刀具轨迹分布式计算及控制模式研究

本文提出了数控加工中的两个新的概念：分布式刀具轨迹计算和ＮＣ 特征单元。其中分布式刀具轨迹计算是针对传统数控加工中的集中式刀具轨迹计算而设计的。其目的是提高数控加工系统的可控性和可观性。而实现分布式刀具轨迹计算的关键是ＮＣ 特征单元的定义和实现。本文分析了基于ＮＣ 特征单元设计原则, 给出了基于ＮＣ 特征单元的数控加工领域产品数据模型。并对基于分布式计算的数控加工控制模式进行了研究。     

Cimatron NC加工

Ｃｉｍａｔｒｏｎ的ＮＣ加工杰出特性是工业界普遍认同的。它可直接在混合模型上计算准确安全的刀具路径。此外Ｃｉｍａｔｒｏｎ可将其设计数据迅速地传递给加工模块处理。为了提高速度, Ｃｉｍａｔｒｏｎ ＮＣ对其所生成的刀具轨迹和沿轨迹加工过程进行优化。加工进程与相关的造型应用模块紧密与流畅地集成在一起,保证所设计的零件精确地制造出来。ＮＣ直接按照设计模型的数据可以为任何数控加工过程生成精确的刀具轨迹。 Ｃｉｍａｔｒｏｎ ＮＣ为２．５－５轴铣削、钻孔、车、冲裁及线切割提供了全面而有效的加工功能,它的仿真模拟功能…     

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。     

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。     

基于Windows的数控加工刀具轨迹仿真

一、 前言在数控机床上加工零件，加工前一般要进行数控程序（NC代码）校验，检查刀具运动轨迹是否正确，判断加工参数选择是否合理，是否存在过切、欠切等。实际加工中随着工件复杂程度增加，ＮＣ代码的错误率成级数级增长。如果用传统试切的方法来检验刀具路径，需要花费大量     

复杂三角网格模型分治加工刀具轨迹生成

为了解决复杂三角网格模型数控加工效率与精度之间的矛盾,提出包括模型分割以及子区域轨迹规划的分治加工方法.针对分治加工的需求,提出一种基于加工区域特征表述的区域生长原则,用于模型的区域生长分割;为避免在子区域中生成过多的短刀具轨迹,对分割后的子区域进行区域优化合并与边界光顺处理,子区域轨迹规划时对不同的特征子区域采用不同的刀具轨迹生成策略.在等残留高度法刀具轨迹生成中,提出初始轨迹生成方法,并改进扩展了刀具轨迹的投影偏置扩展过程,以解决边界不规则子区域的刀具轨迹生成问题.实例结果表明,基于加工区域特征表述的区域生长原则能够有效地驱动加工模型的区域生长分割,不同特征子区域以适当的刀具轨迹生成策略生成了有效的刀具轨迹.     

智能化图象编程系统GNCPPPS的设计原理

本文介绍了一个智能化的图象编程系统.文中论述了系统的设计原理,提出了采用加工单元的方法编程,加工单元先从三维模型中识别出来,然后自动选择刀具和安排加工单元加工顺序,最后自动选择刀具轨迹计算模块,使工艺过程设计和数控编程结合为一体.系统研究中应用了人工智能技术,提出了用概念模型、超级概念模型及规则表示知识,而规则只是对概念模型的一种属性约束.     

测量点数据等残留高度刀具路径规划

在介绍计算几何模型的基础上,提出一种刀具路径算法.首先分别以刀具半径值和残留高度值为等距距离,通过等距计算求出等距点集和残留高度点集;然后以前一行刀具路径为中心构建刀具包络面,并求出刀具包络面与残留高度点集的交点,即过渡点集;最后通过求以过渡点集为中心的刀具包络面与等距点集的交点,得出相邻行刀具轨迹,依次递推,求出所有的刀具路径行.针对计算过程中可能出现的欠切问题,给出了应用密切圆追踪的边界处理方法.通过实例验证了该算法的可行性.与等间距刀具路径生成方法进行比较表明,应用文中算法解决针对测量点数据的数控加工刀具路径生成问题,可缩短刀具路径长度,提高加工效率.     

