磨料水射流微细雕刻技术的研究

根据磨料水射流加工的特点，建立了磨料水射流加工的神经网络模型。用训练好的神经网络模型来预测给定加工条件下的进给速度，并根据加工路径和机床的特性对进给速度进行修正，并编写数控代码。通过控制水射流的进给速度来间接控制其刻蚀深度，同时获得加工轨迹的圆滑过渡，从而实现磨料水射流的雕刻工艺。本文以不锈钢为原材料，以JJ-I数控水射流机床为实验平台，根据机床的特性手工编程，成功雕刻出微型摩托车图形。     

高速高精度加工的几种方法

目的介绍了高速加工的数控编程策略. 方法论述了高速高精度加工的几种方法, 如待加工轨迹监控法、专家系统法、曲线插补法及试切法等. 结果与结论待加工轨迹监控法和专家系统法能够动态调节机床的进给速度, 曲线插补法能够提高机床的平均进给速度, 试切法则可以为任意半径的圆弧段设定一个最高允许进给速度.     

高速加工中速度前瞻控制新算法研究

为了避免在高速加工中高曲率轮廓导致的工件过切和机床的异常振动，提出了一种实时的速度前瞻软件控制新算法.该算法基于S型加减速方案，通过采用三次样条曲线拟合对离散加工路径的分析发现高曲率点，根据加减速特性预估高曲率点处的最优速度，最后对加工路径施加相应的运动学曲线规划，实现了加工速度自适应于加工路径的变化.应用该算法使得加工速度变化平稳，较之传统控制方法大大提高了加工效率.     

适于高速加工的五次参数样条曲线插补及其速度生成算法的研究

为适应高速高精加工,针对传统插补算法和速度控制方式在进给过程中存在柔性冲击的问题,提出了一种五次参数样条曲线插补方法及其速度生成算法.该算法采用二阶连续可导的五次样条和近弧长样条参数提高了进给运动的连续性;速度控制算法保证机床在高速运行过程中加加速度(加速度的变化率)的二次连续、加速度、速度和位移与时间关系的高阶连续变化,并且保证在各自的约束范围内,从而使机床的运动平稳,避免产生大的冲击和振动,同时有利于提高加工质量,减少加工时间.通过仿真验证,表明了这种算法能有效地保证高速加工机床运行过程中进给速度的连续性和运动轮廓的平滑性.     

高速高精度加工的几种方法

目的 介绍了高速加工的数控编程策略。方法 论述了高速高精度加工的几种方法,如待加工轨迹监控法、专家系统法、曲线插补法及度切法等。结果与结论 待加工轨迹监控法和专家系统法能够动态调节机床的进合速度,曲线插补法能够提高机床的平均进给速度,试切法则可以为任意半径的圆弧段设定一个最高允许进给速度。     

高速切削加工技术发展与关键技术

高速切削加工是先进制造技术的重要组成部分,近净形毛坯通过高速机床一次装夹加工是制造业的发展趋势.高速机床不仅要有高的主轴转速和进给速度,而且还需要有高的运动加速度.介绍了高速切削加工的概念和优越性;研究了国外高速机床的技术发展与应用,以及我国高速机床的发展现状和趋势;分析了高速切削机床、高速切削刀具、CNC控制系统等实现高速切削必需的关键技术的发展现状,并探讨了高速切削技术应用领域和高速机床发展趋势.     

大型光学非球面零件超精密切削新方法

超精密切削加工机床的刀具进给一般采用直线导轨实现,分析并提出以刀具的旋转运动代替直线进给运动方式,实施轴向与径向进给,并通过控制车刀的微进给量实现非球面的超精密加工.通过二次曲面曲率分析,给出避免产生过切的非球面最接近球面的求解方法;构建了车刀微进给系统进给的几何模型.计算机模拟表明:该加工方法可以提高大型非球面加工精度,并且制造同等精度设备难度小、成本低,结构紧凑、刚性变形小,可提高生产效率.     

Tricept型并联机床曲面加工的刀轨规划

研究了Tricept型并联机床采用平底刀加工曲面时的刀轨规划问题. 首先简要地介绍了机床的结构组成,并对机床的逆运动学及其位姿作业空间进行了分析. 在此基础上,给出了刀具干涉检验及刀具位姿作业空间检验的有效算法. 借助于传统五坐标数控机床曲面加工的等残高刀轨路径生成方法,提出了适用于Tricept型并联机床的刀轨规划算法.     

粗糙集遗传算法在机器人路径规划中的应用

提出了一种基于粗糙集和遗传算法混合方法的机器人路径规划方法,以提高机器人路径规划的速度和准确性.首先利用粗糙集获得机器人路径的决策规则,建立初始决策表,利用粗糙集理论进行化简,获得最小决策表,从中提出最小决策规则,然后利用所得的最小决策规则训练得出一系列可行路径的集合,最后利用遗传算法对这个种群优化,获得最优行走路线.对于两种不同环境分别进行仿真实验,验证了两种方法的混合算法在提高机器人路径规划速度上的优势.     

