外文翻译-冲压模具设计

毕业设计(论文)外文资料翻译系 部： 专 业： 姓 名： 学 号： 外文出处： The Pofessional English of Design Manufacture for Dies L零件长度，英寸;S极限张力强度，吨/平方英寸；WV或 U形模具的宽度，英寸；T材料厚度，英寸。对于 U形弯曲（槽形弯曲） ，弯曲力大约是 V形弯曲所需要的弯曲压力的两倍，棱边弯曲则大约是 V形弯曲所需要的弯曲压力的 1/2。回弹。所有金属材料均有一个固定的弹性模量，随之而来的是塑性变形，当施加在材料上的弯曲力消除时就会有一些弹性恢复（见图 7） 。在弯曲过程中这种恢复称为回弹。一般而言，这样的回弹在 0.55之间变化，取决于固定的弹性模量、弯曲方式、模具间隙等。磷青铜的回弹则在 1015之间。图 7 弯曲中的回弹减少或消除在弯曲工序中回弹方法可以根据下列工艺方法进行，如图 8所示，在弯曲模具中产生的零件也可以通过等同回弹角度弯曲模上挖凹模或弹性缓冲式弯曲模而被过度弯曲来减少或消除回弹。图 8 减少或消除回弹的方法从应用角度来说，有许多类型的压力机，诸如：闭式双点偏心轴单动机械压力机，冲压成形机，液压成形压力机，液压机，弯板机，三动式压力机，冲模回转压力机，双点压力机，双边齿轮驱动压力机，双点单动压力机，台式压力机，切边压力机，闭式单动（曲柄）压力机，肘杆式压力机，单点单动压力机，开式双柱可倾压力机，开式压力机，四点式压力机，四曲柄压力机，飞轮式螺旋压力机，摩擦传动螺旋压力机，闭式双点单动双曲柄压力机，摇臂式压力机螺旋式压力机和上传动板料冲压自动压力机等。双动式压力机是用于钣金零件的拉深加工。此种类型的压力机有一个外滑块（压边圈） ，并且有一个切断的内滑块（冲头夹紧器） 。在加工工作循环期间，压边圈首先与零件接触，然后施加压力使冲头夹紧器进行适当零件拉深（见图 9） 。图 9 典型通用压力机三动式压力机具有和双动式压力机相同的内、外滑块。另外，三动式压力机床身还有另一个滑块，它可向上运动，从而在一个冲压循环中实现反向拉伸。三动式压力机应用不是很广泛。肘杆式压力机是用于压印加工。这装置的设计是在冲压行程的末端以很高压力。此种压力机利用一个曲柄（曲柄带动违节运动，连节是由两个在上死点到下死点之间进行摆动的连杆组成，连杆摆动时间很短） 在临近冲程底部时慢速移动的滑块具有功率很大的短距离位移。液压机主要是用于成形加工工序中，相比大多散机械式压力机，它有一个比较长的工作周期。液压机的优点足工作压力、冲程和滑块的速度均是可调的（见图 10） 。图 10 典型液压机液压机属于压力限定型的成形机械，液压机的主要用途体现在沿滑块路径外力是必须保持恒定或处于精确摊制锋成形技术领域中。活塞与液压缸的驱动机构是用线性方式实现的，并且直接连接到滑块。液压机框架结构的形式是非常类似于机械式力机。液压驱动装置易于安装在机械框架结构中。因此几种液压机驱动很容易就被制成复杂成形与切断加工（拉深、挤压、切断、模锻等）的单一机械，并且所要求的运动可以容易地定位，弯扳机除了它的长床身之外基本是与开式压力机棚同的，床身长度可为 620 英尺(1.86 米)或更长，它基本上是用在尺寸大的钣金零件上的各种类型的弯曲加工成形，它也可以使用不同整套的刀具分别进行浅冲孔、切口与成形（见图 11） 。这就可以使零件仅通过把复杂的零件分成几个简单的加工工序实现由复杂设计到精确制造的过程，且没有使用昂贵的冲制刀具。此种类型加工工序用于小批量生产或试样零件。图 11 典型弯板机使用带有简单央具的弯扳机可以容易地对钣金进行弯曲。弯板机使用一个用在机械或液压饥上的长模具，适用于小批量生产。模具简单，适于各种类型的成形加工，而且，加工工序很容易实现自动化。弯板机的模具材料可以是硬木（用于低强度材料与小批量生产） ，也可以是硬质合金材料。大多数应用中，一般是使用碳钢或灰铸铁材料模具。附件 2：外文原文Stamping Die DesignThe wide variety of sheet metal parts for both the automobile and electronic industries is produced by numerous forming processes that fall into the generic category of “sheet-metal forming“. Sheet-metal forming ( also called stamping or pressing )is often carried out in large facilities hundreds of yards long.It is hard to imagine the scope and cost of these facilities without visiting an automobile factory, standing next to the gigantic machines, feeling the floor vibrate, and watching heavy duty robotic manipulators move the parts from one machine to another. Certainly, a videotape or television special cannot convey the scale of todays automobile stamping lines. Another factor that one sees standing next to such lines is the number of different sheet-forming operations that automobile panels go through. Blanks are created by simple shearing, but from then on a wide variety of bending, drawing, stretching, cropping , and trimming takes place, each requiring a special, custom-made die.Despite this wide variety of sub-processes, in each case the desired shapes are achieved by the modes of deformation known as drawing, stretching, and bending. The three modes can be illustrated by considering the deformation of small sheet elements subjected to various states of stress in the plane of the sheet. Figure 1 considers a simple forming process in which a cylindrical cup is produced from a circular blank.Figure 1 Sheet forming a simple cupDrawing is observed in the blank flange as it is being drawn horizontally through the die by the downward action of the punch. A sheet element in the flange is made to elongate in the radial direction and contract in the circumferential direction, the sheet thickness remaining approximately constant Modes of sheet forming are shown in Figure 2.Figure2 Modes of sheet formingStretching is the term usually used to describe the deformation in which an element of sheet material is made to elongate in two perpendicular directions in the sheet plane. A special form of stretching, which is encountered in most forming operations, is plane strain stretching. In this case, a sheet element is made to stretch in one direction only, with no change in dimension in the direction normal to the direction of elongation but a definite change in thickness, that is, thinning.Bending is the mode of deformation observed when the sheet material is made to go over a die or punch radius, thus suffering a change in orientation. The deformation is an example of plane strain elongation and contractionA complete press tool for cutting a hole or multi-holes in sheet material at one stroke of the press as classified and standardized by a large manufacturer as a single-station piercing die is shown in Figure3.Any complete press tool, consisting of a pair( or a combination of pars ) of mating member for producing pressworked (stmped）parts, including all supporting and actuating elements of the tool, is a die. Pressworking terminology commonly defines the female part of any complete press tool as a die.The guide pins, or posts, are mounted in the lower shoe. The upper shoe contains bushings which slide on the guide pins. The assembly of