三轴数控铣削加工仿真系统的研究与实现

针对采用传统方法来验证数控加工代码的不足，对数控铣削加工仿真进行了研究。重点论述了三轴数控铣削加工的刀具轨迹仿真技术，并提出了一种基于STL模型的普通立铣刀和球头铣刀加工过程的干涉检测算法；并在此基础上利9IVC＋＋6．0与OpenGL图形系统开发了三轴数控铣削加工仿真系统。试验结果表明该系统具有良好的实用性。     

螺纹数控铣削技术在航空发动机复杂零件上的应用

螺纹数控铣削是当今制造业中比较流行的一种螺纹加工方法,它是采用数控机床的螺旋插补功能(G02/G03)进行螺纹加工的一种新方法(图1),该方法首先流行于欧美,随着数控机床在国内的广泛普及和数控编程技术的提高,螺纹数控铣削方法在中国也得到了广泛的应用.     

数控铣削过程有约束广义 预测控制解析算法1)

通过分析性能指标函数和约束条件的特点,提出并证明了两个关于有约束广义预测控制性质的定理,进而提出了一种解析算法,并将其成功地应用于数控铣削过程.计算机仿真和切削试验表明,算法效率高且输出性能良好.     

数控铣削过程有约束广义预测控制解析算法

通过分析性能指标函数和约束条件的特点,提出并证明了两个关于有约束广义预测 控制性质的定理,进而提出了一种解析算法,并将其成功地应用于数控铣削过程.计算机仿真 和切削试验表明,算法效率高且输出性能良好.     

Master CAM铣削加工中进刀方式的设定

在数控铣削中有很多不同于普通铣削的工艺性问题需要考虑,切削前的进刀方式就是其中之一。切削前的进刀方式有两种形式：一种是垂直进刀方向,另一种是水平进刀方向。对于数控加工来说,这两个方向的进刀都与普通铣削加工不同。下面就此讲述一下数控加工中进刀方式的设定方法。一、垂直进刀方式的设定在普通铣床上加工一个封闭的型腔零件时,垂直进刀方式有两种方式可供选择,一是在零件的实体上事先钻一个孔,然后采用多刃立铣刀来加工型腔轮廓,这是因为立铣刀的端部切削刃没有到铣刀中心,所以立铣刀没有较大切深的垂直进刀能力。第二种…     

浅谈数控铣削曲面零件的走刀路线

数控铣削加工的走刀路线反映了工序的加工过程,走刀路线合理与否,关系到工件的加工质量与生产效率。尤其在数控铣削曲面零件过程中,应认真分析零件的加工要求及其结构特点,找出走刀路线中影响加工效率的因素,在保证零件加工精度和表面粗糙度要求的前提下,应尽量缩短加工路线,从而提高数控机床的加工效率,降低加工成本。     

螺纹数控铣削技术在航空发动机复杂零件上的应用

在某发动机复杂零件加工技术研究中,我们经过实验研究,在接嘴螺纹的加工上应用了螺纹数控铣削技术,效果良好。螺纹数控铣削技术,是一种新型的螺纹加工工艺,与攻丝、车螺纹相比有着独特的优势和更广泛灵活的使用方式和应用场合,本文根据现场实际加工过程,对螺纹数控铣削技术的加工特点及编程方法做了详细介绍。     

数控仿真关键技术的研究与实现

数控仿真系统运行过程中图形的真实感和刷新速率是衡量该系统优劣的两个重要指标.作者从工件模型的几何表示和仿真过程中使用的局部绘制技术两个方面来研究和实现三轴数控铣削加工仿真系统,在真实感图形的效果和刷新速率方面均取得了理想的效果.     

虚拟数控铣削几何及物理仿真系统的研究

本文讨论了一套虚拟数控铣削几何及物理仿真系统,提出了仿真系统的总体框架,建立了几何模型和物理仿真模型,分析了铣削加工过程中的影响因素,并建立了各种标准件库,进行了加工参数优化,实现了虚拟数控几何仿真与物理仿真的集成。     

CAXA制造工程师在数控铣削加工中的应用

CAXA制造工程师是一种集零件建模功能、刀具加工轨迹生成功能和数控代码生成功能于一体的国产数控加工软件,也是历届数控技能大赛指定编程软件,本文就第六届甘肃省数控技能大赛试题为例,介绍了CAXA制造工程师在数控铣削仿真加工中的应用。     

