Local toolpath smoothing for five-axis machine tools

When five axis CNC machine tools follow series linear toolpath segments, the drives experience velocity, acceleration and jerk discontinuities at the block transition points. The discontinuities result in fluctuations on machine tool motions which lead to poor surface quality. This paper proposes to insert quintic and septic micro-splines for the tool tip and tool-orientation, respectively, at the adjacent linear toolpath segments. Optimal control points are calculated for position and orientation splines to achieve C³ continuity at the junctions while respecting user-defined tolerance limits. The geometrically smoothed corners are traveled at a smoothly varying feed with cubic acceleration trajectory profile. The proposed method is experimentally demonstrated to show improvements in motion smoothness and tracking accuracy in five-axis machining of free-form surfaces found in dies, molds and aerospace parts.     

贴片设备的选择

随着电子工业的飞速发展,贴片设备已被广泛应用于大规模电子组装生产上。文章就贴片机选型时应注意的几个关键技术问题作简单介绍,希望对企业选择贴装设备有一定的帮助。     

AHMED experiments on hygroscopic and inert aerosol behaviour in LWR containment conditions: experimental results

Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m³ total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compared to high RH. Thus at high RH (96–97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs. Experimental results were also compared with calculations obtained by severe accident computer codes. These calculated results will be presented in a later paper.     

国外工具磨床发展现状

本文综述了近睥来国外工具磨床技术的发展现状，介绍了由CNC技术带来的几种新的磨削方法，分析了当代工具磨床典型产品的技术水平。     

数控机床手轮进给故障的排故思路

在数控机床加工过程中,由于调整及慢速对刀的需要,通常需要频繁地使用手轮（即手摇脉冲发生器）来控制数控机床伺服轴的运动,因此,在数控机床的诸多故障中,手轮出现故障的次数较多,同时对该故障维修人员的维修水平要求也相对要高。本文以配备有FANuc 0i—mate-TD数控系统的cK0625数控车床为例,系统地介绍了数控机床手轮故障的诊断与分析方法。     

基于STEP-NC的数控系统体系结构的研究

分析了当前主流开放式数控系统的本构模型,建立了系统内部的信息流模型,根据非实时、弱实时和强实时区分信息流。综合考虑数控系统的功能模型、信息流模型,建立STEP-NC数控系统的层次模型为模型应用层、制造规划层和实时控制层。给出了基于PC和嵌入式系统分层架构的STEP-NC数控系统结构。     

数控机床主轴位置自动测量的实现

论述了数控机床主轴的结构以及数控机床主轴位王的测量电路的设计，实现了数控机床主轴位王参数的自动化测量过程。     

开放式计算机数控系统的构建

文章首先指出了研究多轴数控加工技术的重要现实意义和深远意义.对CNC的开放性、开放标准、系统建模、实时性进行了分析研究,在此基础上创新性地提出了一种基于WinCE和DSP的开放式CNC的构建方案.     

工业PC标准开放体系结构数控系统在卧式加工中心上的应用

使用工业PC标准开放体系结构数控系统，进行卧式加工中心电气控制系统的设计，调试及C＋＋语言PMC软件开发，指出NC主机－伺服系统－机床强电－操作面板－手轮－网络－通讯各部分的总体结构，硬件接线方法，模块化的PMC软件开发方法及机电整合调试步骤。     

基于有限元分析的连铸机钢包回转台结构优化设计

本文利用先进的ANSYS工程分析软件对连铸机钢包回转台进行有限元分析,找出整个回转台的应力和变形的分布情况,分析出回转台的薄弱环节,并在有限元分析的基础上进行优化设计,使得优化后的回转台结构在刚度和强度上都有很大提高,从而有针对性地解决了工程实际问题.