外文翻譯-沖壓模具設計

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畢業(yè)設計(論文)外文資料翻譯系 部： 專 業(yè)： 姓 名： 學 號： 外文出處： The Pofessional English of Design Manufacture for Dies L——零件長度，英寸;S——極限張力強度，噸/平方英寸；W——V或 U形模具的寬度，英寸；T——材料厚度，英寸。對于 U形彎曲（槽形彎曲） ，彎曲力大約是 V形彎曲所需要的彎曲壓力的兩倍，棱邊彎曲則大約是 V形彎曲所需要的彎曲壓力的 1/2?；貜?。所有金屬材料均有一個固定的彈性模量，隨之而來的是塑性變形，當施加在材料上的彎曲力消除時就會有一些彈性恢復（見圖 7） 。在彎曲過程中這種恢復稱為回彈。一般而言，這樣的回彈在 0.5°～5°之間變化，取決于固定的彈性模量、彎曲方式、模具間隙等。磷青銅的回彈則在 10°～15°之間。圖 7 彎曲中的回彈減少或消除在彎曲工序中回彈方法可以根據下列工藝方法進行，如圖 8所示，在彎曲模具中產生的零件也可以通過等同回彈角度彎曲模上挖凹?；驈椥跃彌_式彎曲模而被過度彎曲來減少或消除回彈。圖 8 減少或消除回彈的方法從應用角度來說，有許多類型的壓力機，諸如：閉式雙點偏心軸單動機械壓力機，沖壓成形機，液壓成形壓力機，液壓機，彎板機，三動式壓力機，沖?；剞D壓力機，雙點壓力機，雙邊齒輪驅動壓力機，雙點單動壓力機，臺式壓力機，切邊壓力機，閉式單動（曲柄）壓力機，肘桿式壓力機，單點單動壓力機，開式雙柱可傾壓力機，開式壓力機，四點式壓力機，四曲柄壓力機，飛輪式螺旋壓力機，摩擦傳動螺旋壓力機，閉式雙點單動雙曲柄壓力機，搖臂式壓力機螺旋式壓力機和上傳動板料沖壓自動壓力機等。雙動式壓力機是用于鈑金零件的拉深加工。此種類型的壓力機有一個外滑塊（壓邊圈） ，并且有一個切斷的內滑塊（沖頭夾緊器） 。在加工工作循環(huán)期間，壓邊圈首先與零件接觸，然后施加壓力使沖頭夾緊器進行適當零件拉深（見圖 9） 。圖 9 典型通用壓力機三動式壓力機具有和雙動式壓力機相同的內、外滑塊。另外，三動式壓力機床身還有另一個滑塊，它可向上運動，從而在一個沖壓循環(huán)中實現反向拉伸。三動式壓力機應用不是很廣泛。肘桿式壓力機是用于壓印加工。這裝置的設計是在沖壓行程的末端以很高壓力。此種壓力機利用一個曲柄（曲柄帶動違節(jié)運動，連節(jié)是由兩個在上死點到下死點之間進行擺動的連桿組成，連桿擺動時間很短） ．在臨近沖程底部時慢速移動的滑塊具有功率很大的短距離位移。液壓機主要是用于成形加工工序中，相比大多散機械式壓力機，它有一個比較長的工作周期。液壓機的優(yōu)點足工作壓力、沖程和滑塊的速度均是可調的（見圖 10） 。圖 10 典型液壓機液壓機屬于壓力限定型的成形機械，液壓機的主要用途體現在沿滑塊路徑外力是必須保持恒定或處于精確攤制鋒成形技術領域中?；钊c液壓缸的驅動機構是用線性方式實現的，并且直接．連接到滑塊。液壓機框架結構的形式是非常類似于機械式力機。液壓驅動裝置易于安裝在機械框架結構中。因此幾種液壓機驅動很容易就被制成復雜成形與切斷加工（拉深、擠壓、切斷、模鍛等）的單一機械，并且所要求的運動可以容易地定位，彎扳機除了它的長床身之外基本是與開式壓力機棚同的，床身長度可為 6～20 英尺(1.8～6 米)或更長，它基本上是用在尺寸大的鈑金零件上的各種類型的彎曲加工成形，它也可以使用不同整套的刀具分別進行淺沖孔、切口與成形（見圖 11） 。這就可以使零件僅通過把復雜的零件分成幾個簡單的加工工序實現由復雜設計到精確制造的過程，且沒有使用昂貴的沖制刀具。此種類型加工工序用于小批量生產或試樣零件。圖 11 典型彎板機使用帶有簡單央具的彎扳機可以容易地對鈑金進行彎曲。彎板機使用一個用在機械或液壓饑上的長模具，適用于小批量生產。模具簡單，適于各種類型的成形加工，而且，加工工序很容易實現自動化。彎板機的模具材料可以是硬木（用于低強度材料與小批量生產） ，也可以是硬質合金材料。大多數應用中，一般是使用碳鋼或灰鑄鐵材料模具。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 today's 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 hole1—Lower shoe 2,5—Guide bushings 3—Cavity plate 4—Guid pin 6—Spring-loaded stripper 7—Punch 8—Support plate 9—Punch bushing 10—Fan-shaped block 11—Fixed plate 12—Punch-holder plate 13—Backing plate 14—Spring 15—Stepping bolts 16—Upper shoe 17—ShankA 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 Poisson's 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 :T——thickness 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= α(R 十 kT) Where Lb——bend allowance, in (mm).α——bend angle, (radians) (deg).T——sheet thickness, in (mm).R——inside radius of bend, in (mm).k——0.33 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 bock[Figure 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).K——die opening factor: 1.20 for a die opening of 16 times metal thickness, 1.33 for an opening of 8 times metal thickness.L——length of part, in.S——ultimate tensile strength, tons per square in.W——width of V or U die, in.T——metal 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 0.5°to 5°, depending upon finite modulus of elasticity, modes of bending, clearance of die and so on, but phosphor bronze may spring back from 10°to15°. 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 (1.8～6m) 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.