精密接长丝杠制造工艺分析研究

在没有精密长螺纹磨床的情况下,要制造一根总长6 700 mm丝杠,只能采取短丝杠接长的工艺。由于精密接长丝杠的工艺复杂,包括设备、测量仪器、熟练的技术工人、拼接技师等。介绍了几种常见的接长丝杠形式,丝杠的加工和拼接过程,需要克服的难点。由于接长丝杠是由多个短丝杠拼接而成,所以拼接处的受力情况直接影响丝杠的长久精度,通过分析,采取措施加以克服。在加工过程中,注意设备的热平衡,使加工设备的精度始终保持稳定,同时环境温度也要恒定。     

驱动箱研合仪的设计与实现

T1000系列便携式表面粗糙度测量仪驱动箱内部的丝杠与丝母是完成水平方向运动的主要部件,它们之间配合的好坏将直接影响着仪器最终的测量结果。为保证丝杠与丝母之间运行的平稳性,提高产品质量,于是新设计了一个驱动箱研合仪,它能够完成驱动箱内部丝杠与丝母之间长时间反复自动地研合。文中对驱动箱研合仪的构造、设计流程及实现方式进行了详细的说明。     

丝杠拼接的结构型式和工艺要领

采用拼接丝杠主要是由于加工设备长度不足或为了减小螺距累积误差,提高加工精度等所采用的措施。丝杠拼接的结构型式大致可归纳为12种(见图a～1)。它们有各自的优缺点及使用范围(见表)。拼接丝杠的主要工艺要领为:     

滚珠丝杠导程误差计算机辅助动态测量系统的研制

介绍3m滚珠丝杠动态测量系统，它是测量滚珠丝杠(副)导程精度的精密测量仪。系统采用模块式结构设计，具有设备自检、故障自动判别、测量过程自动控制、自动判断精度等级以及数据管理等功能，是一种全新的丝杠动态测量系统。     

浮动螺母

用滚珠丝杠、螺母驱动工作台时,丝杠一般有数十微米的径向跳动,直接影响了工作台的运动精度。为此,日本三丰开发了如图所示的浮动螺母机构。在该机构中,定位板A固定在工作台上。螺母D上装有两个圆术销E,D连同E可相对于内框B在水平面内作微量移动,补偿滚珠丝杠在水平面内的径向跳动。内杠B连同C、D、E可相对于A作上下移动,补偿丝杠在垂直方向上的径向跳动。从而避免丝杠径向跳动工作台运动的精度影响。浮动螺母@刘利     

嵌有压电作动器的滚珠丝杠驱动系统

将压电作动器置入滚珠丝杠驱动系统,可以灵活地控制滚珠丝杠的预紧力和运动;在伺服电动机粗定位的基础上,可以实现纳米级精确定位;通过脉动作用保证了系统的低速运动稳定性。     

大型超长丝杠的加工

介绍了利用指状铣刀、自身仿形法，小批量加工大型超长丝杠的加工方法，并采用量规的原理保证丝杠的加工精度。     

冲床中心线定位装置

对比了以往电动机驱动左右旋丝杠对中形式和以气缸、同步带对中形式的优点和缺点,并采用伺服电动机驱动丝杠来适应变截面纵梁,提高设备的冲压精度。     

JB 2886-81《机床梯形螺纹丝杠、螺母精度》标准介绍

JB 2886-81《机床梯形螺纹丝杠、螺母精度》部标准是在原机床专业标准GC 101-60《梯形螺纹丝杠、螺母公差》的基础上修订的。主要对三个方面作了修订:丝杠精度等级增加一级──4级精度;增加了动态测量指标──螺旋线公差;全长累积允差的合理化。同时,对其它各项精度作些修订和补充。下面就本标准中涉及的主要技术问题作几点说明。 一、动态测量指标和静态测量指标的关系 丝杠副是机床上主要的传动元件,其功用是把主动件的圆周上角位移转换成从动件的轴向线位移,并满足角位移与线位移的关系为一常数的要求,从而保证机床的传动精度,即如下式…     

精密滚珠丝杠副的选用计算

本文介绍了国际公认的滚珠丝杠常用的计算公式，并对精度的选择作了浓缩和整理，可供设计滚蛛丝杠及选用时参考。     

A two-stage vision-based method for measuring the key parameters of ball screws

Ball screws are crucial for improving the reliability and interchangeability of transmission mechanical systems; however, existing contact measurement methods that utilise stylus contact are not efficient, which precludes their use for rapid in-situ geometry evaluation. This paper presents a vision-based two-stage method for rapid measurement of key parameters (raceway arc radii and centre distance) of ball screws. The edge contour information is extracted from the acquired image using the dual-tree complex wavelet transform and non-maximal suppression. In the matching stage, a shape-matching algorithm is used for detecting approximate geometrical centres of raceway arcs. The refinement stage, on the other hand, is implemented for acquiring precise dimensional results. Furthermore, the method of averaging multiple measurements is performed to suppress random noise. A comparative experiment is presented to validate the robustness of the proposed method. Based on experimental results, the calculated mean absolute errors in the measurement of the two raceway arc radii and the centre distance are found to be 0.0082 mm, 0.0079 mm and 0.0055 mm, respectively. This study therefore paves the way for key parameter measurement without removing ball screws.     

