外圆磨削时主轴误差运动的预测补偿控制

外圆磨削时工件的形状精度直接受主轴径向误差运动(SREM)的影响。为了有效地补偿SREM,文章介绍一种预测补偿误差系统,并详细叙述了SREM的在线测量及控制的系统。应用本方法可对外圆磨床上工件主轴的径向误差运动进行分析,而且在理论上可补偿98.4%的误差。比较预测系统和常用的反馈系统的不同超前期,进而确定在线控制时的最佳预测步数。图13幅,表6个,参考文献15则。     

角接触球轴承旋转精度数值仿真分析

根据角接触球轴承的几何和运动关系,建立了考虑外圈沟道圆度误差的轴承外圈径向跳动、轴向跳动数值仿真模型,分析了外圈沟道圆度误差阶次、圆度误差幅值和钢球个数对外圈旋转精度的影响,并进行了理论验证.结果表明,轴承外圈径向跳动和轴向跳动随着圆度误差阶次的变化呈周期性变化;当圆度误差阶次与钢球数满足特定关系时,径向跳动明显增大;...     

CBN砂轮磨削薄壁球轴承内圈滚道的试验研究

提出了用立方氮化硼(CBN)砂轮代替传统的微晶刚玉砂轮磨削薄壁球轴承内圈滚道的方法,探讨了不同工艺参数对工件表面粗糙度和圆度精度的影响.试验结果表明,当CBN砂轮粒度变细时,可以明显改善磨削表面粗糙度,而对工件圆度值的影响较小;随着进给量增大,加工表面粗糙度值和滚道圆度误差值均增大;随着磨削速比降低加工表面粗糙度值增大.得出了最佳工艺参数为:磨削速比值ν工/ν砂=1/24,磨削进给量0.6 mm/min,砂轮粒度80#;其加工效果为:滚道圆度值由4μm稳定降低至2.5μm范围内,表面粗糙度由Ra 0.42 μm降低至Ra 0.28μm,尺寸一致性提高37%,无烧伤现象;生产率比微晶刚玉磨削提高40倍以上,砂轮耐用度提高50倍以上.     

微小振动影响超精密非球面加工精度的研究

超精密磨削已广泛应用于轴对称非球面光学元件及硬脆材料的加工，加工过程中砂轮的不平衡量和机床主轴引起的振动直接影响工件表面精度及粗糙度。为了适应非球面工件超精密加工的要求，本文通过分析加工过程中产生的振动现象，建立磨削中振动引起工件表面轮廓误差的数学模型，研究主轴转速变化及磨削加工参数对工件表面精度的影响；通过建立工件与砂轮之间的运动关系，得出砂轮的振幅、频率及加工速度的变化对工件表面精度的影响条件。研究结果表明：选择合理的加工参数能降低工件表面波纹度，提高工件的表面精度。     

通过恰当选择无心磨削循环时间来提高工件圆度

在无心磨削中可获得的工件圆度直接与磨削过程中所选择的循环时间长短有关。本文提出了一种能通过恰当选择循环时间来达到降低工件圆度误差这一目的的系统方法。本文首先研究了成圆过程中的瞬间特征，且当初始圆度误差被有效排除而棱圆形还未能在工件表面完全展开之时，就能获得上面所提到的工件圆度的最小误差值。然后介绍的是这种应用于切入式无心磨削及通磨无心磨削过程中的计算机模拟方法，它是通过选择最佳的磨削循环时间来达到将工件圆度误差值减至最小值这个目的的。最后介绍的是通磨无心磨削过程中能评估棱圆稳定性的平均增长率概念。     

柱形动压气浮轴承马达轴精密磨削加工工艺研究

针对GT35动压马达轴精密加工精度难以保证、效率低、成本高的难题,开展马达轴精密磨削加工工艺研究。通过开展不同结合剂,不同粒度、浓度的金刚石砂轮磨削对比试验,研究不同砂轮参数对工件形状精度、表面质量、比磨削能等的影响规律,设计超硬磨料砂轮;通过正交试验,确定影响轴精密磨削表面粗糙度、圆度、圆柱度的最优工艺参数;采用最优磨削参数对20件马达轴开展了磨削加工验证试验。研究得到:当工件转速304 r/min、进给速度0.003m/min、进给量1μm时,获得最优的马达轴圆度0.11μm、圆柱度0.34μm、粗糙度Ra0.041μm的合格工件。     