高频窄脉冲电化学加工间隙的在线检测与控制

针对高频窄脉冲电化学加工,对加工间隙进行建模分析,提出了间隙平均电流检测法.通过测量相邻一组平均电流及其方差这2个参数判断间隙状态,从而对进给速度、进给量进行相应调整,实现对加工过程的控制.试验结果表明,间隙平均电流值及其方差能准确反映加工间隙的变化,从而快速调整工具进给速度,使之近似等于工件去除速度,精确地维持恒定的小间隙,实现快速稳定的加工.     

Smoothness-oriented path optimization for robotic milling processes

Industrial robots are increasingly used for five-axis machining operations, where the rotation of the end effector along the toolaxis direction is functionally redundant. This functional redundancy should be carefully resolved when planning the robot path according to the tool path generated by a computer-aided manufacturing(CAM) system. Improper planning of the redundancy may cause drastic variations of the joint motions, which could significantly decrease the machining efficiency as well as the machining accuracy. To tackle this problem, this paper presents a new optimization-based methodology to globally resolve the functional redundancy for the robotic milling process. Firstly, a global performance index concerning the smoothness of the robot path at the joint acceleration level is proposed. By minimizing the smoothness performance index while considering the avoidance of joint limits and the singularity and the constraint of the stiffness performance, the resolution of the redundancy is formulated as a constrained optimization problem. To efficiently solve the problem, the sequential linearization programming method is employed to improve the initial solution provided by the conventional graph-based method. Then, simulations for a given tool path are presented. Compared with the graph-based method, the proposed method can generate a smoother robot path in which a significant reduction of the magnitude of the maximum joint acceleration is obtained, resulting in a smoother tool-tip feedrate profile. Finally, the experiment on the robotic milling system is also presented. The results show that the optimized robot path of the proposed method obtains better surface quality and higher machining efficiency, which verifies the effectiveness of the proposed method.     

A general,fast and robust B-spline fitting scheme for micro-line tool path under chord error constraint

The discontinuity of linear tool path(or G01 blocks) brings about unnecessary feedrate deceleration and fluctuation during machining. To improve the continuity, the linear tool path is usually smoothed by the local transition method or the global fitting method. For micro-line tool path, the transition method will significantly decrease the machining efficiency and introduce feedrate fluctuation. The global fitting method cannot be directly used in the NC interpolation because the indispensable chord error checking and iterative fitting processes are computation-intensive. This paper presents a general, fast and robust B-spline fitting scheme under chord error constraint for high speed interpolation of micro-line tool path. The proposed fitting method guarantees the chord error by utilizing the strong convex hull property of B-spline curves. The knot vector and control points are initially generated by a progressive iterative approximation method and locally refined to conform to the chord error constraint by using an analytical method. The analytical approximation and refining methods avoid solving a linear system of equations that is necessary in the standard B-spline fitting method. The feasibility and efficiency of the proposed scheme has been verified via simulations and experiments. Compared with the traditional fitting method, the proposed scheme can strictly constrain the chord error and can significantly decrease the computational load. Compared with the transition scheme, the proposed scheme can significantly increase the machining efficiency for the same micro-line tool path under the same chord error tolerance.     

Jerk-limited feedrate scheduling and optimization for five-axis machining using new piecewise linear programming approach

In this paper, a new computation method and an optimization algorithm are presented for feedrate scheduling of five-axis machining in compliance with both machine drive limits and process limits. Five-axis machine tool with its ability of controlling tool orientation to follow the sculptured surface contour has been widely used in modern manufacturing industry. Feedrate scheduling serving as a kernel of CNC control system plays a critical role to ensure the required machining accuracy and reliability for five-axis machining. Due to the nonlinear coupling effects of all involved drive axes and the saturation limit of servo motors, the feedrate scheduling for multi-axis machining has long been recognized and remains as a critical challenge for achieving five-axis machine tools' full capacity and advantage. To solve the nonlinearity nature of the five-axis feedrate scheduling problems, a relaxation mathematical process is presented for relaxing both the drive motors' physical limitations and the kinematic constraints of five-axis tool motions. Based on the primary optimization variable of feedrate, the presented method analytically linearizes the machining-related constraints, in terms of the machines' axis velocities, axis accelerations and axis jerks. The nonlinear multi-constrained feedrate scheduling problem is transformed into a manageable linear programming problem. An optimization algorithm is presented to find the optimal feedrate scheduling solution for the five-axis machining problems. Both computer implementation and laboratorial experiment testing by actual machine cutting were conducted and presented in this paper. The experiment results demonstrate that the proposed method can effectively generate efficient feedrate scheduling for five-axis machining with constraints of the machine tool physical constraints and limits. Compared with other existing numerical methods, the proposed method is able to find an accurate analytical solution for the nonlinear constrained five-axis feedrate scheduling problems without compromising the efficiency of the machining processes.     

