航空叶片打磨余量分析及轨迹生成

针对航空发动机叶片打磨加工前,叶身余量分布不均且较小的问题,提出一种基于毛坯点云配准的加工余量分析和自适应打磨轨迹生成方法。利用精确扫描测绘技术获取毛坯三维点云,形成了毛坯/零件数模二者点云配准方法;通过基准对齐、点云轮廓包含等条件约束,实现了毛坯三维加工余量分析;在余量分布点云基础上,通过截面获取加工点云轨迹,对轨迹点云进行珠链排序,将轨迹排序点有效化,计算出连续合适的打磨路径,实现自适应余量打磨。最后在Vericut软件中进行了打磨仿真,验证了提出方法的有效性。     

基于铸件毛坯零件的粗加工方法研究

本文针对铸件毛坯零件的特点，提出Z向式、法向式和毛坯余量均切式等加工方法，系统地解决了该类毛坯的粗加工问题。该方法对零件造型没有特殊要求，可根据给定的毛坯余量和轨迹层数生成零件的分层加工刀具轨迹。     

基于Renishaw和Delcam的加工中心在线检测技术

该文针对数控机床在线检测技术的应用,提出了Renlshaw＋Delcam加工中心的在线检测系统。作者以Renishaw OMP60测头和PowerlNSPECT检测软件为例,介绍了加工中心的组成、原理和检测方法。并对在线检测技术的应用和发展做了展望。     

机械加工MBD毛坯模型的特征识别设计方法

为了解决基于模型的定义(MBD)环境下机械加工毛坯辅助设计问题,采用特征识别技术辅助创建三维毛坯模型.首先分析了机械加工工艺设计环节MBD毛坯模型的组成要素与模型要求,并建立零件模型的属性面邻接图;根据零件模型上加工特征的特点划分简单特征、体积特征和表面特征;通过属性面邻接子图的模式从特征集合中识别出简单特征与体积特征,并利用补特征法与半空间法抑制这2种特征;最后,根据工艺员输入的表面加工余量创建抑制表面特征的实体.在整个毛坯设计推理过程中研究了三维制造标注的维护方法,最终达到辅助工艺员快速设计MBD毛坯模型的目的.     

数字制造助大连机床集团转型

2010年4月，南京，第六届中国数控机床展现场。加工中心里，近l米长的合金汽轮叶片毛坯正在加工中。随着铣头的前行，毛坯褪去了粗糙的“外衣”，显露出精细、光亮的形体……“真是高水平啊。”一位飞机制造企业专家兴奋地说。     

基于Deform的航空发动机叶片金属锻造仿真

针对航空发动机叶片形状复杂、材料变形困难,导致锻造过程中材料利用率较低,且工件完整度不高的问题,提出基于Deform的航空发动机叶片金属材料锻造仿真.结合叶片工件制造状态与功能,构建状态模型,将锻造演化过程分为毛坯态、中间态与成形态,建立信息组织原则,有助于对不同锻造阶段数据做综合管控;研究刮板与温度对成形的影响,通过对矩形求解域分析,设计均匀性描述指标;采用线性加权法优化目标函数,选取设计变量范围;确定材料、变形温度与速度、网格分割数量等工艺参数,设置5次热交换与锤击操作,完成叶片金属材料锻造.仿真结果证明,所提方法能有效模拟出锻件变形系数变化过程,提高材料利用率,增加工件完整度.     

大型定子叶片铸件的数字化测量及误差评定

随着航空、航天、船舶、汽车和模具工业的飞速发展,复杂曲面的数字 化测量与误差评定技术对曲面加工精度起着越来越重要的作用。利用激光跟踪测量设备对大 型定子叶片铸件进行了数字化测量,对测量点云进行了去噪、精简等数据处理,并将测量点 云与理论模型进行了基准匹配,计算出了定子叶片铸件各部位的误差分布,实现了对大型定 子叶片铸件的误差评定;测量及误差分析结果可以用于优化叶片在后续加工中的装夹姿态, 使叶片各部位的加工余量趋于均匀,有效提高产品制造精度和加工效率。     

一种高精度玻璃丝径测量算法

在自聚焦透镜生产中涉及到一个重要的质量检测问题：毛坯玻璃丝的在线直径测量。针对这项检测要求非接触、高精度特点，该文提出了一种基于高精度图像测量技术的亚像素插值算法，动态测控毛坯玻璃丝的直径，解决了毛坯生产的批量化问题。实践证明，这个算法具有精度高、速度快、稳定性好的特点。     