数控铣削加工中刀具半径补偿的有关问题

在数控铣床上进行工件轮廓的数控铣削加工时,由于存在刀具半径,使得刀具中心轨迹与工件轮廓(即编程轨迹)不重合.如果数控系统不具备刀具半径自动补偿功能,则只能按刀心轨迹,即在编程时给出刀具的中心轨迹,如图1所示的点划线轨迹进行编程.其计算相当复杂,尤其是当刀具磨损、重磨或换新刀而使刀具直径变化时,必须重新计算刀心轨迹,并修改程序.这样既复杂繁锁,又不易保证加工精度.当数控系统具备刀具半径补偿功能时,数控程序只需按工件轮廓编写,加工时数控系统会自动计算刀心轨迹,使刀具偏离工件轮廓一个半径值,即进行刀具半径补偿.     

技术文摘

技术文摘曲面加工的刀具轨迹计算北京航空航天大学制造工程系冉瑞江王亚平马德昌讨论了曲面加工的刀具轨迹计算方法，给出了刀具偏置的基本计算公式。行距与步长的控制方法，接触轨迹曲线的定义和干涉检查与修正算法。最后，讨论了对几种典型的曲面加工情形的处理方式，包...     

基于Z-map模型的自由曲面无干涉刀具轨迹生成算法研究

刀具轨迹生成是自由曲面零件数控加工中重要的研究内容.本文分析了自由曲面数控加工中常用的刀具轨迹生成策略和方法,设计和实现了一种基于Z-map结构的自由曲面无干涉刀具轨迹生成算法.本算法采用进化算法进行刀具干涉检测,不仅解决了生成刀具轨迹时因走刀步长不合理而产生的过切问题,而且也确保了生成的刀具轨迹为无干涉刀具轨迹.     

Iso-planar piecewise linear NC tool path generation from discrete measured data points

This article presents a method of generating iso-planar piecewise linear NC tool paths for three-axis surface machining using ball-end milling directly from discrete measured data points. Unlike the existing tool path generation methods for discrete points, both the machining error and the machined surface finish are explicitly considered and evaluated in the present work. The primary direction of the generated iso-planar tool paths is derived from the projected boundary of the discrete points. A projected cutter location net (CL-net) is then created, which groups the data points according to the intended machining error and surface finish requirements. The machining error of an individual data point is evaluated within its bounding CL-net cell from the adjacent tool swept surfaces of the ball-end mill. The positions of the CL-net nodes can thus be optimized and established sequentially by minimizing the machining error of each CL-net cell. Since the linear edges of adjacent CL-net cells are in general not perfectly aligned, weighted averages of the associated CL-net nodes are employed as the CL points for machining. As a final step, the redundant segments on the CL paths are trimmed to reduce machining time. The validity of the tool path generation method has been examined by using both simulated and experimentally measured data points.     

An integrated framework of tool path planning in 5-axis machining of centrifugal impeller with split blades

Centrifugal impeller is a complex part commonly used in aerospace, energy, and air-conditioning industries. Its manufacture involves multi-axis free form machining, a time consuming and error-prone process. Tool path planning is considered a critical issue in the process but still lacking of systematic solutions. This paper proposes a tool path planning framework for 5-axis machining of centrifugal impeller with split blades. It provides several CAM functions that assist the users to generate collision-free cutter motions with smooth tool orientations. First, the machining process is divided into four operations and the planning tasks of each operation are standardized. Second, the hub surfaces are properly decomposed, re-grouped, and re-parameterized to facilitate calculation of quality tool path with reduced cutter retraction and plunging. Finally, geometric algorithms are developed to automatically detect tool collisions and then correct the erroneous tool orientations. An optimization scheme is applied to minimize the total amount of tool posture changes after the correction. An impeller is machined with the NC codes generated from the framework. The result shows the effectiveness of this work in automating the tool path planning in 5-axis machining of highly intricate impeller.     

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.     