the lower and upper shoes with guide pins and bushings is a die set. Die sets in many sizes and designs are commercially available. The guide pins are shown in Figure 3.Figure3 Typical single-station die for piercing hole1Lower shoe 2,5Guide bushings 3Cavity plate 4Guid pin 6Spring-loaded stripper 7Punch 8Support plate 9Punch bushing 10Fan-shaped block 11Fixed plate 12Punch-holder plate 13Backing plate 14Spring 15Stepping bolts 16Upper shoe 17ShankA punch holder mounted to the upper shoe holds two round punches (male members of the die) which are guided by bushings inserted in the stripper. A sleeve, or quill, encloses one punch to prevent its buckling under pressure from the ram of the press. After penetration of the work material, the two punches enter the die bushings for a slight distance.The female member, or die, consists of two die bushings inserted in the die block. Since this press tool punches holes to the diameters required, the diameters of the die bushings are larger than those of the punches by the amount of clearance.Since the work material stock or workpiece can cling to a punch on the upstroke, it may be necessary to strip the material from the punch. Spring-loaded strippers hold the work material against the die block until the punches are withdrawn from the punched holes. A workpiece to be pierced is commonly held and located in a nest (Figure 2-3) composed of flat plates shaped to encircle the outside part contours. Stock is positioned in dies by pins, blocks, or other types of stops for locating before the downstroke of the ram.Bending is one of the most common forming operations. We merely have to look at the components in an automobile or an appliance-or at a paper clip or a file cabinet-to appreciate how many parts are shaped by bending. Bending is used not only to form flanges, seams, and corrugations but also to impart stiffness to the part ( by increasing its moment of inertia ).The terminology used in bending is shown in Figure 4. Note that, in bending, the outer fibers of the material are in tension, while the inner fibers are in compression. Because of the Poissons ratio, the width of the part (bend length, L) in the outer region is smaller, and in the inner region is larger than the original width. This phenomenon may easily be observed by bending a rectangular rubber eraser.Minimum bend radii vary for different metals, generally, different annealed metals can be bent to a radius equal to the thickness of the metal without cracking or weakening. As R/T decreases (the ratio of the bend radius to the thickness becomes smaller), the tensile strain at the outer fiber increases, and the material eventually cracks (Figure 5). Figure 4 Bending terminologyFigure5 Poisson effectThe minimum bend radius for various materials is given in Table 1 and it is usually expressed in terms of the thickness. such as 2 T, 3 T, 4T.Table 1 Minimum bend radius for various materials at room temperatureConditionMaterialSoft HardAluminum alloys 0 6TBeryllium copper 0 4TBrass,low-leaded 0 2TMagnesium 5T 13TSteelsAustenitic stanless 0.5T 6TLow-carbon,lowalloy,HSLA0.5T 4TTitanium 0.7T 3TTitanium alloys 2.6T 4TNote :Tthickness of materialBend allowance as shown in Figure 4 is the length of the neutral axis in the bend and is used to determine the blank length for a bent part. However, the position of the neutral axis depends on the radius and angle of bend (as described in texts on mechanics of materials).An approximate formula for the bend allowance, Lb is given byLb= (R 十 kT) Where Lbbend allowance, in (mm).bend angle, (radians) (deg).Tsheet thickness, in (mm).Rinside radius of bend, in (mm).k0.33 when R is less than 2T and 0.50 when JR is more than 2T.Bend methods arc commonly used in press tool. Metal sheet or strip, supported by-V bockFigure 6(a),is forced by a wedge-shaped punch into the block. This method, termed V bending, produces a bend having an included angle which may be acute, obtuse, or 90.Friction between a spring-loaded knurled pin in the vee die and the part will prevent or reduce side creep of the part during its bending. Edge bending Figure 6(b) is cantilever loading of a beam. The bending punch forces the metal against the supporting die. The bend axis is parallel to the edge of the die. The workpiece is clamped to the die block by a spring-loaded pad before the punch contacts the workpiece to prevent its movement during downward travel of the punch.Figure 6 Bending methodsBending Force can be estimated by assuming the process of simple bending of a rectangular beam. The bending force in that case is a function of the strength of the material. The calculation of bending force is as follows:P=KLST2/W Where P-bending force, tons (for metric usage, multiply number of tons by 8.896 to obtain kilonewtons).Kdie opening factor: 1.20 for a die opening of 16 times