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. 磨削是通過采用旋轉(zhuǎn)磨輪去除金屬的制造工磨削是通過采用旋轉(zhuǎn)磨輪去除金屬

2、的制造工藝。磨輪用非常大量的微型切削刃模仿銑刀進行藝。磨輪用非常大量的微型切削刃模仿銑刀進行切削。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，磨削被認為是一種通常用于獲得高尺一般而言，磨削被認為是一種通常用于獲得高尺寸精度和較好表面光潔度的精加工作業(yè)。寸精度和較好表面光潔度的精加工作業(yè)。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.磨削通過采用被稱為磨床的特殊機床能在平面、磨削通過采用被稱為磨床的特殊機床能在平面、圓柱面甚至內(nèi)表面上進行。圓柱面甚至內(nèi)表面上進行。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.顯然，磨床根據(jù)結(jié)構(gòu)和功能的不同有所區(qū)別，使顯然，磨床根據(jù)結(jié)構(gòu)和功能的不同有所區(qū)別，使用何種形式的磨床主要取決于被磨削表面的幾何用何種形式的磨床主要取決于被磨削表面的幾何形狀和物理性質(zhì)。例如，圓柱面在外圓磨床上磨形狀和物理性質(zhì)。例如，圓柱面在外圓磨床上磨削。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：就像其名稱暗示的那樣，表面表面磨削：就像其名稱暗示的那樣，表面磨削和平面磨削直接有關(guān)。圖磨削和平面磨削直接有關(guān)。圖8.1表示了兩種可表示了兩種可能的變化：臥式磨床主軸或

6、立式磨床主軸。能的變化：臥式磨床主軸或立式磨床主軸。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.在第一種情況在第一種情況(臥式主軸臥式主軸)，臥式磨床通常具有安，臥式磨床通常具有安裝工件的刨床式往復工作臺。而立式主軸磨床既裝工件的刨床式往復工作臺。而立式主軸磨床既可以像臥式主軸磨床那樣具有刨床式工作臺也可可以像臥式主軸磨床那樣具有刨床式工作臺也可以具有旋轉(zhuǎn)工作臺。以具有旋轉(zhuǎn)工作臺。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.而且在這種情況下，磨削動作是通過砂輪端面完而且在這種情況下，磨削動作是通過砂輪端面完成的成的(圖圖8.1b)，這與通過砂輪周邊磨削工件的臥，這與通過砂輪周邊磨削工件的臥式主軸磨床正好相反。式主軸磨床正好相反。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.圖圖8.1a和和b同時簡述了用于估計諸如加工時間和同時簡述了用于估計諸如加工時間和金屬去除率之類的磨削作業(yè)不同參數(shù)的方程式。金屬去除率之類的磨削作業(yè)不同參數(shù)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.在平面磨削時，重的工件用夾具固定或用壓板等在平面磨削時，重的工件用夾具固定或用壓板等夾緊在磨床工作臺上，而小的工件則通常是用電夾緊在磨床工作臺上，而小的工件則通常是用電磁卡盤固定的。磁卡盤固定的。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. 圓柱面磨削。在圓柱面磨削中，作業(yè)時工圓柱面磨削。在圓柱面磨削中，作業(yè)時工件支撐在兩頂尖之間，砂輪轉(zhuǎn)動是導致回轉(zhuǎn)切削件支撐在兩頂尖之間，砂輪轉(zhuǎn)動是導致回轉(zhuǎn)切削運動的動力源，如圖運動的動力源，如圖8.2所示。所示。In fact, cylindrical grinding can be carried out by employing any of the following methods:實際上，圓柱面磨削能通過采用下列任意方法來實際上，圓柱面磨削能通過采用下列

12、任意方法來實現(xiàn)。實現(xiàn)。(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) 橫向方法：這種方法中砂輪與工件均旋橫向方法：這種方法中砂輪與工件

