, formed a droplet like dross formation on the lower surface. On the other hand, the temperature difference between regions led to large thermal stress. When the thermal stress exceeded the material strength, warping deformation occurred on the top area and affected the subsequent powder laying process. The powder could not be spread on the warping zone so it was remelted when the next layer is processed. As the number of forming layers increased, the original powder area became solid after fusion and solidification, so the thermal conductivity and stiffness increased continuously, the variation of temperature tended to be stable and the deformation of the top area gradually decreases. The study of warping and dross formation process was helpful to understand the defect change process in overhang manufacturing process.

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Section: The Temperature Eld and Dross Formationmentioning

confidence: 94%

Research on warping and dross formation of overhang structure manufactured by Laser Powder Bed Fusion

Lin¹,

Wang²,

Vyacheslav³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…To modify the part geometry for a more stable fabrication, the area requiring support must be identified. Meanwhile, collapse detection requires the consideration of thermal and structural aspects [ 11 ]. Although thermal and structural attributes should be addressed to precisely detect collapsed regions, overestimated support regions determined based on the overhang angle have been extensively adopted to reduce the simulation time.…”

Section: Introductionmentioning

confidence: 99%

Facet Connectivity-Based Estimation Algorithm for Manufacturability of Supportless Parts Fabricated via LPBF

Lee

Yang

et al. 2023

Materials

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Recent advances in additive manufacturing have provided more freedom in the design of metal parts; hence, the prototyping of fluid machines featuring extremely complex geometries has been investigated extensively. The fabrication of fluid machines via additive manufacturing requires significant attention to part stability; however, studies that predict regions with a high risk of collapse are few. Therefore, a novel algorithm that can detect collapse regions precisely is proposed herein. The algorithm reflects the support span over the faceted surface via propagation and invalidates overestimated collapse regions based on the overhang angle. A heat exchanger model with an extremely complex internal space is adopted to validate the algorithm. Three samples from the model are extracted and their prototypes are fabricated via laser powder bed fusion. The results yielded by the fabricated samples and algorithm with respect to the sample domain are compared. Regions of visible collapse identified on the surface of the fabricated samples are predicted precisely by the algorithm. Thus, the supporting span reflected by the algorithm provides an extremely precise prediction of collapse.

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“…The conventional AM process is constrained in the single material accumulation direction that creates support structures underneath the overhang surfaces, specifically for the metal AM process. These supports must be removed using extra post-processing steps, and meanwhile, it could lead to a larger thermal distortion on the overhanging volumes [ 1 ]. In contrast, robotic AM achieves the continuous change of building orientation during the material deposition process, transforming overhang surfaces into a support-free manner under a different orientation.…”

Section: Introductionmentioning

confidence: 99%

Autonomous Robotic Feature-Based Freeform Fabrication Approach

Xiao

2021

Materials

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Robotic additive manufacturing (AM) has gained much attention for its continuous material deposition capability with continuously changeable building orientations, reducing support structure volume and post-processing complexity. However, the current robotic additive process heavily relies on manual geometric reasoning that identifies additive features, related building orientations, tool approach direction, trajectory generation, and sequencing all features in a non-collision manner. In addition, multi-directional material accumulation cannot ensure the nozzle always stays above the building geometry. Thus, the collision between these two becomes a significant issue that needs to be solved. Hence, the common use of a robotic additive is hindered by the lack of fully autonomous tools based on the abovementioned issues. We present a systematic approach to the robotic AM process that can automate the abovementioned planning procedures in the aspect of collision-free. Typically, input models to robotic AM have diverse information contents and data formats, hindering the feature recognition, extraction, and relations to the robotic motion. Our proposed method integrates the collision-avoidance condition to the model decomposition step. Therefore, the decomposed volumes can be associated with additional constraints, such as accessibility, connectivity, and trajectory planning. This generates an entire workspace for the robotic additive building platform, rotatability, and additive features to determine the entire sequence and avoid potential collisions. This approach classifies the uniqueness of autonomous manufacturing on the robotic AM system to build large and complex metal components that are non-achievable through traditional one-directional AM in a computationally effective manner. This approach also paves the path in constructing an in situ monitoring and closed-loop control on robotic AM to control and enhance the build quality of the robotic metal AM process.

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The Effects of Overhang Forming Direction on Thermal Behaviors during Additive Manufacturing Ti-6Al-4V Alloy

Cited by 9 publications

References 36 publications

Research on warping and dross formation of overhang structure manufactured by Laser Powder Bed Fusion

Research on warping and dross formation of overhang structure manufactured by Laser Powder Bed Fusion

Facet Connectivity-Based Estimation Algorithm for Manufacturability of Supportless Parts Fabricated via LPBF

Autonomous Robotic Feature-Based Freeform Fabrication Approach

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