机床主轴径向回转误差的测量与研究

主轴回转误差严重制约着机床工作精度,本文对机床主轴产生回转误差的原因进行分析,并对其测量方法进行研究,在对现有的线位移三点法误差分离方法的研究的基础上,采用了一种优化算法——矩阵算法,代替傅里叶变换实现圆度误差分离。采用最小二乘法和圆图像的误差值对分离出的主轴圆度误差和回转误差进行评定。基于仿真软件,开发主轴动态回转精度测试系统,该系统用于主轴回转误差测量,通过对测量数据进行处理,得到较高精度的误差分离结果,对主轴回转误差的有效分离具有指导意义。     

某型数控机床主轴系统回转误差动态测试研究

高速主轴的回转误差运动直接影响到被加工零件的加工精度与产品的使用寿命。为了对数控机床的加工性能进行合理评价,分析了同步径向误差运动与工件圆度以及异步误差运动与工件表面粗糙度之间的关系,并采用美国Lion Precision公司开发的主轴误差分析仪对某型数控机床的主轴系统进行回转误差及漂移的测量,根据测量结果对所测主轴加工性能进行评价,为实际生产加工提供了参考。     

高精度无心磨削圆度保证和成圆过程解析

为了对无心磨削的圆度误差进行研究,讨论了影响高精度无心磨削过程的关键因素,包括稳定性、磨削参数、砂轮和导轮,给出了改进圆度误差的措施。在时域内对无心磨削成圆过程进行了解析。在解析研究中考虑了成圆过程的非线性环节,通过工件的轮廓和工件与砂轮、托板和导轮之间的作用研究工件的成圆过程。实验结果和理论结果的对比显示,解析模型可以对成圆过程进行准确预测。     

铝飞轮壳车削加工圆度超差分析与解决方案

针对某型号汽车发动机飞轮壳产品立车加工圆度超差问题,建立飞轮壳有限元模型,利用Altair Simlab与ANSYS Workbench等软件对工件在旋转状态下进行有限元仿真分析计算,得到工件的变形分布状况。结果表明:工件旋转产生的离心力引起的工件变形不是造成圆度误差的主要原因,而工件夹具系统偏心造成主轴轴承磨损产生间隙引起主轴的跳动才是最根本问题。根据最后的分析结果,针对夹具设计提出相应的改进方案。该结果可以为减少飞轮壳的加工圆度误差提供参考,提高产品的加工质量。     

Effects of process parameters on workpiece roundness in tangential-feed centerless grinding using a surface grinder

The present authors proposed a new centerless grinding method using a surface grinder in their previous study [Wu, Y., Kondo, T., Kato, M., 2005. A new centerless grinding technique using a surface grinder. J. Mater. Process. Technol. 162–163, 709–717]. In this method, a compact centerless grinding unit composed mainly of an ultrasonic elliptic-vibration shoe is installed onto the worktable of a multipurpose surface grinder to perform tangential-feed centerless grinding operations. However, for the complete establishment of the new method it is crucial to clarify the workpiece rounding process and the effects of process parameters such as the worktable feed rate, the stock removal and the workpiece rotational speed on the machining accuracy, i.e., workpiece roundness, so that the optimum grinding conditions can be determined. In this paper, the effects of the process parameters on workpiece roundness are investigated by simulation and experiments. For the simulation analysis, a grinding model taking into account the elastic deformation of the machine is created. Then, a practical way to determine the machining-elasticity parameter is developed. Further, simulation analysis is carried out to predict the variation of workpiece roundness during grinding and to discover how the process parameters affect the roundness. Finally, actual grinding operations are performed by installing the previously constructed unit onto a CNC surface grinder to confirm the simulation results. The obtained results indicate that: (1) a slower worktable feed rate and higher workpiece rotational speed give better roundness; (2) better roundness can be also obtained when the stock removal is set at a larger value; (3) the workpiece roundness was improved from an initial value of 23.9 μm to a final value of 0.84 μm after grinding.     

