Generating NC tool paths from random scanned data using point-based models

This paper presents a new approach for the generation of NC tool paths from random scanned data. Instead of using smooth or triangulated surfaces reconstructed from raw data, which is usually a time-consuming reverse engineering approach, the point-based surfel models computed by a GPU (graphics processing unit) are used to generate NC tool paths. The tool-path generation is highly efficient and still maintains the advantage of having accurate and smooth machining result. The word “surfel” itself is the combination of the two words “surface” and “element”. It is originally applied to the rendering of scanned data. In this paper, the point-based model is created using an elliptical Gaussian re-sampling filter that is based on a signal re-sampling algorithm. Since the input scanned data is of discrete and random nature, the warping process is utilized to transform the input data into a continuous surface and then re-sample the continuous surface by using GPU. Because the re-sampled data can accurately represent the original surface, tool paths can be generated based on the point data set. For cutting tools with various sizes, adaptive re-sampling schemes are employed to generate sufficient sampled points for the generation of accurate and smooth tool-paths.     

三维曲面高速数控加工工艺分析

现代模具零件数控加工中，曲面所占比例越来越大，加工质量要求不断提高，对数控加工工艺提出了更高的要求。从机床、刀具、工艺参数等方面分析了影响模具零件三维曲面高速数控加工质量的相关因素，提出了提高数控加工质量的具体措施。     

A manufacturing model of helical groove on rotary burr and a universal post processing method

A systematic machining theory and precision method to determine cutter location in a grinding system is presented for rotary burr. First, the helical cutting edge on various kinds of revolving surfaces is built. Then, based on the geometry model of the helical cutting edge, the smooth spiral rake surface with constant normal rake angle and flank surface can been formed during the one-pass grinding process by this method. No interference between the grinding wheel and workpiece happens by the wheel special rotation. The method has the characteristic of detaching the grinding wheel path solution from specified machining conditions. The grinding wheel path is suitable for different NC machine tools through post processing. Meanwhile, a mechanism kinematic model of the NC machine tool is built, and a generalized algorithm for post-processing of multi-axis NC machine tools is presented. This model is applied to arbitrary configuration of NC machine tool, and the motion value for each axis will be generated by the inputting structure and motion parameters of the machine tool. The model, together with the machining method mentioned in this paper, make the calculation and generation of the grinding wheel path simpler and universal. At last, the validity of the method given in the paper is identified by an example of grinding.     

数控加工中刀具的选用

随着数控设备的逐年增加,数控加工逐渐成为零件加工的主要方式,为了提高数控设备的加工精度和效率,首先要合理的选用刀具和切削用量,现在数控加工多采用标准的机夹式刀具,由专业的厂家制造,对于操作者来说主要的任务是选择适合的刀具和切削参数,充分发挥刀具的效能.本文从实际应用的角度出发.详细介绍了数控刀具的种类、选用方法和切削用量的选用原则,对实际生产具有一定的指导意义.     

面向导弹天线罩精密加工的三维曲面重构

导弹天线罩的精密加工,属于自由曲面精密加工的范畴,它对天线罩以及导弹的性能起着至关重要的作用。根据测量所得的天线罩几何表面的离散数据点,结合对其综合电气性能测试数据的处理和分析,实现原始曲面的重构,并由此构造出要求的曲面,再进行分析和规划,实现按需去除加工,是实现对其精密加工的关键。以及三次B样条曲面方法为工具,利用其良好的几何特性以及简单有效的算法,实现了天线罩廓形曲面的重构,为在计算机上实现曲面绘制提供了理论基础。求算的等距面方程,为数控加工中刀具轨迹的规划奠定了基础。     

集合逆向工程与数控加工的分析制造

实现逆向工程的关键在于对曲面部件建立点云数据并进行适当的数据处理,使曲面模型满足加工制造要求。采用三维扫描仪完成曲面零件的扫描工作得到呈高度密集的点云数据,在Geomagic Studio环境下对密集点云进行数据处理,输出封装文件,并在Geomagic Design X中实现封装文件的建模,导入Geomagic Qualify进行误差检测同时生成分析报告。进入SIEMENS NX加工模块实现逆向模型的工艺编程,后处理操作输出数控加工程序。在SIEMENS NX和CIMCO Edit环境下模拟数控加工过程,验证数控程序的工艺可靠性。实验证实,将Geomagic、SIEMENS NX和CIMCO Edit结合起来的方法可以实现复杂曲面零件的逆向制造,提高逆向加工工艺的可靠性。     

基于数控加工机床的弧齿锥齿轮建模

基于数控螺旋锥齿轮加工机床,根据实际切齿过程建立了齿面方程,并利用MATLAB求解非线性方程组得到齿面上的坐标,通过SolidWorks拟合齿面上的曲线,将线连成面,最后建立精确的齿轮三维实体模型用于理论分析.     

