scholarly journals A Robust Fast Bridging Algorithm for Laser Cutting

2021 ◽  
Author(s):  
Qirui Hu ◽  
Zhiwei Lin ◽  
Jianzhong Fu
Keyword(s):  
Laser Cutting ◽  
Point Cloud ◽  
Effective Strategy ◽  
Discrete Point ◽  
Line Segments ◽  
Easy Task ◽  
Delaunay Triangles ◽  
Bridge Length ◽  
Cutting Experiments ◽  
Different Parts

Abstract Bridging the different parts together is considered a simple but effective strategy to reduce the number of piercing operations during laser cutting. However, fast bridging is never an easy task. In this paper, we present a near-linear bridging algorithm for the input parts with the shortest total bridge length. At first, the input part contours are discretized into a point cloud, then the point cloud is triangulated with the Delaunay standard. The shortest line segments between any two adjacent parts are found in the triangles connecting the two parts. These segments are finally extended into bridges. To solve the problem of the damages to the contour characteristics caused by the bridges, some restrictions are set on the screening of the discrete point cloud and the Delaunay triangles. This algorithm not only ensures the minimum total distance of all bridges, but also avoids the problem of generating bridge loops. Computational experiments show that the proposed bridging algorithm is much faster than that in existing commercial software. The feasibility and superiority of the algorithm are verified by actual lasering cutting experiments.

scholarly journals A Complete Method for Reconstructing an Elevation Surface of 3D Point Clouds

2015 ◽  
Vol 4 (3-4) ◽  
Author(s):  
Van Sinh Nguyen ◽  
Manh Ha Tran ◽  
Ba Cong Nhan
Keyword(s):  
Point Cloud ◽  
Input Data ◽  
Smooth Surface ◽  
Point Clouds ◽  
Triangular Mesh ◽  
Second Step ◽  
Discrete Point ◽  
The Third ◽  
Input Surface ◽  
3D Point Clouds

Reconstructing the surface of 3D point clouds is a reconstruction from a cloud of 3D points to a triangular mesh. This process approximates a discrete point cloud by a continuous/smooth surface depending on the input data and the applications of users. In this paper, we propose a complete method to reconstruct an elevation surface from 3D point clouds. The method consists of three steps. In the first step, we triangulate an elevation surface of 3D point cloud structured in a 3D grid. In the second step, we remove the outward triangles to deal with concave regions on the boundary of the triangular mesh. In the third step, we reconstruct this surface by filling the hole of triangular mesh. Our method could process very fast for triangulating the surface, preserve the topology and characteristic of the input surface after reconstruction.

scholarly journals An Improved Building Reconstruction Algorithm Based on Manhattan World Assumption and Line-Restricted Hypothetical Plane Fitting

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xiaoguo Zhang ◽  
Guo Wang ◽  
Ye Gao ◽  
Huiqing Wang ◽  
Qing Wang
Keyword(s):  
Line Segment ◽  
Point Cloud ◽  
Mean Shift ◽  
Reconstruction Algorithm ◽  
Triangle Mesh ◽  
Line Segments ◽  
Plane Fitting ◽  
Fitting Method ◽  
Dense Point ◽  
Seed Points

An improved patch-based multiview stereo (PMVS) algorithm based on Manhattan world assumption and the line-restricted hypothetical plane fitting method according to buildings’ spatial characteristics is proposed. Different from the original PMVS algorithm, our approach generates seed points purely from 3D line segments instead of using those feature points. First, 3D line segments are extracted using the existing Line3D++ algorithm, and the 3D line segment clustering criterion of buildings is established based on Manhattan world assumption. Next, by using the normal direction obtained using the result of 3D line segment clustering, we propose a multihypothetical plane fitting algorithm based on the mean shift method. Then, through subdividing on the triangle mesh constructed based on the building hypothetical plane model, semidense point cloud can be quickly obtained, and it is used as seed points of the PMVS pipeline instead of the sparse and noisy seed points generated by PMVS itself. After that, dense point cloud can be obtained through the existing PMVS expansion pipeline. Finally, unit and integration experiments are designed; the test results show that the proposed algorithm is 15%∼23% faster than the original PMWS in running time, and at the same time, the reconstruction quality of buildings is improved as well by successfully removing many noise points in the buildings.

