A study on automatic on-machine inspection system for 3D modeling and measurement of cutting tools

A 3D model of the maximum rotating envelope of a milling cutter with tool holder is required for Computer Aided Manufacturing (CAM) process design and machining simulation. The user may define the 3D model of the whole tool assembly in the tool library of CAM software. However, it is not convenient and reliable. Considering these problems, a new method based on single view 3D reconstruction algorithm has been proposed in previous research work, which is able to quickly reconstruct the 3D model of a cutter with tool holder while they are installed onto the spindle. As the extension of this work, this paper focuses on the recent progresses in order to improve the automation, accuracy, efficiency and reliability of tool modeling system. First, an improved flexible on-machine camera calibration procedure is proposed. The accurate motion of machine tool axis is used to calibrate the camera on machine tool instead of a physical calibration board. The whole procedure of calibration can be conducted automatically by running NC code. Therefore, the automation of vision system can be guaranteed. Second, the contour extraction module is improved by using a method of silhouette image composition. This method is applied to solve the problem of translucent and fuzzy cutter profile induced by motion blur. Third, the new algorithm for contour partitioning and classification are proposed, which is more reliable and robust. The reliability and accuracy of the vision system can be guaranteed. Finally, the vision system with an 8 mm lens and 1 mm extensions has been tested on different type of machine tool with smaller cutters. The average measurement accuracy is about 35 microns verified by comparison with a commercial tool setting system.     

Appearance-driven conversion of polygon soup building models with level of detail control for 3D geospatial applications

In many 3D applications, building models in polygon-soup representation are commonly used for the purposes of visualization, for example, in movies and games. Their appearances are fine, however geometry-wise, they may have limited information of connectivity and may have internal intersections between their parts. Therefore, they are not well-suited to be directly used in 3D geospatial applications, which usually require geometric analysis. For an input building model in polygon-soup representation, we propose a novel appearance-driven approach to interactively convert it to a two-manifold model, which is more well-suited for 3D geospatial applications. In addition, the level of detail (LOD) can be controlled interactively during the conversion. Because a model in polygon-soup representation is not well-suited for geometric analysis, the main idea of the proposed method is extracting the visual appearance of the input building model and utilizing it to facilitate the conversion and LODs generation. The silhouettes are extracted and used to identify the features of the building. After this, according to the locations of these features, horizontal cross-sections are generated. We then connect two adjacent horizontal cross-sections to reconstruct the building. We control the LOD by processing the features on the silhouettes and horizontal cross-sections using a 2D approach. We also propose facilitating the conversion and LOD control by integrating a variety of rasterization methods. The results of our experiments demonstrate the effectiveness of our method.     

皮革裁切加工算法

给出了用直刀、圆弧刀冲切皮革的加工算法．根据裁切方向和轮廓特点,分别给出两种轨迹计算方式．第一种直接采用等误差逼近计算直刀刀位,第二种则采用等误差、等步长相结合的逼近方式来计算直刀、圆弧刀组合刀位,其间通过在刀具库中搜索合适刀具和绕刀具自身轴心摆转来避免过切．最后用Improved Greedy—opt2算法对冲孔轨迹进行路径优化,给出了加工实例,取得了满意的效果。     

Analytical calculation of the envelope surface for generic milling tools directly from CL-data based on the moving frame method

Two closed-form solutions for calculating tool envelope surfaces are proposed based on the moving frame method. They have several advantages: (a) Given a sequence of cutter location (CL) data before post-processing into NC code, although we do not know the special configuration of machine tool, the tool envelope surface can be calculated accurately; (b) The two methods fit for a generic milling tool with a surface of revolution, such as a cylindrical cutter, conical cutter, drum cutter, and so on; (c) Since the calculation is developed based on the representation of the parametric form of the generating curve, it is convenient to use Bézier method, B-Spline or NURBS to unify the representation of the cutters and calculation of tool envelope surfaces. Several examples are presented to prove their effectiveness and good adaptability. The two methods can be used for NC machining simulation, evaluation and correction of the tool path.     

