Numerical and experimental analysis of transient state micro-bounce of aerostatic guideways caused by small pores

Aerostatic guideways have been applied to precision machine elements. Recently, downsizing and the increased use of high-density technology in IT devices have generated demand for higher accuracy in aerostatic guideways. It has been pointed out that the micro-bounce occurs when the slider passes over the aerostatic guideway with small pores. This transient state micro-vibration decreases the accuracy of aerostatic guideways and, thus, it is now expected to be suppressed. The purpose of this study is to analyze the micro-bounce mechanism of aerostatic guideways caused by pores, and to propose new designs for the suppression of micro-bounce.     

Design Procedure of Pneumatic Half-Floating Slideway with Load Compensation and its Application to Machining Center

It is known that slideway friction plays an important role for machine tool performance, and therefore a proper amount of solid frictional force is preferable to satisfy various requirements of static and dynamic properties, accuracy and stiffness etc. This frictional force, however, changes in accordance with the feeding conditions of slider, in particular, that of the load and speed. The present paper shows the design procedure of a new type of slideway which can keep the frictional force being almost constant independent of the feeding conditions. The principle uses Pneumatic Half-Floating Slide way, in which the slider is supported by either an externally pressurized aerostatic force and a metal to metal contact force. If the load, mostly the workpiece weight and the static cutting force, applied on the slider increases, the increment can be compensated by a special device which is composed of a load detector (a type of air micrometer) and a pressure amplifying valve. By the application of this new slideway design to an existing machining center, it was revealed that the frictional force could be kept at almost constant independent of the applied load and the feed speed. Consequently, the amount of backlash and lost motion could also remain the same under different working conditions, which could improve, under the load of 500 kgf, both the positioning and the contour accuracies up to several micron meter better than those obtained by the conventional machine.     

空调机外机维修罩模具设计

空调机外机维修罩结构复杂,为避免在制品外侧使用抽芯机构,模芯采用有角度的放置方案,在产品内侧设置了必要的抽芯机构,包括以下内容:2个三角形倒钩(间距84.5mm),2个扁形倒钩(间距19.8mm),底部的斜圆槽排水沟和顶部的线性卡槽。其中,底部斜圆槽排水沟采用了油缸长距离抽芯机构,顶部的线性卡槽选用了斜导柱滑块抽芯机构,倒钩选用了斜推杆抽芯机构。经过生产实践证明,所设计的模具成型性能稳定,符合大批量生产的要求。     

成型塑件无推杆印推出结构及注射模设计

以注射模中实现成型塑件上无推杆印的推出结构作为研究对象,通过模具结构优化并采用滑块结构减少对成型塑件的抱紧力,有助于塑件脱模,并不会在成型塑件上留下推杆印,满足成型塑件的质量要求。     

电流变传动系统的时间序列建模

电流变传动机构是一种重要的、有发展前途的传动装置.文章开发一种双驱动式电流变传动机构,通过测试数据,用时间序列分析方法建立电流变传动系统的自回归求和模型,并求出系统的自功率谱密度函数.实验和理论推导结果表明时间序列分析方法用在电流变传动机构的建模中是有效的、可信的,具有推广意义.     

An experimental evaluation of coefficients of static friction of common workpiece–fixture element pairs

Most machining fixtures utilize clamping forces and friction at fixture–workpiece joints to help prevent the workpiece from slipping out of the fixture during machining. The magnitudes of the clamping forces required are a direct function of the coefficients of static friction at the joints. Recently, analytical methods have been developed to predict minimum clamping forces. However, these methods require accurate estimates of the friction coefficients.One source of friction data are handbooks. However, these data are typically listed relative to the materials of the contacting elements and are otherwise completely generalized. This paper will illustrate that the coefficient of static friction for typical fixture–workpiece joints is not a simple function of the workpiece materials. Instead it is also a function of factors such as fixture element geometry, workpiece surface topography, clamping forces, the presence or absence of cutting fluids, and normal joint rigidity.     