A new in-feed centerless grinding technique using a surface grinder

This paper deals with the development of an alternative centerless grinding technique, i.e., in-feed centerless grinding based on a surface grinder. In this new method, a compact centerless grinding unit, composed of an ultrasonic elliptic-vibration shoe, a blade and their respective holders, is installed onto the worktable of a surface grinder, and the in-feed centerless grinding operation is performed as a rotating grinding wheel is fed in downward to the cylindrical workpiece held on the shoe and the blade. During grinding, the rotational speed of the workpiece is controlled by the ultrasonic elliptic-vibration of the shoe that is produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body (stainless steel, SUS304). A simulation method is proposed for clarifying the workpiece rounding process and predicting the workpiece roundness in this new centerless grinding, and the effects of process parameters such as the eccentric angle, the wheel feed rate, the stock removal and the workpiece rotational speed on the workpiece roundness were investigated by simulation followed by experimental confirmation. The obtained results indicate that: (1) the optimum eccentric angle is around 6°; (2) higher machining accuracy can be obtained under a lower grinding wheel feed rate, larger stock removal and faster workpiece rotational speed; (3) the workpiece roundness was improved from an initial value of 19.90 μm to a final one of 0.90 μm after grinding under the optimal grinding conditions.     

A new through-feed centerless grinding technique using a surface grinder

This paper proposes an alternative centerless grinding technique, i.e., through-feed centerless grinding using a surface grinder. In the new method, a compact centerless grinding unit, composed of a guide plate, an ultrasonic shoe, a blade, and their respective holders, is installed onto the worktable of a surface grinder, and the through-feed centerless grinding operation is performed as the workpiece located on the guide plate is fed into the space between the grinding wheel and ultrasonic shoe. The ultrasonic shoe, produced by bonding a piezoelectric ceramic device onto a metal elastic body, is tilted at a small angle so as to provide sufficient force to control the workpiece rotational motion and to feed the workpiece along its axis by the ultrasonic elliptic-vibration. In this paper, the workpiece motion control tests were carried out firstly to make sure that the workpiece rotational speed and through-feed rate can be exactly controlled by the ultrasonic shoe which is essential for performing high-precision grinding operations. Then, the effects of major process parameters such as the workpiece eccentric angle, the stock removal, the ultrasonic shoe tilt angle and the applied voltage amplitude on the machining accuracy (i.e. workpiece cylindricity and workpiece roundness) were clarified experimentally. The obtained results indicate that: (1) the workpiece rotational speed can be adjusted by changing the applied voltage amplitude, whereas its through-feed rate can be adjusted by changing both the applied voltage amplitude and the ultrasonic shoe tilt angle; (2) the optimum eccentric angle is 6°, and a larger stock removal, a smaller tilt angle, or a higher applied voltage is better for higher machining accuracy; (3) the workpiece cylindricity and roundness were improved from the initial value of 16.63 μm and 14.86 μm to the final ones of 1.49 μm and 0.74 μm under the optimal grinding conditions.     

Continuous workpiece speed variation (CWSV): Model based practical application to avoid chatter in grinding

The continuous variation of rotation speeds provides a means of avoiding chatter instability in different machining processes. This paper presents a time domain dynamic model that simulates chatter vibration during infeed centerless grinding for any continuously variable work rotation speed strategy. As a result of taking machine dynamics and main non-linear effects of the process into account, part roundness error is predicted for the whole grinding cycle. Lastly, experimental results have validated the model and verified that adequate speed variation strategies are capable of avoiding chatter and improving workpiece roundness and roughness, both for infeed and throughfeed centerless grinding.     

氮化硅陶瓷轴承外圈磨削的双目标工艺优化

陶瓷轴承套圈的加工质量对轴承的回转精度和服役性能具有重要影响。首先,基于大量外圆磨削试验,通过最小二乘法分别建立陶瓷表面粗糙度和沟道圆度在不同工艺参数下的一元模型;其次,在一元模型基础上,通过粒子群优化算法(PSO算法)分别建立其表面粗糙度和沟道圆度在不同工艺参数下的多元模型;最后,通过PSO算法对表面粗糙度和沟道圆度进行双目标优化,得出轴承外圈加工时的最优工艺参数。结果表明:表面粗糙度在不同工艺参数下的多元复合模型的预测值和实际加工值的相对误差范围为5.83%～8.99%,沟道圆度多元复合模型的预测值和实际加工值的相对误差范围为4.62%～8.01%;双目标函数优化得到的工艺参数为砂轮线速度56.0 m/s、径向进给量0.012 mm/min、工件转速215 r/min。多元模型可较为准确地预测实际加工情况,最优工艺参数下的粗糙度值和圆度值分别为0.130 μm和2.20 μm,相比其他参数下的值较小。      

