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.     

Force Characteristics in Continuous Path Controlled Crankpin Grinding

Recent research on the grinding force involved in cylindrical plunge grinding has focused mainly on steady-state conditions.Unlike in conventional external cylindrical plunge grinding,the conditions between the grinding wheel and the crankpin change periodically in path controlled grinding because of the eccentricity of the crankpin and the constant rotational speed of the crankshaft.The objective of this study is to investigate the effects of various grinding conditions on the characteristics of the grinding force during continuous path controlled grinding.Path controlled plunge grinding is conducted at a constant rotational speed using a cubic boron nitride(CBN)wheel.The grinding force is determined by measuring the torque.The experimental results show that the force and torque vary sinusoidally during dry grinding and load grinding.The variations in the results reveal that the resultant grinding force and torque decrease with higher grinding speeds and increase with higher peripheral speeds of the pin and higher grinding depths.In path controlled grinding,unlike in conventional external cylindrical plunge grinding,the axial grinding force cannot be disregarded.The speeds and speed ratios of the workpiece and wheel are also analyzed,and the analysis results show that up-grinding and down-grinding occur during the grinding process.This paper proposes a method for describing the force behavior under varied process conditions during continuous path controlled grinding,which provides a beneficial reference for describing the material removal mechanism and for optimizing continuous controlled crankpin grinding.     

Failure mechanisms and structural optimization of shredder hammer for metal scraps

Recycling retired cars can relieve the environmental pollution and resource waste efficiently. However, a few publications can be found on the failure mechanisms and optimization method of recycling equipment, shredders. Thus, the failure mechanisms and structural optimization of shredder hammers for retired cars are studied aiming improving shredding efficiency and reducing cost. Failure types of shredder hammer are studied theoretically, and it is found that wear failure and fatigue failure are the two main failure types of shredder hammer. The shredding process of metal scraps is analyzed by finite element method, and it can be divided into four stages based on the stress states: initial stage, collision stage, grinding stage and separation stage. It is proved that the shredding efficiency can be improved by increasing cutouts on the hammer head. Finally, it is determined that the hammer with two cutouts is the optimal structure for metal scraps, which can improve the shredding efficiency by 20% and lengthen the hammer life by 15%. This study provides scientific basis for the industry application and theoretical foundation for further research.     

Designing and Optimization of an Off-line Programming System for Robotic Belt Grinding Process

Off-line programming (OLP) system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the OLP system. A new type of grinding robot and a novel robotic belt grinding workcell are forwarded, and their features are briefly introduced. An open and object-oriented off-line programming system is developed for this robotic belt grinding system. The parameters of the trimmed surface are read from the initial graphics exchange specification (IGES) file of the CAD model of the workpiece. The deBoor-Cox basis function is used to sample the grinding target with local contact frame on the workpiece. The numerical formula of inverse kinematics is set up based on Newton’s iterative procedure, to calculate the grinding robot configurations corresponding to the grinding targets. After the grinding path is obtained, the OLP system turns to be more effective than the teach-by-showing system. In order to improve the grinding workspace, an optimization algorithm for dynamic tool frame is proposed and performed on the special robotic belt grinding system. The initial tool frame and the interval of neighboring tool frames are defined as the preparation of the algorithm. An optimized tool local frame can be selected to grind the complex surface for a maximum dexterity index of the robot. Under the optimization algorithm, a simulation of grinding a vane is included and comparison of grinding workspace is done before and after the tool frame optimization. By the algorithm, the grinding workspace can be enlarged. Moreover the dynamic tool frame can be considered to add one degree-of-freedom to the grinding kinematical chain, which provides the theoretical support for the improvement of robotic dexterity for the complex surface grinding.     