复合式土压平衡盾构刀盘CAD系统开发

在结合盾构刀盘构型、开口和刀具布置规律等理论基础上,以三维软件SolidWorks为开发平台,以Visual Basic作为开发工具,开发了一种复合式土压平衡盾构刀盘CAD系统。该CAD系统采用编程法与尺寸驱动法两种开发方式,设计了刀盘选型模块、开口设计模块、刀具选型模块和刀具布置模块等八个模块,实现对复合式土压平衡盾构刀盘、刀具进行三维参数化优化设计。针对某地铁施工工程需求,应用所开发的复合式土压平衡盾构刀盘CAD系统,设计了直径6.28 m,开口率为32%,装配有滚刀35把,正面刮刀40把,边缘刮刀8把的刀盘。     

基于二维轮廓序列的膝关节三维重建

提出了一个基于二维轮廓序列的四面体网格生成方法,用于医学图像三维几何模型重构.该方法首先对各选定的断层图像提取目标轮廓并做分支匹配等处理,然后生成各轮廓内部平面域的三角网格,最后在相邻断层之间根据三角网格连接四面体单元.该方法被应用于人体膝关节虚拟手术系统的三维几何建模,得到的膝部股骨模型包含494个节点和2 046个四面体单元,膝部脂肪模型包含2 854个节点和14011个四面体单元,这些模型被成功地应用于膝关节手术仿真,从而证明了该三维模型重建方法的可行性和有效性.     

Development of a new spindle motor for a hard disk drive

A new spindle motor is developed with a sloped permanent magnet (PM) for a hard disk drive (HDD). In a conventional spindle motor, a pulling plate is installed at the stationary part under the rotating PM to pull down rotating bodies. This axial force is required for stable operation of the spindle motor using a hydrodynamic bearing. However, the pulling plate has considerable iron loss and a negative torque opposing the direction of rotation due to the induced eddy currents. Our proposed model has a sloped PM surface to generate the required axial force as well as torque without the pulling plate. Optimal design is carried out by a response surface methodology, and the new spindle motors are prototyped. The resulting electrical and mechanical performance of the prototyped motors is compared with that of conventional models, showing the possibility of adapting the proposed model for an HDD spindle motor.     

Optimize tool paths of flank milling with generic cutters based on approximation using the tool envelope surface

This paper presents a global optimization method to generate a tool path for flank milling free-form surfaces with a generic cutter based on approximation using the tool envelope surface. It is an extension of our previous work [Gong Hu, Cao Li-Xin, Liu Jian. Improved positioning of cylindrical cutter for flank milling ruled surfaces. Computer Aided Design 2005; 37:1205–13]. First, given initial tool path or tool axis trajectory surface, the grazing points of the tool envelope surface can be calculated. Second, the errors between the tool envelope surface and the designed surface along the normal direction of the tool envelope surface are calculated. Based on this new definition of error, an optimization model is established to get the global optimized tool axis trajectory surface. In order to simplify the calculation, two variants of this method based on the least square criterion are proposed to solve this model. Since this method is really based on the tool envelope surface, it can reduce the initial machining errors effectively. The proposed method can be used not only for cylindrical cutters and conical cutters, but also for generic cutters with a surface of revolution. In addition to ruled surfaces, it also can be used for machining non-ruled surfaces. Finally, several examples are given to prove its effectiveness and accuracy. The generated tool paths and calculated grazing points for test are available in supplementary files for the readers’ convenience in verifying this work in different CAD/CAM systems.     

一种自动鲁棒的三维人脸重建方法

三维人脸模型已经广泛应用到视频电话、视频会议、影视制作、电脑游戏、人脸识别等多个领域。目前三维人脸建模一般使用多幅图像，且要求表情中性。本文提出了基于正、侧面任意表情三维人脸重建方法。首先对二维图像中的人脸进行特征提取，然后基于三维人脸统计模型，通过缩放、平移、旋转等方法，及全局和局部匹配，获得特定的三维人脸。基于二维图像中的人脸纹理信息，通过纹理映射，获得完整的三维人脸。通过对大量实际二维人脸图像的三维人脸重建，证实了该方法的有效性和鲁棒性。     

微铣削刀具磨损状态监测方法研究

为提高金属微铣削过程中刀具磨损状态在线监测系统的预测效率与精度,提出一种基于线性判别分析与改进型BP神经网络模型识别刀具磨损的方法;该方法通过传感器与数据采集系统采集微铣削过程振动信号,提取其时域和频域特征并通过线性判别方法进行降维约简;将降维后的特征输入经灰狼优化改进的BP神经网络模型,从而实现微铣刀磨损状态特征的分类;结果表明,提出的微铣刀在线监测方法能够准确识别微铣刀的各种磨损状态;此外,和其它分类算法相比,提出的基于灰狼优化算法的BP神经网络模型在分类精度和计算效率方面具有综合优势;这对实际生产过程中微铣刀的磨损状态监测具有非常重要的实际意义.     

