MECHANICAL-ELECTRIC COUPLING DYNAMICAL CHARACTERISTICS OF AN ULTRA-HIGH SPEED GRINDING MOTORIZED SPINDLE SYSTEM

On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply, taking high-frequency converting current of inverter power switches into further consideration, a modified mechanical-electric coupling model is created. The created model consists of an inverter, a motorized spindle, a grinding wheel and grinding loads. Some typical non-stationary processes of the grinding system with two different supplies, including the starting, the speed rising and the break in grinding loads, are compared by making use of the created model. One supply is an ideal sinusoidal voltage source, the other is an inverter. The theoretical analysis of the high-order harmonic is also compared with the experimental result. The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.

Thermal Model of High-Speed Spindle Units

For the purpose to facilitate development of high-speed Spindle Units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Temperature prediction model for a high-speed motorized spindle based on back-propagation neural network optimized by adaptive particle swarm optimization

To predict the temperature of a motorized spindle more accurately,a novel temperature prediction model based on the back-propagation neural network optimized by adaptive particle swarm optimization(APSO-BPNN)is proposed.First,on the basis of the PSO-BPNN algorithm,the adaptive inertia weight is introduced to make the weight change with the fitness of the particle,the adaptive learning factor is used to obtain different search abilities in the early and later stages of the algorithm,the mutation operator is incorporated to increase the diversity of the population and avoid premature convergence,and the APSO-BPNN model is constructed.Then,the temperature of different measurement points of the motorized spindle is forecasted by the BPNN,PSO-BPNN,and APSO-BPNN models.The experimental results demonstrate that the APSO-BPNN model has a significant advantage over the other two methods regarding prediction precision and robustness.The presented algorithm can provide a theoretical basis for intelligently controlling temperature and developing an early warning system for high-speed motorized spindles and machine tools.

Model of Rotation Accuracy of High-Speed Spindles on Ball Bearings

For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.

Research Progress of Key Technology of High-Speed and High Precision Motorized Spindles

High speed machining and high precision machining are two tendencies of themanufacturing technology worldwide. The motorized spindle is the core component of the machine toolsfor achieving the high speed and high precise machining, which affects the general developmentlevel of the machine tools to a great extent. Progress of the key techniques is reviewed in thispaper, in which the high speed and high precision spindle bearings, the dynamical and thermalcharacteristics of spindles, the design technique of the high frequency motors and the drivers, theanti-electromagnetic damage technique of the motors, and the machining and assembling technique areinvolved. Finally, tha development tendencies of the motorized spindles are presented.

Lightweight design of 45000r/min spindle using full factorial design and extreme vertices design methods

Factors for determining the spindle size are the shaft diameter, positions of bearing and motor, and entire length of the spindle. Then, it is important to find the assembling of the optimal design variables, which satisfy the stiffimss and rotational speed required to the spindle. A general full factorial design method was used to verify some factors that affect the natural frequency of a spindle. It is verified that the shorter shaft length and bearing span length represent the higher natural frequency, and there are some effects according to the change in the levels of factors. The detailed spindle dimension is determined by applying an EVD method, which can define the optimal bearing position through considering the limiting condition. Based on the estimated regression model, the optimal spindle size and bearing distance that can improve the primary natural frequency are obtained, and the influence of design factors on the natural frequency is also analyzed.

Determination of amphetamines,ketamine and their metabolites in hair with high-speed grinding and solid-phase microextraction followed by LC-MS

