Part 1 Unit 08 Grinding

1、vIntroductionvTypes of Grinding OperationsvGrinding WheelsGrinding is a manufacturing process that involves the removal of metal by employing a rotating abrasive wheel. The latter simulates a milling cutter with an extremely large number of miniature cutting edges. 磨削是通过采用旋转磨轮去除金属的制造工磨削是通过采用旋转磨轮去除金属

2、的制造工艺。磨轮用非常大量的微型切削刃模仿铣刀进行艺。磨轮用非常大量的微型切削刃模仿铣刀进行切削。切削。Generally, grinding is considered to be a finishing process that is usually used for obtaining high-dimensional accuracy and better surface finish.一般而言，磨削被认为是一种通常用于获得高尺一般而言，磨削被认为是一种通常用于获得高尺寸精度和较好表面光洁度的精加工作业。寸精度和较好表面光洁度的精加工作业。Grinding can be perform

3、ed on flat, cylindrical, or even internal surfaces by employing specialized machine tools, which are referred to as grinding machines.磨削通过采用被称为磨床的特殊机床能在平面、磨削通过采用被称为磨床的特殊机床能在平面、圆柱面甚至内表面上进行。圆柱面甚至内表面上进行。Obviously, grinding machines differ in construction as well as capabilities, and the type to be empl

4、oyed is determined mainly by the geometrical shape and nature of the surface to be ground, e.g., cylindrical surfaces are ground on cylindrical grinding machines.显然，磨床根据结构和功能的不同有所区别，使显然，磨床根据结构和功能的不同有所区别，使用何种形式的磨床主要取决于被磨削表面的几何用何种形式的磨床主要取决于被磨削表面的几何形状和物理性质。例如，圆柱面在外圆磨床上磨形状和物理性质。例如，圆柱面在外圆磨床上磨削。削。1. Surfa

5、ce grinding. As the name surface grinding suggests, this operation involves grinding of flat or plane surfaces. Fig.8.1 indicates the two possible variations, either a horizontal or vertical machine spindle. 1. 表面磨削：就像其名称暗示的那样，表面表面磨削：就像其名称暗示的那样，表面磨削和平面磨削直接有关。图磨削和平面磨削直接有关。图8.1表示了两种可表示了两种可能的变化：卧式磨床主轴或

6、立式磨床主轴。能的变化：卧式磨床主轴或立式磨床主轴。In the first case (horizontal spindle), the machine usually has a planer-type reciprocating table on which the workpiece is held. However, grinding machines with vertical spindles can have either a planer type table like that of the horizontal-spindle machine or a rotating

7、worktable.在第一种情况在第一种情况(卧式主轴卧式主轴)，卧式磨床通常具有安，卧式磨床通常具有安装工件的刨床式往复工作台。而立式主轴磨床既装工件的刨床式往复工作台。而立式主轴磨床既可以像卧式主轴磨床那样具有刨床式工作台也可可以像卧式主轴磨床那样具有刨床式工作台也可以具有旋转工作台。以具有旋转工作台。Also, the grinding action in this case is achieved by the end face of the grinding wheel (Fig.8.1b), contrary to the case of horizontal-spindle ma

8、chines, where the workpieces ground by the periphery of the grinding wheel.而且在这种情况下，磨削动作是通过砂轮端面完而且在这种情况下，磨削动作是通过砂轮端面完成的成的(图图8.1b)，这与通过砂轮周边磨削工件的卧，这与通过砂轮周边磨削工件的卧式主轴磨床正好相反。式主轴磨床正好相反。Fig.8.1a and b also indicate the equations to be used for estimating the different parameters of the grinding operation,

9、such as the machining time and the rate of metal removal.图图8.1a和和b同时简述了用于估计诸如加工时间和同时简述了用于估计诸如加工时间和金属去除率之类的磨削作业不同参数的方程式。金属去除率之类的磨削作业不同参数的方程式。During the surface-grinding operations, heavy workpieces are either held in fixtures or clamped on the machine table by strap clamps and the like, whereas small

10、er workpieces are usually held by magnetic chucks.在平面磨削时，重的工件用夹具固定或用压板等在平面磨削时，重的工件用夹具固定或用压板等夹紧在磨床工作台上，而小的工件则通常是用电夹紧在磨床工作台上，而小的工件则通常是用电磁卡盘固定的。磁卡盘固定的。2. Cylindrical grinding. In cylindrical grinding, the workpiece is held between centers during the grinding operation, and the wheel rotation is the sou

11、rce and cause for the rotary cutting motion, as shown in Fig.8.22. 圆柱面磨削。在圆柱面磨削中，作业时工圆柱面磨削。在圆柱面磨削中，作业时工件支撑在两顶尖之间，砂轮转动是导致回转切削件支撑在两顶尖之间，砂轮转动是导致回转切削运动的动力源，如图运动的动力源，如图8.2所示。所示。In fact, cylindrical grinding can be carried out by employing any of the following methods:实际上，圆柱面磨削能通过采用下列任意方法来实际上，圆柱面磨削能通过采用下列

12、任意方法来实现。实现。(1) The transverse method, in which both the grinding wheel and the workpiece rotate and longitudinal linear feed is applied to enable grinding of the whole length. The depth of cut is adjusted by the cross feed of the grinding wheel into the workpiece.(1) 横向方法：这种方法中砂轮与工件均旋横向方法：这种方法中砂轮与工件

