数控铣床丝杆间隙对加工的影响分析

数控机床随着使用时间的增加,丝杆会出现磨损等情况,其间隙会不断增大,导致机床加工误差增大。本文详细分析数控铣床的丝杆间隙在不同加工情况下对加工精度的影响,并提出几种解决方法,以降低这种影响,提高零件的加工精度。     

数控龙门铣床主轴磨削工艺

数控龙门铣床主轴的加工精度,对机床精度标准中几项主要精度有着直接的影响,鉴于其结构和精度要求,在加工过程中对定位基准面的选择、深孔加工和热处理变形等方面,应给予足够的重视。通过对数控龙门铣床主轴XK2127/22310技术条件的分析和工艺过程的讨     

机床滚珠丝杠温度场热特性分析

机床加工过程生成热导致滚珠丝杠热变形,影响加工精度.以往的研究主要通过传统的解析方法计算得到滚珠丝杠热变形量,并没有考虑机床运行过程生成热引起机件热变形的影响.考虑热源的温度场影响,应用有限元分析法建立模型,并进行仿真,从而得到滚珠丝杠的热变形量和热变形的影响因素.研究结果为分析滚珠丝杠热变形对加工精度的影响和提高机床加工精度的优化设计提供了参考,为机床加工的误差补偿提供了理论依据.     

基于支持向量机回归的滚齿机热误差补偿模型

研究数控加工精度优化控制问题,由于滚齿加工过程中机床关键部件发热导致主轴热变形、实际加工点发生偏移,引起齿轮加工误差.针对零传动数控滚齿机存在的热误差,对机床结构特征进行分析,并确定热误差形成的原因和关键热源点.为解决上述问题,提出分别在工件轴向、水平径向和滚刀轴向针对热变形量与热源点温度关系建立非线性误差补偿模型.采用支持向量机回归方法建模,并结合贝叶斯理论,实现了估计系统噪声水平,同时提出确定模型超参数的方法,将超参数搜索范围限定在二维直线上,可避免搜索的盲目性,时间开销小于传统方法.实验结果表明,改进模型比常用最小二乘法有更好的误差拟合效果且效率较高,模型输出值作为误差补偿量可有效提高齿轮加工精度.     

基于NX二次开发的数控刀具管理与选取系统

随着机械技术不断发展,在现代机械加工中,越来越多的企业引入加工中心、数控车床和数控镗铣床等数控加工设备,从而使数控刀具代替传统刀具,被大量应用在生产的第一线中,成为数控加工中的主要角色.在实际加工中,数控刀具的质量和性能对加工效率、工件尺寸精度和表面粗糙度等相关指标产生直接影响.因此刀具的性能、质量以及管理在对产品质量、生产成本和生产效率等企业效益方面起着极其重要的作用.据数据统计:16%的计划作业停止由于缺乏刀具造成,30%～60%的刀具库存不在控制之中,机床操作人员20%的时间花费在查找刀具上等.     

基于西门子PLC的智能工业机电一体化机床控制研究

针对机床加工精度低和稳定性差的问题，提出以数控机床为研究对象，设计一种基于PLC的智能工业机电一体化机床控制系统。首先构建热误差建模算法，然后通过PLC实现热误差的补偿控制调节，可提高机床的加工精度和稳定性。具体实现为，由状态信息采集模块实现机床温度的测量；再在上位机数据处理模块中，通过建立机床温度与热误差同步测量系统，实现对热误差值的预测；再将预测值输入PLC控制模块，由PLC控制程序完成热误差预测值的补偿；并且对SIEMENS系统温度补偿功能的热误差补偿方法进行了研究。实验结果证明：在热误差补偿功能开启后，热误差最大值降低了78.9%。由此可知，本研究构建的机床控制系统可有效提高机床的加工精度以及稳定性，在实际应用中具有可行性。     

数控回转工作台的几何误差测量和建模

作为五轴数控机床的关键零部件,数控回转工作台能够实现C轴和A轴的回转进给与定位,其精度在很大程度上决定了数控机床的加工精度。以此为研究背景,建立了回转工作台的空间误差模型,对回转工作台的几何误差进行测量,并建立了误差补偿的数学模型,为最终进行机床的误差补偿提供依据,从而实现数控加工中心加工精度的提高。     

