线接触回转铣削加工的研究

点接触加工是广泛采用的曲面加工方式。文章分析了现行的点接触加工和线接触曲面加工的方法,提出了线接触回转铣削加工曲面的方法,研究了线接触回转铣削加工各种曲面的运动实现,设计了其实现机构。相对于点接触加工,线接触回转铣削加工采用无廓形理论误差的加工方式,增加了刀具与工件的接触长度,是基于面的加工方式。加工过程中用尽可能少的轴甚至单轴进给,提高了加工精度。     

线接触曲面加工方法的研究

针对高效率加工曲面的生产要求,研究了一种线接触加工曲面的方法。通过对现有数控机床结构形式的分析,提出一种可以使刀具侧切削刃与工件理论廓形接触,同时主轴座的回转模拟车削加工的机床结构形式。并采用Denarit-Hartenbarg方法,对该刀具机构的运动进行了分析。以此为基础,结合曲面特征,研究刀位轨迹。最后,将五坐标点接触加工方法和五坐标线接触加工方法与本方法的效率和精度进行对比,得到了该方法优于以上两种方法的结论。     

锥度螺旋面加工用盘形刀具的轮廓解析法

刀具设计曲面与加工工件的锥度螺旋面接触线为一条空间几何曲线,由此建立了刀具设计廓形的数学模型,提出了锥度螺旋面加工刀具的廓形设计原理,并给出了刀具设计的计算公式。     

多自由度周向包络铣削异形螺杆研究

提出盘形铣刀加工异形螺杆工艺方法周向无瞬心包络法,先是加工出工件的一个端面廓形,然后沿螺旋方向移动刀具加工下一个截面廓形。根据加工不同异形螺杆要求,分析加工所需运动联动控制方法。建立盘形刀具、工件数学模型和接触迹计算模型,根据模型和铣削工艺,研究盘形刀具包络铣削加工异形螺杆接触迹“有向最短距离”计算方法,用高级语言编程进行了实例计算。     

基于刀具实际廓形的数控加工刀具轨迹计算

刀具轨迹生成是自由曲面零件数控加工中最重要同时也是研究最为广泛深入的内容,在自由曲面的多坐标数控加工中,刀具轨迹的优劣直接影响其加工精度和加工效率。传统的刀具轨迹计算方法是利用实际刀具的理想廓形进行的,提出利用刀具的实际廓形进行复杂曲面加工,是通过检测旋转刀具加工工件时的实际廓形,利用实际廓形对已知曲面进行刀具轨迹计算。这种计算方法能有效的提高加工精度,并可以检测新生产出来的刀具是否符合标准。该方法适用于加工刀具为旋转运动的数控加工轨迹计算。     

加工螺旋槽用成形盘状刀具截形计算

生产中经常会遇到螺旋槽成形表面的加工,如螺杆、圆柱形铣刀及圆柱斜齿轮等。这就要求设计计算出加工用成形盘状刀具(如盘状铣刀、成形砂轮。本文简称“刀具”)的截形。工件螺旋槽表面是刀具切削刃回转面相对于工件作螺旋运动时所形成的包络面,刀具回转面与工件螺旋槽的接触线不在刀具轴向剖面内,而是一条空间曲线。因此,刀具回转面的轴向截形既不同于螺旋槽的法向廓形,也不同于工件任何剖面中的廓形。为此,刀具截形的设计计算方法可有图解法和计算法。     

基于反向误差补偿的螺旋曲面成形加工干涉消减方法

为有效提高螺旋曲面成形加工的精度,根据螺旋曲面与成形刀具的相切接触原理,建立了螺旋曲面与成形刀具之间的正反算数学模型;提出一种基于误差反向补偿的干涉消减方法,通过在工件理论廓形上反向补偿干涉量,形成螺旋曲面新的虚拟计算廓形,再以该廓形反向计算成形刀具截形并进行迭代,最终得到可减小干涉误差的成形刀具截形;构建了螺旋曲面成形加工干涉量的计算模型,给出了螺旋曲面成形加工干涉消减流程,并讨论了所提方法的效率和适用范围。通过计算实例验证了所提方法的有效性。     

新型斜齿圆柱测量齿轮螺旋面铣削刀具的廓形设计

以一种新型斜齿圆柱测量齿轮为研究对象,铣削传统测量齿轮轮齿对称中线一侧的半个轮齿,并提出一种铣削加工其螺旋面的盘形铣刀的廓形设计理论和方法。根据铣削过程中盘形铣刀与斜齿轮之间的运动关系,建立了螺旋面的端面截形线方程,以及螺旋面的数学模型,并求解出其特性方程。根据刀具和工件的接触条件,建立了接触线方程。     

单螺杆泵定子内螺旋曲面包络铣削技术研究

单螺杆泵定子具有复杂的曲面形状,相比普通曲面不易加工。提出了单螺杆泵定子加工的新方法即包络铣削技术。该方法以单螺杆泵定子截面型线数学模型为基础,根据螺杆-定子副的往复直线运动关系,利用数控机床的多轴联动来实现。通过分析刀具与工件之间具体的运动形式,阐述了包络铣削螺杆泵定子的可行性。     

成型磨削砂轮廓型的设计计算

针对螺旋曲面加工过程中工件与刀具空间啮合关系的特点,主要研究螺旋曲面磨削加工过程中的刀具廓形计算。根据刀具回转曲面与工件螺旋曲面间的空间共轭关系,灵活运用啮合原理,通过数学建模、空间坐标转换等方法计算出砂轮的廓形,为后续研究提供了数学思路和理论支持。由于各类共轭曲面存在相似的共性,提出的算法对各类共轭曲面的计算与设计均有一定的帮助。     

A study of tool wear using statistical analysis of metal-cutting acoustic emission

Many aspects of the interactions between cutting tools, workpiece material and the chips formed during machining that affect the wear and failure of the tool are not fully understood. The analysis of acoustic emission signals generated during machining has been proposed as a technique for studying both the fundamentals of the cutting process and tool wear and as a methodology for detecting tool wear and failure on line. A brief review of the theory of acoustic emission is presented. Acoustic emission data from reduced contact length machining experiments and tool flank wear tests are analyzed using distribution moments. The analysis shows that the skew and kurtosis of an assumed β distribution for the r.m.s. acoustic emission signal are sensitive to both the stick-slip transition for chip contact along the tool rake face and progressive tool wear on the flank of the cutting tool.     