metal thickness, 1.33 for an opening of 8 times metal thickness.Llength of part, in.Sultimate tensile strength, tons per square in.Wwidth of V or U die, in.Tmetal thickness, in.For U bending (channel bending) pressures will be approximately twice those required for V bending, edge bending requires about one-half those needed for V bending.Springback in that all materials have a finite modulus of elasticity, plastic deformation is followed, when bending pressure on metal is removed, by some elastic recovery (see Figure 7). In bending, this recovery is called springback. Generally speaking, such a springback varies in sheet from 0.5to 5, depending upon finite modulus of elasticity, modes of bending, clearance of die and so on, but phosphor bronze may spring back from 10to15. Figure 7 Springback during bendingMethods of reducing or eliminating springback in bending operations can be made according to the following operations, shown in Figure 8, and parts produced in bending die are also overbent through an angle equal to the springback angle with an undercut or relieved punch.Figure8 Methods of reducing or eliminating springbackFor the applications, there are many types of the presses, such as the single-action straight-slide eccentric mechanical press, punch press, hydro-former press, hydraulic press, press brake, triple-action press, turret press, two-point press, twin-drive press, two point single-action press, watch press, trimming press, closed-type single-action crank press, knuckle-lever press, one-point single-action press, open-back inclinable press, open-side press, four-point press, four-crank press, flywheel-type screw press, friction screw press, straight-side single-action double-crank press, rocker-arm press, screw press and top-drive sheet-metal stamping automatic press and so on. A double-action press is used for large, or deep drawing operations on sheet metal parts. This type of press has an outer ram ( blank holder ) and a section inner ram ( punch holder ) . During the operating cycle, the blank holder contacts the material first and applies pressure to allow the punch holder to properly draw the part (Figure 9).Figure9 Typical versatile pressA triple-action press has the same inner and outer ram as the double-action press, but a third ram in the press bed moves up allowing a reverse draw to be made in one press cycle. The triple-action press is not widely used.A knuckle press is used for coining operation. The design of the drive allows for very high pressures at the bottom of the ram stroke. This type uses a crank, which moves a joint consisting of two levers that oscillate to and from dead center and results in a short, powerful movement of the slide with slow travel near the bottom of the stroke.A hydraulic press is used basically for forming operations and has a slower operating cycle time than most mechanical presses. The advantages of hydraulic presses are that the working pressure stroke, and speed of the ram are adjustable (Figure 10).Hydraulic presses belong to the force-constrained type of forming machines . Their main use is found in those areas of forming technology where the force along the path of the ram must remain constant or under accurate control. The drive mechanism of piston and cylinder acts in a linear manner and is directly connected to the ram. The form of frame construction of hydraulic presses is largely similar to that of mechanical presses. The hydraulic drive units are easily accommodated in the machine frame. Consequently, several hydraulic drives can readily be built into a single machine for complicated forming and cutting operations (drawing, extruding, cutting, swaging, etc.), and the required motions may be easily coordinated.A press brake is essentially same as a gap-frame press except for its long bed from 6 to 20 feet (1.86m) or more. It is used basically for various bending operations on large sheet metal parts. It can also be used with a series of separate sets of press tools to do light piercing, notching, and forming (Figure 11). This allows parts of a complex design to be accurately made without a high-cost press tool by simply breaking the complex part down into several simple operations. This type of operation is used on low-run or prototype parts.Figure 10 typical hydraulic press Figure 11 Typical press brakeSheet metal can be bent easily with simple fixtures using a press brake. This press brake utilizes long dies in a mechanical or hydraulic press and is suitable for small production runs. The tooling; is simple, and it is adaptable to a wide variety of shapes, furthermore, the process can be easily automated. Die materials for press brakes may range from hardwood (for low-strength materials and small production runs) to carbides. For most applications, carbon-steel or gray-iron dies are generally used.