基于ANSYS的机床模态分析

振动现象是机床设计中所面临的问题之一,它会产生加工误差,影响零件的加工精度。模态分析主要用于确定结构或机器部件的振动特性,本文建立了某型立铣床床身的三维有限元模型,并利用大型有限元分析软件ANSYS对其进行模态分析,从而得出床身前十阶固有频率和振型。     

数控龙门铣床数据采集系统综述

龙门铣床是机床族的重要机型,其应用广泛,尤其是数控龙门铣床在航空制造领域的地位举足轻重。数据采集系统是机床监控系统的前端子系统和关键组成部分,数据采集系统设计的成功与否,决定了机床监控系统的数据有效性。对应用于龙门铣床的数据采集系统进行研究,具较大的现实意义。在介绍数控龙门铣床的结构及功能的基础上,分析了数控龙门铣床的数据采集的核心需求,针对性地分析和总结了数据采集的手段和方法,并概述了数控龙门铣床数据采集系统的发展方向。为数控龙门铣床数据采集系统的设计提供了技术支撑。     

基于ANSYS的机床模态分析

振动现象是机床设计中所面临的问题之一,它能造成加工误差,影响零件的加工精度。模态分析主要用于确定结构或机器部件的振动特性。本文建立了某型立铣床床身的三维有限元模型,并利用大型有限元分析软件ANSYS进行了模态分析,得出了床身前十阶固有频率和振型。     

An epitrochoidal pocket—A new canned cycle for CNC milling machines

A machining strategy for milling a particular set of pockets with epitrochoidal boundary is proposed. The method is suitable to be integrated into the controller of a CNC milling machine and is particularly useful for machining chambers of rotary internal combustion engines (Wankel), rotary piston pumps and generally epitrochoidal-shaped housings. Motion generation is achieved by an algorithm which utilizes real-time CNC interpolation providing the highest possible accuracy, of which the milling machine is capable. The surface quality is controlled by applying roughing and finishing passes. The whole machining task can be programmed in a single block of the part program. Finally, the effectiveness of the proposed method is verified by simulation tests of the generated tool path.     

A CNC machine tool interpolator for surfaces of cross-sectional design

A machining strategy for milling a particular set of surfaces, obtained by the technique of cross-sectional design is proposed. The surfaces considered are formed by sliding a Bezier curve (profile curve) along another Bezier curve (trajectory curve). The curves are located in perpendicular planes. The method employs a three-axis CNC milling machine equipped with suitable ball-end cutter and is based on the locus-tracing concept. The algorithm described, utilizes a real-time CNC interpolator providing the highest possible accuracy, of which the milling machine is capable. The surface quality is controlled by keeping the distance between scallops within a programmed value. Finally, the whole machining task can be programmed in a single block of the part program.     

数控铣齿机主轴系统温度场有限元分析

热误差是影响机床加工精度的主要因素之一。主轴的热变形是机床总的热变形的重要组成部分。因此本文在分析数控铣齿机主轴热源的基础上,计算发热量,确定边界条件,并利用有限元软件abaqus建立主轴系统的温度场模型并进行了数字模拟仿真,为主轴系统的进一步热变形控制提供了基础。     

一种新颖铣床智能数控系统的体系结构及其硬件实现

提出了一种新颖的开放式铣床智能数控系统的体系结构。该结构具有多层次、面向任务、模拟化的特征。在功能上加入了智能控制模块和刀具状况监视模块，以此提高数控机床的加工效率，并使加工精度得到保证。详细介绍了智能数控系统硬件的实现方法，该系统的硬件配置具有功能强、成本低、软件资源丰富、实用性好等特点。     

Computer numerical control for assuring the machining accuracy of contour milling

In this paper, a software technology for improving the machining accuracy in contour milling is discussed, in which the continuous path control is thoroughly investigated from the viewpoint of system synthesis, and the computer numerical control is effectively used. It is shown that the proposed “real-time cutter path rectification” offers an effective means to overcome the serious problem of the thermal deformation of workpieces. In this case, it is necessary to take many factors into consideration; the diversity of shapes, the change of cutting conditions, the unstable thermal situation, and so on. Therefore, the adaptive control is applied to compensate the thermal displacement of the contour during the cutting process. Relating to this subject, the effective cutter radius, which depends on cutter wear, is also evaluated in real-time operation; and the cutter diameter compensation is included in the “cutter path rectification”. In order to assure the machining accuracy, a new approach to contour measurement is proposed, in which the continuous path control by CNC system is used. It is certified through some experiments that the method proposed in this paper is useful to realize the flexible automation with high machining accuracy.     