<Emphasis Type="Bold">Prediction of Surface Topomorphy and Roughness in Ball-End Milling</Emphasis>

Milling is today the most effective, productive and flexible-manufacturing method for machining complicated or sculptured surfaces. Ball-end tools are used for machining 3D freeform surfaces for dies, moulds, and various parts, such as aerospace components, etc. Milling data, such as surface topomorphy, surface roughness, non-deformed chip dimensions, cutting force components and dynamic cutting behaviour, are very helpful, especially if they can be accurately produced by means of a simulation program. This paper presents a novel simulation model, the so-called MSN-Milling Software Needle program, which is able to determine the surface produced and the resulting surface roughness, for ball-end milling. The model simulates precisely the tool kinematics and considers the effect of the cutting geometry on the resulting roughness. The accuracy of the simulation model has been thoroughly verified, with the aid of a wide variety of cutting experiments. Many roughness measurements were carried out on workpieces, which were cut using a 5-axis machining centre. The calculated roughness levels were found to be in agreement with the experimental ones. The proposed model has proved to be suitable for determining optimal cutting conditions, when finishing complex surfaces. The software can be easily integrated into various CAD-CAM systems.     

浅析刀具对数控加工质量的影响

数控加工中,刀具的选择很重要,不仅影响机床的加工效率,而且直接影响加工质量。对数控刀具总的要求是安装调整方便、刚性好、精度高、耐用度好,在此基础上综合考虑工件材料的切削性能,机床的加工能力,数控加工工序的类型,切削用量以及与机床和数控装置工作范围有关的诸多因素。     

<Emphasis Type="Bold">CNC Rake Grinding for a Taper Ball-End Mill with a Torus-Shaped Grinding Wheel</Emphasis>

A new grinding method using a torus-shaped grinding wheel and a machining path generation method with a novel moving coordinate system are proposed. With this new grinding method, the smooth spiral rake surface of a taper ball-end mill with constant helical angle and constant normal rake angle can be formed during one grinding process and the normal rake angle can be obtained accurately. The novel moving coordinate system is established based on taking account of both the cutting edge curve and the cutter body surface. By means of the novel moving coordinate system, the machining path generation becomes very simple. The proposed grinding method and the machining path generation method are verified by 3D simulation results.     

基于表面粗糙度预测的数控车削加工物理仿真模型的研究

通过分析数控加工中表面粗糙度的产生原因,提出了表面粗糙度仿真系统模型的结构,建立了切削力、振动和表面粗糙度的数学模型,为通过物理仿真预测加工表面粗糙度提供了理论依据。     

面向加工特征的刀具和切削参数计算机辅助选择系统

切削刀具制造商面临围绕大量工件材料和加工特征为客户提供合理刀具和切削参数的现状,切削工艺规划的核心步骤也是刀具和切削参数的确定。确定刀具和切削参数一般多从零件材料角度出发,可能导致工件与刀具不匹配。文中提出面向加工特征的刀具和切削参数计算机辅助选择系统的开发。系统包括车削特征、铣削特征、钻削和镗削加工特征,系统利用特征图形作为用户交互式接口,采用关系数据库结合数据驱动和规则推理逻辑来选择刀具和切削参数,利用数学模型计算过程参数包括单工步加工工时、切削功率、最大粗糙度等,并辅助制定工序。以车刀和车削参数选择为例,介绍该系统的实现方法。该系统可以辅助设计师及工艺人员选择合理的刀具和切削参数。     

UG在三元叶轮加工中的应用及研究

以数控加工过程中有很大难度的风机三元叶轮为研究对象,在UG NX软件中进行建模,同时进行图形交互式编程和仿真,并生成了数控代码,导入数控机床进行试切,加工试验效果良好,总结出一套比较完善的三元叶轮数控加工方法,使夹持长度与刀柄的尺寸之间实现参数化设计。模型输入模拟机床,就可以得到一个5轴后置处理,设置具体参数。从而减少设计更改所需的时间和成本,实现了经济效益的提高。     

Fuzzy Nets Based on-line Cutting Power Recognition in Milling Operations

A self-organising fuzzy-nets optimisation system was developed to generate a knowledge bank able to demonstrate the required cutting power on-line for a short length of time in an NC verifier. This fuzzy-nets system (FNS) uses a five-step self-learning procedure, and was examined for end-milling operations on a Fadal VMC40 vertical machining centre. Data collected from the operations were used to train and test the FNS. Three approaches were employed to predict the cutting power: 1. Metal cutting theory model. 2. Fuzzy-nets model using theoretical data for training. 3. Fuzzy-nets model using experimental data for training. To compare the quality of the data obtained from these approaches, three hypotheses were formulated for this study. The results showed that the FNS possessed a satisfactory range of accuracy with the intended applications of the model.     