超高速冲压滑动夹持成形工位的改善

为提高冲压模具成形速度,研究了用于超高速冲压(UHSS)平台成形母端子PIN和BOX部位冲压模具的滑动夹持成形工位。发现在模具的成形期间,成形滑块表面在半径接触点开始表现出磨损,然后向下产生较长的磨损,分析了滑动表面的几何形状及造成磨损的主要因素,成形滑块在成形期间磨损的主要形式是粘着磨损和分层磨损,夹持块的几何形状和滑动表面的角度是造成磨损的重要原因。对滑动夹持成形工位进行了重新设计,对线性驱动和从动轮廓进行了改进,从开始到结束都采用面滑动,同时原始的滑动面的角度设计变小,减轻了磨损和旋转问题,增加了工位的可调节。     

压铸模设计中的过定位及改进措施

以滑块抽芯机构为例，对压铸模结构中的过定位问题进行了研究，提出了具体的结构改进措施。变滑块与侧型芯之间的刚性联接为浮动联接，使滑块只能在必要的轴向对侧型芯有强制作用而在其它方向上不予限制．侧型芯可以完全按照镶块型芯孔的约束来确定自己的位置，从而简化滑块抽芯机构的机加、装配难度。降低压铸模的制造费用。     

多孔质气体静压丝杠螺母副研究

气体静压丝杠螺母间的气体薄膜使气体静压丝杠螺母之间的摩擦、磨损极小,极大地提高了静压丝杠螺母副的使用寿命.螺母所采用的多孔质材料可提供众多的微小节流孔,使气体静压多孔质丝杠螺母副具有高承载能力、高阻尼和很好的稳定性等优点.本文根据气体静压丝杠螺母副的几何模型与气体静压圆锥轴承的几何模型的相似性,即气体静压丝杠螺母副可看作是相对的气体静压圆锥轴承以一定的螺距沿轴方向排列而成的,通过对气体静压圆锥轴承的分析和有限元推导,分析了气体静压丝杠螺母副的静态性能.并通过实验验证了理论推导的正确性.     

海洋桩基平台调平器夹紧工作机制的分析

海洋桩基平台调平器是一种精密的水下作业机械,桩基平台安装过程中,需要调平器进行调平,其夹紧工作负荷常常会达到几千吨。介绍了桩基平台调平器系统结构,分析了其上夹紧机构和下夹紧机构的力学模型。采用有限元方法分析了夹紧块工作时桩基导管和桩脚裙套的变形和受力。建立了桩基调平器实验系统,验证了调平器工作过程,获取了导管和裙套夹紧时的变形受力特点,与理论分析结果基本吻合。该结果为桩基平台调平器的夹紧装置优化设计提供了一定的理论基础。     

饮料瓶盖注射模设计

介绍了一款饮料瓶盖热流道注射模结构,模具采用双推板强制推出机构以及T形块+滑块的侧向抽芯机构,模具脱模机构复杂,冷却系统结构设计合理,生产效率高。塑件脱模后无拉伤、变形,质量符合设计要求。     

基于ANSYS的多连杆机构性能优化

多连杆机构是拉延类机械压力机采用的主传动机构,通过参数优化能够实现拉延过程中滑块速度低而平稳、快速回程的功能,提高拉延件的质量和工作效率.针对压力机传动结构中最常用的八连杆机构,应用ANSYS/AP-DL开发多连杆机构参数化建模分析和优化程序,程序分为前处理、求解、后处理、优化计算四部分.在前处理模块输入机构参数,建立...     

基于有限元技术的折弯机滑块分析与改进设计

滑块是数控板料折弯机的重要组成部分,对加工工件的精度有着重要影响。本文采用ANSYS有限元分析软件建立了折弯机整体有限元模型,对折弯机滑块进行了静力学分析,研究了滑块的应力分布与变形情况,研究发现液压缸活塞杆与滑块安装的方形开口周围应力过大。为提高该处结构强度,提出几种改进设计方案,通过有限元计算结果的比较,最终确定最合理的设计方案。     

双点压力机滑块有限元分析与优化

在分析双点压力机的滑块的结构特点与工作方式的基础上,对其进行有限元计算分析;对滑块进行拓扑优化、结构优化;比较了原滑块与优化后滑块的结构特点,并对滑块优化方案作了验证。     

封头接管移栽夹持机构设计与实验

在工业机器人自动焊接领域中,实现对焊接工件夹持与焊枪协同焊接的移栽夹持机构在焊接过程中发挥着重要的作用。通常在工业领域中,焊接工件的形状与焊接情况不同,因此需要设计专用夹具。针对一种圆柱形工件夹持问题,设计一个内壁柔性夹持移栽机构,应用于视觉辅助多机械臂焊接工况中,将焊接零件准确移栽到指定焊接位置上,与焊接机器人协同实现自动焊接。设计移栽夹持机构,展开静力学仿真验证模型正确性,最后搭建实物验证环境进行夹持实验。结果表明:第一阶段实验放置成功率达到100%,第二阶段实验移栽机构满足焊接距离2 mm精度要求,为封头接管的移栽提供良好的条件,有利于封头接管自动焊接。     

