三轴数控镗铣床加工截割头体多角度空间平面

针对截割头体表面按螺旋线分布多个空间平面零件加工特点,进行参数分析,设计夹具,计算坐标,科学选用刀具,设计数控加工编程,使用三轴联动镗铣床（相当T6113）代替五轴联动数控设备完成该零件加工。     

三维调制靶模板的快速刀具伺服加工技术

采用快速刀具伺服技术(FTS)实现了非回转对称三维调制靶模板的精密车削加工.阐明了调制靶模板车削加工的基本原理,并提出一种基于坐标变换的金刚石刀具几何参数选择方法,推导了车削加工此类表面时金刚石刀具刀尖圆弧半径、前角和后角所需满足的条件.基于此提出了一种基于三次Hermite插值的刀尖圆弧半径补偿算法,并详细讨论了插值节点的计算方法.由刀尖圆弧半径补偿仿真结果可以看出,此补偿算法精度优于2 nm.在自行研制的精密金刚石车床上实现了X、Y方向上波长均为100μm、幅值均为0.7μm的正弦网格调制结构的加工.采用白光干涉仪对所加工的调制结构进行测量,并提取二维轮廓进行分析,其轮廓误差为0.31μm,表面粗糙度为13.3 nm.测量结果表明采用基于快速刀具伺服的非回转对称车削是实现三维调制靶模板制作的有效手段.     

超硬材料小直径内螺纹数控铣削加工研究

本文研究的是利用数控机床的三轴联动功能,及两到三个螺距形成的螺纹铣刀,并附加参数化的数控程序,以完成超硬材料零件小直径内螺纹的铣削加工。通过数控程序中的圆弧指令和在轴向增量编程的方法,将螺纹线分解为两种运动方式——圆弧运动和垂直于圆弧所构成的平面方向的直线运动。该方法的推广对于系列的超硬材料零件小直径内螺纹加工有着重要意义。     

数控机床的刀具半径补偿功能及应用

在数控加工中刀具半径补偿功能是应用很广的一项功能,应用此功能可以减少大量繁复的尺寸计算,而且可以省掉零件粗、精加工时反复编写相似程序的麻烦,灵活应用刀具半径补偿可以起到事半功倍的效果。     

浅谈FANUC系统数控铣床刀具半径补偿的应用技巧

在数控铣床上进行轮廓加工时,因为铣刀有一定的半径,所以刀具中心（刀心）轨迹和工件轮廓不重合,如不考虑刀具半径,直接按照工件轮廓编程是比较方便的,而加工出的零件尺寸比图样要求小了一圈（加工外轮廓时）,或大了一圈（加工内轮廓时）,为此必须使刀具沿工件轮廓的法向偏移一个刀具半径,这就是所谓的刀具半径补偿指令。应用刀具半径补偿功能时,只需按工件轮廓轨迹进行编程,然后将刀具半径值输入数控系统中,执行程序时,系统会自动计算刀具中心轨迹,进行刀具半径补偿,从而加工出符合要求的工件形状,当刀具半径发生变化时也无需更改加工程序,使编程工作大大简化,同时便于加工操作。     

基于有效交叉点搜索的点串等距边界环生成算法

提出了一种根据零件截面点串边界曲线生成等距加工轨迹的新算法。当点串边界曲线的等距环自交或内外环相交时,根据边界上交叉点的穿越深度判定出有效交叉点,在有效交点处的四段进出边中选取一对转角最大的进边与出边连入环中,形成环形加工轨迹。该算法已在自主开发的RPM数据处理软件中成功应用。该算法提高了已有数据处理软件的稳定性;并在此基础上实现了RPM的OFFSET加工轨迹的生成。     

基于非线性规划解的双圆柱螺线样条的局部构造

给出基于非线性规划解的双圆柱螺线样条局部构造法,把平面几何样条－双圆弧样条推广到常曲率和常挠率的空间几何样条。一对G^1拼接的圆柱螺线段可插值空间两端点位矢和单位切矢,且可适应不同的设计要求,如逼近在双圆柱螺线段两端点处的主法矢,使曲线光顺等。本方法在数控加工和显示中有良好的应用前景。     

