基于改进CC路径截面线法的机器人铣削加工刀具轨迹生成方法

机器人铣削加工技术是当前机器人技术发展的重要方向之一,而刀具轨迹的自动生成是实现机器人铣削加工的一个关键环节。以Open Cascade为几何造型技术开发平台,以改进的CC路径截面线法为轨迹生成方法,通过对约束面间距进行动态调整,改进了传统CC路径截面线法刀轨疏密不一致的问题,从而能够提高机器人铣削加工精度。在此基础上,开发出相应的CAD/CAM软件系统,实现了自由曲面精粗加工刀具轨迹的自动生成。最后,通过仿真和实验对生成的刀具轨迹进行了验证,验证了方法的可行性和准确性。     

基于元启发式算法的凸轮从动机构优化设计研究

针对传统的凸轮从动机构设计方法不能满足凸轮从动机构多因素和多层次的设计要求,提出用元启发式算法对凸轮从动机构进行设计优化。构建凸轮从动机构简化示意图,采用元启发式算法实现凸轮从动机构的设计优化,并对优化效果进行仿真验证。分析凸轮从动机构的结构,建立凸轮从动机构数学模型;定义3个优化目标,同时添加8个约束条件。开发元启发式优化算法蚂蚁优化器,编写相应代码。采用MATLAB软件对凸轮从动机构进行仿真,与传统计算法计算结果进行对比和分析。仿真结果表明:采用元启发式算法优化后,机构尺寸最大减小9.5%、提升从动机构所需力最大减少2.4%、最大接触应力最大减少12.1%,从动机构位移跟踪误差、速度以及加速度的最大值也大大减少。验证了采用元启发式算法能有效实现凸轮从动结构的设计优化。     

A three-dimensional CAD/CAM/CAE integration system of sculpture surface die for hollow cold extrusion

In this paper, a CAD/CAM/CAE integration system for a sculptured surface die for hollow cold extrusion has been developed by using C language for Windows. A sculptured surface model with variable control points is incorporated with a general three-dimensional velocity field to analyze the extrusion process. The profiles of the product and the billet are generated in the CAD module. The fitting points are generated to interpolate the profiles of the product and the billet. The initial guess of control points are created by using the offset of corresponding fitting points in the axial direction. The control points are varied automatically to obtain the optimum die surface by using the upper-bound method and optimization procedure. The CAM module generates the cutter locations by using the optimized die surface model. The gouging areas of the tool path are detected and removed. The calculated cutter locations are verified through the tool path simulation. The NC codes are generated automatically by using the gouging-free cutter locations and then sent directly to a three-axis CNC machine centre to manufacture the EDM electrodes. The extrusion die cavity is made by using an EDM process. Extrusion experiments have verified the proposed CAD/CAM/CAE integration system is successful.     

The form error prediction in side wall machining considering tool deflection

In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy.     

Digital manufacture of large-grade hydro turbine's blades

The blade is one of the vital components and the most difficulty in manufacturing of large hydro turbines. In order to cost-effectively and productively manufacture these kinds of blades, a series of innovative digital techniques have been developed. It includes the digital design of hydro turbine blades based on manufacturers’ requirements, computer-aided location and the machined error evaluation with three-dimensional digitized measure, tool path generation strategy for enhancing machining efficiency and controlling deviation in NC machining, tool path generation and NC machining simulation by means of a virtual NC machining environment for blades, and feasible strategy and the systematic scheme for manufacturing of large blades with 5-axis simultaneous CNC machining technology. The developed innovative digital manufacture techniques have been successfully applied in the manufacturing of both the large grade Kaplan and Francis hydraulic turbine blades. It has been shown that the higher efficiency and the better surfaces finish accuracy can be achieved in practical engineering.     

Spiral cutting operation strategy for machining of sculptured surfaces by conformal map approach

Although compound surfaces and polyhedral models are widely used in manufacturing industry, the tool path planning strategies are very limited for such surfaces in five-axis machining and high speed machining. In this paper, a novel conformal map based and planar spiral guided spiral tool path generation method is described for NC machining of complex surfaces. The method uses conformal map to establish a relationship between 3D physical surface and planar circular region. This enables NC operation to be performed as if the surface is plat. Then through inversely mapping a planar spiral defined by a mathematical function into 3D physical space, the spiral cutter contact paths are derived without inheriting any corners on the boundary in the subsequent interior paths. The main advantage of the proposed method is that a smoother, longer and boundary conformed spiral topography tool path is developed. Therefore, the machined surface can be cut continuously with minimum tool retractions during the cutting operations. And it allows both compound surfaces and triangular surfaces can be machined at high speed. Finally, experimental results are given to testify the proposed approach.     

