基于刀具进让式进给数控加工技术的研究

通过分析常规数控加工中存在的问题,提出了一种刀具在进给方向上可进让式进给切削工件曲面轮廓的新工艺方法,建立了进让式进给切削数学模型,并从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况等方面,具体分析了采用该方法对加工精度的改善情况,并给出了算法步骤。试验结果表明,新方法有利于减小工艺系统的变形,显著提高了工件的加工精度。     

提高虚拟车削仿真质量的工件建模方法

根据车削加工工件的几何外形和成形特点 ,提出了包含加工误差信息的回转体类工件半剖轮廓多边形建模方法和记录、组织加工误差信息的刀具轨迹法。在虚拟加工中 ,刀具扫描体被简化表示为刀具扫描体轮廓多边形 ,简化了仿真计算。同时还对加工过程仿真和反映加工误差的已加工表面形貌的构建等关键问题进行了研究。该建模方法在VMIS虚拟加工与检测系统中获得了应用     

数控轮廓铣削的切入和切出程序

在数控铣削轮廓加工中,铣刀从起始位置快速移动到即将以工作进给速度开始切削位置的程序,称为切入程序。因此,切入程序的终点就是开始切削的程序的起点,这一点称为切入点。切削完毕后,铣刀应返回起始位置。铣刀由切削终了时的位置返回起始位置的程序,称为切出程序。编制数控铣削轮廓加工程序时,必须合理地安排切入和切出程序。一、切入程序的编制切入程序要把刀具从起始位置调到开始切削的位置,为切削加工做好准备。而刀具开始切削的位置与其切入工件的方式有关。加工中,为了避免在工件加工表面的切入处留下刀痕,所以当加工表面质量要求较高时,应使铣刀沿工件轮廓的切线方向或工件轮廓     

基于刀具沿进给方向蠕动式进给的数控加工技术研究

通过对数控加工中存在的问题分析,提出了一种在数控加工中,刀具在被加工工件曲面上沿进给方向蠕动式切削加工的方珐,通过刀具与工件时续分离和切削,改善了工艺系统的刚性,从而使工件的加工精度得到改善,并具体从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况方面,分析了采用该方珐对加工精度的改善情况。     

径向槽回转切削运动学及加工误差分析

提出采用无分度运动的回转切削方法加工径向槽,建立了刀尖相对于工件的运动轨迹方程和两种理论加工误差模型(轮廓倾斜误差模型和轮廓周向误差模型),结合实例分析了中心距、刀具半径等参数对理论加工误差的影响.结果表明,采用回转切削方法加工径向槽不仅可以提高自动化程度和生产效率,而且通过合理选择中心距和刀具半径等参数,可将理论加工误差控制在允许的范围内.     

超声振动精密切削振幅对工件尺寸误差的影响

精密超声振动切削是将一定振幅的高频振动添加到刀具的运动过程中的一种加工方式,具有切削力小,加工精度高,加工表面质量好等特点。采用动力学分析方法利用二自由度的振动切削工件-刀具系统模型,并借鉴普通切削中对切削力的分析方法,首次从理论上实现了对振动切削中刀具振幅对工件变形影响的研究,并采用数值模拟的方法给出它的变化规律:在精密振动切削使用的振幅范围内,刀具振幅的变大会使工件的净位移减小、进而使工件的尺寸误差减小。同时,给出了不同刀具前角、切削速度和切削深度条件下,工件尺寸误差随振幅变化的规律。     

数控机床三维建模与加工仿真技术研究

采用实体几何法建模思想,建立机床（刀具）模型,采用基于三角网格的方法对工件毛坯建模,构建数控仿真系统的虚拟加工环境。运用VC＋＋与三维图形库软件Open Inventor编程,进行机床运动仿真及切削仿真。     

基于凹轮廓特征的粗加工轨迹生成算法研究

在加工具有凹轮廓特征的工件时,由于走刀路线的原因,在切削过程中切削力波动较大.笔者针对这一问题进行研究.从改变刀具轨迹的角度出发,减少切削力的波动,给出了一种适合凹轮廓特征工件的粗加工刀具轨迹产生方法.     

