基于元结构的精密机床床身结构动态分析和优化

为提高某精密数控机床床身抗振性能,运用结构动态优化原理和有限元法的变量化分析方法,对精密机床床身元结构进行动态特性分析。并以元结构分析结果为依据,提出了该床身结构的2种结构优化方案。比较分析2种结构优化方案与原床身结构方案的动态性能,分析结果表明,优化方案床身的动态性能得到了明显提高。     

Thermal error reduction based on thermodynamics structure optimization method for an ultra-precision machine tool

Thermal error is one of the main errors in ultra-precision machine tools. This paper presents a thermodynamics-based structure optimization method to reduce the thermal displacements of machine tools during operation. The method makes use of the thermal–structure coupled model to analyze the thermal behavior considering the thermal contact resistance and the temperature rise of the oil film in hydrostatic spindle. The structure of the motor link, spindle, and headstock of grinder are optimized by setting appropriate gaps in the contact region of two neighboring parts to change the heat transfer distribution and minimize the thermal displacement of the spindle center position. The proposed method is validated by an equivalent thermal conductivity-based simulation method and experiment on an ultra-precision grinding machine tool. Experimental results show that the proposed method can provide an important instruction on how to reduce the thermal error for the design of the precision machine tools, especially for those with key parts placed near the heat sources.     

多轴数控专用机床床身动态特性的可靠性优化研究

针对多轴数控专用机床床身重量大、成本高的问题,将可靠性优化方法应用到床身的优化中。研究了床身的动态特性,集成Pro/E、ANSYS和Isight建立了可靠性优化的响应面近似数学模型,分析了设计变量对床身动态特性的影响;将床身重量最轻作为优化目标,以床身动态特性的可靠度为性能约束,采用多岛遗传算法对床身的壁厚、加强筋的厚度和数量进行了可靠性优化设计。研究结果表明,优化后的床身重量减小15.23%,动态特性的可靠度由99.971%提高到99.999 99%。     

Design and dynamic optimization of an ultra-precision micro grinding machine tool for flexible joint blade machining

The influences of tool setting errors on skiving accuracy are discussed in this paper. Firstly, a method for the calculation of error-free cutting edge of skiving cutter is proposed. Based on the theories of cutter enveloping gear, the gear profile deviations, which are affected by the tool position and orientation errors in skiving, are analyzed. Results show that the profile deviations are insensitive to this kind of setting error of the cutter. Then, the effects of tool eccentricity error on skiving accuracy are analyzed. Results show that the waves on the tooth flanks, which are caused by the tool eccentricity error, have obvious influences on the helix deviations and the profile deviations of the workpiece. The waves on the tooth flanks are periodic ones and can be obviously affected by the number of teeth of the cutter.     

Design and dynamic optimization of an ultraprecision diamond flycutting machine tool for large KDP crystal machining

This paper presents the design and dynamic optimization of an ultraprecision diamond flycutting machine tool for producing flat half-meter-scale optics. A novel tool holder is designed, which can achieve micron-level axial feeding and tool angle accurate adjustment, and new technology is also used to allow alignment of the spindle axis to the horizontal-slide travel. The design and characteristic analyses of this machine tool are presented, including the static, modal, harmonic, and rotor dynamic analysis for predicting its static and dynamic performance. A prototype is built based on the analysis and FE model considering the joint parameters. The machining test shows that this machine tool can successfully produce 415?×?415-mm surfaces on aluminum and crystalline optics, with 1.3-μm flatness and 2.4-nm rms roughness. Moreover, the differences of design concepts are discussed between the ultraprecision machine tool for optical parts machining and the conventional machine tool.     

基于混联机床立卧转换加T的机床运动控制算法研究

介绍了一种新型立卧转换式三杆混联机床-3-TPS混联机床,对该机床的结构进行了分析.文中给出了该机床在实现立卧转换加工时的坐标变换过程及变换方程,给出了实现立卧转换加工时的后置处理算法及数学模型,并分析了该机床在两种不同加工方式下所能够实现的三轴联动加工、四轴联动加工.文中所给的算法简单、直观、实用,方程为显示.     

基于多学科设计优化的数控机床综合误差补偿

将多学科设计优化理论应用于数控机床综合误差补偿技术中,通过对数控机床进行系统划分,建立各个系统的误差分析模型,并运用多学科设计优化的方法对数控机床综合误差补偿过程进行优化,最终得到精密的数控加工指令.该方法能够避免用几何误差和热误差简单相加来代替综合误差的近似计算,从而提高数控机床的综合误差补偿精度.     

Counterweight optimization for reducing dynamic effects of clearance at a revolute joint

An optimal design formulation is developed to reduce undesirable dynamic effects due to clearance at a joint. The objective function to be minimized is the maximum ratio of the rate of change of the joint force direction ( ) to the magnitude of the joint force (R), i.e. max ( ) as calculated from the nominal mechanism without clearances. Design variables are the magnitude and the location of an added mass attached to each link.

Numerical examples for an offset slider crank mechanisms are considered. To check suitability of the objective function, the initial and optimized systems are simulated dynamically by integrating the system model equations and the phenomena of contact loss compared. It is found that although max ( ) is not a function of the magnitude of clearances and not of dimensionless form, it is a reasonable indicator of the contact loss phenomena for the single clearance system considered. The input torques have also been obtained and compared, shown to be more uniform in the optimized system.     