Optimization of the dressing parameters in cylindrical grinding based on a generalized utility function

The existing studies, concerning the dressing process, focus on the major influence of the dressing conditions on the grinding response variables. However, the choice of the dressing conditions is often made, based on the experience of the qualified staff or using data from reference books. The optimal dressing parameters, which are only valid for the particular methods and dressing and grinding conditions, are also used. The paper presents a methodology for optimization of the dressing parameters in cylindrical grinding. The generalized utility function has been chosen as an optimization parameter. It is a complex indicator determining the economic, dynamic and manufacturing characteristics of the grinding process. The developed methodology is implemented for the dressing of aluminium oxide grinding wheels by using experimental diamond roller dressers with different grit sizes made of medium- and high-strength synthetic diamonds type АС32 and АС80. To solve the optimization problem, a model of the generalized utility function is created which reflects the complex impact of dressing parameters. The model is built based on the results from the conducted complex study and modeling of the grinding wheel lifetime, cutting ability, production rate and cutting forces during grinding. They are closely related to the dressing conditions(dressing speed ratio, radial in-feed of the diamond roller dresser and dress-out time), the diamond roller dresser grit size/grinding wheel grit size ratio, the type of synthetic diamonds and the direction of dressing. Some dressing parameters are determined for which the generalized utility function has a maximum and which guarantee an optimum combination of the following: the lifetime and cutting ability of the abrasive wheels, the tangential cutting force magnitude and the production rate of the grinding process. The results obtained prove the possibility of control and optimization of grinding by selecting particular dressing parameters.     

成形砂轮磨齿工艺中磨削烧伤缺陷的研究与防止对策

根据成形砂轮磨齿工艺的特点,说明磨削烧伤产生的原因,经过分析研究与实践,给出烧伤缺陷的防止对策.     

定制髋关节假体数字化设计与制造技术研究

针对人体的髋关节具有个性化特征以及传统假体与股骨匹配后力传递不稳定等问题,对人体髋关节假体数字化设计、有限元力传递分析、基于机器人磨削的数字化加工进行了研究,提出了在设计、仿真和加工过程中将髋关节假体模型统一的方法,实现了定制式假体数字化设计、有限元力传递的分析和机器人磨削加工的一体化,初步建立了髋关节假体的数字化设计与制造、产品生命周期的服务模型,为数字化设计与制造技术在髋关节假体等骨科植入物中的应用建立了基础。实验结果表明:采用机器人数字化磨削加工定制式假体,保持机器人软件空间与实际工作空间一致,可以有效提高假体的制造精度,实现假体与股骨髓腔的最优匹配。     

手持叶片砂带磨床的研制

介绍了叶片的砂带磨削工艺方法及其手持叶片砂带磨削设备的主要结构,并经试验证明,该设备能高效、经济地解决采用手工磨削小型叶片的难题.     

关于面齿轮磨削加工机床的研究

对面齿轮的磨削加工机床进行了研究,从建立加工坐标系入手分析了磨削机床设计原理,并在此基础上初步建立了磨削机床的几何模型.还对磨床的操作进行了分析,包括手动安装调试和数控加工过程.     

砂轮对圆锥滚子轴承挡边加工的质量影响浅析

圆锥轴承挡边加工过程中,砂轮直径的选择合理与否直接影响产品质量。通过分析与实践,总结出了合理选用砂轮特性参数的方法,对提高圆锥轴承挡边加工质量具有一定的指导意义。     

多晶体金刚石磨轮磨削光学玻璃的研究

采用冲击压缩法(Shock Compression Method,SCM)合成的多晶体金刚石磨粒,设计磨削光学玻璃的实验装置.实验结果表明,采用该方法磨削光学玻璃,与单晶体金刚石磨粒磨削光学玻璃相比,采用多晶体金刚石磨粒加工光学玻璃能得到良好的加工表面.     

磨削表面微观形貌的研究

用近似旋转椭圆体单一磨削微粒切削被加工表面的模拟方法,展示微观切削过程和被加工表面的参数变化规律,确定磨削加工过程中磨具材料单位体积中磨削微粒数量Z、磨削微粒前面切削刃面积、切屑厚度的计算方法;提出切削中材料分离过程和变形过程所在变形区厚度的定义;又从单一磨削微粒切削过渡到宏观切削,模拟出磨削微粒前面m×n个元素矩阵对被加工表面相互作用而形成大面积宏观磨削的状况,为确定被加工表面微观形貌的类型和选择最佳加工用量提供了解决问题的思路.     