基于开放式系统的曲面加工误差动态补偿控制

将基于传感器信息的智能型开放加工系统应用于曲面的高精度加工,提出了曲面加工误差的动态补偿方法。为预测加工误差的补偿量,建立了刀具弯曲模型,分析了刀具弯曲对加工误差的影响。实验结果表明,本系统可有效地提高加工精度,使加工误差降低1／3－1／4。     

基于进给优化的五轴机床高精度加工研究

介绍五轴机床最佳进给率和高性能精密控制算法加工方式,并进行实验验证。通过引入进给率调度算法,以最大限度地减少五轴弯曲刀具路径的循环加工时间。在寻找沿刀具路径的最佳进给时,考虑了五轴驱动器的速度、加速度和加加速度限制,以确保伺服驱动器以最小的跟踪误差平稳和线性运行。为设计一个精确的轮廓控制器,开发分析模型来估计五轴加工实时过程中的轮廓误差,通过考虑刀尖与参考路径的法向偏差和刀轴方向与参考方向轨迹的法向偏差来定义两种类型的轮廓误差。     

叶轮零件的五轴数控制造质量与关键技术研究

叶轮叶面的制造质量直接影响其运行的效率、性能、流体动力稳定性、工作可靠性和使用寿命等.从具体叶轮零件结构与工艺性分析人手,通过叶轮叶面的三维建模和加工程序调试、仿真分析与刀具轨迹验证,研究叶轮数控加工策略和加工关键技术.经过分析叶轮零件的加工质量,明确了控制插补弦长、插补周期和进给速度、刀轨残留误差,可以控制五轴数控加工的误差,保证制造质量.以叶面造型的轴向截线为加工依据,解决了刀具切削间隔的计算和刀路轨迹的求解,并进行了仿真分析.实践证明:采用五轴数控加工中心对叶面进行截面法加工,避免了加工干涉,容易实现曲面间的光滑走刀,提高了叶片的加工效率和质量,降低了加工成本.     

The form error reduction in side wall machining using successive down and up milling

In this paper, the form error reduction method is presented in side wall machining. Cutting forces and tool deflection are calculated considering surface profile generated by the previous cutting such as roughing and semi-finishing. Using the form error prediction from tool deflection curve, the effects of tool teeth numbers, tool geometry and cutting conditions on the form error are analyzed. The characteristics and the differences of generated surface shape in up and down milling are also discussed and over-cut free condition in up milling is presented. The form error reduction method through successive down and up milling has been suggested. The effectiveness and usefulness of the suggested method are verified from a series of cutting experiments under various cutting conditions. It is confirmed that the form error prediction from tool deflection in side wall machining can be used in proper cutting condition selection and real time surface error simulation for CAD/CAM systems. This research also contributes to cutting process optimization for the improvement of form accuracy in die and mold manufacture.     

Development of a Five-axis Milling Tool Path Generation Algorithm based on Faceted Models

This paper describes the development of a 5-axis milling tool path generation algorithm based on faceted or tessellated models. In a first step, the developed algorithm optimises the tool inclination angle for maximal material removal rate in each cutter contact point. This is obtained by matching the tool profile of a flat end cutter with a temporary spline representing the curvature of the part surface in the tool contact point. In a second step, the elimination of gouging between the tool and the surface and a smooth behaviour of the tool inclination angle along the tool path is obtained by a combination of tool inclination angle adaptation and tool lifting along the normal vector. Finally, the paper describes some experimental results.     

CAD orientated mathematical model for determination of profile helical surfaces

A mathematical model is developed for the determination of the profile of the helical surface when the profile of the initial tool surface profile and the parameters determining the tool orientation towards the blank are specified. It also encompasses the cases when the tool is inclined towards the vertical line. The specification of the tool surface profile is discrete (by coordinates). There are no limits for the application of this method and the complexity and variety of the form of the specified tool profile. The developed mathematical model for solving the reverse task is CAD orientated and may be used as a basic part of a specialized CAD system.     

Real-time generation and control of cutter path for 5-axis CNC machining

This paper presents a new approach to real-time generation and control of the cutter path for 5-axis machining applications. The cutter path generation method comprises real-time algorithms for cutter-contact path interpolation, cutter offsetting, and coordinate conversion. In addition, a global feedback loop is closed by the CNC interpolator so as to augment the controlled accuracy in practical cutter path generation. An error compensation algorithm and a feedrate adaptation algorithm for the control loop are developed, respectively.     