Additive manufacturing of laser cutting nozzles by SLM: processing, finishing and functional characterization

2018 ◽  
Vol 24 (3) ◽  
pp. 562-583 ◽  
Author(s):  
Marco Anilli ◽  
Ali Gökhan Demir ◽  
Barbara Previtali
Keyword(s):  
Functional Analysis ◽  
Additive Manufacturing ◽  
Laser Cutting ◽  
Post Processing ◽  
Production Chain ◽  
Content Type ◽  
Nozzle Geometries ◽  
Finishing Processes ◽  
Cutting Experiments ◽  
Double Chamber

Purpose The purpose of this paper is to demonstrate the use of selective laser melting for producing single and double chamber laser cutting nozzles. The main aim is to assess a whole production chain composed of an additive manufacturing (AM) and consecutive finishing processes together. Beyond the metrological and flow-related characterization of the produced nozzles, functional analysis on the use of the produced nozzles are carried out through laser cutting experiments. Design/methodology/approach SLM experiments were carried out to determine the correct compensation factor to achieve a desired nozzle diameter on steel with known processibility by SLM and using standard nozzle geometries for comparative purposes. The produced nozzles are finished through electrochemical machining (ECM) and abrasive flow machining (AFM). The performance of nozzles produced via additive manufacturing (AM) are compared to conventional ones on an industrial laser cutting system through cutting experiments with a 6 kW fibre laser. The produced nozzles are characterized in terms of pressure drop and flow dynamics through Schlieren imaging. Findings The manufacturing chain was regulated to achieve 1 mm diameter nozzles after consecutive post processing. The average surface roughness could be lowered by approximately 80 per cent. The SLM produced single chamber nozzles would perform similarly to conventional nozzles during the laser cutting of 1 mm mild steel with nitrogen. The double chamber nozzles could provide complete cuts with oxygen on 5 mm-thick mild steel only after post-processing. Post-processing operations proved to decrease the pressure drop of the nozzles. Schlieren images showed jet constriction at the nozzle outlet on the as-built nozzles. Originality/value In this work, the use of an additive manufacturing process is assessed together with suitable finishing and functional analysis of the related application to provide a complete production and evaluation chain. The results show how the finishing processes should be allocated in an AM-based production chain in a broader vision. In particular, the results confirm the functionality for designing more complex nozzle geometries for laser cutting, exploiting the flexibility of SLM process.

scholarly journals Accurate Volume Calculation Driven by Delaunay Triangulation for Coal Measurement

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yong Liu ◽  
Yanwei Zheng
Keyword(s):  
Delaunay Triangulation ◽  
Integral Method ◽  
Point Cloud ◽  
Calculation Formula ◽  
3D Point Cloud ◽  
Base Plane ◽  
Volume Calculation ◽  
Good Balance ◽  
Running Time ◽  
Delaunay Triangles

Volume calculation from 3D point cloud is widely used in engineering and applications. The existing methods either have large errors or are time-consuming. This paper focuses on the coal measurement. Based on the triangular mesh generated from the point cloud, each triangle is projected downward to the base plane to form a voxel. We derive the calculation formula of voxel by an integral method, which is more efficient than the method of decomposing voxel into tetrahedrons and more accurate than slicing methods. Furthermore, this paper proposes a Delaunay triangulation-driven volume calculation (DTVC) method. DTVC does not preserve the Delaunay triangles but directly calculates the volume in the process of triangulation. It saves memory and running time. Experimental results show that DTVC has achieved a good balance between error and efficiency.

scholarly journals Presence of Pseudomonas syringae pv actinidiae the causal agent of bacterial canker of kiwifruit on symptomatic and asymptomatic tissues of kiwifruit

2011 ◽  
Vol 64 ◽  
pp. 241-245 ◽  
Author(s):  
J.L. Vanneste ◽  
J. Yu ◽  
D.A. Cornish ◽  
S. Max ◽  
G. Clark
Keyword(s):  
Pseudomonas Syringae ◽  
Vascular System ◽  
Causal Agent ◽  
Bacterial Canker ◽  
Effective Strategy ◽  
Bacterial Isolation ◽  
Chain Reaction ◽  
Leaf Spots ◽  
Polymerase Chain ◽  
Different Parts