基于编解码网络的人脸对齐和重建算法

针对现有的三维人脸重建模型复杂度较高和对多种人脸姿态重建效果不佳的问题, 本文提出了一种可以在不同人脸姿态条件下, 有效地实现人脸对齐并从单张二维人脸图片重建出三维人脸的卷积神经网络. 首先设计了由密集卷积网络模块和转置卷积模块构成的编解码网络, 并在损失函数中引入图像结构相似度评价, 构造新的损失函数, 通过训练神经网络得出模型, 模型实现了人脸对齐和三维人脸重建任务. 在AFLW2000-3D数据集上验证性能,实验表明该网络有效提升了人脸对齐和人脸重建的效果.     

A hybrid comprehensive performance evaluation approach of cutter holder for tunnel boring machine

Cutter holder is a crucial component of tunnel boring machine (TBM), whose performance evaluation and selection needs to consider many factors, which is a challenging Multiple criteria decision-making (MCDM) problem. To enhance the TBM overall construction manifestation, it is fundamental to synthetically evaluate and accurately select the most suitable cutter holder from alternatives according to the engineering requirements and geological conditions. This paper develops a hybrid fuzzy comprehensive evaluation approach for cutter holder. In this approach, the weights of criteria are determined by Fuzzy Analytic Hierarchy Process (FAHP), and the max-min linear normalization is employed to integrate the information of qualitative and quantitative indicators of alternatives. Finally, the ranking and further comparison are achieved in the form of radar chart. A case study of cutter holder selection from six alternatives is carried out to validate the proposed approach. It shows that the proposed approach is effective, reasonable, complete and easy to operate, which can be promoted to the evaluation and selection of non-standard crucial components for large mechanical engineering equipment.     

Reshaping 3D facial scans for facial appearance modeling and 3D facial expression analysis

3D face scans have been widely used for face modeling and analysis. Due to the fact that face scans provide variable point clouds across frames, they may not capture complete facial data or miss point-to-point correspondences across various facial scans, thus causing difficulties to use such data for analysis. This paper presents an efficient approach to representing facial shapes from face scans through the reconstruction of face models based on regional information and a generic model. A new approach for 3D feature detection and a hybrid approach using two vertex mapping algorithms, displacement mapping and point-to-surface mapping, and a regional blending algorithm are proposed to reconstruct the facial surface detail. The resulting models can represent individual facial shapes consistently and adaptively, establishing facial point correspondences across individual models. The accuracy of the generated models is evaluated quantitatively. The applicability of the models is validated through the application of 3D facial expression recognition using the static 3DFE and dynamic 4DFE databases. A comparison with the state of the art has also been reported.     

球面铣刀修磨几何模型研究

文中给出球面铣刀的制造模型,探讨了运用同一机构磨制邻近规格的不同球面铣刀的可行性问题。为了充分利用现有的磨制机构,提出了斜等距曲面的概念及相应公式,介绍了它在球面铣刀修磨模型中的应用,并给出与制造相关的几何模型,最后用实例验证了模型的可行性与可靠性。该模型为实现复杂刀具的ＣＡＤ／ＣＡＭ提供了方法模型。     

Flank milling with flat end milling cutters

One situation encountered in industry is that two curves on the machined surface are known, such as the top and bottom profiles of a blade. The shape of the surface is not known and is to be determined by a tool sliding along the generating rails. In this paper, we give a detailed mathematical understanding of flank milling with flat end cutters, which we then use to develop a method for milling with such a cutter. This method slides the cutter along two rails, keeping the cutter tangent to both curves at every parameter value. Examples are given to illustrate the method, along with simulations and error analysis.     

基于单类Kinect的人体三维重建与优化

使用单一运动的类Kinect深度相机重建和优化静态3D全身人体模型.首先针对类Kinect深度相机产生噪声原因提出一种降噪处理方法进行降噪.结合深度信息和RGB信息获取匹配块,使用高斯混合模型进行局部配准和逐层封闭曲线拟合方法进行全局配准,结合改进方向距离函数进行合并,最后使用泊松表面重建方法获取三维模型.实验结果表明,该方法能够重建出较高精度的三维人体模型.     