五轴联动加工中工装及旋转误差补偿方法的研究

文章提出了一种工装及旋转误差补偿后置处理方法,根据机床运动求解,建立了工作台/刀具回转摆动型机床VMC1250的数学模型.通过VB语言,开发了该五轴机床的后置处理软件.通过叶片的加工验证了该后置处理器的正确性和实用性,能够满足工程使用的要求.     

Application of homogenous transformation matrix to measurement of cam profiles on coordinate measuring machines

A kinematic model is presented to aid the cam profile design task and to determine the NC data required to move an inspection probe to the necessary locations to inspect the surface profile of a spatial cam on a coordinate measuring machine (CMM). The cam profile is designed in accordance with the principles of conjugate surface theory. Homogenous transformation matrices are then employed to derive the CMM ability function matrix and the measuring probe location matrix. The required NC data are obtained by equating the elements in the ability function matrix with the corresponding elements in the probe location matrix in order to solve the CMM link variables. The validity of the proposed approach is verified by carrying out the automatic inspection of a machined cam on a CMM using the NC data computed by the developed algorithm. The methodology presented in this study combines the cam design, machining and inspection activities, and makes possible a flexible and automatic spatial cam design and manufacturing process.     

连续变焦系统凸轮槽建模及加工方法优化

在机械补偿连续变焦光学系统中,核心零件曲线套筒变倍凸轮槽和补偿凸轮槽两侧面的加工精度和表面质量直接影响变焦系统在连续变焦过程中能否成像清晰、稳定。采用直纹面加厚的方式完成了凸轮槽建模,且在曲线点阵拟合的过程进行了公差控制。用四轴联动全顺铣的走刀方式,对进、退刀点进行特别处理完成凸轮槽的加工。经过实际加工验证,采用该方法大幅地提高了凸轮槽的加工精度和表面质量。     

An NC tool path translator for virtual machining of precision optical products

In this paper, a virtual machining system (VMS) for the ultra-precision diamond turning is presented, and the NC tool path translator function module of the VMS is discussed. The developed VMS is based on the NC program not as some commercial CAD/CAM software which is based on the cutter location DATA file. In the VMS, the virtual machine tool is controlled through the NC program used by the actual machine tool. The NC tool path translator consists of accidence analysis, lexical-analyzer, grammar and semantic parse, driving code generator, etc. The manufacture of a mould insert for a diffractive lens was used as a case study to illustrate the performance of the developed VMS.     

The Computer Integrated Manufacturing (CIM) of net shape forged bevel gears

Computer Integrated Manufacturing (CIM) offers American industry a method of improving forge tool quality while lowering forge part costs. These costs savings are achieved by reducing machining stock allowances and eliminating trial and error tool development. The development of forge tooling for most new parts is normally a trial and error process. This is especially true when developing tooling for net or near-net shape forged bevel gears. Even with years of experience, the tool designer relies on numerous trials to design and manufacture forge tooling. The CIM approach takes the guesswork out of the design, analysis and manufacture of forge tooling for net shape bevel gears. Computer techniques have been developed which enable the design and manufacture of forge tooling, while bypassing the trial and error stage of tool development. This paper discusses the application of CIM techniques in the design and manufacture of forge tooling for net shape bevel gears.     

基于误差分析的复杂曲面可侧铣判定方法研究

基于复杂曲面侧铣加工误差计算,提出了一种曲面能否通过侧铣实现高精度加工的判定方法,该方法适用于任意直纹和非直纹曲面。侧铣加工误差为待加工理论曲面与刀具运动包络曲面之间的距离,在此基础上,应用整体最优刀具路径下的最大几何偏差进行曲面可侧铣判定依据。数值仿真算例表明:该方法不仅能够有效地判定曲面能否侧铣,同时能够输出满足误差要求的最优刀具路径,加工实验也表明该方法能够极大地提高加工效率。     

Optimized tool path generation based on dynamic programming for five-axis flank milling of rule surface

This paper presents a computation scheme that generates optimized tool path for five-axis flank milling of ruled surface. Tool path planning is transformed into a matching problem between two point sets in 3D space, sampled from the boundary curves of the machined surface. Each connection in the matching corresponds to a possible tool position. Dynamic programming techniques are applied to obtain the optimal combination of tool positions with the objective function as machining error. The error estimation considers both the deviation induced by the cutter at discrete positions and the one between them. The path planning problem is thus solved in a systematic manner by formulizing it as a mathematical programming task. In addition, the scheme incorporates several optimization parameters that allow generating new patterns of tool motion. Implementation results obtained from simulation and experiment indicate that our method produces better machining quality. This work provides a concise but effective approach for machining error control in five-axis flank milling.