单刃刀具工艺装备夹具毕业外文文献翻译/中英文翻译/外文翻译

南华大学机械工程学院毕业论文  第 1 页     共 12 页  附页：  单刃刀具  刀具有切削部分（或产生切屑的部分）和刀杆，常用于车床、转塔车床、龙门刨床、牛头刨床、镗床及类似的机床。图 2.30 为一典型的单刃刀具，其最重要的特征是切削刃及相邻的刀面。如图所示，可定义如下：  1. 前刀面是切屑流经的表面；  2. 后刀面是与工件已加工面相对的表面；  3. 切削刃是刀面担负切削任务的边缘，主刀刃是切削刃中担负工件过渡表面上切削任务的部门，其余是副刃；  4. 刀尖是主、副刃相连接处的以小段刀刃，它可以是曲线或直线，也可以是主副刀刃的交点。  一般而言，刀具切削时，相对于工件的运动有两个方面：  1. 来自机床主运动的相对运动，可以称为刀具的主运动。  2. 来自于机床进给运动的相对运动（如图 2.31）  这两个运动的合成就称为合成切削运动，定义为机床主运动和进给运动而产生的合成运动  应该注意，机床作进给运动时，如刀具并不接触工件，则合成切削运动就等于主运动。当连续进给运动时，主运动与合成运动间的夹角叫做切削速度角。这个角度通常很小，多数情况下可以假设为零。另外，切削速度 v-主刀刃上不同南华大学机械工程学院毕业论文  第 2 页     共 12 页  选顶点相对于工作的瞬时速度，沿主切削刃可能时变化的，而进给速度 fv刀刃   上不同 选定点相对于工件的进给运动的大小是固定不变的，总之，合成速度ev-刀刃上选顶相对于工作瞬时合成切削运动的大小可以表示 :cosvve ，但因为对大多数实际加工 很小，通常可以假设 vve ，考虑切削刀具几何角度时，一个很重要的角度就是主偏角 rk 。在刀刃上选定点切下的切削层厚度ca 未变形切削厚度，极大地影响着切削功率，严格地说，ca应在既垂直切削刃又垂直合成切削运动方向上地测量。然而实际如前所述，因为 很小，ca就在垂直于主运动方向测量，因此在图 2.32 和后续各图中，ca就按此测量。所以，由图 2.32可知，rfc kaa sin其中 ra 为进给量 ，即沿进给运动方向测量地切削层参数。单刃刀具切削时， ra 就等于进给量 f。  南华大学机械工程学院毕业论文  第 3 页     共 12 页  rc kfa sin. 切削层地横截面积 Ac近似表示为pc faA ，其中为背吃刀量，以前叫切削度，背吃刀量是在包含主运动与进给运动所在平面地垂直方向测量地切削层尺寸（图2.31），一般而言，背吃刀量决定单刃刀具从工件切下材料地厚度。  *图 2.30 典型单刃刀具。刀柄，  切削部分，刀 具轴线，副切削刃，基面，副后刀面，主切削刃，刀尖，前刀面，主后刀面。 * *图 2.31 外圆车削时合成切削运动。刀具主运动矢量，合成切削速度角，合成切削运动矢量，刀刃上选定点，刀具进给运动矢量。 * *图 2.32 单刃刀具切削。  进给量，刀杆，主偏角，切削层截面，前刀面，背吃刀量（切削深度），主切削刃，副切削刃，未变形切削厚度，刀尖，包括主运动及进给运动地平面。  夹具  如前所示，工件必须相对于刀具在一定的位置定位并夹紧。工件在划线以后加工之前，还必须确定出相对于机床运动的位置，并将其夹紧。  当需要加工若干相同工 件时，通过使用夹具，可无须对每个工件进行划线。但如果加工的是铸件或者锻件，则仍需要对工件进行划线，以确保加工出合格的南华大学机械工程学院毕业论文  第 4 页     共 12 页  工件，而不至于造成肋条、内孔等位置便宜。  钻模和其它夹具相似，都是确保工件正确定位和夹紧装置，但也有不同之处，钻模具有在实际加工过程能导引刀具装置，而其它夹具则没有。实际上，在切削过程中，只有对钻头、绞刀以及类似刀具才能进行引导，所以与钻削加工有关的夹具是钻模，而与其它加工有关的则是夹具。夹具可装有调整刀具相对于定位工件位置的装置。  夹具的优点可概括如下：  可以省去划线及其它测量、调整等手续； 由于能使工件正确定位，刀具能正确地导引和调整，不熟练的工人也能有把握地快速进行操作；  便于零件的装配，因为所有零件的一致性好，尺寸公差的范围较小，所以可以省去“试装”和“锉配”工作；零件具有互换性，如果产品广销各地，备件的供应问题将为之简化。用于装螺栓的螺栓孔通常有 1.5 3.0mm 的间隙，读者可能怀疑，对这样的零件是否有必要制造精密夹具。应该牢记，夹具一经制造出来，便可用以加工厂许多零件精密制造夹具的附加成本可分摊给为数众多的工件。此外，在机构的装配过程中，即使是很小的误差，累积起来也是很大的。公差一经规 定，最好确保其要求，而不允许随意划线使尺寸超出规定值。  （ 1）  工件的定位。图 2.27 表示在空间完全不受约束的刚体，此时，它具有 6 个自由度。考虑这些自由度时，可用三个互相垂直的坐标轴 XX、YY、 ZZ 来表示。物体可沿任一坐标轴移动，因此，它具有三个移动自由度。它还可以绕任一坐标轴转动，因此，又有三个转动自由度，故共有6 个自由度。工件定位时，必须限制尽可能多的自由度，以确保加工时获得所需的精度。应尽可能提前加工出合适的定位面来保证精度，并用它人微言轻所有加工面的定位基面，除非有其它原因必须使用另外的定位面。而即使是要用 另外的定位面，也必须根据原有的定位面加工新的定位面。  （ 2）  工件的夹紧。夹紧机构必须夹紧工件，使之能承受切削力，但夹紧力不可过大，以免造成工件变形或损坏。工件夹紧点下方应有支承，以确保力由夹具的主体承受，然后转由机床的工件台和床身承受。设计夹具时，应保证其夹紧机构既能施加合适的夹紧力，又能使夹紧操作迅速、安全。  南华大学机械工程学院毕业论文  第 5 页     共 12 页  （ 3）  内容提要。  1）小批量生产时要对工件进行划线，并用它作为切削的标志线，对铸件、锻件毛坯也要进行划线，以检验是否有足够的加工余量。  2）如果批量允许，工件采用夹具定位夹紧，而不采用划线。夹具上有使工件定 位和夹紧的机构，钻模还有切削过程中对刀具导引的元件，而其它夹具则有可在切削前调刀的装置。  南华大学机械工程学院毕业论文  第 6 页     共 12 页  译文 : Single Point Tools Single-point tools are cutting tools having one cutting part (or chip producing element) and one shank. They are commonly used in lathes, turret lathes, planers, shapers, boring mills, and similar machine tools. A typical single-point tool is illustrated in Fig.2.30. The most important features are the cutting edges and adjacent surfaces. These are shown in the figure and defined as follows: the face is the surface or surface over which the chip flows. The flank is the tool surface or surfaces over which the surface produced on the work-piece passes. The cutting edge is that edge of the face which is intended to perform cutting. The tool major cutting edge is that entire part of the cutting edge which is intended to be responsible for the transient surface on the work-piece. The tool minor cutting edge is the remainder of the cutting edge. The corner is the relatively small portion of the cutting edge at the junction of the major and minor cutting edges; it may be curved or straight, or it may be the actual intersection of these cutting edges. 