Design of a decision support system for machine tool selection based on machine characteristics and performance tests

Economic globalization, together with heightened market competition and increasingly short product life cycles are motivating companies to use advanced manufacturing technologies. Use of high speed machining is increasingly widespread; however, as the technology is relatively new, it lacks a deep-rooted knowledge base which would facilitate implementation. One of the most frequent problems facing companies wishing to adopt this technology is selecting the most appropriate machine tool for the product in question and own enterprise characteristics. This paper presents a decision support system for high speed milling machine tool selection based on machine characteristics and performance tests. Profile machining tests are designed and conducted in participating machining centers. The decision support system is based on product dimension accuracy, process parameters such as feed rate and interpolation scheme used by CNC and machine characteristics such as machine accuracy and cost. Experimental data for process error and cycle operation time are obtained from profile machining tests with different geometrical feature zones that are often used in manufacturing of discrete parts or die/moulds. All those input parameters have direct impact on productivity and manufacturing cost. Artificial neural network models are utilized for decision support system with reasonable prediction capability.     

A novel approach to CNC machining center processing parameters optimization considering energy-saving and low-cost

NC machining is currently a machining method widely used in mechanical manufacturing systems. Reasonable selection of process parameters can significantly reduce the processing cost and energy consumption. In order to realize the energy-saving and low-cost of CNC machining, the cutting parameters are optimized from the aspects of energy-saving and low-cost, and a process parameter optimization method of CNC machining center that takes into account both energy-saving and low -cost is proposed. The energy flow characteristics of the machining center processing system are analyzed, considering the actual constraints of machine tool performance and tool life in the machining process, a multi-objective optimization model with milling speed, feed per tooth and spindle speed as optimization variables is established, and a weight coefficient is introduced to facilitate the solution to convert it into a single objective optimization model. In order to ensure the accuracy of the model solution, a combinatorial optimization algorithm based on particle swarm optimization and NSGA-II is proposed to solve the model. Finally, take plane milling as an example to verify the feasibility of this method. The experimental results show that the multi-objective optimization model is feasible and effective, and it can effectively help operators to balance the energy consumption and processing cost at the same time, so as to achieve the goal of energy conservation and low-cost. In addition, the combinatorial optimization algorithm is compared with the NSGA-II, the results show that the combinatorial optimization algorithm has better performance in solving speed and optimization accuracy.     

基于模态区间-马尔科夫链的动刚度预测

动刚度反映着数控加工过程中的稳定性,对加工精度有直接影响.对动刚度进行预测,预知动刚度的变化趋势,可为处理数控机床动刚度劣化问题提供指导作用.传统的马尔科夫链模型预测方法难以处理不确定性问题,将降低预测结果的可靠性.将模态区间数学理论应用于传统马尔科夫链中,提出一种基于模态区间-马尔科夫链模型的预测方法,以提高预测结果的可靠性.为了验证提出的预测方法的有效性,设计了一个数控机床相对激振实验.通过相对激振方法获取历史动刚度数据,采用模态区间-马尔科夫链模型对动刚度劣化趋势进行预测.结果表明:提出的预测方法有一个更好的预测精度.     

Open-architecture of CNC system and mirror milling technology for a 5-axis hybrid robot

This paper presents an open-architecture of CNC system and mirror milling technology for a new-type 5-axis hybrid robot named TriMule. The CNC system with dual CPUs is developed first to achieve human-computer interaction and motion control. Then, three key technologies are integrated in the system for improving the control quality, including singularity avoidance, feedforward control considering joint couplings and real-time error compensation by using externally mounted encoders. Based on these control technologies for single robot system, a collaborative machining strategy on the mirror milling system that consists of two TriMule robots is proposed to control the machining wall thickness of large thin-walled structural parts. Experiments on the TriMule robot and mirror milling system verify that the acceptable machining accuracy on the NAS test part and large thin-walled structural part can be ensured by using the developed CNC system and technologies. The root mean square of wall thickness error using the collaborative machining strategy can be 41.67% lower than the case without using the strategy.