后置处理中平面轮廓拐角加工程序自动生成技术

为解决早期数控程序中没有考虑拐角加工问题,本文提出了围绕NC代码识别拐角并自动生成拐角加工数控程序算法,以满足产品升级与加工高要求之需,进一步确保数控加工安全与零件表面质量。为实现拐角识别,首先总结归纳常见数控代码结构;其次还原NC代码的几何形态并采用线链表示,计算线链走向、线链边之切矢;将拐角分为点式拐角与圆弧式拐角两大类型,综合拐角的离散结构与线链的封闭性,给出了拐角的识别原理与相应准则。拐角加工按分层铣削加工,从刀具轴向上减少刀具在拐角位置处加工瞬时的切削量;各层拐角加工刀轨由进刀、切入、拐角加工、切出与退刀五段组成;层间刀轨采用进退刀连接线衔接。最后用实例验证了该算法的正确性。     

曲面映射法生成等残留环切加工刀具轨迹

在数控加工中，对组合曲面的高速加工变得越来越重要。高速加工是一种高质量和高效率的制造技术，但是传统的刀具轨迹生成方法并不能满足高速加工的需要。曲面映射法是依据加工后零件表面材料余量呈现“等残留高度”的要求，设计的一种生成空间等距环切加工刀具轨迹的新方法。该方法巧妙地将三维曲面简化为二维平面进行处理，避免了对曲面的复杂计算，解决了用投影法不能处理竖直面或曲面竖直区域的问题。     

N-3M立式炮塔铣床盘铣刀的改进

该文介绍N-3M立式炮塔铣床在加工平面时,使用盘铣刀加工平面零件时机床、刀具产生较大振动,工件表面粗糙度差,吃刀量较浅的问题,经过改进后得出的直柄小型盘铣刀适合N-3M立式炮塔铣机床的使用,可以解决加工平面零件时出现的刀具与主轴的振动和背吃刀量的问题,提高了零件表面粗糙度,满足加工平面零件的需求,提高生产效率和加工质量。     

New method of tool orientation determination by enveloping element for five-axis machining of spatial cam

A new methodology is presented for the determination of a feasible tool orientation of a ball-end milling cutter for collision and gouging avoidance in five-axis machining of spatial cam. Since the meshing element is used as a generating element for a spatial cam, the meshing element is in tangency with the spatial cam. The notion of the proposed collision-free method is that the ball-end milling cutter is confined within the meshing element. Based on envelope theory, homogeneous coordinate transformation and differential geometry, curvatures of the cam surface and the cutting tool are evaluated for interference checking. To evaluate machining efficiency, the contact length is calculated for various tool orientations. The toolpath is verified through a solid cutting simulation. The proposed methodology can be used to automate the programming of tool paths for five-axis machining of spatial cam.     

A control algorithm for improving the accuracy of five-axis machine tools

An algorithm for reducing the influence of geometrical, thermal, kinematic and stiffness errors in five-axis machine tool components on the desired tool position and orientation is given. This new algorithm is based on the calculation of the cutting tool error matrix for orthogonal machine tools. In the new model of this matrix, all angular errors of the machine links are considered as infinitesimal rotations. The error matrix is a function of the commanded machine component positions and the errors in these positions. To correct errors in the three translational and two angular tool positions, a matrix of commanded tool position and orientation is multiplied by the inverse error matrix in every period of the tool trajectory interpolation. This corrected matrix of the tool position and orientation provides the inverse kinematics used for calculation of the successive links positions required for achieving the given tool trajectory. The control algorithm for five-axis machine tools with the error compensation is implemented both in the CNC system and in the postprocessor. The proposed algorithm is applied on a vertical five-axis turning centre with two translational and three rotational axes. Twenty-four errors that could cause inaccurate machining are recognised on this machine. The machine links and their coordinate frames are denoted using the Denavit–Hartenberg parameters.     

Adaptive nonlinear tool path optimization for five-axis machining

Current tool path computation in the CAM algorithms approximates the surface by piecewise linear interpolation. In the case of three-axis machining on a CNC machine the tool will exactly reproduce this computed tool path. However in the case of five-axis simultaneous machining the real tool path on the CNC machine will not follow the linear approximation computed by the conventional CAM algorithm. A new CAM algorithm is proposed which approximates the surface to be machined by a piecewise curved approximation. This curve represents the real tool path followed on the five-axis machine. This piecewise curved approximation is further optimized by formulating the tool path computation as the generation of a grid based on a variational smoothness penalty function. This new algorithm considerably improves the accuracy and reduces the number of blocks and machining time.     

