虚拟车削中原始误差对圆柱零件的影响

运用虚拟仿真方法研究分析了原始制造误差对圆柱零件加工的影响。通过建立误差数学模型以及虚拟加工环境,利用OpenGL对加工过程进行物理仿真。最后以实例模拟分析了原始误差对圆柱零件加工的影响规律。     

薄壁件铣削加工误差补偿方法

采用双三次B样条曲面插值方法得到薄壁件铣削加工误差模型。设计了一种多层次循环误差补偿方法。进行了有限元仿真分析和试验研究。     

关节式坐标测量机初始位姿对误差影响研究

采用Denavit-Hartenberg方法建立了关节式坐标测量机的数学模型,分析了影响关节式坐标测量机的误差源,并对第一关节的误差分布进行了仿真。通过关节式坐标测量机的第一关节在不同初始位姿下对被测工件进行测量与真值进行比较,分析在不同初始位姿下所测得结果的不同,得到了其第一关节的误差分布。实验表明关节式坐标测量机在采用相对角度编码器时,第一关节选择最佳初始位姿,可以有效地提高测量精度,减小误差。     

基于误差补偿的叶片铣削加工过程仿真研究

对发动机叶片在现有夹具定位下的螺旋铣削加工状态进行了研究,建立了基于瞬时铣削力的叶片变形模型,提出了基于加工表面静态误差预测、补偿的离线多层次误差补偿方案,利用有限元模拟技术结合铣削力模型,迭代求解各个刀位点处的弹性让刀变形量,据此修正原始的数控刀具轨迹代码,达到消除加工变形误差的目的;并通过有限元ANSYS仿真,得到实时误差补偿刀位轨迹,通过实验验证补偿方案的正确性和实用性。     

薄壁圆环零件加工过程中变形控制研究

针对薄壁零件加工过程中受夹紧力、切削力作用易产生变形问题,以薄壁圆环零件为研究对象,优化设计及加工工艺、装夹方式和专用夹具,通过弹性力学分析计算得出圆环零件在各道工序所能承受的最大压力,控制各道工序所需夹紧力大小。运用UGNX10软件对圆环零件各道工序工况进行有限元模拟仿真验证理论计算结果。将上述方案、计算结果运用于生产实际,圆环零件加工精度得到保障。     

薄壁圆环零件加工过程中传热问题研究

研究了的薄壁圆环零件加工过程中的热传导问题,将其简化为一维、旋转的周期性脉冲热源传热问题,结果表明由旋转角速度ω、热物性参数、几何尺寸组合而成的拟贝克数Pe_1,拟贝克数Pe_2,毕奥数Bi对传热过程起决定性作用,实验测试和数值仿真结果吻合得较好,尤为重要的是,数值仿真对每周转的温度分布给出了微观的“精细”结构,显示了上述几个无量纲准则数的相对关系对传热特性的影响。     

球面铣削中对刀误差的影响及其对策

生产实践与理论分析证明,要进一步提高球面铁削的精度,保持铣刀对工作相对位置的正确性是十分重要的。实现这种正确性的技术操作称为对刀。对刀不准确或者说对刀误差,主要是指铣刀的回转轴线未对准工件的回转轴线,即二者异面不相交,其间有偏距δ(见图1)。由于对刀误差δ的存在,导致铣出的球面形状不正确。本文对δ与球面形状精度的关系进行分析,并推导出实用的计算误差公式,从而提出消除或控制对刀误差的基本对策。     

薄壁深腔零件铣削加工误差仿真分析

为避免薄壁深腔零件侧壁加工过程中因铣削力引起的让刀变形而导致加工精度较低的问题,提出一种基于有限元的铣削加工误差仿真算法。考虑工件/刀具系统的让刀变形及工件的回弹变形,计算生成刀齿微元的连续运动轨迹,并基于点的六面体映射算法对材料进行去除,从而得到连续加工过程和加工面上任意点的加工误差及加工面形貌。以某典型薄壁深腔开口框体结构为加工对象进行了仿真分析,通过实验验证了所提仿真方法的准确性。     

一种串并联型机床及其误差分析

多杆件并联及串并联型机床是正在致力研究和开发的新型加工设备,分析了一种新研制的串联型机床的结构及空间误差,推导并验证了主轴平台空间运动误差的数学模型,通过示例计算探讨了连杆的制造误差和滑座的进给误差给刀具空间运动位置精度和平台姿态的影响。     

薄壁零件的高速铣削稳定性研究

薄壁结构零件在加工过程中极易发生变形和切削振动,这对提高加工质量和加工效率十分不利.在考虑刀具和工件两个方向自由度的基础上,分析了薄壁零件的动态铣削模型.针对2A12铝合金薄壁结构零件,利用MIKRON UCPDUR0800 高速加工中心和相关仪器、软件,通过铣削力辨识实验和模态实验,进行了高速铣削薄壁零件的稳定域分析和实验验证.     

Influence of manufacturing errors on the dynamic characteristics of planetary gear systems

A dynamic analysis using a hybrid finite element method was performed to characterize the effects of a number of manufacturing errors on bearing forces and critical tooth stress in the elements of a planetary gear system. Some tolerance control guidelines for managing bearing forces and critical stress are deduced from the results. The carrier indexing error for the planet assembly and planet runout error are the most critical factors in reducing the planet bearing force and maximizing load sharing, as well as in reducing the critical stress.     

