Selective laser melting （SLM） is one of the most popular additive manufacturing （AM） technologies for metal parts. slicing result, especially for the different dimensional slicing geometry and its topology, plays ...
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Selective laser melting （SLM） is one of the most popular additive manufacturing （AM） technologies for metal parts. slicing result, especially for the different dimensional slicing geometry and its topology, plays an important role because of the thermodynamic behavior of metal powders. To get correct geometry and reliable topology, a slicing strategy for SLM is proposed. The unavoidable numerical error caused by sampling and geometric transformation is suppressed firstly, according to shifting the z-coordinate of a vertex with a small value such the shifted vertex is on a slicing plane. The result of vertex-shifting makes it possible to identify different geometric features such as skin surfaces, overhang surfaces, extreme edges and volumetric solid. Second, from geometric primitives a hierarchy of axis-aligned bounding boxes （AABBs） is constructed and used to speed up intersection of slicing planes against sets of triangles. All intersecting segments are given different signs to depict their geometric or topological information. Based the different signs, the different dimensional geometry that is eventually represented by simple and anticlockwise oriented polygons, are identified. Finally, the polygons are classified and nested in a multi-tree data structure set to produce correct topological relations. The result of digital and physical experiments shows the proposed slicing strategy is feasible and robust.
Optical coherence tomography(OCT) is a powerful and noninvasive imaging technique for eye ground imaging. This method is usually used to assist glaucoma diagnosis nowadays. We propose a novel automated method for the ...
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Optical coherence tomography(OCT) is a powerful and noninvasive imaging technique for eye ground imaging. This method is usually used to assist glaucoma diagnosis nowadays. We propose a novel automated method for the segmentation of choroid layer in OCT image. Our approach is based on normalized cut algorithm, which aims at extracting the global impression of an image and treat image segmentation as a graph partitioning problem. However, due to the complexity of the layer structure of eye ground and choroid layer itself, we employ a series of preprocessing algorithms to make the cut more deterministic and accurate. Furthermore, to make the cutting algorithm focused on cutting in a horizontal manner instead of meaningless vertical cuts, we slice the image into small slices plumb and run the normalized cut algorithm respectively on these slices. After that, we combine them together to get a global cut on the original image. We calculate the thickness of choroid layer, which is a key factor for diagnosis. We used the thickness as the major factor to measure our performance. The mean relative error of the algorithm is about 0.04 compared with manual segmentation performed by oculists. The proposed method was tested on a database including more than eight hundred images of fifty healthy people between 20 and 50 years old.
Robot based fused filament fabrication (FFF) has various advantages compared to normal FFF. A major disadvantage is that there is no software which can generate the needed robot code. Therefore, a software was develop...
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Robot based fused filament fabrication (FFF) has various advantages compared to normal FFF. A major disadvantage is that there is no software which can generate the needed robot code. Therefore, a software was developed, which is able to process a model in the form of a STL file in such a way, that a finished robot code is created. This code can be executed directly on an ABB robot (other robots can be easily implemented). The software is capable of using all six degrees of freedom (DOF) of the used robot and of calculating possible collisions during the printing process.
Finite difference method(FDM) is one of the most popular method for explosion ***-scale,accuracy and automatic grid generation is the essential for numerical *** kinds of grid generation method are wildly used:ray cas...
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Finite difference method(FDM) is one of the most popular method for explosion ***-scale,accuracy and automatic grid generation is the essential for numerical *** kinds of grid generation method are wildly used:ray casting method and slicing *** this paper,the ray casting method is optimized and some special cases of algorithm are analyzed,which improved the efficiency and stability for large-scale grid generation.A facet searching method is proposed to improve the performance of ray casting *** efficient data storage method is proposed for storing and visualizing grid data,which makes it possible to display trillions of *** advantages of modified ray casting algorithm are presented through performance comparison between ray casting and slicing method in different ***,examples of grid generation and explosion simulation are *** accuracy and practicability of algorithm is proved.
Additive manufacturing technology is a systematic process based on discrete accumulation principle, which is derived by the dimension of parts. Aiming at the dimension mathematical model and slicing problems in additi...
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Additive manufacturing technology is a systematic process based on discrete accumulation principle, which is derived by the dimension of parts. Aiming at the dimension mathematical model and slicing problems in additive manufacturing process, the constitutive relations between micro-beam plasma welding parameters and the dimension of part were investigated. The slicing algorithm and slicing were also studied based on the dimension characteristics. By using the direct slicing algorithm according to the geometric characteristics of model, a hollow thin-wall spherical part was fabricated by 3D additive manufacturing technology using micro-beam plasma.
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