基于AutoCAD的圆柱面上非规则曲线三维建模方法

分析了轧制各种形状花纹板材刀具轨迹的共同特征,研究了各种形状花纹板材的平面设计图与刀具轨迹的对应关系,提出了对平面设计曲线进行二维数据处理的一般方法,对二维数据处理结果向圆柱面上非规则曲线进行变换的三维建模和数据处理方法。在AutoCAD 环境下,利用 Autolisp 语言的编程功能,针对生产实际中切削刀具平面设计图,实现了圆柱面上非规则曲线的三维建模。该模型为刀具的数控加工提供了走刀轨迹仿真依据和走刀加工三维数据。     

An efficient algorithm for automatic machining sequence planning in milling operations

Machining sequence planning can be considered as one of the most important functions of manufacturing process planning. However, less attention has been paid to automation of this function in contemporary computer-aided process planning systems. This paper describes an efficient algorithm for automatic machining sequence planning in 2.5D milling operations. It is programmed in LISP and forms the machining sequence planning module of a CIM system. This module is integrated with a feature-based design system that determines required machining operations and parameters for each machining operation. This information is then sent to the machining sequence planning module for determining proper machining sequence plans for producing the part. The algorithm generates feasible machining sequences based on the bilateral precedence between machining operations. The algorithm results in minimized tool changes.     

一种基于多步回溯算法的铣削稳定性预测方法

在加工过程中,由于薄壁件的弱刚性易发生加工颤振,从而对工件表面质量和刀具寿命等造成不良的影响,对铣削过程的稳定性进行预测是至关重要的。通过提出一种多步回溯算法来预测铣削过程的稳定性,将铣削过程离散化成时滞周期方程,在每个时间间隔上采用多步回溯的方法来近似时间周期及时滞项。通过构建状态转移矩阵,根据Floquet理论获得了铣削稳定性边界参数。最后,通过仿真对比实例验证了算法的计算精度和收敛率。结果表明,多步回溯算法具有快速收敛及高计算精度等特点,尤其在低速铣削的稳定性预测中具有良好的应用前景。     

Three-dimensional reference pulse linear and circular interpolators for CNC systems

Three-dimensional (3D) linear and circular interpolations are a basic element in the machining of complex shapes. Because of the lack of accurate and efficient algorithms for the generation of 3D lines and circles, a full realization for the available machine tool resolution is difficult. This paper presents new algorithms for 3D linear and circular interpolation in the reference pulse technique. In 3D space, the line or circle cannot be represented as a general implicit equation. The natural way to represent a line or circle is as the intersection of two surfaces. Based on these facts, interpolation algorithms were designed to follow intersection curves in searching for a minimum path error strategy, and a real-time 3D linear and circular interpolator was developed in software using a PC. The software implementations in a PC and the hardware implementation on a retrofitted milling machine have shown promising results in interpolation error and speed performance. It is expected that this can be applied to the computerized numerical control systems for the machining of 3D lines, circles and some other complex shapes.     

Fast tool path generation by the iso-scallop height method for ball-end milling of sculptured surfaces

This article reports on tool path generation by the iso-scallop height method for the three-axis ball-end milling of sculptured surfaces. In order to achieve the specified machining accuracy, constant scallop height machining requires an understanding of the three-dimensional machining geometry and the use of iterative approaches. Feng and Li have accomplished such work using the bisection method to search the scallop curves and the tool centre curves. This paper presents an analytic and geometric study of the machining aspects. Analysing the local properties of the distance functions, which indicate where the scallop point and the tool are centred, the bisection method can be replaced by the Newton iterative algorithm which converges faster. The derivatives of the functions are formulated by their Taylor approximations with a small error. The initial guesses are obtained by considering the local machining geometry. The proposed method significantly reduces the total computing time necessary to generate tool paths.     

Greedy tool heuristic approach to rough milling of complex shaped pockets

The milling of complex pockets bounded by NURBS surfaces is usually broken into rough and finish milling, with the former taking up the bulk of the machining time. The total machining time can be reduced if the proper combination of end-mills of different sizes are used to machine in different regions. This paper presents a new greedy tool heuristic approach to the determination of the machining volume that should be allocated to different tools selected from among a large set of available tools. Subsequent machining planning can then be performed by repeated application of standard 2-D milling algorithms. The proposed new approach of multi-tool rough milling promises to reduce the machining time of complex shaped parts such as molds and casting patterns. The presented techniques can be used in CAD/CAM systems to automate NC tool path generation for complex pockets machining.     

一种新的隐藏曲线消除算法及其应用

基于非可见性数和关键点的概念,提出了一种新的隐藏曲线的消除算法,并应用该算法来确定三轴数控铣削的可加工性区域,从而可避免相应的刀具干涉,为数控加工中的干涉检查及消除提供一种新的途径。