南华大学机械工程学院毕业论文  第 7 页     共 12 页  In general, when a tool is applied to a work-piece, its motion relative to the work-piece has two components: The motion resulting form the primary motion of the machine tool, which can be called the primary motion of the tool. The motion resulting form the feed motion of the machine (Fig.2.31). The resultant of these two tool motions is called the resultant cutting motion and is defined as the motion resulting from simultaneous primary and feed motions. It should be noted that in machine tools where the feed is applied while the tool is not engaged with the work-piece (as in shaping or planning, for example ),the resultant cutting motion is identical to the primary motion. When the feed motion is applied continuously, the angle between the direction of primary motion and the resultant cutting direction is called the resultant cutting-speed angle . This angle is usually extremely small and for most practical purposes can be assumed to be zero. 南华大学机械工程学院毕业论文  第 8 页     共 12 页  Further, the cutting speed , the instantaneous velocity of the primary motion of the selected point on the cutting edge relative to the work-piece, can vary along the major cutting edge. The feed speed f, the instantaneous velocity of the feed motion of the selected point on the cutting edge relative to the work-piece, is constant. Finally, the resultant cutting speed e,the instantaneous velocity of the resultant cutting motion of the selected point on the cutting edge relative to the work-piece, is given by , cose,but since for most practical operations  is very small, it can generally be assumed that , e. One of the important tool angles when considering the geometry of a particular machining operation is the angle in Fig.2.32 called the major cutting-edge angle r .The thickness of the layer of material being removed at the selected point on the cutting edge, known as the under-formed chip thickness chip thickness ca,significantly affects the power required to perform the operation. Strictly, this dimension should be measured both normal to the cutting edge and normal to the resultant cutting direction. However, for all practical purposes, since  is small, as described above, cacan be measured normal to the direction of primary motion; thus in Fig.2.32 and all subsequent figures, cawill be measured this way. From Fig.2.32, therefore, cais given by farsin , where fais the feed engagement, the instantaneous engagement of the tool cutting edge with the work-piece measured in the direction of feed motion. For single-point cutting operations fais equal to the feed, and therefore, ca rf sin. The cross-sectional area cAof the layer of material being removed 南华大学机械工程学院毕业论文  第 9 页     共 12 页  (cross-sectional area of the uncut chip) is approximately giver by, pc faA ,where pais the base engagement, previously known as depth of cut. The back engagement is the instantaneous engagement of the tool with the work-piece,  measured perpendicular to the plane containing the directions of primary and feed motion(Fig.2.31). In general the back