复杂曲面笔式加工的直接插补算法

复杂曲面笔式加工时的工具轨迹是位于曲面上的自由曲线轨迹．针对此类形式的轨迹，给出一种复杂曲面笔式加工时的自由曲线型刀轨的直接插补算法，即对位于曲面上以投影方式形成的任意自由曲线形式的刀轨进行插补计算，生成控制机床运动的指令．该方法的实现扩充了CNC系统的轨迹控制功能，提高了复杂曲面的加工效率．仿真和试切的结果证明算法可行而且有效．该算法也可以应用到整体曲面加工中．     

蜂窝芯零件五坐标加工无干涉建模

从曲面整体连续性、可加工性的角度，提出了一种组合曲面整体G^1连续模型的建立方法，并推导出曲面过渡区域五坐标加工时无局部过切干涉的条件．为了保证方向舵表面铺层和蜂窝芯之间的胶结强度，避免加工过程中的局部过切干涉，分析了复杂过渡曲面区域的设计方法，获得了既能保证整体连续性又能保证可加工性的高品质曲面模型．     

基于MasterCAM的曲面雕刻数控加工

本文结合曲面雕刻加工实例探讨了在FANUC数控系统的加工中心机床上应用MasterCAM软件进行曲面雕刻的方法,包括建立曲面文字的雕刻模型,根据加工工艺要求选择加工方法和设置加工参数,将软件生成的刀具轨迹G代码传输至FANUC数控加工中心,实现了曲面文字雕刻的实际加工。此方法突破了手工编程的局限性,避     

数控加工无干涉刀具轨迹生成的偏置算法

提出了用偏置方法来检查复杂曲面ＮＣ加工的刀具干涉及生成相应的刀具轨迹。通过对加工曲面进行上包络偏置表面操作，以及边界曲线“保护表面”的引入和导动平面与加工曲面求交时出现的非唯一性问题的处理，可获得一种生成３轴ＮＣ加工无干涉刀具轨迹的通用算法。该方法实现简单，算法稳定，具有广泛的适用范围。     

CATIA沿面加工方法

沿面加工(Isoparametric),加工的切削路径是由所加工曲面等参数线U、V所决定的。其加工操作对话框如图1所示。在几何参数选项页中,需要选择加工曲面以及四个端点。单击图1中示意图的红色区域,对话框消失,到几何显示区中选择需要加工的曲面,选择如图2所示的连续曲面。     

曲面直接插补和组合曲面的自适应加工

为了提高组合曲面的加工精度和效率，本文论述了曲面直接插补算法和组合自由曲面的混合数控加方法，提出了曲面自适应三角化方法和沿曲面／曲线交线自适应步长加工，这些自适应策略可大大强混合数控加工方法加工组合曲面的能力。     

基于SolidWorks的复杂曲面仿真加工系统

本文以SolidWorks为二次开发平台,VB为开发工具,充分利用SolidWorks API的方法和属性,研发了一套面向工程设计人员的复杂曲面仿真加工CAD系统,实现了复杂曲面加工的计算机模拟。随着科学技术和社会的发展,机械产品中采用了越来越多的复杂曲面,复杂曲面的应用和加工已成为机械学科研究的重要课题。对于复杂曲面,通常采用多轴数控机床加工。但是,对于复杂形状零件的加工,数控编程和反复试切又制约着机床使用效率,增加了制造成本。在未来制造技术     

加工仿真系统中弯管类零件加工工艺信息的自动提取

在加工仿真系统中 ,加工工艺信息的自动生成对于提高仿真系统的自动化、实用化水平 ,减少工艺人员的工作负荷至关重要。该文针对弯管零件加工仿真系统 ,提出了加工工艺信息自动提取方法。该方法根据弯管零件的数字化模型 ,自动判断曲面的类型 ,生成各曲面间的拓扑关系 ,提取每个曲面的几何参数及相关曲面的位置关系信息 ,并将这些信息转为工艺参数 ,输入工艺知识库 ,再根据相应的工艺知识 ,生成加工工艺信息。     

组合曲面参数线五坐标加工刀具轨迹的计算

提出了组合曲面间拓扑关系的建立方法．通过对曲面相邻边界及相邻角点拓扑信息查询，完成刀具路径的合理组织；针对目前在给定加工精度时确定参数增量算法存在的不足，提出基于等参数线的走刀步长追踪法，并对曲率半径趋于无穷大的情况及直纹面加工的情况进行单独处理，保证了算法的稳定性和有效性．在此基础上，系统地阐述了组合曲面加工中刀触点、刀位点的计算以及刀具轨迹的合理化组织。     