Assessment of the impacts of surface topography, off-nadir pointing and vegetation structure on vegetation lidar waveforms using an extended geometric optical and radiative transfer model

In order to prioritize the measurement requirements and accuracies of the two new lidar missions, a physical model is required for a fundamental understanding of the impact of surface topography, footprint size and off-nadir pointing on vegetation lidar waveforms and vegetation height retrieval. In this study, we extended a well developed Geometric Optical and Radiative Transfer (GORT) vegetation lidar model to take into account for the impacts of surface topography and off-nadir pointing on vegetation lidar waveforms and vegetation height retrieval and applied this extended model to assess the aforementioned impacts on vegetation lidar waveforms and height retrieval.Model simulation shows that surface topography and off-nadir pointing angle stretch waveforms and the stretching effect magnifies with footprint size, slope and off-nadir pointing angle. For an off-nadir pointing laser penetrating vegetation over a slope terrain, the waveform is either stretched or compressed based on the relative angle. The stretching effect also results in a disappearing ground peak return when slope or off-nadir pointing angle is larger than the “critical slope angle”, which is closely related to various vegetation structures and footprint size. Model simulation indicates that waveform shapes are affected by surface topography, off-nadir pointing angle and vegetation structure and it is difficult to remove topography effects from waveform extent based only on the shapes of waveform without knowing any surface topography information.Height error without correction of surface topography and off-nadir pointing angle is the smallest when the laser beams at the toward-slope direction and the largest from the opposite direction. Further simulation reveals within 20° of slope and off-nadir pointing angle, given the canopy height as roughly 25 m and the footprint size as 25 m, the error for vegetation height (RH100) ranges from − 2 m to greater than 12 m, and the error for the height at the medium energy return (RH50) from − 1 m to 4 m. The RH100 error caused by unknown surface topography and without correction of off-nadir pointing effect can be explained by an analytical formula as a function of vegetation height, surface topography, off-nadir pointing angle and footprint size as a first order approximation. RH50 is not much affected by topography, off-nadir pointing and footprint size. This forward model simulation can provide scientific guidance on prioritizing future lidar mission measurement requirements and accuracies.     

基于三角面模型的虚拟轮廓铣削仿真研究

针对基于三角面片构建的带内腔毛坯模型,在轮廓铣削仿真时,由于在不完全被切除的三角面片中未被切除顶点的不移动,所造成被切削轮廓面不光顺的问题,提出了沿刀具切削包络面的法向,未被切除的顶点移动到包络面上的方法,解决了轮廓面不光顺的问题;而对于仿真铣削带内腔毛坯时,就内外表面如何关联的问题,首先提出了判断刀具进出模型内外表面的算法,然后给出了轮廓面与内腔面关联的方法,完善地解决了这一问题.基于本研究提出的方法,通过VirtoolsDev开发平台,对带内腔的三角面片模型,获得了具有光顺切削表面的仿真效果.同时,使得铣削仿真精度也得到了根本性的改善.     

Modelling of surface roughness in inclined milling operations with circle-segment end mills

There is currently a lack of knowledge in the manufacturing of high complexity aerospace components. Impellers or blade-integrated disks (blisks) are expensive, and manufacturers tend to prefer reliability over productivity. Thus, manufacturing times are higher than they should be. These challenging parts need to be machined using new advanced tools for several reasons, such as requirement of 1) special and complex tool paths, 2) smoother cutting forces, and 3) good accessibility. Circle-segment or oval-form cutters have recently demonstrated their usefulness and adaptability in the machining of profile and free-form surface operations, and are becoming a solution for a wide range of applications and materials. However, machinists who use them know very little about such tools. In fact, there has been a lack of real-world modelling applications. This paper proposes for the first time a geometrical model that allows the prediction of the surface topography in flank-milling operations using circle-segment end mills. This time-domain model includes the most important mechanical and kinematical parameters during cutting: the tool geometry, feed rate, radial immersion, and tool runout. Tool orientation angles commonly used in 5-axis operations are also included. The developed model was positively verified against experimentally measured values in a milled wall made of aluminium Al7075T. This knowledge-based tool is useful for manufacturing companies and suppliers interested in optimizing and controlling their production parameters.     