Pseudomonas syringae pv actinidiae (Psa) the causal agent of bacterial canker of kiwifruit has recently been found in New Zealand This pathogen has been the object of few studies and little is known about its epidemiology Yet the development of an effective strategy of control requires an understanding of the life cycle of the pathogen in particular determining the location of the bacteria in tissues In this study the presence of Psa on flowers symptomatic and asymptomatic leaves and different parts of canes showing symptoms was determined by polymerase chain reaction (PCR) or by direct bacterial isolation Psa was found associated with angular necrotic leaf spots with white exudate and in canes In canes Psa seemed to be either in the parenchyma leading to production of exudate or in the vascular system leading to wilting Psa was also found on asymptomatic tissues where it was probably surviving as an epiphyte

scholarly journals Fast plane segmentation with line primitives for RGB-D sensor

2016 ◽  
Vol 13 (6) ◽  
pp. 172988141666584 ◽  
Author(s):  
Lizhi Zhang ◽  
Diansheng Chen ◽  
Weihui Liu
Keyword(s):  
Point Cloud ◽  
Computational Cost ◽  
Data Sets ◽  
Line Segments ◽  
Line Extraction ◽  
Extraction Algorithm ◽  
Segmentation Approach ◽  
On Line

This article presents a fast and robust plane segmentation approach for RGB-D type sensor, which detects plane candidates by line segments extracted from 2-D scanline projected from row or column points. It neither requires high computation to calculate local normals for the entire point cloud as most of approaches do nor randomly chooses plane candidates such as RANSAC-like approaches. First, a line extraction algorithm is utilized to extract line segments. Second, the plane candidates are detected by estimating local normal of points lying on line segments. Finally, the plane having most inlier is recursively extracted from the plane candidates as the result plane. Experiments were conducted with different data sets and the segmentation performances were evaluated quantitatively and qualitatively. We demonstrated the efficiency and robustness of our proposed approach, especially in the none plane scenario, the approach needs little computational cost.

scholarly journals Feature curve extraction from point clouds via developable strip intersection

2015 ◽  
Vol 3 (2) ◽  
pp. 102-111 ◽  
Author(s):  
Kai Wah Lee ◽  
Pengbo Bo
Keyword(s):  
Point Cloud ◽  
Point Clouds ◽  
Approximation Procedure ◽  
Developable Surface ◽  
Line Segments ◽  
Sequencing Algorithm ◽  
Shape Approximation ◽  
Feature Line ◽  
Data Points ◽  
The Given

Abstract In this paper, we study the problem of computing smooth feature curves from CAD type point clouds models. The proposed method reconstructs feature curves from the intersections of developable strip pairs which approximate the regions along both sides of the features. The generation of developable surfaces is based on a linear approximation of the given point cloud through a variational shape approximation approach. A line segment sequencing algorithm is proposed for collecting feature line segments into different feature sequences as well as sequential groups of data points. A developable surface approximation procedure is employed to refine incident approximation planes of data points into developable strips. Some experimental results are included to demonstrate the performance of the proposed method.

scholarly journals CENTRAL AXIS ESTIMATION FOR ANCIENT CHINESE PAGODAS BASED ON GEOMETRIC MODELLING AND UAV-BASED PHOTOGRAMMETRY

2020 ◽  
Vol XLIII-B2-2020 ◽  
pp. 751-756
Author(s):  
T. O. Chan ◽  
L. Xia ◽  
J. Tang ◽  
M. Liu ◽  
W. Lang ◽  
...  
Keyword(s):  
Point Cloud ◽  
Geometric Model ◽  
Geometric Modelling ◽  
Central Axis ◽  
Asian Countries ◽  
Historical Structures ◽  
Estimated Parameters ◽  
Proposed Model ◽  
Structural Aspects ◽  
Different Parts

Abstract. Pagodas are common historical structures in China and some other Asian countries. Symmetries of the pagodas play an important role on cultural and structural aspects. In this paper, we proposed a method estimating the central axis of a typical ancient pagoda in China for examination of its symmetry. We developed a novel geometric model to fit to the point cloud of the pagoda obtained from photogrammetric reconstruction based on UAV imagery. More specifically, we developed a novel geometric model possessing 16 parameters to fit to the point cloud of different parts of the pagodas simultaneously to estimate a central axis for the symmetry. The results show that the proposed model is superior to the conventional cylindrical models for the central axis estimation. More importantly, the estimated parameters are in realistic ranges, as well as the reconstructed central axis and the sextant number are well visualized, so the symmetry of the pagodas can be readily analysed.

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