Modeling and synchronous control of a single-axis stage driven by dual mechanically-coupled parallel ball screws

This paper presents a synchronous control scheme and system modeling technique for a single-axis stage driven by dual parallel ball screws/servo motors. The slide tables of the two ball screws are bridged with an aluminum bar, and each end of the bar is firmly fixed to one slide table. The thrust can, thus, be jointly output via this coupling. Such an arrangement aims to solve the potential skew problem that would occur on large scale machine tools whose stages have a long span between the two linear guides. This layout can also improve the system dynamics, speed and accuracy for large gantry-type machine tools. However, the precise synchronization of the two coupled parallel ball screws is a major challenge to overcome. Hence, in this paper, a system identification technique is first developed to construct a mathematical model of the coupled system, which is experimentally verified to be effective in improving performance. Three types of synchronous control schemes are then employed for control of the system. The performances of the three control schemes are experimentally compared in terms of positioning accuracy, tracking ability and reduction of the synchronization error between the two ball screws. Appropriate control schemes are suggested based on the experimental results.     

精密滚珠丝杠副伺服加载试验台设计

针对伺服传动系统中的精密滚珠丝杠副,设计出基于FCS多通道协调加载系统的伺服加载试验台,利用该试验台可测试精密滚珠丝杠副的多变载荷承载能力、轴向刚度、传动效率和启动力矩等性能,为用户提供准确可靠的检测报告.机械结构、多通道数据采集系统、电动机控制模块,是伺服加载试验台的关键部件.     

机载装备紧固螺钉强度分析与设计改进

为了解决某机载装备内部滤波器模块的紧固螺钉在耐久随机振动过程中发生的断裂问题,对紧固螺钉开展了强度校核和应力仿真分析,给出了机载装备小尺寸螺钉在耐久随机振动中剪切应力和挤压应力的估算方法,并应用ANSYS Workbench仿真软件对紧固螺钉在振动过程中的受力情况进行了仿真分析。强度校核和仿真分析结果对比表明,螺钉承受的剪切应力和挤压应力均高于许用限值,在振动中存在断裂风险,与试验现象吻合。依据螺钉强度校核和仿真分析结果,在紧固螺钉的螺纹直径方面进行了设计改进。经整机试验验证,改进后的紧固螺钉可满足耐久随机振动试验的强度要求,改进措施有效,表明文中给出的强度校核和仿真分析方法具有一定可信度,可作为类似结构的设计参照。     

Dual systems of finite displacement screws in the screw triangle

It has recently been shown that finite displacement screws of a particular form enter into linear patterns of combination—displaying the familiar structures of the screw systems—when they are used to describe incompletely specified displacements. Certain kinematic situations demonstrate the same simple linearity if normal usage is extended to admit dual coefficients of combination, the system then being referred to as a dual system. The screw triangle rule for composing the resultant displacement screw of two given finite displacement screws is examined in this paper. On regarding the lines of the given screws as fixed, and the displacement movements about them as variable, it is found that all available resultant screws occupy a structure which can be variously described as a dual 3-system (which contains infinitely many real 3-systems) or as the sum of two axially-orthogonal dual 2-system (each of which contains all linear combinations, using complementary dual sinusoidal coefficients, of two basis screws). The basis screws and nodal lines for these systems are found to lie on the triad of mutually orthogonal mirror-symmetry axes for the lines of the given screws.     

基于模糊理论的吊具起吊螺栓设计

将模糊数学理论引入螺栓联接的可靠性设计中,根据螺栓失效方式的不同,给出了动载荷疲劳破坏和剪切破坏两种失效形式的螺栓模糊可靠度的计算方法，为工程中选用螺栓及设计提供了依据。     

基于等效刚度仿真应力的螺钉强度校核

为解决系统级仿真中螺钉连接难以覆盖的难题,提出利用理论计算获得连接螺钉的轴向刚度与剪切刚度.通过等效刚度模型表征螺钉的承载特性,建立了带简化螺钉的系统级有限元模型,准确地获得了系统连接中螺钉部位的支反力.通过搭建冲击试验环境,测试相同部位的应力水平并加以比对,反向佐证了连接部位的支反力与实际情况相符.采用第四强度理论对...     

Apparatus to test insertion and removal torque of bone screws

This paper describes affordable equipment for testing bone screw torque, corresponding to ASTM standard F543-00 for testing metallic medical bone screws. Correct testing of thin and long bone screws is essential due to screw failures during insertion and removal of the screws. Furthermore, insertion torque is an important factor in predicting fixation strength, screw pull-out force and effects of surface treatment of screws. The capability of the custom-built tester was determined using polytetrafluoroethylene and wood disc samples and bone screws. Bovine cortical bones allowed testing to the failure limit, i.e. the torque increased in long screws to the fracture limit. For 2.7 and 3.5 mm thick self-tapping cortical bone screws, the failure torques were 30-50 per cent higher than the minimum values required by the standard (1.0 and 2.3 N m respectively). The equipment provided reproducible results and fulfilled the ASTM standard very well. Preliminary testing with amorphous diamond coated bone screws showed good durability of the coating and on average 10-15 per cent lower torque values compared with uncoated screws. The equipment can be used to measure insertion and removal torques as described in the standard. Furthermore, it also allows testing of normal screws and bolts.     

90°沉孔与90°沉头螺钉的加工要点

在机械加工和装配中,用于固定和联结的平板类零件,经常采用90°沉孔作为90°沉头螺钉或其标准件的配合孔.但是在实际加工过程中,由于两种零件分别加工,到装配现场时,经常有沉孔和沉头不匹配的问题.文中根据现场零件的返修案例,探讨沉孔和沉头螺钉在加工时应注意的工艺性.     

牵引销紧固螺钉断裂分析

分析了牵引销紧固螺钉失效断裂的原因,对失效螺钉的化学成分、显微组织和裂纹及断口特征等进行了综合分析。结果表明：失效螺钉表层脱碳,在交变应力作用下,致螺纹齿根处疲劳损伤直至断裂。建议应严格控制热处理质量,避免脱碳;或以螺栓取代螺钉或将螺钉尺寸加大。