VARIABLE INERTIAL DAMPER AND ITS APPLICATION IN ZERO-DRIVE GEAR HOBBING MACHINE

A variable inertial damper, whose viscous damping coefficient can be adjusted by changing the gap between inertia wheel and motor spindle, is designed in servomechanism of zero-drive hobbing machine and is directly attached on the motor spindle. The mathematical model of servo system with inertial damper is built. By using theoretical analysis and system simulation, it is demonstrated that the variable inertial damper with optimal damping coefficient and moment of inertia should lead to no resonance point in wider frequency range of exciting force. Therefore, its application in zero-drive hobbing machine makes this system not only achieve higher system stiffness to overcome load torque fluctuation, but also gain better stability.

Research and Development on NC System of Gear-hobbing Machine based on Zero-programming Technology

By the analysis of roller gear processing technology, combining with gear meshing mechanism and motion relationship, models for rolling gear machining parameter and zero-programming are established. In this paper, the automatic generation technology of NC program for CNC gear machining process has been studied and the zero-programming system architecture of open CNC gear-hobbing machine has been presented. In the design and development of the system, human computer interaction, programming algorithm and the design of each function module have bean done. Application test shows that the expected design requirements have been achieved.

A precision generating hobbing method for face gear with assembly spherical hob

In order to improve the processing precision and shorten the hob manufacturing cycle of the face gear,a precision generating hobbing method for face gear with the assembly spherical hob is proposed.Firstly,the evolution of the cylindrical gear to spherical hob basic worm is analyzed,then the spherical hob basic worm is designed,thus the basic worm and spiral angle equation of spherical hob are obtained.Secondly,based on the design method of the existing hob,the development method of the assembly spherical hob is analyzed,the cutter tooth and the cutter substrate of the assembly hob are designed,and the whole assembly is finished.Thirdly,based on the need of face gear hobbing,a numerical control machine for gear hobbing is developed,and the equation of the face gear is obtained.Fourth,for reducing the face gear processing errors induced by equivalent installation errors,the error analysis model is established and the impacts of each error on the gear tooth surface are analyzed.Finally,the assembly spherical hob is manufactured and the gear hobbing test is completed.According to the measurement results,the processing parameters of face gear hobbing are modified,and the deviation of tooth surface is significantly reduced.

STUDY ON WEAR AND DESTRUCTION OF HOB IN GEAR HOBBING

The wear and destruction appearances of hobs are researched. The reasons ofthe wear and destruction of hob are analyzed. And the influence of the change of the hobbing forceand the hobbing temperature on the wear and destruction of hob in gear hobbing is also analyzed. Ingear hobbing, the main wear mechanisms are adhesion and ploughing when cutting the 20CrMnTi gearusing W18Cr4V high-speed steel hob.

Cutting Force Fluctuation Suppression and Error Homogenization of Noncircular Gear Hobbing Based on the Tool Shifting Method

The current research on noncircular hobbing mainly focuses on the linkage model and motion realization.However,the intermittent cutting characteristics of hobbing would increase uncertainties in the manufacturing process.In this paper,a hobbing machining model with tool-shifting characteristics was proposed to solve the problems of cutting force fluctuation and inconsistency of tooth profile envelope accuracy at different positions of the pitch curve in noncircular gear hobbing.Based on the unit cutting force coefficient method,the undeformed chip volume generated by interrupted cutting was used to characterize the fluctuation trend of the hobbing force.The fluctuation characteristics of the cutting force generated by different hobbing models were compared and analyzed.Using the equivalent gear tooth and hob slotting numbers,an analysis model of the tooth profile envelope error of the noncircular gear was constructed.Subsequently,the tooth profile envelope errors at different positions of the pitch curve were compared and analyzed based on the constructed model.The transmission structure of the electronic gearbox was constructed based on the proposed hobbing model,and the hobbing experiment was conducted based on the selfdeveloped noncircular gear CNC hobbing system.This paper proposes a hobbing method that can effectively suppress the fluctuation of the peak and whole circumference cutting force and reduce the maximum envelope error of the whole circumference gear teeth.