水轮机叶片的五轴数控加工工艺规划及轨迹优化

针对大型水轮机叶片的五轴联动数控加工要求,制定出适合国内技术条件的工艺规划。提出在计算叶片五轴联动加工刀位时采用等残余高度刀位规划,并考虑三维非线性误差来计算走刀步长的刀位轨迹生成策略。为了避免刀具后跟角干涉的要求,提出根据叶片的曲面性态分析来确定叶片五轴联动加工中的刀轴控制和刀位轨迹优化计算方法。将该方法与CAM软件结合,用于大型混流式和轴流式叶片数控加工,结果表明：该方法既能严格控制加工误差,又要能提高加工效率。     

Real-time Bezier interpolation satisfying chord error constraint for CNC tool path

G01 code generated by a computer-aided manufacture (CAM) system is the most common form of tool trajectory in computer numerical control (CNC) machining. A tool path composed of short line segments has discontinuous tangency and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings in these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining: (1) chord error should be rigidly constrained; (2) G01 points should be interpolated; (3) curvature should be continuous (G²); (4) machining should be applicable to spatial cases; (5) real-time performance of computation is required. Based on these various requirements, this study proposes an interpolation scheme using cubic Bezier curves and includes an adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G², chord-error-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable to 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpolation in surface quality and machining efficiency.     

SiCp／Al窄槽的铣磨实验研究——磨削力

针对SiCp／Al复杂曲面加工中大去除量、高精度的需求,以窄槽的铣磨加工工艺为例,实验研究SiCp／Al窄槽铣磨加工中加工参数、铣磨工具对铣磨力的影响规律．实验结果表明:加工参数和铣磨工具均对铣磨力有影响．在实验参数取值范围内,铣磨力随砂轮线速度、进给速度的增大而增大,进给速度对铣磨力的影响最大;采用螺旋槽铣磨工具可显著降低铣磨力,但铣磨力波动较大,并随螺旋角的增大而减弱．在实验条件下,可优选铣磨力波动相对较小的50°螺旋角的开槽砂轮进行窄槽的粗加工．     

切削加工过程的仿真方法研究与实现

为提供虚拟的加工环境和验证工艺设计的正确性,对切削加工过程的计算机仿真方法进行了研究,以OpenGL作为图形支持系统,用VC++开发了切削加工仿真系统。该系统实现了车、铣、刨、磨等多种加工方式的仿真,可对刀具运动和材料切出情况进行实时监控,且可通过工艺参数(如切削速度、进刀量等)对切削过程进行控制,并能自动计算和优化切削时间、成本等参数。系统界面友好,操作方便,运行可靠,能有效地帮助工艺人员对整个加工过程进行直观的评估和验证。     

氧化锆义齿铣削工艺参数优化及其加工实验

为合理选择初次烧结氧化锆陶瓷义齿在铣削加工时的工艺参数以及加工路径规划方式,以提高加工效率及质量,建立以提高材料去除率和降低表面粗糙度为目标的函数,采用理想点法、最小偏差法和线性组合法,优化出精加工阶段的工艺参数;以磨牙冠表面加工为例,采用UG CAM系统规划刀具加工路径,粗加工采用型腔铣,精加工分别采用固定轴铣中的曲面铣削往复模式、区域铣削跟随周边模式及区域铣削往复模式3种规划方法.实际加工结果对比表明:在相同工艺参数及刀具条件下,区域铣削往复模式规划方法加工得到的牙冠表面质量最好.     

自由曲面砂带磨削轨迹规划与误差控制分析

砂带磨削是提高自由曲面工件型面精度和表面质量的重要手段之一,针对目前自由曲面砂带磨削加工在效率和精度方面存在不足,基于砂带磨削加工的特性,提出了一种基于加工精度控制的自由曲面砂带磨削加工的轨迹规划方法。首先,对实现无曲率干涉的接触轮半径及满足加工允差的接触轮宽度进行了公式推导,结合轮与曲面上加工点主曲率关系,通过双倍体的遗传算法优选出满足自由曲面要求的加工允差,并获取无曲率干涉加工需求的接触轮尺寸参数。然后,基于加工点的主曲率方向实现加工轨迹的自适应宽行距规划,同时采用柔顺处理算法对其点导动规划过程中当曲面存在扭曲时的磨头潜在的大幅往复摆动运动进行了柔顺处理,获得了行距稳定且满足加工时接触轮在磨削点处始终与自由曲面达到最佳贴合效果的磨削轨迹。最后,应用该方法对某航空发动机叶片型面进行轨迹规划,并在数控砂带磨床上进行了加工验证。结果表明：规划的磨削加工轨迹能够使得叶片轮廓截面精度较好地满足加工要求,提高了叶片型面的表面质量和精度,证实了该方法的有效性和实用性。本文提出的轨迹规划方法可科学合理地控制曲面预期加工允差,解决了在自由曲面砂带磨削过程中因接触轮尺寸参数选择不当而引起的局部干涉的计算难题,能够有效提高砂带磨削加工的效率和精度。     

Development of Virtual Simulation System for Remote Collaborative Surface Machining

1 Introduction Many parts of aerospace ,automobile and mold industries are high precision and complex-shaped. There-fore ,it needs multi-axis machining. Multi-axis machining has advantages of i mproving efficiency and surfaceprecision,reducing production expense and shortening ti me to market . Although there are many advantages inmulti-axis machining,there are many steps on process planningfor complexsurface .And every step needs engi-neers to make appropriate decisions by their professional…