未知曲面数控加工干涉区域求取算法研究

质量和效率是自由曲面零件数控加工所追求的一对相互矛盾的目标,曲面的分片加工可以较好地解决这这一问题,而自由曲面零件分片加工方法中一个关键问题是如何求取自由曲面的干涉区域,提出了在对自由曲面密集采样测量的基础上,利用未知曲面测点信息,通过参数曲面局部逼近和干涉区域测点问几何关系遍历求取干涉区域的算法,该方法避开了烦琐的自由曲面重建处理,仿真和实验研究的结果验证了算法的有效性。     

汽车车身曲线曲面光顺处理方法的研究

本文根据车身曲线曲面的造型特点，提出了车身曲线曲面的光顺准则；重点介绍了用圆曲率法进行曲线曲面光顺的方法；还讨论了在实际车身曲面造型中，如何进行曲面光顺处理及检验曲面光顺的方法；最后介绍曲线曲面光顺方法在整车外表面设计中的应用。     

基于Marching cubes的三维目标表面积估算方法

三维目标表面积参数广泛应用于石油地质,医学,制造行业等领域。在介绍一种基于Marching cubes的局域配置方法来估算三维目标的表面积的过程中,针对Marching cubes分类的14种模型元,给出了一种简单和易于实现的分类方法,避免了重新实现Marching cubes算法或者使用一系列复杂的三维表面探测算法。基于Marching cubes的表面积估算方法对于规则和不规则目标表面积的估算均适用。通过实验数据对比几种不同的估算方法结果的精确度,说明基于Marching cubes的估算方法精确度是非常高的,可以应用于实际工程中。     

数控仿真技术的回顾与评述

本文在对当前国内外数控切削加工几何仿真和切削过程力学仿真的两个并行发展的研究领域的研究现状和成果的分析评述的基础上，指出了仿真的发展趋势，并提出一种几何仿真和力学仿真相结合的更精确的试切模型。     

Conditions of proper sculptured surface machining

Multi-axis machining of sculptured surfaces is in wide use in Conventional and Rapid Prototyping. Topic of the paper is in the area of sculptured surface machining (SSM). The problem under consideration is: how to define and how to analytically describe a set of necessary and sufficient conditions of proper SSM. The similar problem is already solved with respect to machining of regular surface [Facta Univ, Mech Engng, Univ Nis? 1 (1998) 637]. Here this problem is enhanced up to the area of machining of sculptured surface on multi-axis NC machine. The general approach to solve the problem is developed. The input data to the approach presented later is a complete information of topology of a sculptured surface to be machined and of the machining surface of a form cutting tool to be applied. The set of six necessary and sufficient conditions of proper SSM is developed as a result. This set of analytically described conditions can be considered as a sort of restrictions on the geometrical and kinematical parameters of a machining operation. An application of the set of conditions stated in the paper is useful and of importance in developing software for machining of sculptured part surface on multi-axis NC machine. The methodology presented here is a general one. It combines the activities of exploration of topology of a given sculptured surface, of the machining surfaces of a form cutting tool, and of kinematics of relative motion of these surfaces in machining operation, thus making the production process for conventional and rapid prototyping flexible, automatic and controllable. The effectiveness of the proposed approach is verified from numerical simulation and numerous practical applications, whose implementation will not detailed here.     

Non-uniform recursive Doo–Sabin surfaces

This paper presents a generalization of Catmull–Clark-variant Doo–Sabin surfaces and non-uniform biquadratic B-spline surfaces called Non-Uniform Recursive Doo–Sabin Surfaces (NURDSes). One step of NURDS refinement can be factored into one non-uniform linear subdivision step plus one dual step. Compared to the prior non-uniform Doo–Sabin surfaces (i.e., quadratic NURSSes), NURDSes are convergent for arbitrary n-sided faces. Closed form limit point rules, which are important for applications in adaptive rendering and NC machining, are given as well.     