Research on Applying Nano Cutting Oils in Spur Gear Hobbing Process

Nanolubricant mixing the normal lubricant with nanoparticles, gradually becomes a new trend study for metal cutting enhancement. An addition of the nanoparticles improves lubricating properties and convective heat transfer coefficient (cooling properties) of nanolubricants. In the present work, nanolubricant is formulated by using dispersions of 0.3% Al2O3 nanoparticles in normal industrial oil VG46 for enhancement of gear machining performance of SCM420 steel. Comparative study of flank wear, crater wear and gear profile error in gear hobbing with normal oils in the existing production line as well as nanolubricant is studied. This study clearly reveals that tool wear, and gear profile error are reduced by the use of nanolubricant compared to that of normal oils. The paper results not only contribute the deeper understanding of the novel performance of nanoparticles in conventional cutting fluids, but also show a very promising solution to achieve the engineering economy effectiveness in gear machining.

Investigation of Nanofluids as Potential Cutting Fluids in Gear Hobbing Processes of AISI 4118 Steel

The present work focuses on the performance of nanofluids called CN46-NanoAl2O3.80 formulated by using dispersions of nano aluminum oxide （Al2O3） in the ISO VG46 industrial oil on machining performance during gear hobbing of AISI 4118 steel. In machining gears, hobbing is one of the most important processes, especially to produce various gear shapes for adapting to diverse applications. However, the demand for high quality brings attention to product quality, particularly the roughness of the machined gear surface because of its effect on product appearance, function, and reliability. For additional improvement, applying nanofluids may produce superior product quality, as the rolling action of billions of nanoparticle units in the tool chip interface can significantly decrease the friction led to reduce the cutting forces. In addition, the characteristics of heat transfer of nanoparticles can contribute to reduce tool wear. In this experimental study, the performance of nanolubricant compared with the case of using ordinary cutting-fluid systems in the existing production line is investigated. The experimental results reveal that the tool life of the hob is significantly enhanced of 55.2%, gear surface roughness is smaller （27.3%）, and gear accuracy is significantly increased by using the nanofluid. This result, therefore, shows a promising solution to achieve the engineering-economy effectiveness in gear machining.

YKJ3180H Economy NC Gear Hobbing Machine

The YKJ3180H Economy NC GearHobbing Machine is a new variety,developed recently by the ChongqingMachine Tools Works to meet clients’demands. Its most prominent feature is its highproduction efficiency ( able to complete awork cycle automatically), high processingprecision (Grade 7 or higher according to theGB 10095) and its cost competitiveness. This product is used in the machinetool and machinery industries at automobiles,tractors, gears and gear box factories. It canbe used for processing spur gears and helicalgears, automatic radial feed wormwheels,tapered gears and crowning gears; so it isespecially applicable in factories usingcrowning gear couplings, such as metallurgy,mining, lifting transport and the chemicalmachinery.

STUDY ON THE CUTTING TEMPERATURE IN GEAR HOBBING

According to work tool thermocouple principle,the equipment for measuring hobbing temperature is developed.The changing character of cutting temperature in gear hobbing,the relation between cutting conditions and hobbing temperature,and the influence of cutting conditions on hobbing temperature are discussed by means of experiments.All these have provided the reference standards for the equitably selecting cutting conditions and geometrical parameter of hob,prolonging the life of gear hobs,and predicting processes of gear hobbing.

车轴滚齿加工工艺参数GA-BP模型NSGA-Ⅱ优化

研究了高速条件下的滚齿工艺参数设置与优化方面的工作,采用新的非支配遗传算法NSGA-Ⅱ设计了相应的优化数学模型,优化达到最低能耗以及最长的刀具使用期限,再以遗传反向传播算法(GABP)神经网络为目标设置预测模型并建立适应度函数,完成迭代优化后获得匹配滚齿工艺的Pareto最优条件。研究结果表明:这里预测模型经过5次循环计算后,均方差为10-5,得到0.000425的最优值,推断上述网络满足良好的稳定性。刀具寿命误差相对后者降低16%,降低了36%的能量损耗,发现GABP算法具备更优收敛能力。Pareto解集获得了比相近加工样本集更优的性能,因此采用多目标优化模型可以确保加工能耗和刀具使用寿命同时达到最佳状态。该研究对提高的滚齿加工工艺参数以及提高机加工效率具有很好的实际应用价值。