箱体类零部件指南系统设计与分析

本文详细介绍了根据产品的性能、成本、制造周期、质量保证等要素要求,在机箱、机壳类零件毛坯选择技术、成型技术、工艺规程优化技术以及相关加工工艺方法研究的基础上,编写的箱体类零部件指南系统,为工艺技术人员确定该类零件制造工艺方法提供技术支持。     

铣削过程双参数自适应控制系统

极值型自适应控制系统,目前在金属切削机床中获得了应用。在毛坯加工余量和硬度变化的情况下,这种系统通过调节进给量,将切削过程的某些动力参数(主传动功率、主轴力矩、切削力等等)稳定在给定的水平上,这样就提高了加工生产率。     

A time-varying geometry modeling method for parts with deformation during machining process

Deformation due to residual stress is a significant issue during the machining of thin-walled parts with low rigidity. If there are multiple processes with deformation during machining, some process suitability issues will appear. On this occasion, the actual geometric state of the deformed workpiece is needed for process adjustment. However, it is still a challenge to obtain the complete geometry information of deformed workpiece accurately and efficiently. In order to address this issue, a time-varying geometry modeling method, combining cutting simulation and in-process measurement, is proposed in this paper. The deformed workpiece model can be reconstructed via transforming the deformed workpiece with only a small amount of the measurement points by superimposing material removal and workpiece deformation simulation according to a time sequence, which takes advantage of the proposed Curved Surface Mapping based Geometric Representation Model (CSMGRM). Machining experiment of a typical structural part has shown that the deformed geometry model of the whole workpiece can be reconstructed within the error of 0.05mm, which is less than one tenth of the finish machining allowance in general cases, and it is sufficient to meet the accuracy requirements for interference or overcut/undercut analysis and process adjustment.     

Optimal blank design based on finite element method for blades of large Francis turbines

Metal pressing process that is widely used in industries has advantages over casting process for producing large Francis turbine blades from thick plates. Prior to the pressing process, blank design is firstly performed to determine flat blanks. The traditional trial and error approach is not applicable to blade design for Francis turbines that are not standard due to hydraulic characteristics of power plant sites. The rapid development of computing technology makes it possible to obtain optimal flat blanks by numerical modelling and simulation. In this paper, inverse finite element approach is investigated for blank design and an elasto-plastic model has been built using the well-known commercial software ANSYS. Numerical simulations for blade unfolding models with thick shell elements, solid elements and shell elements have given results with negligible differences. Unfolding tests with simple geometries have been carried out and the numerical results agree well with the analytical solutions. A large and thick shape of a Francis turbine blade for a hydropower plant has been successfully unfolded by inverse FE model. Sensibility analysis shows that the middle surface of the flat blank is independent of blade thickness. For ensuring the machining of the blade after the pressing process, a new contour is obtained by extending the boundary of the flat blank provided by the numerical model. This research may provide a useful tool for optimal blank design of Francis turbine blades.     

Digital Twin-driven machining process for thin-walled part manufacturing

Thin-walled parts are widely used in the aerospace, shipbuilding, and automotive industry, but due to its unique structure and high accuracy requirements, which leads to an increase in scrapped parts, high cost in production, and a more extended period in the trial machining process. However, to adapt to fast production cycles and increase the efficiency of thin-walled parts machining, this paper presents a Digital Twin-driven thin-walled part manufacturing framework to allow the machine operator to manage the product changes, make the start-up phases faster and more accurate. The framework has three parts: preparation, machining, and measurement, driven by Digital Twin technologies in detail. By establishing and updating the workpiece Digital Twin under a different status, various manufacturing information and data can be integrated and available to machine operators and other Digital Twins. It can serve as a guideline for establishing the machine tool and workpiece Digital Twin and integrating them into the machining process. It provides the machine operator opportunities to interact with both the physical manufacturing process and its digital data in real-time. The digital representation of the physical process can support them to manage the trial machining from different aspects. In addition, a demonstrative case study is presented to explain the implementation of this framework in a real manufacturing environment.     