A novel hair sample pre-treatment method based on high-speed grinding and solid-phase microextraction(SPME)had been applied for the determination of amphetamines,ketamine and their metabolites in hair samples by liquid chromatography mass spectrometry(LC-MS).A 20mg sample of hair was ground with 2 mL of saturated sodium carbonate solution using a high-efficiency hair grinder with 70 Hz osillation for 2min at 4℃.After centrifuging,1.5mL of the supernatant was transferred and treated with SPME by direct immersion(DI-SPME).The target analytes extracted by fibre were desorbed and analysed using LC-MS.Under the optimum conditions,a recovery of 90.2%-95.8%was obtained for all analytes.The analytical method was linear for all analytes in the range from 0.2 to 10 ng/mg with the correlation coefficient ranging from 0.9985 to 0.9993.The detection limits for all analytes were estimated to be 0.067 ng/mg.The accuracy(mean relative error)was within±6.9%and the precision(relative standard error)was less than 6.8%.The combination of high-speed grinding of hair and SPME had the advantages of being easy to perform,environment-friendly and high in detection sensitivity.The proposed method offered an altermative ana lytical approach for the sensitive detection of drugs in hair samples for forensic purposes.

Comparative investigation on high-speed grinding of TiCp/Ti–6Al–4V particulate reinforced titanium matrix composites with single-layer electroplated and brazed CBN wheels

In order to develop the high-efficiency and precision machining technique of TiCp/Ti - 6Al-4V particulate reinforced titanium matrix composites （PTMCs）, high-speed grinding experiments were conducted using the single-layer electroplated cubic boron nitride （CBN） wheel and brazed CBN wheel, respectively. The comparative grinding performance was studied in terms of grinding force, grinding temperature, grinding-induced surface features and defects. The results display that the grinding forces and grinding temperature obtained with the brazed CBN wheel are always lower than those with the electroplated CBN wheel. Though the voids and microcracks are the dominant grinding-induced surface defects, the brazed CBN wheel produces less surface defects compared to the electroplated wheel according to the statistical analysis results. The max mum materials removal rate with the brazed CBN wheel is much higher than that with the electroplated one. All above indicate that the single-layer brazed CBN super-abrasive wheel is more suitable for high-speed grinding of PTMCs than the electroplated counterpart.

面向全型面精加工的整体叶盘铣磨组合加工技术研究

整体叶盘由多个叶片呈圆周阵列布置在轮毂上,由于叶身型面为弱刚性零件,精加工时刀具磨损、颤振及让刀变形较为严重,影响了加工质量的进一步提高。提出一种面向全型面精加工的整体叶盘铣磨组合加工工艺,叶片型面采用磨削加工工艺,叶根、流道区域采用铣削加工工艺,通过控制磨削与铣削刀轨重叠区域的接刀误差实现叶盘全型面加工。试验结果表明,铣磨组合加工工艺表现出较好的加工质量,接刀误差控制在0.01 mm以内,轮廓误差小于0.04 mm,并通过加工试验验证了多主轴阵列加工的可行性,在保证加工质量的同时可大幅度提升加工效率。

蜗杆砂轮磨齿机主轴动态性能测试

砂轮主轴是蜗杆砂轮磨齿机的关键部件,主轴的动态回转误差直接影响着工件加工质量。介绍了采用主轴动态误差测试仪测量主轴误差的原因,使用主轴动态误差分析仪对磨齿机主轴几种常用转速进行了动态回转误差测量,测量的数据包括同步运动误差、非同步运动误差、总误差、径向跳动,通过分析对比可知主轴转速在4000 r/min时误差最小,采用该转速磨削可取得较好加工质量。测量主轴转速在4000 r/min时的温度变化和热误差可知,主轴热误差的变化趋势与温度变化趋势一致,控制主轴温度保持恒温是提高磨齿精度的关键。

液体动静压电主轴关键技术综述

液体动静压主轴以其高回转精度、高动态刚度、高阻尼减振性和长寿命等性能优势,在高速精密机床领域获得广泛应用,但进一步适应超高速超精密加工需要,发展成为将机床主轴与高速电动机功能从结构上融为一体的液体动静压电主轴,还需解决高速化和结构集成化带来的轴承温升控制和电机性能优化等技术难题,需进一步从机理层面研究轴承特性和电动机高频电磁损耗等科学问题。因此有必要对现有研究成果进行系统分析和深入总结。回顾液体动静压机床主轴轴承技术的发展历史;从轴承油腔结构、节流器、轴颈偏斜、轴瓦弹性变形、轴承副表面形貌、液体惯性效应、热效应、润滑介质可压缩性及非牛顿特性、水润滑动静压轴承等方面,对影响液体动静压电主轴轴承特性的关键技术进行逐一分析和评述;从高速电主轴对电动机几何特性、转速—力矩特性、热特性、振动及噪声特性的要求等角度,全面评述电动机性能的电磁参数设计方法、电磁损耗机理及计算方法和电磁损伤故障防治技术;具体分析动静压电主轴整机特性优化中的关键技术难题;对液体动静压电主轴技术的未来发展趋势进行预测和展望。