Improved Relief Grinding Method of Gear Hob with Equal Relief Angle

The regrinding error is the main factor affecting the eligible length of hob tooth,how to decrease the regrinding error is a hot issue in the research area of hob grinding.At present,researches focus on changing the trajectory of relief moving,because of no unified relief grinding path planning method,the research result is restricted in the practical application.For solving the problem,the calculation model of the hob relief angle is established with the Archimedes relieving motion to analyze the interaction between the increasing relief angle of the hob and the accelerating tooth profile errors.Based on it,the improved relief grinding method of gear hob is proposed with equal relief angle（ERA）.Furthermore,the relief grinding method with ERA is developed with the following two steps.Firstly,the convergence numerical solution algorithm of the tooth top curve is designed to form the wheel motion path which is compared with that of traditional grinding.The second step is to establish the solution model of ERA grinding wheel.In order to verify the effect of the method,hob grinding simulation system of 3D solid was built under the AutoCAD environment.The regrinding errors is analyzed by intercepting the hob axial profiles of the various regrinding angles with Boolean operations and further converting it to basic rack tooth,then the simulation example of zero rake straight flute hob is used to compare the regrinding errors between ERA grinding and traditional grinding.Finally,the experiments were implemented on the five-axis CNC relief grinder with the relief motion of ERA grinding driven by cam.The results of experiments show that the method can effectively reduce the regrinding errors of hob and grind expediently gear hob of AA rank and over.This research provide an effective model of relief moving path plan reducing regrinding error,and have practicable value in CNC relief grinder.

Mathematical Model and Machining Method for Spiral Flute Rake Faces of Hourglass Worm Gear Hob

To improve the cutting performance of an hourglass worm gear hob and the accuracy of the resulting worm gear,the rake angles of the teeth on the pitch circle should be reduced.A method of forming the spiral flutes by using a variable transmission ratio was developed.This method ensures that the rake angles on the indexing torus of each tooth are approximately 0°.Based on the gear meshing theory and the hourglass worm forming method,the discretization mathematical model of the rake face of a planar double enveloping worm gear hob was established by using cylindrical generating surface,and the feed parameters for machining the rake face for a variable transmission ratio were obtained.The spiral flute was simulated and the hob was machined on a four axis CNC milling machine.A contourgraph was used to measure the rake angle.The measurement results showed that the proposed method can reduce the absolute value of the rake angle on both sides of the cutting teeth,which can be used for machining the spiral flute rake face of an hourglass worm gear hob.

Design and Machining of Combination Gear Cutter Hob

This paper takes the escapement plate of a mechanical pendulum clock as an example,analyses the design of combination form cutter hob for special profile gears, selection of parameters and calculation for tooth profile coordinates and discusses the grinding of cutter hob tooth profile on optical contour grinder.

A New Manufacturing Method for Hourglass Worm Gear Hob Based on a Semi⁃automatic CAD

The top relief surfaces of an hourglass worm gear hob are ground manually in the traditional manufacturing process,which cannot ensure the width of the land surfaces of the hob.Moreover,each geometric feature of the hob has been produced through different manufacturing techniques and machine tools,which results in low efficiency.To solve this problem,we propose a semi-automatic computer aided design(CAD)method for hobs.The point clouds of each feature surface of a hob are calculated by combing mathematical equations of the top relief surfaces built by the proposed method with other existing equations of hob surfaces.According to the point clouds,the method can achieve the automatic modeling for the hob in three-dimensional(3D)software by classifying and extracting the parameter information of the feature-hierarchical knowledge of the hob.Based on the generated 3D model,the entire surfaces of the hob can be manufactured on a four-axis computer numerical control(CNC)milling machine through only twice clamping.Verification of the width of the land surface of the hob manufactured by semi-automatic CAD method on a measuring projector proved the precision of the designed width can be ensured.The edge of the contact area on the worm wheel in a meshing experiment is clear and distinct,which means the worm gear drive is meshed well and the hob manufactured by the proposed method has improved machinability.The method simplifies the processing technique,and improves the design efficiency and production accuracy.