Process intermittent measurement of tools and workpieces

This paper describes the application of surface sensing probes in unmanned machining. The aim is to automate tool setting, workpiece alignment, machining allowance test, and also to provide workpiece inspection capability. Special emphasis is given to the mathematical aids for the compensation of the machine tools systematic errors. A hardware-software system has been designed to solve this problem. It is an integrated part of the control unit and executes the necessary transformations of the subsequent numerical control sentences.     

Robotic grinding of complex components: A step towards efficient and intelligent machining – challenges,solutions, and applications

Robotic grinding is considered as an alternative towards the efficient and intelligent machining of complex components by virtue of its flexibility, intelligence and cost efficiency, particularly in comparison with the current mainstream manufacturing modes. The advances in robotic grinding during the past one to two decades present two extremes: one aims to solve the problem of precision machining of small-scale complex surfaces, the other emphasizes on the efficient machining of large-scale complex structures. To achieve efficient and intelligent grinding of these two different types of complex components, researchers have attempted to conquer key technologies and develop relevant machining system. The aim of this paper is to present a systematic, critical, and comprehensively review of all aspects of robotic grinding of complex components, especially focusing on three research objectives.For the first research objective, the problems and challenges arising out of robotic grinding of complex components are identified from three aspects of accuracy control, compliance control and cooperative control, and their impact on the machined workpiece geometrical accuracy, surface integrity and machining efficiency are also identified. For the second aim of this review, the relevant research work in the field of robotic grinding till the date are organized, and the various strategies and alternative solutions to overcome the challenges are provided. The research perspectives are concentrated primarily on the high-precision online measurement, grinding allowance control, constant contact force control, and surface integrity from robotic grinding, thereby potentially constructing the integration of “measurement – manipulation – machining” for the robotic grinding system. For the third objective, typical applications of this research work to implement successful robotic grinding of turbine blades and large-scale complex structures are discussed. Some research interests for future work to promote robotic grinding of complex components towards more intelligent and efficient in practical applications are also suggested.     

机器故障的柔性加工与装配作业车间分批联合调度算法

针对传统的加工与装配分阶段独立调度中资源利用率不高的问题,将加工与装配联合同时进行调度。在考虑工件批量和批次的前提下提出一种改进遗传算法求解该问题,以最小化最大完工时间为优化目标建立数学模型,根据问题特性提出一种工件末工序前移的邻域结构,提升了算法的局部搜索能力进而改善整体求解质量。设计了一种基于装配设备负载均衡的混合贪婪解码方法,完成了装配设备选择。考虑到实际车间中机器故障的特点,提出了相应的响应策略和染色体更改规则,解决了动态调度问题。最后通过算例分析验证了所提算法和策略求解该问题的可行性和有效性。     

The stencil buffer sweep plane algorithm for 5-axis CNC tool path verification

A new algorithm based on the sweep plane approach to determine the machined part geometry in 5-axis machining with general APT tools is presented. Undercut and overcut can be determined. Collision detection between the toolholder, workpiece and workpiece fixture can also be detected. The subtraction of the removed material is obtained for each sweep plane by using a stencil buffer. A flat plane is swept through the blank part, fixture and tool swept volume geometry. The intersections of sweep planes and the swept tool volume are computed based on the canonical representation of a cone, torus and sphere. The necessary data to compute all the intersections is stored in a text file, here called the M-Plane file (Memory Plane). The equations of the intersections are approximated by a polygon with variable accuracy. The resulting APT tool intersection in each sweep plane is then clipped against the blank workpiece intersection with the current sweep plane. The stencil buffer provides automatically the union of all tool intersections and the subtraction from the blank workpiece. This algorithm provides a 3D geometric model of the tool swept volume. The display algorithm is based on the Painter's algorithm, but there is no time consuming sorting from back to front required, as the sweep proceeds from back to front. The accuracy of the algorithm can be varied as a function of the requirements by changing the polygon approximation and the distance between the sweep planes.     

Distortion behavior of hydro turbine blade castings during heat treatment processes under variation of seasonal temperature

Distortion often appears at the corners of heavy turbine blade castings during heat treatment processes,so a great machining allowance is generally set in production which directly results in cost increase. In this paper,a novel real-time measuring technology is developed for non-contact measuring the deformation behavior of heavy steel castings in heat treatment process. It was employed to measure the distortion and the temperature field of a batch of heavy turbine blade castings at cooling stage in normal...