13、均旋轉(zhuǎn)且采用線性縱向進給以保證能磨削整個長度。轉(zhuǎn)且采用線性縱向進給以保證能磨削整個長度。切削深度通過改變砂輪對工件的橫向進給來進行切削深度通過改變砂輪對工件的橫向進給來進行調(diào)整。調(diào)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：這種方法通過砂輪的橫切削方法：這種方法通過砂輪的橫向進給完成磨削而不采用軸向進給。正如料想的向進給完成磨削而不采用軸向進給。正如料想的那樣，這種方法只在要磨削表面比所用砂輪寬度那樣，這種方法只在要磨削表面比所用砂輪寬度短時才使用。短時才使用。(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：這種方法除了一次加工就全深度方法：這種方法除了一次加工就能去除磨削余量外其它與橫向方法相同。這種方能去除磨削余量外其它與橫向方法相同。這種方法通常在磨削較短剛性軸時推薦使用。法通常在磨削較短剛性軸時推薦使用。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. 內(nèi)表面磨削：內(nèi)表面磨削用于相對較短的孔，內(nèi)表面磨削：內(nèi)表面磨削用于相對較短的孔，如圖如圖8.3所示。工件安裝在卡盤或特殊夾具上。所示。工件安裝在卡盤或特殊夾具上。作業(yè)時砂輪和工件都回轉(zhuǎn)并且采用縱向進給。作業(yè)時砂輪和工件都回轉(zhuǎn)

17、并且采用縱向進給。 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.通過砂輪的橫向進給能得到任意所需的切削深度。通過砂輪的橫向進給能得到任意所需的切削深度。這種方法的一個變體是行星式內(nèi)表面磨削，當工這種方法的一個變體是行星

18、式內(nèi)表面磨削，當工件較重不能用卡盤固定時推薦使用。件較重不能用卡盤固定時推薦使用。 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.在這種情況下，砂輪不但繞自身軸線回轉(zhuǎn)，同時在這種情況下，砂輪不但繞自身軸線回轉(zhuǎn)，同時還繞被磨削孔的中心線旋轉(zhuǎn)。還繞被磨削孔的中心線旋轉(zhuǎn)。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.無心磨削。無心磨削用于加工圓柱形工件，無心磨削。無心磨削用于加工圓柱形工件，工件由托板支撐，在兩輪即砂輪和調(diào)節(jié)或進給輪工件由托板支撐，在兩輪即砂輪和調(diào)節(jié)或進給輪之間通過去。之間通過去。 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.砂輪完成實際磨削，而調(diào)節(jié)輪負責旋轉(zhuǎn)工件和產(chǎn)砂輪完成實際磨削，而調(diào)節(jié)輪負責旋轉(zhuǎn)工件和產(chǎn)生縱向進給。由于調(diào)節(jié)輪通常用橡膠粘結(jié)的磨料生縱向進給。由于調(diào)節(jié)輪通常用橡膠

21、粘結(jié)的磨料制成，其摩擦特性使這成為可能。制成，其摩擦特性使這成為可能。 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.正如在圖正如在圖8.4中所看到的那樣，調(diào)節(jié)輪的軸與砂中所看到的那樣，調(diào)節(jié)輪的軸與砂輪軸傾斜一個微小角度。因此調(diào)節(jié)輪的圓周速度輪軸傾斜一個微小角度。因此調(diào)節(jié)輪的圓周速度可以分解為兩個分量，即工件回轉(zhuǎn)速度和縱向進可以分解為兩個分量，即工件回轉(zhuǎn)速度和縱向進給。給。 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).其值可由下列公式給出：其值可由下列公式給出：V工件工件V調(diào)節(jié)輪調(diào)節(jié)輪cos 軸向進給軸向進給V調(diào)節(jié)輪調(diào)節(jié)輪csin式中式中c是考慮工件和調(diào)節(jié)輪之間滑動的恒定系數(shù)。是考慮工件和調(diào)節(jié)輪之間滑動的恒定系數(shù)。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.調(diào)節(jié)輪的速度是可控的并被用于實現(xiàn)工件任調(diào)節(jié)輪的速度是可控的并被用于實現(xiàn)工件任意所需的轉(zhuǎn)動速度。意所需的轉(zhuǎn)動速度。 角通常取角通常取1到到5，這角度，這角度越大則縱向進給也將越大。越大則縱向進給也將越大。 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.當當取取0時，即砂輪和調(diào)節(jié)輪軸線平行時，則時，即砂輪和調(diào)節(jié)輪軸線平行時，則工件沒有縱向進給。工件沒有縱向進給。 Grinding wheels are composed of abrasive grains having similar size and a binder. The actual grinding process is performed by the abrasi