开滦集团全息数字化矿山管理平台的研究与设计

全息数字化矿山管理平台依托3D-GIS技术和虚拟仿真技术,通过构建一体化的三维可视化平台,将矿山地形地貌、地表设施、井巷工程、矿体围岩等客观空间构造,在平台系统中真实再现,充分利用现代空间分析、数据采矿、知识挖掘、虚拟现实、可视化、网络、多媒体和科学计算技术,为矿产资源评估、矿山规划、开拓设计、生产安全和决策管理进行模拟、仿真和过程分析提供新的技术平台和强大工具。     

Mean dynamic topography and surface circulation in the western Labrador Sea and Newfoundland offshore: satellite observations and ocean modelling

Mean dynamic ocean topography and surface circulation for the western Labrador Sea and Newfoundland offshore are computed using a three-dimensional, high-resolution, non-linear finite-element ocean model and monthly-mean climatologies of temperature, salinity and wind stress. The agreement of the model surface topography and circulation with estimates from satellite altimetry, drifter data and hydrographic measurements, and from satellite and in situ gravity data, is good in the continental slope and deep sea but poor in some coastal and shelf regions. The surface currents from the altimetry and gravity data also compare favourably with satellite-tracked drifter data. The present study suggests that the model sea surface topography can be useful for more accurate determination of the marine geoid and therefore altimetry-derived absolute sea surface heights and geostrophic currents off Newfoundland and Labrador.     

基于小波分解和ROI的数字高程模型表面建模

将小波多尺度分解和ROI应用于数字高程模型(DEM)的表面建模中,首先用非均匀B样条曲面进行数字高程模型地形表面建模,然后用小波多尺度的特征将地表曲面进行压缩和光顺处理.对复杂地表曲面,可能只对某些局部区域感兴趣,因此在小波多尺度分解过程中要结合感兴趣区域(ROI)的方法.本文阐述了地表曲面小波分解和ROI多分辨率表示的原理,给出了具体曲面的小波分解算法和实现结果,有效减少了曲面存储所需的空间并提高了曲面的光顺程度.     

真实感水力侵蚀地形建模与绘制

水力侵蚀地表是现实生活及虚拟场景中常见的一种自然现象。为研究水力对地表 的侵蚀现象,提出一种采用光滑粒子流体动力学(SPH)模拟流体对地形表面的湿润以及侵蚀过程 的真实感仿真模型。通过对自然界中真实溅蚀现象进行合理简化描述,建立一种包含 3 个阶段 的地形水力溅蚀模型：首先,利用弹丸冲击平板靶材变形模型模拟水流冲击地表变形效果;其 次,构建基于达西定律的水流渗透量计算方法以确保地表吸水与水分扩散的真实性;最后,提 出将地表湿润度因素对地表侵蚀的影响考虑在内的新型计算模型,实现与冲蚀相融合模拟积水 继续运动对地表冲蚀作用。实验结果表明,该模型能够真实地模拟出不同方向的水流对地表的 侵蚀效果以及侵蚀过程中地表吸水与湿润扩散现象。     

无线传感器网络三维表面k覆盖多连通部署方法*

无线传感器网络中覆盖连通问题是基本且重要的问题,三维表面作为无线传感器网络中的一种特殊情形,对应于现实世界中的山体,为了解决这类与实际应用密切相关的问题,提出了三维表面k覆盖多连通部署方法。该方法结合三维表面的地形特征,首先在目标区域自由选择网格大小进行划分,接着在各网格之间建立多连通关系,再通过方向梯度概率感知模型在网格内先构造k覆盖集,然后利用最小生成树算法构造连通图,最后找出关节点构造双连通图。大量仿真实验表明,该方法能够对目标区域进行完全覆盖和连通,并且能保证网络的健壮性。     

Relating halftone dot quality to paper surface topography

Most printed material is produced by printing halftone dot patterns. One of the key issues that determine the attainable print quality is the structure of the paper surface, but the relation is non-deterministic in nature. We examine the halftone print quality and study the statistical dependence between the defects in printed dots and the topography measurement of the unprinted paper. The work concerns SC paper samples printed by an IGT gravure test printer. We have small-scale 2D measurements of the unprinted paper surface topography and the reflectance of the print result. The measurements before and after printing are aligned with subpixel resolution, and individual printed dots are detected. First, the quality of the printed dots is studied using Self Organizing Map and clustering and the properties of the corresponding areas in the unprinted topography are examined. The printed dots are divided into high and low print quality. Features from the unprinted paper surface topography are then used to classify the corresponding paper areas using Support Vector Machine classification. The results show that the topography of the paper can explain some of the print defects. However, there are many other factors that affect the print quality, and the topography alone is not adequate to predict the print quality.