Super-precision cylindrical machining

A study has been made of the theory and techniques of turning precise circular components. The possibility of such high accuracy cylindrical machining was analysed according to the principle of making a precise circle. In the study, a form of chucking-type preciison cylindrical machining was developed by combining an insensitive vibration cutting mechanism - using a main spindle system which features an air bearing - with superposition superfinishing. In the first process, the work is chucked on the main spindle and machined using a continuously and systematically pulsating cutting force. In the second process, the work is finished by a newly developed superposition superfinishing device which features equivalent grades of ultrasonic vibration stone. Key points of the techniques are a torsional vibration mode tool for producing accurate, high amplitude vibration of the cutting point, and a contrivance for making accurate movements of the superposition superfinishing device. Machined roundness of 0.1–0.2 μm and surface roughness of 0.03–0.09 μm R_max were obtained with plain carbon steels, stainless steels and hardened steels (H_RC 41, 53, 60). It is considered that turning to roundness ≈ 0, cylindricity ≈ 0 and surface roughness ≈ 0 can be realized by means of this new machining process and its lathe.     

考虑不同光伏渗透率影响的配电网风险规划研究

针对含光伏电源的配电网规划问题,考虑光伏输出特性受天气影响和因此造成配网潮流方向的改变和产生电压偏差等影响因素,提出了一种考虑不同光伏渗透率和电网运行风险的配电网规划方法。将天气状态大致归为3类,得到3种典型的光伏出力曲线。采用两状态天气模型,用不同天气条件下的线路故障率和光伏出力来表征天气状况对网架线路规划方案的影响,并通过系统切负荷期望值评估了规划方案的运行风险。提出了用于对不同光伏渗透率下规划方案经济性进行了评估的光伏发电投资收益比,综合给出合理的规划方案,并用不同的配电规划系统进行了测试。研究结果表明,光伏渗透率对光伏投资收益比和网架线路规划有重要影响。     

基于刀具进让式进给数控加工技术的研究

通过分析常规数控加工中存在的问题,提出了一种刀具在进给方向上可进让式进给切削工件曲面轮廓的新工艺方法,建立了进让式进给切削数学模型,并从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况等方面,具体分析了采用该方法对加工精度的改善情况,并给出了算法步骤。试验结果表明,新方法有利于减小工艺系统的变形,显著提高了工件的加工精度。     

数控车床加工过程中的刀具声发射试验研究

利用SWAES声发射检测仪提取数控加工过程中金属切削声发射信号,对信号进行频谱分析,找出主要频段,并利用金属切削过程中的声发射模型及试验数据,对影响声发射信号的因素进行分析,指出进给速度和主轴转速对声发射信号影响较大.     

Tool path optimization in postprocessor of five-axis machine tools

Generally, tool path is generated in a computer-aided manufacturing software considering only the geometry of machining parts. It is converted into numerical control (NC) codes in the postprocessor based on the particular machine kinematics. For some special types of five-axis machine tools, e.g., non-orthogonal five-axis machine tools, the generated NC codes may produce unqualified parts because of the existence of the non-linear error. Conventional commercialized postprocessors usually do not have the function of non-linear error checking. Observing that the tool path is a non-smooth trajectory full of corners and a series of connected line segments, cubic spline interpolation is applied to smooth the tool path at regular points in this study. The cutter tip center points are computed by the cubic spine interpolation, while the cutter posture vectors are obtained via linear interpolation. At the splines (for regular points) and the line segments (feature points), more points are chosen to be converted into NC codes to reduce the non-linear error, which is called data densification. Using the cubic spline to smooth the tool path and the data densification to reduce the non-linear error, a novel tool path optimization algorithm in postprocessor is proposed. Experiments were carried out on an inclined rotary spindle axis non-orthogonal five-axis machine tool. It shows that the proposed tool path optimization provides improved accuracy and surface quality.     

特种回转面刀具螺旋槽的通用几何模型

针对数控磨削螺旋槽的特点 ,提出了基于一般特种回转面刀具刀刃曲线和刀面截形的螺旋槽通用几何模型。该模型采用统一的形式表示螺旋槽 ,为特种回转面刀具的设计和数控加工提供了理论基础。该模型也适用于其它类型的回转刀具