异形链条附板直线进给靠模仿形铣工装设计

靠模仿形铣削加工是成型轮廓加工方法之一.设计制造了直线进给靠模仿形铣滑台,根据不同的工件轮廓设计专用靠模轨迹槽和刀具系统、对刀系统、工件定位装夹系统.必须使刀具中心轨迹与靠模轨迹槽中心形状完全相同并方向一致,同时经过对刀和工件定位,使刀具、工件轮廓、靠模轨迹槽有正确的相对位置.     

用不同断面轮廓的麻花钻钻孔

<正> 1、引言用麻花钻加工孔的质量取决于很多因素,通常可以归纳为四个主要方面,即有关的机床、工件、切削过程和刀具。刀具方面的影响因素包括麻花钻钻尖的几何形状、动静态刚度、表面光洁度、刀具材料和钻头总的轮廓,特别是横断面的轮廓形状。切削力和切削温度形成与钻削过程有关的主要影响因素,而工件材料、工件几何形状和夹具则形成与工件相关的主要影响因素。类似的分析也可以用以处理     

基于切削载荷的余量规划策略

针对高速铣削加工的切削载荷控制问题,提出一种适用于平头立铣刀2.5维铣削加工,考虑切削载荷的余量规划策略——恒力余量。通过加工试验证实了该策略的有效性,并讨论了走刀方向、刀触点轨迹线的连续性、刀具浸入包角和刀具半径对恒力余量规划结果的影响。与传统的几何等距余量规划方法相比,恒力余量策略能够显著改善切削载荷的波动情况,避免切削载荷的突变,为控制铣削载荷提供有效途径。     

圆弧刃刀具切削时理论粗糙度的计算

在圆弧刃刀具切削直线廓形时理论粗糙度计算的基础上，着重研究圆弧刃刀具切削圆弧廓形时理论粗糙度的计算方法。研究表明，工件已加工表面理论粗糙度取决于工件已加工表面的廓形、刀具切削刃形状和刀具切削运动方式，优化选取刀刃半径和刀具进给量后，可以有效地减小理论粗糙度值并提高切削效率。     

基于OpenGL的数控车削动态仿真过程及图形显示

针对数控车削虚拟仿真系统,介绍了数控车削动态仿真的计算过程及图形显示.首先根据译码结果提取加工信息,然后运用插补运算得到加工轨迹坐标从而控制刀具与工件的相对运动,并在这个运动过程中快速进行刀具与毛坯的布尔运算,根据运算结果重新绘制场景.最后利用OpenGL的双缓存技术在计算机屏幕上显示工件的动态切削过程.     

Cutter workpiece engagement region and surface topography prediction in five-axis ball-end milling

Based on the machining tool path and the true trajectory equation of the cutting edge relative to the workpiece, the engagement region between the cutter and workpiece is analyzed and a new model is developed for the numerical simulation of the machined surface topography in a multiaxis ball-end milling process. The influence of machining parameters such as the feed per tooth, the radial depth of cut, the angle orientation tool, the cutter runout, and the tool deflection upon the topography are taken into account in the model. Based on the cutter workpiece engagement, the cutting force model is established. The tool deflections are extracted and used in the surface topography model for simulation. The predicted force profiles were compared to the measured ones. A reasonable agreement between the experimental and the predicted results was found.     

车铣加工切削机理分析

车铣加工通过将车刀更换为铣刀,增加铣刀转动自由度,基于工件转动和铣刀转动的合成运动,完成对工件的加工.车铣加工具有断屑更容易、切削温度低、切削力小等优点,即使工件低速旋转,也能实现高速切削.对车铣加工的切削机理进行了分析,具体包括刀具磨损机理、切屑形成机理、工件表面质量、难加工材料切削等.     