engagement determines the depth of material removed from the workpiece in a single point cutting operation. Jigs and Fixtures It has already been stated the work-piece must be located relative to the cutting tool, and be secured in that position. After the work-piece has been marked out, it is still necessary to position it with respect to the machine movement, and to clamp it in that position before machining is started. When several identical work-piece are to be produced the need to mark out each part is eliminated by the use of jigs and fixtures, but if a casting or forging is involve, a trail work-piece is marked out, to ensure 南华大学机械工程学院毕业论文  第 10 页     共 12 页  that the work-piece can be produced from it, and to ensure that ribs, cores, etc. have not become misplaced. Jigs and fixtures are alike in that they both incorporate devices to ensure that the work-piece is correctly located and clamped, but they fifer in that they both incorporate means of tool guiding during the actual cutting operation, and fixtures do not. In practice ,the only cutting tools that can be guided while actually cutting are drills, reamers, and similar cutters; and so jigs are associated with drilling operations, and fixtures with all other operations. Fixtures may incorporate means of setting the cutting tools relative to the location system. The advantage of jigs and fixtures can be summarized as follows: 1. marking out and measuring and setting out methods are eliminated; 2. unskilled workers may proceed confidently and quickly in the knowledge that the work-piece can be positioned correctly, and the tools guided or set; 3. the assembly of parts is facilitated, since all components will be identical within small limits, and trying  and filing of work is eliminated; 4. the parts will be interchangeable, and if the product is sold over a wide area, the problem of spare parts will be simplified. Bolt holes often have 1.5mm or even 3.0mm clearance for the bolt, and reader may doubt the necessity of making precision jigs for such work. It must remembered that the jigs, once made, will be used on many components, and the extra cost of an accurately made jigs is spare over a large output. Further more, it is surprising how small errors accumulate in a mechanism during its assembly. When a clearance is specified, it is better to ensure its observance, rather than allow careless marking out and machining to encroach upon it. (1)the location of work-piece. Fig 2.27 represent a body that is completely free in space; in this condition it has six degrees of 南华大学机械工程学院毕业论文  第 11 页     共 12 页  freedom. Consider these freedom, with respect to the three mutually perpendicular axes XX,YY and ZZ. The body can move along these axes; it therefore has three freedoms of translation. It can also rotate about any of the three axes; it therefore has three freedoms of rotation .the total number of freedoms is six. When work is located, as many of these freedoms as possible must be eliminated, to ensure that the operation is performed with the required accuracy. Accuracy is ensured by machining suitable location features as early as possible, and using them for all location, unless other considerations mean the other location features must be used. If it is necessary, the new location features must be machined as a result of location from the former location features.