加工中心热误差补偿的研究

热误差是加工中心的最大误差源。通过对机床热特性的实验和分析，利用神经网络模型对热误差进行了补偿，取得比较好的效果。     

The geometric dynamic errors of CMMs in fast scanning-probing

Quasi-stiffness model is effective for the compensation of the geometric errors of coordinates measuring machines (CMMs) in slow probing, but degrade the error compensation accuracy due to the generation of dynamic errors in fast probing. It is usually regarded that acceleration is the major origin of dynamic errors; and yet the dynamic effects that rise from the quick fluctuation of geometric errors in fast probing had attracted little attentions. This paper presents a model for the dynamic effects of the geometric errors of CMMs in fast probing, and investigates their properties with experiments. The error model is built with recursive least squares (RLS) identification technique by taking probing acceleration and the 6 geometric errors of X slideway for the inputs while the positioning error of probe tip for output. Then the positioning error of probe tip is decomposed into 7 components corresponding to the 7 inputs. Analyses on the experiments show that the angular errors around Y and Z axes, ε_Y(x) and ε_Z(x), can induce remarkable dynamic effects, especially in a CMM with low stiffness air bearing. Error compensation with RLS identification seems feasible theoretically, but it is not recommendable due to the veracity uncertainty of identification. Nevertheless smoothening the sharp corners of the curves of geometric errors, especially ε_Y ∼ x and ε_Z ∼ x, in terms of probing speed and Y coordinates of probe tip is considered as a simple but effective and reliable method to improve the accuracy of CMMs errors compensation in fast probing.     

基于球面渐开线齿面的锥齿轮铣削加工研究

针对传统斜齿锥齿轮成对啮合中不能正确啮合的问题,提出一种基于产形线切齿法的齿轮啮合误差修正方法.结合球面渐开线原理和渐开线齿面方程,利用基锥螺旋角计算节锥螺旋角的方式,对齿面方程的几何参数进行确定;利用求出的几何参数,对凹齿面切齿运动进行分析,推导出产形线方程;最后通过切齿实验对上述推导方程进行验证,取得良好效果,从而验证了该修正方法的可行性.     

Influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors

Hybrid finite element analysis was used to analyze the influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors. The effects of changes in stiffness were similar for most of the manufacturing errors. State variables were most affected by the stiffness of the planet bearings. Floating either the sun or carrier helps to equal load sharing and minimizes the critical tooth stress. The effects of a floating sun and carrier are similar, but it is not recommended that both float, because this can induce greater critical tooth stress. Planet bearing stiffness should be optimized. Both load sharing and critical tooth stress should be considered to determine optimal bearing stiffness.     

初始状态对径向滑动轴承热瞬态过程的影响

研究了径向滑动轴承在阶跃载荷扰动下的瞬态绝热行为.通过对轴承油膜压力、温度和各组成部分的动力学参数进行建摸,应用数值方法对模型求解.获得了大栽荷扰动工况下径向滑动轴承热瞬态运动参数的非线性响应.在此基础上讨论了初始稳态压力和转速对轴承热瞬态过程的影响.     

利用等离子弧熔覆的薄壁件快速成型工艺研究

介绍一种基于等离子弧熔覆的直接金属快速成型工艺。研究了薄壁件成型时成型轨迹截面形状对成型质量的影响、尾缩控制、成型温度控制,以及力学性能等关键工艺问题。研究结果表明,扁平截面的成型轨迹有利于保证成型质量;采用末端减速法可以有效地避免薄壁件的尾缩现象;采用减小热输入与直接水冷相结合的成型方式,能够避免成型时液态金属的过度流淌等缺陷;薄壁件的抗拉强度和延伸率与填充金属丝相当,水平方向的性能优于垂直方向。     

Wall thickness error prediction and compensation in end milling of thin-plate parts

End milling has been widely adopted to machine the thin-plate parts that play increasingly important role in the aerospace industry, due to the advantages of high machining accuracy and fine machined surface quality. In this paper, a systematic method is proposed to predict and compensate the wall thickness errors in end milling of thin-plate parts. The errors are caused by the static deflections induced by the varying cutting force imposed on the weakly rigid part. To improve the efficiency of computing the part deformation, a novel FE model is firstly developed by combing the methods of substructure analysis, special mesh generation and structural static stiffness modification. Then, the time- and position-dependent deformations of the part are calculated based on the proposed FE model to predict the wall thickness errors left on the finished part. It reveals for the first time that the surface topography of the finished thin-plate part is formed by the repeated cutting with the bottom edge of the cutter (BEC) in end milling. Owing to the coupling between the axial cutting depth (ACD) and the force-induced deflection, the modified ACDs for compensation of the static wall thickness errors are finally determined by an iterative adjustment method. The proposed method is verified by three-axis end milling experiments. The experiment results show that the predicted wall thickness errors match well with the really measured ones, and the errors are reduced by 77.18% with the help of the proposed compensation method. Moreover, the proposed FE model reduces the computational time elapsed for error prediction by 67.44% as compared with the benchmark FE model.     

A/C轴双摆头几何精度误差的预防与补偿方案

通过A/C轴双摆头误差预防与误差补偿工艺方案的研究,设计了A/C轴双摆头装配工艺方案以及两轴回转中心的误差检测与补偿方案.将此研究方案应用于沈阳机床某A/C轴双摆头试制,效果良好.     

STL文件缺陷分析及修补算法研究

STL(Stereolithography)文件是一种三维实体表述文件,广泛应用于快速成型以及其它领域。这里分析了STL文件的规范以及其缺陷特点,给出了不同类型缺陷的修补策略。特别是针对STL文件不含拓扑信息的特点,引进哈希表构造了一种用于表达STL拓扑信息的数据结构,提高了建立拓扑信息的速度以及识别和修补缺陷的效率。本文对最复杂形式的孔-连环孔进行了研究,彻底解决了孔隙的修补问题。实践证明该修补算法稳定可靠。