Condition monitoring of ball screw feed drives using convolutional neural networks

Ball screw feed drives are widely used in machine tools and significantly determine the manufacturing quality and efficiency. With their degradation, machining accuracy and economic efficiency decrease. Therefore, monitoring the condition of ball screws is of great interest. Past investigations showed that condition monitoring of ball screws is possible. Nevertheless, practical applications of a condition monitoring system for ball screw drives are rare, as it is unclear how well they perform on unseen components. In this paper a data-driven approach is presented, which can assess the condition of unseen ball screws with an accuracy of up to 98%.     

钢基NiMoCrFeCo-WC涂层螺杆承载应力-扭矩的有限元分析

为研究高强度塑料注射成型过程中碳化钨陶瓷涂层螺杆的承载规律,采用ANSYS有限元模拟计算不同螺棱结构的碳化钨涂层螺杆承载特征,分析钢基材对三段式碳化钨涂层螺杆承载的影响规律,模拟碳化钨涂层螺杆在扭矩载荷作用下的应力/应变变化规律,讨论碳化钨涂层螺杆的承载扭矩与最大应力和最大应变的对应关系,建立碳化钨涂层螺杆临界扭矩的判...     

Integrated autonomous monitoring of ball screw drives

In ball screw drives wear occurs which results in decreasing dynamic performance and accuracy and can finally lead to machine breakdown. In order to avoid unacceptable machining results and failures, ball screws are changed based on previously calculated motion cycles and loads. State dependent maintenance requires monitoring of the wear progress. Here, an integrated sensory ball screw double nut system is presented. It measures the pre-stress as a wear indicator by strain gauges or sensory thin layers. Sensor information is processed by integrated electronics and communicated wirelessly. Energy harvesting and hybrid energy supply strategies are introduced. Measurement results are discussed.     

Effect of surface coating on the screw loosening of dental abutment screws

Regardless of the type of performed restoration, in most cases, a screw connection is employed between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices. The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloy screws and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (field emission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Innovation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of the abutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test. Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant load and thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than that of other screws and it also had abundant ductility and malleability compared with titanium and gold screws. The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon. The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommended as a means of preventing screw loosening.     

行星滚柱丝杠滚柱载荷差异分析与研究

基于行星滚柱丝杠中各滚柱啮合位置的差异,提出了各滚柱在丝杠和螺母两侧螺纹牙载荷分布的计算方法。通过分析得出若实现各滚柱啮合位置完全相同,丝杠和螺母的螺纹头数应是滚柱个数的整数倍。综合考虑行星滚柱丝杠滚柱啮合位置及轴段变形、螺纹牙接触变形和弯曲变形等因素,根据变形协调方程和牛顿第二定律,计算分析了各滚柱的载荷分布规律,并通过有限元算法验证结果的正确性。结果表明,当滚柱啮合位置不同时会造成各滚柱的载荷差异,并且啮合位置最高的滚柱两侧承受的载荷最大。     

Influences of oil additives on the wear behavior of ball screws

The lubrication in a tribosystem has a significant influence on the resulting friction and wear behavior. The spectrum of the used base oils for lubrication preparation increases continuously. That affects especially the use of environmentally friendly substances in order to save the environment. Regardless of the chemical origin, the lubrication systems should primarily take over the function of positive influencing of the friction and wear behavior. The ball screw as a central component of the machine tool feed axis transforms the rotational motions of the servo motor to a linear motion of the slide and takes over the fine positioning function in machine tools. According to the roller bearing lubrication specifications a grease or oil lubrication for ball screws is indispensable. The lifetime calculation is based on an elastohydrodynamic lubrication film. Within the research activities of the collaborative research center (CRC 442) ball screws with additived oils and nonadditived synthetic ester, which are developed within the collaborative research center, are tested on the test stand. The aim is to clarify the question, which influence the oil additives have on the wear behavior and preload loss in ball screws for machine tool applications. Investigations have clarified that oil additives have a significant influence on the preloading of the ball screws which are operated in the mixed friction area. The investigations of the axial rigidity as well as the investigations of the no-load torques clearly showed that oil additives cause a lower preload loss in ball screws compared to nonadditived oils.     

Surface characteristics of clinically used dental implant screws

Surface alteration of implant screws after function may be associated with mechanicalffailure. This type of metal fatigue appears to be the most common cause of structural failure. The purpose of this study was to evaluate surface alteration of implant screws after function through an examination of used and unused implant screws via scanning electron microscopy (SEM). In this study, abutment screws (Steri-oss, 3i, USA), gold retaining screws (3i, USA), and titanium retaining screws (3i, USA) were retrieved from patients, New, unused abutment, and retaining screws were prepared for a control group. Each of the old, used screws was retrieved with a screwdriver. The retrieved implant complex of a Steri-oss system was also prepared for this study. SEM investigation and energy dispersive spectroscopy (EDS) analysis of the abutment and retaining screws were then performed, as well as SEM investigation of a cross-sectioned sample of the retrieved implant complex in the case of new, unused implant screws, as-manufactured circumferential grooves were regularly examined and screw threads were sharply maintained. Before ultrasonic cleansing of old, used implant screws, there was a large amount of debris accumulation and corrosion products. After ultrasonic cleansing of old, used implant screws, circumferential grooves were examined were found to be randomly deepened and scratching increased. Also, dull screw fhreads were observed. More surface alterations after function were observed in titanium screws than in gold screws. Furthermore, more surface alteration was observed when the screws were retrieved with a driver than without a driver. These surface alterations after function may result in screw instability. Regular cleansing and exchange of screws is therefore recommended. We also recommend the use of gold screws over titanium screws, and careful manipulation of the driver.     

