机械工程英语翻译unit.ppt

Grinding 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 造工艺。磨轮用非常大量的微型切削刃模 仿铣刀进行切削。 Generally, grinding is considered to be a finishing process that is usually used for obtaining high-dimensional accuracy and better surface finish. Grinding can be performed on flat, cylindrical, or even internal surfaces by employing specialized machine tools, which are referred to as grinding machines. 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。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。 Obviously, grinding machines differ in construction as well as capabilities, and the type to be employed 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 面在外圆磨床上磨削。 Type of Grinding Operations 磨削作业的类型 1. Surface 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 磨削和平面磨削直接有关。图8.1表示了 两种可能的变化：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 worktable. 在第一种情况(卧式主轴)，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。 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 machines, 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 面完成的(图8.1b)，这与通过砂轮周边磨 削工件的卧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, such as the machining time and the rate of metal removal. 图8.1a和b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。 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 smaller 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。 2. Cylindrical grinding. In cylindrical grinding, the workpiece is held between centers during the grinding operation, and the wheel rotation is the source and cause for the rotary cutting motion, as shown in Fig.8.2. In fact, cylindrical grinding can be carried out by employing any of the following methods: 2. 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 转切削运动的动力源，如图8.2所示。实 际上，圆柱面磨削能通过采用下列任意方 法来实现： (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 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 ground is shorter than the width of the grinding wheel used. (2) 插入-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。 (3) The full-depth method, which is similar to the transverse method except that the grinding allowance is removed 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 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。 Internal grinding. Internal grinding is employed for grinding relatively short holes, as shown 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，如图8.3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。 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。这种方法的一个变体是行星式内表 面磨削，当工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， 同时还绕被磨削孔的中心线旋转。 Centerless grinding. Centerless grinding involves 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，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。 The grinding wheel does the actual grinding, while the regulating 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 和产生纵向进给。由于调节轮通常用橡胶 粘结的磨料制成，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 longitudinal feed. 正如在图8.4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 的圆周速度可以分解为两个分量，即工件 回转速度和纵向进给。 These can be given by the following equations: VworkpieceVregulating wheelcos Axial feedVregulating wheelcsin Where c is a constant coefficient to account for the slip between the workpiece and the regulating wheel (c=0.940.98). 其值可由下列公式给出： V工件V调节轮cos 轴向进给 V调节轮csin 式中c是考虑工件和调节轮 之间滑动的恒定 系数(c=0.940.98)。 The velocity of the regulating wheel is controllable and is used to achieve any desired rotational speed of the workpiece. The angleis 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 工件任意所需的转动速度。角通常取1到 5，这角度越大则纵向进给也将越大。 Whenis taken as 0, i.e., the two axes of the grinding and regulating wheels are parallel, there is no longitudinal feed of the workpiece. 当取0时，即砂轮和调节轮轴线平行时， 则工件没有纵向进给。 Grinding Wheels 砂轮 Grinding wheels are composed of abrasive grains having similar size and a binder. The actual grinding process is performed by the abrasive grains. Pores between the grains within the binder enable the grains to act as separate single-point cutting tools. 砂轮由具有相近尺寸的磨料颗粒和粘合 剂组成。实际磨削作业由磨粒完成。在粘 合剂中磨粒之间的孔隙使磨粒能象独立的 单刃切削刀具一样工作。 These pores also provide space for the generated chips, thus preventing the wheel from clogging. In addition, pores assist the easy flow of coolants to enable efficient and prompt removal of the heat generated during the grinding process. 这些孔隙同时还为产生的切屑提供空间以防 砂轮堵塞。另外孔隙帮助冷却液容易流动 ，从而使在磨削作业中产生的热量能有效 而迅速地散发。 Grinding wheels are identified based on their shape and size, kind of abrasive, grain size, binder, grade (hardness), and structure. 砂轮根据它们的形状和尺寸、磨料的类 型、磨粒的大小、粘合剂、等级(硬度)和 结构组织来分类。 Shape and size of grinding wheels. Grinding wheels differ in shape and size, depending upon the purpose for which they are to be used. Various shapes are shown in Fig.8.5 and include the following types: 砂轮的形状和尺寸：根据砂轮的用途， 它们的形状和尺寸是不同的。各种形状如 图8.5所示，其中包括： 1)Straight wheels used for surface, cylindrical, internal, and centerless grinding. 2)Bevelled-face or tapered wheels used for grinding threads, gear teeth, and the like. 3)Straight recessed wheels for cylindrical grinding and facing. 1)用于表面、圆柱面、内部和无心磨削的直 轮。 2)用于磨削螺纹、齿轮轮齿之类的斜面或锥 形轮。 3)用于圆柱面和端面磨削的直凹轮。 4)Abrasive disks for cutoff and slotting operations. (thickness 0.02 up to 0.2in. (0.5 to 5mm). 5)Cylinders, straight cups, and flaring cups are used for surface grinding with the end face of the wheel. 4)用于切断和开槽作业的砂轮片(其厚度从 0.02到0.2英寸(0.5到5毫米)。 5)用其端面进行表面磨削的圆柱、直杯及外 展杯状砂轮。 The main dimensions of a grinding wheel are the outside diameter D, the bore diameter d, and the height H. These dimensions vary widely, depending upon the grinding process for which the wheel is to be used. 砂轮的主要尺寸有外径D、孔径d和厚 度H。根据采用砂轮的磨削工艺，这些尺 寸变化很大。 Kind of abrasive. Grinding wheels can be made of natural abrasives such as quartz, emery, and corundum or of industrially prepared chemical compounds such as aluminum oxide or silicon carbide (known as carborundum). 磨料的类型：砂轮可以由象石英、金刚 砂、刚玉之类的自然磨料制成，或者由象 氧化铝或碳化硅(也称人造金刚砂)之类的 工业制备的化学化合物制成。 Generally, silicon carbide grinding wheels are used when grinding low-tensile- strength materials like cast iron, whereas aluminum oxide wheels are employed for grinding high-strength metals such as alloy steel, hardened steel, and the like. 当磨削象铸铁类低拉伸强度材料时，一般采 用碳化硅砂轮，而磨削合金钢、淬火钢等 高强度金属则要用氧化铝砂轮。 Grain size of abrasive used. As you may expect, the grain size of the abrasive particles of the wheel plays a fundamental role in determining the quality of ground surface obtained. 所用磨粒的尺寸：正如料想的那样，砂 轮磨粒的尺寸对决定所得磨削表面的质量 起着根本的作用。 The finer the grains, the smoother the ground surface is. Therefore, coarse- grained grinding wheels are used for roughing operations, whereas fine- grained wheels are employed in final finishing operations. 磨粒越细，磨削表面越光滑。所以，粗粒砂 轮用于粗加工，而细粒砂轮则用于最后精 加工。 The grade of the bond. The grade of the bond is actually an indication of the resistance of the bond to pulling off the abrasive grains from the grinding wheel. Generally, wheels having hard grades are used for grinding soft materials and vice versa. 粘结体的等级：粘结体的等级实际上是 其抵抗将磨粒从砂轮上拉脱的指标。一般 而言，具有较硬等级的砂轮用于磨削较软 材料，反之亦然。 If a hard-grade wheel were to be used for grinding a hard material, the dull grains would not be pulled off from the bond quickly enough, thus impeding the self- dressing process of the surface of the wheel and finally resulting in clogging of the wheel and burns on the