曲柄驱动双肘杆传动机构的设计与优化

为加工高强度、回弹大的轻量化板材,设计了一种曲柄驱动的立式传动肘杆伺服压力机。采用ADAMS软件对比分析了两种不同传动机构的工作特性。针对曲柄立式传动肘杆机构,通过矢量法建立滑块变速移动特性的运动学方程;运用ADAMS对传动机构各尺寸变量进行敏感度分析,以减少设计变量,再运用遗传算法对传动机构进行多目标优化,以减小滑块最大速度、滑块最大加速度和机构高度为优化目标。研究结果表明,优化后的曲柄立式传动肘杆机构的工作性能有较大提高,滑块最大速度降低了8.5%,滑块最大加速度降低了37.6%,曲柄最大扭矩降低了9%,机构高度降低了1%;同时该机构具有良好的保压性能和急回特性。     

A theoretical and experimental investigation into five-DOF dynamic characteristics of an aerostatic bearing spindle in ultra-precision diamond turning

In ultra-precision diamond turning (UPDT), spindle vibration has great influence on machining precision of high precision optical components. However, the spindle-vibration mechanism has not been fully understood. In this study, mathematical solutions for a proposed five-degree-of-freedom (FDOF) dynamic model of an aerostatic bearing spindle are derived to explore natural mechanisms of spindle vibration. Thus, the potential benefits of the solutions are to be applied for the prediction and optimization of the effects of spindle vibration on surface generation. Its dynamic characteristics possess three translational frequencies along the radial and axial directions, a spindle rotational frequency (SRF), and a pair of coupled tilting frequencies (CTFs) around the radial directions influenced the SRF. The theoretical results are identified by the frequency characteristics of thrust cutting forces, and the periodic, concentric, spiral, radial and two-fold patterns (PCSRPs) of the machined and simulated surface topographies, respectively.     

新型微孔节流气体静压轴承的特性研究

针对狭缝节流静压气体止推轴承的狭缝加工质量难以保证的问题,提出了一种微孔节流气体静压止推轴承。基于Fluent软件,保证轴承的总节流面积相同,通过改变气膜厚度、节流孔(缝)深度,对比研究了狭缝节流和微孔节流静压气体止推轴承的承载力、刚度及耗气量;其后对轴承的总节流面积取不同值时的轴承特性进行分析对比,从而判断了两种轴承在一定条件下是否具有互换性。结果表明:气膜厚度、节流孔(缝)深度、轴承的总节流面积取不同值时,微孔节流静压气体止推轴承在承载力、刚度及耗气量上都与狭缝节流静压气体止推轴承有较高的一致性;在一定的工况下,微孔节流静压气体止推轴承可以代替狭缝节流静压气体止推轴承。     

液压锁紧轴套锁紧扭矩计算与实验研究

液压锁紧轴套是五轴联动机床的关键部件,能够在压力载荷作用下发生较大的弹性变形,锁紧进给轴的转动自由度,对机床定位锁紧和加工精度有重要的影响,锁紧扭矩是液压锁紧轴套设计的重要参数。为研究轴套壁厚、压力载荷、配合间隙及轴套长度4个参数对液压锁紧轴套锁紧进给轴时产生的锁紧扭矩影响,首先用有限元方法计算了液压锁紧轴套工作时的变形、轴套与进给轴之间的接触应力分布;然后在进给轴外表面对接触压力积分得到轴套作用在进给轴上的正压力,进而得到锁紧扭矩;最后在自主设计的实验台上进行锁紧扭矩测试实验,对有限元方法计算数据进行验证。结果表明:有限元方法计算得到的理论数据相对实验数据相对偏差均小于4.87%,验证了有限元方法计算的理论数据可靠性。该有限元方法计算的理论数据可以对液压锁紧轴套结构设计提供参考。     

串珠机物流套注射模设计

设计了带双层哈夫滑块脱模机构的三板模实现串珠机物流套的注射成型,针对塑件外壁脱模困难,使用2层哈夫滑块机构对塑件的外壁实施侧抽芯脱模,两层哈夫滑块的驱动分别由三板模的2次分型驱动。实践证明,模具结构和脱模机构布置合理,具有一定的参考作用。