13、均旋转且采用线性纵向进给以保证能磨削整个长度。转且采用线性纵向进给以保证能磨削整个长度。切削深度通过改变砂轮对工件的横向进给来进行切削深度通过改变砂轮对工件的横向进给来进行调整。调整。(2) The plunge-cut method, in which grinding is achieved through the cross feed of the grinding wheel and no axial feed is applied. As you can see, this method can be applied only when the surface to be groun

14、d is shorter than the width of the grinding wheel used.(2) 插入插入-切削方法：这种方法通过砂轮的横切削方法：这种方法通过砂轮的横向进给完成磨削而不采用轴向进给。正如料想的向进给完成磨削而不采用轴向进给。正如料想的那样，这种方法只在要磨削表面比所用砂轮宽度那样，这种方法只在要磨削表面比所用砂轮宽度短时才使用。短时才使用。(3) The full-depth method, which is similar to the transverse method except that the grinding allowance is rem

15、oved in a single pass. This method is usually recommended when grinding short rigid shafts.(3) 全深度方法：这种方法除了一次加工就全深度方法：这种方法除了一次加工就能去除磨削余量外其它与横向方法相同。这种方能去除磨削余量外其它与横向方法相同。这种方法通常在磨削较短刚性轴时推荐使用。法通常在磨削较短刚性轴时推荐使用。Internal grinding. Internal grinding is employed for grinding relatively short holes, as shown

16、in Fig.8.3. The workpiece is held in a chuck or a special fixture. Both the grinding wheel and the workpiece rotate during the operation and feed is applied in the longitudinal direction. 内表面磨削：内表面磨削用于相对较短的孔，内表面磨削：内表面磨削用于相对较短的孔，如图如图8.3所示。工件安装在卡盘或特殊夹具上。所示。工件安装在卡盘或特殊夹具上。作业时砂轮和工件都回转并且采用纵向进给。作业时砂轮和工件都回转

17、并且采用纵向进给。 Any desired depth of cut can be obtained by the cross feed of the grinding wheel. A variation from this type is planetary internal grinding, which is recommended for heavy workpieces that cannot be held in chucks.通过砂轮的横向进给能得到任意所需的切削深度。通过砂轮的横向进给能得到任意所需的切削深度。这种方法的一个变体是行星式内表面磨削，当工这种方法的一个变体是行星

18、式内表面磨削，当工件较重不能用卡盘固定时推荐使用。件较重不能用卡盘固定时推荐使用。 In that case, the grinding wheel not only spins around its own axis but also rotates around the centerline of the hole that is being ground.在这种情况下，砂轮不但绕自身轴线回转，同时在这种情况下，砂轮不但绕自身轴线回转，同时还绕被磨削孔的中心线旋转。还绕被磨削孔的中心线旋转。Centerless grinding. Centerless grinding involves

19、passing a cylindrical workpiece, which is supported by a rest blade, between two wheels, i.e., the grinding wheel and the regulating or feed wheel.无心磨削。无心磨削用于加工圆柱形工件，无心磨削。无心磨削用于加工圆柱形工件，工件由托板支撑，在两轮即砂轮和调节或进给轮工件由托板支撑，在两轮即砂轮和调节或进给轮之间通过去。之间通过去。 The grinding wheel does the actual grinding, while the regul

20、ating wheel is responsible for rotating the workpiece as well as generating the longitudinal feed. This is possible because of the frictional characteristics of that wheel, which is usually made of rubber-bonded abrasive.砂轮完成实际磨削，而调节轮负责旋转工件和产砂轮完成实际磨削，而调节轮负责旋转工件和产生纵向进给。由于调节轮通常用橡胶粘结的磨料生纵向进给。由于调节轮通常用橡胶

21、粘结的磨料制成，其摩擦特性使这成为可能。制成，其摩擦特性使这成为可能。 As can be seen in Fig.8.4, the axis of the regulating wheel is tilted at a slight angle with the axis of the grinding wheel. Consequently, the peripheral velocity of the regulating wheel can be resolved into two components, namely, workpiece rotational speed and l

22、ongitudinal feed.正如在图正如在图8.4中所看到的那样，调节轮的轴与砂中所看到的那样，调节轮的轴与砂轮轴倾斜一个微小角度。因此调节轮的圆周速度轮轴倾斜一个微小角度。因此调节轮的圆周速度可以分解为两个分量，即工件回转速度和纵向进可以分解为两个分量，即工件回转速度和纵向进给。给。 These can be given by the following equations:VworkpieceVregulating wheelcosAxial feedVregulating wheelcsinWhere c is a constant coefficient to account f

23、or the slip between the workpiece and the regulating wheel (c=0.940.98).其值可由下列公式给出：其值可由下列公式给出：V工件工件V调节轮调节轮cos 轴向进给轴向进给V调节轮调节轮csin式中式中c是考虑工件和调节轮之间滑动的恒定系数。是考虑工件和调节轮之间滑动的恒定系数。The velocity of the regulating wheel is controllable and is used to achieve any desired rotational speed of the workpiece. The a

24、ngleis usually taken from 1to 5and the larger the angle, the larger the longitudinal feed would be.调节轮的速度是可控的并被用于实现工件任调节轮的速度是可控的并被用于实现工件任意所需的转动速度。意所需的转动速度。 角通常取角通常取1到到5，这角度，这角度越大则纵向进给也将越大。越大则纵向进给也将越大。 When is taken as 0, i.e., the two axes of the grinding and regulating wheels are parallel, there is no longitudinal feed of the workpiece.当当取取0时，即砂轮和调节轮轴线平行时，则时，即砂轮和调节轮轴线平行时，则工件没有纵向进给。工件没有纵向进给。 Grinding wheels are composed of abrasive grains having similar size and a binder. The actual grinding process is performed by the abrasi