基于Z-MAP方法的球头铣刀铣削力的建模

瞬时刚性切削力的建模是铣削加工物理仿真的基础,然而,球头铣刀的刀齿形状复杂,加工过程中姿态多变,瞬时刚性铣削力的建模难度较大。在考虑刀具姿态调整的情况下,通过齐次坐标变换建立了刀齿的运动轨迹,提出了一种识别刀具和工件瞬时接触区的改进Z-MAP算法,通过计算当前刀齿的参考线与工件的边界面或刀齿扫掠面的交点求出瞬时未变形切屑厚度,并采用非线性回归的方法辨识了切削力系数,在此基础上使用微元积分法建立了瞬时切削力的计算模型。为了验证仿真模型的可靠性,分别进行了垂直加工和倾斜加工试验,试验和仿真结果具有较高的一致性,表明该建模仿真方法是有效的,可以为实际加工中参数的选择和优化提供理论依据。     

Modelling of dimensional and geometric error prediction in turning of thin-walled components

In die-mold manufacturing and aircraft industry, many components that have thin-walled features are produced by turning operation. The major problem encountered during internal or external turning is cutting force induced deflection of workpiece along the periphery as well as axial length of a component. The present research work aims to develop a mathematical model for estimating dimensional and geometric errors during turning of thin-walled hollow cylinder qualitatively and quantitatively. In the proposed model, a mechanistic approach which is semi-analytical in nature is followed to achieve accuracy of the predicting results. First of all, process geometry model for thin-wall turning is developed based on process geometry variables such as uncut chip thickness, actual feed per revolution, actual depth of cut, peripheral cutting speed, effective cutting area etc. Using these process geometry variables and mechanistic cutting constants, a force model of turning is developed to estimate the tangential and radial force components. Later on, based on the predicted forces, tool-workpiece combined deflection model is developed to estimate radial, diametric and various geometric errors of the turned surface. The developed models are able to predict radial, diametric and various geometric errors such as straightness, circularly and cylindricity errors without conducting expensive actual machining operation. Hence, the present study will be helpful to take care of precautionary measures for controlling of dimensional and geometric errors more efficiently and reliably. Therefore, an attempt has been made to provide a basic platform to machining practitioners and process planners for in-depth comprehension and characterization of dimensional and geometric errors of the entire turned surface for varying machining conditions.     

Integration of cutting force control and chatter suppression control into automatic cutting feed adjustment system design

Abstract

This study designed an automatic cutting feed adjustment system for computer numerical control (CNC) turning machine tools, which integrate the operational characteristics of cutting force control and chatter suppression control to shorten the machining time and maintain the quality of workpieces. The setting of appropriate machining conditions (such as cutting feed, spindle speed and depth of cut) to consider both machining quality and efficiency often causes difficulties for machine tool operators. Therefore, this study uses cutting force control to design an automatic cutting feed adjustment method for cutting tools, and then, the chatter suppression control design is used to modify the cutting force command to suppress cutting chatter. The experimental results of the CNC turning machine tool show that the use of the cutting force control to adjust the cutting feed can shorten the machining time; however, the cutting chatter results in larger surface waviness on the workpiece surface. When the cutting force command is properly modified by actuating the chatter suppression control, the workpiece shows better surface roughness with prolonged machining time. Therefore, the cutting tests demonstrate that the proposed system is feasible for satisfying the machining requirements of the manufacturing processes of mechanical parts for high speed and high accuracy.     

The monitoring of flank wear on the CBN tool in the hard turning process

In precision hard turning, tool flank wear is one of the major factors contributing to the geometric error and thermal damage in a machined workpiece. Tool wear not only directly reduces the part geometry accuracy but also increases the cutting forces drastically. The change in cutting forces causes instability in the tool motion, and in turn, more inaccuracy. There are demands for reliably monitoring the progress of tool wear during a machining process to provide information for both correction of geometric errors and to guarantee the surface integrity of the workpiece. A new method for tool wear monitoring in precision hard turning is presented in this paper. The flank wear of a CBN tool is monitored by feature parameters extracted from the measured passive force, by the use of a force dynamometer. The feature parameters include the passive force level, the frequency energy and the accumulated cutting time. An ANN model was used to integrate these feature parameters in order to obtain more reliable and robust flank wear monitoring. Finally, the results from validation tests indicate that the developed monitoring system is robust and consistent for tool wear monitoring in precision hard turning.