超高速磨削机床主轴系统模态分析

针对液体动静压轴承支撑的超高速磨削主轴系统工作的特殊性,在机床工作过程中,主轴高速旋转,动静压轴承的支撑刚度随转速动态变化。为了解主轴系统工作过程中的动态特性,应用Flunent软件求解液体动静压轴承的动态支撑刚度,而后在此基础上利用有限元分析软件ANSYS建立超高速磨床主轴系统的三维有限元模型,并对其进行模态分析,得到了各阶固有频率和振型。通过设置不同转速下轴承的支撑刚度,获得主轴系统模态分析结果,并利用图解法求解出主轴系统的临界转速。分析结果表明主轴系统在高速旋转状态下,系统的结构刚度会发生变化,使主轴系统的固有频率改变,并且随着转速提高差异越显著。通过振动试验测试验证仿真分析的可靠性,经分析可知,试验与仿真的误差主要来源于支撑模型的简化。

螺旋锥齿轮磨齿机砂轮位置误差与齿轮齿面误差的关系

研究砂轮主轴偏心误差及垂直度误差对齿面误差的影响规律,目的是研究它们之间的定量关系。基于展成法加工大轮,由啮合原理建立无误差砂轮与有误差砂轮情况下的大轮齿面方程,通过理论齿面与误差齿面的差曲面得到实际齿面的法向误差。提出主轴偏心误差及垂直度误差的误差敏感方向概念和确定误差敏感方向的计算方法,得到误差敏感方向上砂轮位置度误差量与齿面误差的关联规律,以及发生砂轮位置度误差时齿面误差的分布规律。研究内容与方法有助于螺旋锥齿轮齿面误差溯源与齿面加工反调。

高速磨削中的快速现场动平衡技术

本文研究高速高精度磨削中的快速现场动平衡技术。利用线性系统的基本理论对砂轮—主轴系统的不平衡响应进行了分析。论证了快速现场动平衡技术的基本原理并提出了一种实用的快速现场动平衡方法。平衡过程由预平衡和现场动平衡两个步骤构成。对一定安装条件的砂轮 -主轴系统 ,通过预平衡测定不平衡量与轴承座振动幅值的比例常数及振动量相对于不平衡量的滞后角。利用测出的比例常数和滞后角 ,对高速磨削过程中出现的不平衡振动 ,可实现转子系统一次试加重的快速动平衡。可在数分钟内使转子的残余不平衡量降低至原始不平衡量的 5 %以下。实验表明该方法具有平衡精度高 ,平衡速度快 ,易实施的特点。

微细磨削技术及微磨床设备研究现状分析与探讨

采用微磨床及微磨具的微细磨削技术,可以实现多种材料复杂形状三维微小零件的加工,且设备体积小、能耗少、成本低,已受到国内外研究人员的广泛关注。但是目前微细磨削技术的研究还处于起步阶段,在微细磨削机理、微磨床及微磨具等方面存在大量问题需要解决。因此非常有必要深入分析微细磨削技术的研究现状、存在的问题及发展趋势。明确了微细磨削技术的内容范畴;全面总结了微细磨削机理及工艺、微磨床及其关键部件、微磨棒等方面的研究现状;在此基础上,深入探讨了微细磨削技术在磨削机理及工艺、微磨床和微磨棒等方面存在的基础性问题,并进一步指出微细磨削技术还应关注其向多种材料应用、复合化加工、高效高精及智能化柔性化的发展方向,以期促进微细磨削技术在我国的推广应用,提升我国超精密微小零件的加工制造水平。