Analytical study of maximal tapping torque during forming screw process

Forming screws lead to a bolted assembly forming the threads of the work-piece by displacing material. The automotive industry is one of the largest markets for forming screws, which have been developed in the last ten years. One of the problems facing the designer of bolted assemblies using forming screws is the knowledge of the forming torque during the process.This study proposes an analytical model based on a previous study concerning radial penetration of a rigid acute wedge into a perfectly plastic material. The method uses the slip-line method with a model taking into account the interaction between two consecutive formed threads and enables the mean pressure on the thread flank to be obtained as a function of the formed thread height. From these results and a knowledge of the forming screw end geometry, an analytical method is proposed for the maximum forming torque, the physical phenomena of the displacement of material in the tapping process is illustrated and the significantly influential parameters highlighted. An experimental study seeks to determine the optimal lead hole on the work piece for an M8 screw. This sets limits on the forming torque and conserves a sufficiently well formed thread shape for good stripping resistance. The experimental results are compared favorably with the results of the analytical study in order to validate the forming screw model.     

基于连续小波的螺杆压缩机气阀状态监测方法研究

针对实测螺杆压缩机气阀在不同状态下振动信号的特点,采用连续小波变换的方法得到信号在尺度上的平均能量分布,即信号的平均尺度-小波能量谱.根据气阀不同状态下振动信号在尺度上的能量分布差异,提出了基于平均尺度-小波能量的标准特征向量判断压缩机气阀状态的方法,能够很好地识别出螺杆压缩机气阀的状态类型.该方法为螺杆压缩机状态监测及故障诊断提供了一种新的有效途径.     

生产厚螺旋叶片的锥辊轧机的研究

螺旋叶片应用越来越广泛，目前能够生产厚螺旋叶片的企业在国内还很少，其生产的专用机床的研制已经成为新的课题。本文通过对锥辊轧机的分析。提出生产螺旋叶片轧机的合理方案。     

高承载滚珠丝杠接触变形与磨损的研究

基于Hertz接触理论和Archard黏着磨损模型,分别分析和计算了高承载滚珠丝杠副的接触变形和磨损量;在此基础上,为了进一步研究高承载滚珠丝杠副的变形情况,提出了一种综合考虑高承载滚珠丝杠副弹性接触变形、弹塑性接触变形和Archard黏着磨损这几种影响因素的分析和计算方法;结果表明:利用这种方法可以更加全面地分析与计算出滚珠丝杠副在受载时及卸载后的总变形量。研究结果为深入开展高承载滚珠丝杠副的接触变形和磨损理论的相关研究提供了理论依据。     

精确预拉伸技术在高精度数控机床设计中的应用

为提高高精度数控机床的精度稳定性,从对精度及精度稳定性影响最大的丝杠传动结构优化入手,研究新的丝杠精确预拉伸方法,解决其他丝杠预拉伸方法不能精确控制丝杠预拉伸量,导致丝杠滚道变形量不能达到设计值,最终在丝杠热变形时无法精确抵消热变形而影响定位精度的缺陷。这种精确预拉伸技术操作简便、拉伸量控制精度高、稳定性好,可广泛应用于各种高精度数控机床的丝杠传动结构,可有效提高机床整机的定位精度及精度稳定性。     

Experimental study of forming and tightening processes with thread forming screws

Thread forming screws are being increasingly used, particularly in the automobile industry. They are designed to directly assemble two parts by displacing material to form their own thread. This specificity implies knowledge of the screwing torque needed for the thread to be formed in the lower plate of the assembly and of the tightening torque necessary so as to establish the preload in the assembly. The experimental study presented in this paper is divided into two parts.The first concerns the thread forming process and shows the influence of the geometrical parameters of the thread forming screw and of the work-piece, and the influence of the process parameters on the maximum forming torque. A compromise can be proposed for the choice of the lead hole diameter, which is the most important parameter to be considered in order to keep a reasonable forming torque while obtaining threads deep enough to avoid stripping problems.The second part concerns the tightening process. An original experimental device is used to enable an empirical formula to be proposed, based on the ISO standard screw formula giving the tightening torque according to the preload applied inside the assembly.     