基于ANSYS的磨削热分析中移动热源加载技巧

介绍利用ANSYS进行磨削热分析时移动热源的加载方法,阐述当磨削面为曲面时移动热源的加载技巧,对曲面(如齿轮)磨削过程热状态研究具有指导意义.     

基于模块化设计理论的数控成形磨齿机模块化结构

模块化设计有许多优点.机床模块设计包括模块划分和模块集成两方面内容.详细阐述模块化设计原理的基础上,指出了机械产品模块化设计的一般步骤.并以数控成形磨齿机为例,依据模块化设计理论,分析了该机床的功能,并对机床结构进行了模块划分和模块集成,实现了该机床的模块化设计.     

圆环内孔磨削温度场的有限元仿真

运用传热学原理,结合圆环内孔磨削实际情况,并进行合理的简化和假设,建立了圆环内孔磨削的热传导数学模型,利用有限元分析软件ANSYS,对热传递过程进行了仿真,得出了工件内部温度场分布云图,进而分析了磨削过程中温度的分布及变化情况.模拟结果较真实的反映了圆环内孔磨削热状况,为解决圆环内孔磨削表面热损伤和热变形等问题提供了依据.     

复合金属型模具群铸磨球工艺早期失圆机理的数值分析

在对铸造磨球凝固过程进行理论分析的基础上,利用华铸CAE软件对复合金属型模具群铸磨球工艺进行充型凝固特性三维数值模拟研究,确定了造成磨球出现早期失圆和缩松缩孔缺陷的主要原因,为进一步改进复合金属型模具群铸磨球工艺奠定了理论基础.     

40Cr调质钢磨削强化效果的研究

磨削强化处理技术是利用磨削热替代感应淬火热源对钢件表层进行强化处理,是将磨削加工与表面强化合为一体的工艺.该工艺可获得与感应表面淬火基本一致的强化条件和强化效果,其表层组织为马氏体硬化层,表层硬度53HRC左右,探明40Cr调质钢磨削强化的可行性.     

高速砂轮基体截面的优化设计

运用ANSYS提供的参数化语言(APDL)建立高速砂轮基体的模型,并以最大的环向应力减去最小环向应力之差最小化为目标函数,求解高速砂轮基体优化设计的问题,给出了优化后砂轮基体的截面形状和应力分布结果.结果表明:经过优化设计后,可以明显降低最大环向应力值,同时大大缩小了环向应力变化范围.     

数控成形砂轮磨齿机的在机测量方法研究

在机测量技术可以在线检查工件的质量,一方面充分利用了良好的数控资源,另一方面避免了工件因检测而反复装夹、安装基准变化等因素对加工精度、效率、检测精度等的影响,保证了加工精度,提高了生产效率,节约了时间,以较低的成本及时地检测出现的误差,并迅速得以修正.为此,提出了利用数控成形砂轮磨齿机高精度数控轴实现齿轮精度检测的在机测量方法.基于数控磨齿机的回转运动(C轴)和径向进给运动(X轴)形成理论渐开线,建立了在机测量的数学模型,借助于高精度测头获取机床伺服轴的运动位置,最后经过综合解析得到测量结果,实现了各项齿轮误差的在机测量.测量实验结果同高精密齿轮测量仪进行对比后表明该方法有效可行.     

高速电主轴用陶瓷轴承套圈内表面磨削试验研究

采用金刚石砂轮对热等静压氮化硅(HIPSN)陶瓷轴承套圈进行精密磨削试验,通过磨削表面粗糙度和扫描电子显微镜(SEM)照片,分析不同磨削参数对工件磨削表面质量的影响,获得陶瓷轴承套圈内表面精密磨削加工的最佳工艺参数.试验还进行了磨削过程中磨削力的测试和比磨削能的计算,分析了陶瓷材料的去除机理.