基于神经网络和遗传算法的机床床身优化设计研究

机床的床身的动态特性和静刚度直接影响加工精度、生产效率以及机床的使用寿命,目前机床正朝着高速、高精度、复合化以及高自动化的方向发展,因此研究机床床身的动态特性和静刚度十分必要。为提高某机床床身和横梁的动态特性和静刚度,综合运用结构动态优化原理,神经网络和遗传算法,对床身和横梁进行了结构动态特性分析,提出了该床身结构的优化方案。分析结果表明,优化方案的床身和横梁的动态性能和静刚度得到了明显提高。可供相关机床床身优化设计参考。     

基于模态试验技术的机床动态特性研究

对HMC 630rp卧式加工中心进行了试验模态分析,获得了其低阶固有频率和振型。通过对整机各阶模态振型的分析,找到了加工中心结构的薄弱环节并提出了修改建议,从而为结构的优化设计指出了方向。     

基于动态灵敏度分析的数控机床床身结构优化设计

基于有限元分析方法,在结构动态特性灵敏度分析的基础上,对床身进行结构与动态性能优化,保证其良好动态刚性的同时,减轻床身质量,减少材料消耗,降低生产成本。文中的优化设计过程与方法可推广到机床其他部件的结构动态性能优化中,从而为机床整体结构动态特性的改进、机床整体结构的优化设计提供了重要的方法和理论依据。     

基于混联机床立卧转换加工的机床运动控制算法研究

介绍了一种新型立卧转换式三杆混联机床—3-TPS混联机床,对该机床的结构进行了分析。文中给出了该机床在实现立卧转换加工时的坐标变换过程及变换方程,给出了实现立卧转换加工时的后置处理算法及数学模型,并分析了该机床在两种不同加工方式下所能够实现的三轴联动加工、四轴联动加工。文中所给的算法简单、直观、实用,方程为显示。     

数控机床动态特性优化

考虑了滚动结合面和主要固定结合面的影响,对机床进行模态分析和谐响应分析,找出了其薄弱模态;通过分析可知改变各结合面刚度对整机动态特性的影响,识别出对整机动态特性影响较大的结合面,并对这些结合面刚度值进行优化,提高了整机的动态特性.     

Kinematic calibration of gantry hybrid machine tool based on estimation error and local measurement information

This paper presents the kinematic calibration of a four degrees-of-freedom (DOF) hybrid machine tool based on a novel planar 3-DOFs parallel mechanism and a long movement of the worktable. Closed-form solutions are developed for both the inverse and direct kinematics about the parallel mechanism. The error model is built and the mechanism accuracy is investigated. Two types of kinematic calibration method are proposed by a simple measurement device. The first type of calibration method is based on estimation error, and can easy improve the machine tool accuracy quickly by estimating the error trends. The second type of kinematic calibration method is based on local measurement information, which includes the position errors and does not include the pose errors of the machine tool. The calibration tests showed the effectiveness of the calibration methods, which can be useful for the similar types of parallel machine tool.     

面向制造的机床并行公差优化设计

运用并行公差优化设计方法对精密卧式加工中心线性轴进行公差分配.在保证机床现有精度条件下,综合分析机床各线性轴制造误差的敏感度和加工成本,优化了给定结构机床线性轴导轨选型和导轨基面工序公差的精度设计,节约了机床制造成本.     

机床外观设计混合建模技术研究

为满足概念设计初期机床外观设计的要求,对传统参数化建模和非参数化建模技术进行了研究,提出了基于参数化建模和非参数化建模的混合建模方法,通过分析两种建模技术的优势和不足,给出混合建模思路、原则、流程,归纳出采用简化结构、使用贴图、建立模型库等提高建模效率的方法,最后将混合建模方法在实例中进行了验证.     

Graph-based optimization of five-axis machine tool movements by varying tool orientation

There is a relatively vast class of tool path optimization methods that minimize cost functions depending on a whole tool path. In these methods, cost functions are usually limited to convex function because the used optimization approaches cannot either handle nonsmooth functions or perform with an acceptable computational time. This paper describes a developed optimization method that finds a sequence of tool orientations that can minimize various cost functions including displacement of machine rotary axes. Every posture, tool feasible orientation can be represented in discrete fashion as nodes of a directed graph in which the edge weights denote an objective. Shortest paths are sought iteratively by applying Dijkstra’s algorithms and narrowing intervals of feasible tool orientations around the previous solution. The developed algorithm is a derivative-free optimization method working in a linear time.     

微型机床的结构动态特性分析

利用有限元和实验的方法,对微型机床试验台进行了结构动态特性分析。通过实验测试数据与理论计算结果对比分析,验证了有限元模型的合理性,并对测试及计算中造成误差的因素进行了讨论,为后续的微小型化机床系统动力学研究奠定基础。     

混联式机床的并联机构刚度解析

了混联式机床中的3－RPS并联机构刚度的边界元解析方法。采用关节合成的方法对并联杆系机构的机械结构系统进行静力学建模;将构件作为柔性体,利用边界元法对并联机构的静力学特性进行了。得出了3－RPS并联机构各分支的受力状态及系统的刚度。