机械零部件基准的选择

零部件机加工中定位实际上是以零部件上的某些基准面与夹具上定位元件保持接触的,从而限制工件的自由度。零部件上哪些面与夹具的定位元件相接触,这就是基准的选择问题。基准选择的合理与否,很大程度上决定了零部件加工质量的好坏,装配后产品能否安全可靠地运转、保持优越的工作性能,即基准的选择对产品质量起着决定性的作用。     

数控电火花线切割锥度加工

锥度数控线切割CTW系列机床的主要特点是,丝架导轮微量坐标u,v轴的移动采用独特的四杆连接技术,及无反向间隙补偿的双片齿轮消隙机构,实现工件精密锥度加工.锥度加工前后的走丝机构、导轮调整和坐标工作台移动参数等的介绍,以及在快走丝往复加工时频繁断丝原因分析,为更好掌握锥度线切割加工技术提供了科学依据.     

One-step FEM-based evaluation of weld line movement and development of blank in sheet metal stamping with tailor-welded blanks

Currently, more and more tailor-welded blanks (TWBs) are used in the automobile industry. It is very important to locate the weld line and predict its movement during the forming process. The initial weld line can be predicted by one-step finite-element analysis according to the desired weld line in the final workpiece. Meanwhile, weld line movement during the deformation process can be evaluated in advance. In this paper, the procedures of finite-element analysis of one-step FEM with TWBs are established. The contact between tool and blank and the effect of restraining forces under the blankholder due to drawbead and blankholder pressure are considered as well. Forming limit diagram (FLD) is used to show not only the tendency of reduction in thickness and fracture but also of increase in thickness and wrinkle. Hydraulic controlled pads used to clamp the weld line during the deep drawing process are simplified as static external force to eliminate the movement of the weld line. In order to speed up and ensure the convergence of Newton-Raphson iterations, energy-based 3D mesh mapping algorithm is introduced to obtain the initial solution. The above-mentioned methods have been implemented in the authors’ in-house one-step FEM code InverStamp. A rectangular cup drawing case demonstrates that this approach can be easily implemented to evaluate weld line movement and develop initial blank in sheet metal stamping with tailor-welded blanks.     

快速点磨削周边磨削层模型及参数

为深入研究快速点磨削机理及工艺,根据快速点磨削的技术与几何学特征,建立点磨削周边接触层及参数的数学模型,对砂轮和工件的等效速度和直径、磨削参数进行理论分析。在已建立快速点磨削接触层及参数的理论模型基础上,推证计及点磨削变量角度和磨削深度的砂轮周边理论接触宽度的计算公式,并对超薄快速点磨 削砂轮周边理论接触宽度和表面粗糙度进行数值仿真。结果表明：与普通外圆磨削不同,砂轮周边与工件实际接触宽度并不恒等于砂轮宽度,点磨削变量角度和磨削深度显著影响砂轮周边的实际接触宽度与工件表面粗糙度 数值。     

基于逆向工程技术的形状误差检测方法

提出了在没有工件数学模型情况下,运用逆向工程的三维数字化测量技术和数据处理技术进行工件形状误差检测的方法.通过实例,详细阐述了在形状误差检测中采用接触式和非接触式测量方式的区别,并在Imageware 软件中完成了测量数据的处理,获取了工件的形状误差值.     

基于Pro／E的剃齿修形有限元分析

在剃齿的运动过程中,剃齿刀齿面带动工件做扭转啮合运动。在运转过程中,剃齿刀和轮齿发生了弹塑性变形。文中基于Pro／E平台进行剃齿修形的有限元分析,根据剃齿刀的变形和轮齿工件的渐开线齿廓的情况,对剃齿刀的弯曲应力、接触强度、变形量进行分析,得出其符合材料力学和剃齿理论的条件。     

干涉法激光-光纤表面粗糙度传感器设计

根据光波的干涉原理,在分析了现有光纤表面粗糙度传感器某些缺陷的基础上,设计了新型干涉型激光－光纤表面粗糙度传感器,为新型非接触式表面粗糙度测量提供了新方法。     

A study of deformation of the machined workpiece and tool under different low cutting velocities with an elastic cutting tool

To understand the effects of cutting velocity, tool elastic deformation generated by high normal stresses during metal cutting processing and artificial tool flank wear on the cutting process, an iterative mathematical model for calculating the tool–workpiece contact problem was developed in this paper under the assumption of elastic cutting tools. In this model, the finite element method is used to simulate cutting of mild steel by the P20 cutting tool with constant artifical tool flank wear under the condition of three different cutting velocities. The results obtained in the simulation were found to match the experimental data reported by related studies. The simulation results also indicate that the thrust and the cutting forces are functions of cutting velocity. Besides, both the normal stress on the tool rake face and the residual stress of machined workpiece generally decrease with increase in cutting velocity. According to the findings in this study, though the residual stress of the machined workpiece decreases as the cutting velocity increases, its value is still higher than that in ordinary conditions due both to the influence of tool flank wear and tool elastic deformation. Also, the phenomenon of curvature at the workpiece end easily occurs.