Effectiveness of continuous workpiece speed variation (CWSV) for chatter avoidance in throughfeed centerless grinding

The continuous rotation speed variation is demonstrated to be an efficient method to avoid regenerative chatter in different machining processes. This paper presents a time-domain dynamic model for throughfeed centerless grinding process that can predict chatter by means of part roundness error evolution. Continuous workpiece speed variation (CWSV) has been implemented in this model to analyze the influence of this disturbing method on the dynamic instability. Experimental results have validated the model and verified the effectiveness of CWSV for chatter avoidance and surface finish and dimensional tolerances improvement. It has been demonstrated that the selection of the optimal variation parameters is an important factor not only for chatter avoidance, but also for the stability of surface finish and dimensional tolerances since workpiece speed variation has a direct influence on throughfeed rate and grinding forces.     

车削激励下主轴高精度轴心轨迹在线测试研究

数控机床主轴是机床上的一个重要部件,它是刀具或工件的相对位置基准和运动基准。主轴轴心的动态运动特性直接影响着被加工零件的加工精度及表面粗糙度,同时主轴的轴心轨迹作为机床主轴运行的重要图形征兆,能够形象、直观地反映机床设备综合性的误差状况。针对主轴轴心轨迹在线测试问题,搭建了适用于工业现场环境的在线测试系统。通过对友嘉FTC-20型数控车床进行测试,研究了主轴在空载、车削两种状态下轴心轨迹的变化,并对实验结果进行了分析。实验表明:该系统能够准确地分离主轴的圆度误差和主轴轴心轨迹,为后续进行机床主轴的故障评估及建立故障自动识别系统提供基础。     

A study on the effect of regulating wheel error on the roundness of workpiece in centreless grinding by computer simulation

This paper deals with a simulated study of the centreless grinding operation to understand the role played by the regulating wheel errors on the roundness of the workpiece. Regulating wheels with a flat and specific number of lobes as errors were used for this study. A flat on the regulating wheel increases the roundness error of the work and a projection is formed on the workpiece whenever the flat contacts the workpiece. A lobed regulating wheel produces components with high roundness error and this error shoots up to higher values whenever the number of lobes on the regulating wheel equals a full multiple of regulating wheel-work diameter ratio.     

An experimental investigation of rotary diamond truing and dressing of vitreous bond wheels for ceramic grinding

Experiments of rotary diamond truing and dressing of vitreous bond grinding wheels were conducted to investigate the effects of feed, speed ratio, and overlap ratio on cylindrical grinding of zirconia. The applications of ceramic engine components with complex and precise form and the lack of technology for precision truing of diamond grinding wheels have driven the need to study the use of vitreous bond CBN and SiC wheels for form grinding of ceramics. Truing and grinding forces and the roundness and surface finish of ground zirconia parts were measured. By varying truing process parameters, a wide range of surface finish and roundness could be achieved. Experimental results showed that wheels trued at speed ratio below −1.0 could grind parts with fine surface finish and good roundness. The analysis of truing and grinding results showed the trend of increasing grinding force at higher specific truing energy and better surface finish at higher grinding force. The lack of speed control of the direct–drive, variable–speed truing spindle was observed and its effect on the reverse of direction of truing force at positive speed ratios was studied.     

基于LSSVM的磨加工主动量仪圆度误差在线评定方法研究

圆度误差作为重要的几何误差指标直接影响机械零部件装配精度和使用寿命,面向智能制造的在线测量对圆度评定方法的快速性、准确性提出了更高的要求。针对在线圆度误差评定,结合磨加工主动量仪提出一种基于最小二乘支持向量机（LSSVM）的最小区域评定方法。LSSVM采用误差的二范数和等式约束代替了传统支持向量机中的误差和不等式约束,将二次规划问题转化为求解线性方程,降低了计算的复杂度,有效提高了求解速度。通过对比单纯形算法、遗传算法、支持向量机和LSSVM四种算法的圆度误差评定结果,验证了基于LSSVM的圆度误差最小区域评定方法的准确性和可行性,发现它在处理庞大提取数据时的高效性,可实现磨加工主动量仪在生产过程中对圆度误差的在线评定,提高加工效率。