氢气-空气混合物中瞬态爆轰过程的二维数值模拟

对高温火团引发的氢气 空气混合气的瞬态爆轰过程进行了二维数值模拟,考虑了H2 O2 N2的详细化学反应动力学机理,该机理包含了19个基元反应和9种组分。采用分裂格式处理带化学反应的Euler方程,其中使用全耦合的TVD格式求解流场,使用基于Gear算法的微分方程解法器求解化学反应过程。计算结果表明:在H2∶O2∶N2=0 4∶0 4∶0.2(摩尔比)的混合气中,高温气团初始温度为T/T0=5.3时可诱导爆轰,爆轰波以2300m/s的速度传播,同时爆轰波阵面在管壁会形成反射波。还对计算的爆轰波后组分的浓度和温度进行了讨论,为理解爆轰波后结构提供信息。

滚齿-剃齿-热处理工序加工误差的回归分析

本文对20CrMnTi汽车齿轮加工中三道工序误差进行了详细的实验研究,首次将数理统计学中多元回归分析、逐步回归分析以及偏相关系数引入滚-剃-热加工工序中。全面、系统地论证了三道工序中误差的相关关系以及工序间误差的转换关系;指出了齿轮加工中各道工序主要超差的项目;并从理论上对误差之间的关系进行了推导和分析。实验结果和理论分析二者是吻合的。本文的结论对进一步深化齿轮误差理论的研究及进一步稳定7级齿轮加工精度是有益的。

摩擦对滚-磨工艺齿轮齿根应力的影响

采用有限元法研究了齿面摩擦力对滚-磨工艺制造的、齿根部有沉切的齿轮齿根应力的影响。结果表明:摩擦对滚-磨工艺齿轮齿根应力的影响不容忽视,考虑摩擦时,齿根最大拉、压应力随摩擦因数的增大而增大,其中最大拉应力增加的幅度比最大压应力大,当摩擦因数从0增大到0.2时,齿根最大拉应力增加比率为19.08%,最大压应力增加比率为3.16%;有沉切时齿面摩擦力对齿根弯曲应力的影响比没沉切时要大。

基于齿面位姿-几何误差模型的大规格滚齿机关键误差识别

为研究影响大规格滚齿机加工精度的关键几何误差,提出了一种基于齿面位姿-几何误差模型结合Sobol法的机床关键几何误差识别方法。首先,基于齐次坐标变换理论,建立了刀具位姿-几何误差模型,通过求解滚齿双参数包络方程,获得了加工齿面接触迹点坐标值,建立了机床齿面位姿-几何误差模型;然后,考虑几何误差的随机性和互耦性,利用Sobol法对该模型进行敏感性分析,计算了几何误差的敏感度系数以识别出关键几何误差;最后,进行了关键几何误差虚拟仿真修正和对比验证。研究结果表明,所提方法能有效识别大规格滚齿机的关键误差项。

回转窑等转筒设备传动开式齿轮的研究(Ⅶ)--大齿圈齿形主要加工设备现状分析

从回转窑等转筒设备大齿圈传统加工设备的现状和存在问题分析入手,对如何扩大设备加工范围、提高大齿圈加工精度和效率进行了研究。介绍了主要加工设备多铣头铣齿机、数控滚齿机和传统滚齿机扩径改造的关键技术、国内主要大型齿形加工设备的现状;阐述了提高大齿圈加工能力和效率所需具备的设备条件。通过对比分析得出结论:用数控铣齿机进行粗加工,可使齿轮精加工余量控制在较小范围;多铣头数控铣齿机与滚齿机配合加工,能够使齿轮加工效率成倍提高;大型数控滚齿机采用大直径高精度蜗轮双蜗杆边缘传动和零传动技术,有利于提高机床运转平稳性和加工精度;传统小直径重型滚齿机在传动结构不变的情况下新增大直径静压支承工作台、加长床身、加大电动机功率是扩径改造的理想途径;分析了现行齿形设备现状,有利于制造商把握齿形加工设备的发展方向,有利于用户选择合格的大齿圈制造商。

THEORY OF HELICOID OF SPHERICAL HOB

The mechanism of spherical hob's cutting internal gear is explained and the new coneeptof generating gear of spherical hob is presented. The reason why there is theoretical error and thenew method of decreasing the error are also analysed. Some new equations about the mainparameters, the equations of helicoids, the equations of cutting edges and the flank angles of spheri-cal hob are given.