钢管辊拔的理论解析

分析了钢管辊拔的特征，推导出辊拔时辊拔力的解析式。该解析解与实验结果较为吻合。以积分中值定理与水平力平衡条件确定了辊模压力。可供钢管辊拔计算时参考。     

航天器高速角接触球轴承生热及温度场仿真分析

高速角接触球轴承在高速运转条件下生热主要是由于滚子与滚道相互摩擦引起的,其中转速、载荷、材料和润滑状态等都是主要的影响因素。根据滚动轴承生热计算模型,基于MATLAB计算平台对航天器高速角接触球轴承B7005进行生热计算。另外,基于ANSYS有限元分析平台对轴承进行温度场仿真分析。最后比较两种方法的结果,分析表明,理论计算与有限元分析结果接近,验证了所介绍的温度场仿真分析方法具有较高的可靠性,也是热-结构耦合分析和寿命分析的重要基础。     

三螺杆泵的温度场及热力耦合分析

为适应三螺杆泵高速、高压、大流量的发展趋势,严格控制螺杆变形及其相关间隙以减少泵内泄漏是关键。以三螺杆泵为研究对象,将泵内温度场作为载荷施加在主、从动螺杆表面,并进行温度-结构耦合的数值模拟分析。研究不同工况下三螺杆泵内温度和工作扭矩使主、从动螺杆产生的变形规律,并对比与主、从动螺杆在各单独物理场作用下和耦合作用下的变形和应力变化。结果表明:主、从动螺杆的热变形比力矩变形更明显。随着工作温度升高,主、从动螺杆的热变形量增大,主、从动螺杆产生的热应力与工作温度呈正比关系;在同一工作温度下,主、从动螺杆在X、Y、Z 3个方向的变形量均增加,而Z方向的变形量远大于X和Y方向的变形量。     

Determination of the load on profiled roller guide rails used as ram guides for metal-forming machines

Properties of profiled roller guide rails are high load capacity, high rigidity against tractive and compressive forces, low friction and high accuracy of guidance. The bearing clearance equals zero in profiled roller guide rails due to the pre-stress between carriage, rollers and guideway. For these reasons profiled roller guide rails have been used as ram guides in metal-forming machines for several years. Unlike sliding ram guides, guides with profiled roller guide rails can transmit tractive and compressive forces. Thereby the ram with its guides contributes to the stiffness of the whole machine. The load capacity of profiled roller guide rails is limited to the lifetime of the rollers. The load on the profiled roller guide rails during the production process is the main input for the calculation of the lifetime and can by now only be estimated roughly. The measuring method presented in this paper enables the determination of these loads.     

Total differential methods based universal post processing algorithm considering geometric error for multi-axis NC machine tool

Multi-axis numerical control machining for free-form surfaces needs CAD/CAM system for the cutter location and orientation data. Since these data are defined with respect to the coordinate of workpiece, they need converting for machine control commands in machine coordinate system, through a processing procedure called post processing. In this work, a new universal post processing algorithm considering geometric error for multi-axis machine tool with arbitrary configuration. Firstly, ideal kinematic model and real kinematic model of the multi-axis NC machine tool are built respectively. Difference between the two kinematic models is only whether to consider the machine tool's geometric error or not. Secondly, a universal generalized post processing algorithm containing forward and inverse kinematics solution is designed to solve kinematic models of multi-axis machine tool. Specially, the inverse kinematics solution is used for the ideal kinematic model, while the forward kinematics solution is used for the real kinematic model. Then, a total differential algorithm is applied to improve the calculation speed and reduce the difficulty of inverse kinematics solution. Realization principle of the total differential algorithm is to transform the inverse kinematics solution problem into that one of solving linear equations based on spatial relationship of adjacent cutter locations. Thirdly, to reduce the complexity of geometric error calibration experiment, effect weight of geometric error components is determined by the sensitivity analysis based on orthogonal method, and then the real kinematic model considering geometric error is established. Finally, the universal post processing algorithm based on total differential methods is implemented and demonstrated experimentally in a five-axis machine tool. The results show that the maximum error value can be decreased to one-fifth using the proposed method in this paper.     

透平循环压缩机组运行状态自动监控系统的设计

介绍了透平循环压缩机组运行状态自动监控系统的结构、软硬件配置、技术关键点及特点。该系统以工业控制计算机为中心, 选择与机组运行状况因果关系明显的轴向位置、振动及工艺参数（ 电流、功率、温度） 等信号作为在线监测信号, 采用阈值监测模式, 实时监测机组的运行状态, 实现预警、紧急自动停车、故障诊断和滚动轴承寿命分析等功能。该系统应用于工业现场, 取得了良好的效果。     

循环式行星滚柱丝杠副的热力耦合特性研究

为了研究循环式行星滚柱丝杠副在不同轴向载荷和不同工作温度下的变形和接触应力分布规律,以循环式行星滚柱丝杠副中的丝杠为研究对象,采用热力耦合仿真方法,建立了循环式行星滚柱丝杠副的有限元模型,研究不同工况下滚柱丝杠副的轴向载荷和工作温度使丝杠产生的变形和接触应力规律.对比轴向载荷、工作温度、热力耦合3种工况下丝杠的变形和接...