An efficient human model customization method based on orthogonal-view monocular photos

Human body modeling is a central task in computer graphics. In this paper, we propose an intelligent model customization method, in which customer’s detailed geometric characteristics can be reconstructed using limited size features extracted from the customer’s orthogonal-view photos. To realize model customization, we first propose a comprehensive shape representation to describe the geometrical shape characteristics of a human body. The shape representation has a layered structure and corresponds to important feature curves that define clothing size. Next, we identify and model a novel relationship model between 2D size features and 3D shape features for each cross-section using real subject scanned data. We predict a customer’s cross-sectional 3D shape based on size features extracted from the customer’s photos, and then we reconstruct the customer’s shape representation using predicted cross-sections. We develop a new deformation algorithm that deforms a template model into a customized shape using the reconstructed 3D shape representation. A total of 30 subjects, male and female, with varied body shapes have been recruited to verify the model customization method. The customized models show high degree of resemblance of the subjects, with accurate body sizes; the accuracy of the models is comparable to scan. It shows that the method is a feasible and efficient solution for human model customization that fulfills the specific needs of the clothing industry.     

Disc cutters plane layout design of the full-face rock tunnel boring machine (TBM) based on different layout patterns

The quality of plane layout design of the disc cutters for the full-face rock tunnel boring machine (TBM) directly affects the balance of force distribution on the cutter head during the excavating. Various layout patterns have been adopted in practice during the layout design of the disc cutters. Considering the engineering technical requirements and the corresponding structure design requirements of the cutter head, this study formulates a nonlinear multi-objective mathematical model with multiple constraints for the disc cutters plane layout design, and analyses the characteristics of a multi-spiral layout pattern, a dynamic star layout pattern and a stochastic layout pattern. And then a genetic algorithm is employed to solve a disc cutters’ multi-spiral layout problem, and a cooperative co-evolutionary genetic algorithm (CCGA) is utilized to solve a disc cutters’ star or stochastic layout problems. The emphasis was put on the study of superiority of three different layout patterns. Finally, an instance of the disc cutters’ plane layout design was solved by the proposed methods using three different kinds of layout patterns. Experimental results showed the effectiveness of the method of combining the mathematical model with the algorithms, and the pros and cons of the three layout patterns.     

Optimal barrel cutter selection for the CNC machining of blisk

Barrel cutters have been widely used in the flank milling of blisk. In this paper, a new method is proposed to select an optimal barrel cutter in the interest of the high productivity in the CNC machining of blisk. The geometric properties and location of four types of barrel cutters are firstly introduced. Then the optimal size of the tool flute with a greater barrel radius is determined. Meanwhile, the local gouges and kinematic constraints of the CNC machine tool are also taken into account. Furthermore, in order to avoid the global interferences between the tool shaft and the blade in process, the center point of circular arc generatrix is adjusted. Finally, the tool shaft diameter is optimized to improve tool rigidity and avoid the global interferences between the tool shaft and the adjacent blades. The numerical examples prove that a feasible barrel cutter with the higher productivity can be obtained by the proposed method in this paper. Therefore, this method can be directly applied in the CNC machining of blisk or centrifugal impeller.     

Minimization of the kinematics error for five-axis machining

Kinematics of a particular five-axis milling machine can drastically change the machining accuracy. Therefore, the reduction of the kinematics error is an important problem associated with the tool path planning.Our new optimization method employs a closed form of the kinematics error represented as a function of the positions of the cutter contact points. The closed form is derived from the inverse kinematics associated with a particular five-axis machine and obtained through automatic symbolic calculations.The second component of the algorithm is the optimal setup of the part surface on the mounting table employed in an iterative loop with the generation of the cutter contact points.For a prescribed tolerance the proposed optimization allows for substantial reduction in the number of required cutter contact points. The reduction can be significant and may amount to long hours of machining if the machining time at the programmed feed is less than the sampling time of the controller.In turn, when the number of cutter location points is fixed, the error can be substantially reduced. However, this refers to commanded error wherein the dynamics of machine tool are not taken into account.We present an analysis, systematic numerical experiments and results of real cutting (ball nose and flat-end cutters) as an evidence of the efficiency and the accuracy increase produced by the proposed method. We also evaluate the relative contributions of the setup and the point optimization.The method is shown to work with advanced tool path generation techniques proposed earlier such as the adaptive space filling curves.The numerical and machining experiments demonstrate that the proposed procedure outperforms tool paths based on the equi-arclength principle and paths generated by MasterCam 9.