复合循环指令在内曲面加工中的应用

零件的内曲的加工方法很多，但加工的效率、加工精度、刀具要求、加工质量有较大的区别。在数控车床上利用循环指令进行加工内曲面，降低了加工难度，并有效提高了加工精度和加工效率。本文运用实例，介绍广州数控系统（GSK980TDa）中G71、G72、复合循环指令对内曲面的加工。     

Accurate tool position for five-axis ruled surface machining by swept envelope approach

This paper presents a swept envelope approach to determining tool position for five-axis ruled surface machining. The initial tool position is traditionally located to contact with two directrices of a ruled surface. The swept profile of the tool is then determined based on the tool motion. By comparing the swept profile with the ruled surface, the tool position is corrected to avoid machining errors. The cutter's swept envelope is further constructed by integrating the intermediate swept profiles, and applied to NC simulation and verification. This paper presents the explicit solution for the swept profile of a taper-end cutter in five-axis ruled surface machining. The relation of the ruled surface geometry, the tool motion and the machining errors is developed. Therefore, the error sources can be detected early and prevented during tool path planning. The explicit swept envelope indicates that the machined surface is not a ruled surface in five-axis ruled surface machining. Manufacturing industries should take extra care in high precision ruled surface machining. Computer illustrations and example demonstrations are shown in this paper. The results reveal that the developed method can accurately position tool location and reduce machining errors for five-axis ruled surface machining.     

Prediction and optimization of performance measures in electrical discharge machining using rapid prototyping tool electrodes

In this work, the performance of rapid prototyping (RP) based rapid tool is investigated during electrical discharge machining (EDM) of titanium as work piece using EDM 30 oil as dielectric medium. Selective laser sintering, a RP technique, is used to produce the tool electrode made of AlSi10Mg. The performance of rapid tool is compared with conventional solid copper and graphite tool electrodes. The machining performance measures considered in this study are material removal rate, tool wear rate and surface integrity of the machined surface measured in terms of average surface roughness (Ra), white layer thickness, surface crack density and micro-hardness on white layer. Since the machining process is a complex one, potentiality of application of a predictive tool such as least square support vector machine has been explored to provide guidelines for the practitioners to predict various machining performance measures before actual machining. The predictive model is said to be robust one as root mean square error in the range of 0.11–0.34 is obtained for various performance measures. A hybrid optimization technique known as desirability based grey relational analysis in combination with firefly algorithm is adopted for simultaneously optimizing the performance measures. It is observed that peak current and tool type are the significant parameters influencing all the performance measures.

     

Quick segmentation for complex curved surface with local geometric feature based on IGES and Open CASCADE

Complex curved surface parts with local geometric feature are usually critical parts in high-end equipments. However, the processing for this kind of parts is usually difficult or inefficient due to the adoption of difficult-to-machine material and special structure. Current approaches cannot satisfy the rapid development of high-end equipments. Due to the existence of the local geometric feature for the parts, processing such parts with constant machining parameters is less applicative, restricting the improvement of machining efficiency. By separating the local geometric feature and generating tool path for the local geometric feature and the remaining processing area separately, the more efficient machining with variable machining parameters will be obtained for the complex curved surface with local geometric feature. In this way, the quick segmentation for the complex curved surface with local geometric feature is of great importance to the NC machining with variable machining parameters for this kind of parts, and a quick segmentation system is developed based on Initial Graphics Exchange Specification (IGES) and Open CASCADE (OCC) platform in this study. The complex curved surface model in IGES format is firstly imported into the system and then trimmed into independent surface patches. After computing the feature size of each surface patch, the segmentation for the complex curved surface is achieved by sorting and classifying the surface patches according to their feature sizes. Taking the whole impeller with small splitter blades for an example, the experimental result shows that the segmentation of small splitter blades from the whole impeller is successful and a serialized processing program could be generated, and then the whole impeller could be machined precisely and efficiently with NC equipment. In the machining experiment, it is proved that the machining with various machining parameters can improve the efficiency by 28.18% in the comparison experiment, 20.14% and 12.33% in the estimation. The research provides an important foundation for the high quality and more efficient machining of the complex curved surface with local geometric feature.     

数控加工仿真技术研究综述

数控加工仿真技术可以形象、直观地模拟数控加工的全过程,为验证数控加工程序的可靠性及预测切削加工过程提供了强有力的工具。介绍了数控加工仿真的关键技术——几何仿真技术、物理仿真技术和图像可视化技术,并分别对此3个数控加工仿真关键技术的研究成果进行分析评述,最后提出了数控加工仿真技术的发展趋势。