复杂零件数控加工的仿真与优化研究

复杂零件数控代码繁多,采用人工检测、试切和机床运行的代码检测方法将造成极大的资源浪费。为了减小这方面的浪费及提高复杂零件加工的质量,本文以减速器中的典型零件产品为例,在Vericut里面建立三轴加工环境及方针模型,对数控代码进行仿真。通过仿真,优化了数控代码,精确模拟出实际的加工过程,直观地观察到刀具的轨迹和工艺的可加工性,为复杂零件的高效数控加工提供了借鉴。     

Five-axis pencil-cut planning and virtual prototyping with 5-DOF haptic interface

In this paper, techniques of 5-axis pencil-cut machining planning with a 5-DOF (degree of freedom) output haptic interface are presented. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Five-axis tool path planning has attracted great attention in CAD/CAM and NC machining. For efficient machining of complex surfaces, pencil-cut uses relatively smaller tools to remove the remaining material at corners or highly curved regions that are inaccessible with larger tools. As a critical problem for 5-axis pencil-cut tool path planning, the tasks of tool orientation determination and tool collision avoidance are achieved with a developed 5-DOF haptic interface. A Two-phase rendering approach is proposed for haptic rendering and force-torque feedback calculation with haptic interface. A Dexel-based volume modeling method is developed for global tool interference avoidance with surrounding components in a 5-axis machining environment. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper. The presented technique can be used for CAD/CAM, 5-axis machining planning and virtual prototyping.     

ADAPTIVE STRATEGIES FORNC MACHINING COMPOUND FREE-FORM SURFACES

ＡＤＡＰＴＩＶＥＳＴＲＡＴＥＧＩＥＳＦＯＲＮＣＭＡＣＨＩＮＩＮＧＣＯＭＰＯＵＮＤＦＲＥＥ－ＦＯＲＭＳＵＲＦＡＣＥＳＧａｏＳａｎｄｅ；ＺｈｏｕＹｕｎｆｅｉ；ＺｈａｎｇＸｉｎｆａｎｇ；ＺｈｏｕＪｉＡＤＡＰＴＩＶＥＳＴＲＡＴＥＧＩＥＳＦＯＲＮＣＭＡＣＨＩＮ...     

An integrated manufacturing planning assistant — IMPA

In this paper, we describe our development of a fully integrated manufacturing planning assistant (IMPA) system, which is able to: (1) interpret the finished part requirements directly from the designer's CAD systems or solid modelers without user intervention or special feature coding; (2) check the machinability of a designed part; (3) automatically generate a process plan, a tool path and an NC (numerically controlled) code, and (4) support interactive user modification of the resulting plans, tool paths and NC code. A demonstration version of the system was designed to provide automated assistance for the planning of machining processes on three-axes NC machine tools. The underlying architectural concepts and reasoning algorithms can be extended to more complex machines such as four-or-more-axes NC machines. CAD, CAE, and CAM including robotic, FMS (flexible manufacturing system) and NC machines are widely used in industry today. There is increasing interest in automation of factory control software Merchant, (1988); this includes automating the generation of the control programs — that is, in developing systems which will automatically produce the NC code for machining the part, given a model of the part, the shape of the raw material, and the machine specifications. With such systems, there are several difficulties in the manual preparation of an NC program code such as, long and tedious calculations, high risk of error in data preparation, etc., which need to be eliminated. This is a critical step toward the integration of CAD and CAM into a truly concurrent engineering and manufacturing environment.     

Multiresolution analysis as an approach for tool path planning in NC machining

Wavelets permit multiresolution analysis of curves and surfaces. A complex curve can be decomposed using wavelet theory into lower resolution curves. The low-resolution (coarse) curves are similar to rough-cuts and high-resolution (fine) curves to finish cuts in NC machining. In this paper, we investigate the applicability of multiresolution analysis using B-spline wavelets to NC machining of contoured 2D objects. High-resolution curves are used close to the object boundary similar to conventional offsetting while lower resolution curves are used farther away from the object boundary. Experimental results indicate that wavelet-based tool path planning improves machining efficiency. Tool path length is reduced, sharp corners are smoothed out thereby reducing uncut areas and larger tools can be selected for rough-cuts.