主动混合式砂轮-电主轴系统自动平衡装置研究综述

高速磨削过程中,砂轮-电主轴的不平衡影响工件精度和主轴寿命。因此,自动平衡装置在高速精密加工场合应用广泛。主动混合式自动平衡头是当今应用最多的一类自动平衡装置,阐述了其动平衡原理,并对其按结构特点进行了分类介绍。最后,对自动平衡装置未来发展作了展望,提出了平衡头的设计要求。

高速电主轴单元的振动性能研究

目的高速电主轴单元是实现高速、超高速磨削加工的关键技术之一.主要研究应用陶瓷轴承对电主轴动态性能的影响.方法采用“外点惩罚函数法”与“凑整解法”相结合的算法进行了陶瓷球轴承优化设计,并对电主轴进行了静、动态性能实验研究.结果探讨了陶瓷轴承电主轴单元结构布局形式的选择,分析了高速电主轴的振动性能.结论研究表明,应用陶瓷轴承作为主轴支承,电主轴单元振动小、温升低、运转精度高,有效提升电主轴功率和极限转速,适应高速、高效磨削加工的要求.

机床零部件生命周期碳排放评估与减排策略研究

制造业是我国碳排放的主要源头,机床作为制造业的工作母机,减少其主要零部件制造关键环节的碳排放,是实现我国2020年减排任务的关键。针对机床典型零部件的全生命周期过程及其关键碳排放环节,分析机床零部件生产阶段、加工阶段、使用阶段、回收处理阶段、运输阶段的碳排放情况,提出了基于机床零部件生命周期的碳排放系统运行模型。并重点分析了包括零部件毛坯生产工艺、热处理工艺以及机械加工工艺的整个生产加工过程碳排放情况,建立了基于物料流、能量流、环境排放流的碳排放量化模型,可用于识别和分析各个阶段的碳排放情况。以某企业常用的机床典型零部件主轴套筒作为实例开展研究,计算其生命周期过程的碳排放;基于碳排放对生产加工工艺参数、加工工艺方案进行了分析与优选,提出了相应的减排策略可为我国机床零部件碳排放提供量化方法和思路,进行有针对性的节能减排。

高频变流诱发的电主轴高次谐波振动及其抑制方法

高速电主轴已在超高速磨削中获得成功应用,但由高频变流诱发的高次谐波机电耦合振动严重影响磨削系统的稳定性和磨削质量,而其动力学机理尚不明确。利用传统的砂轮转子机械模型尚不能定量解释高频变流诱发高次谐波机电耦合振动的原因。在传统砂轮转子机械模型的基础上建立了"逆变器-电主轴-砂轮-磨削载荷"系统的机电耦合数学模型。利用该模型研究了启动、升速及突变磨削载荷等条件下磨削系统的几类典型非平稳过渡过程,并在超高速平面磨床上进行了试验研究。揭示了功率开关高频变流诱发超高速磨削系统机电耦合振动的物理机理,提出了通过优化逆变器工作参数抑制机电耦合振动的具体策略。

高速磨削电主轴可靠性加速寿命试验分析

为在短时间内获得高速磨削电主轴的寿命信息,通过加大载荷应力的方式建立起加速寿命试验模型,进行了两组恒定应力加速寿命试验。采用威布尔分布对电主轴寿命进行描述,并借助于最小二乘法对威布尔分布函数的两个参数进行估算,确定出电主轴可靠性寿命的相关指标,最终计算出基准载荷下电主轴的可靠性寿命。数据统计结果表明,电主轴的寿命服从威布尔分布,其加速模型符合逆幂律关系,从而验证了在不改变失效机理的前提下对高速磨削电主轴进行载荷应力加速寿命试验的可行性,极大地提高了产品寿命的预测效率,对电主轴生产厂商和用户均有很强的指导意义。