文献翻译-冲孔模设计

Piercing Die DesignA complete press tool for cutting two holes in work material at one stroke of the press, classified and standardized by a large manufacturer as a single-station piercing die.Any complete press tool ,consisting of a pair( or a combination of pairs ) of mating members for producing pressworked ( stamped ) 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.A punnch 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 .Afer penetration of the work material,the two punches enter the die bushing for a slight distance.The female member, or die, consists of two die bushings inswetwd in 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the material from the punch .Spring-loaded strippers hold the work material against the die block until the punches are withdrawn from the punched holes .A workpiece to be pierced is commonly held and located in a nest composed of flat plates shaped to encircle the outside part contours.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 Dies DesignBending is the uniform straining of material, usually flat sheet or strip metal, around a straight axis which lies in the neutral plane and normal to the lengthwise direction of the sheet or strip set after removal of the applied stress. The inner surface of a bend is in compression; the outer surface is in tension. A pure bending action doe not reproduce the exact shape of the punch and die in the metal ;such a reproduction is one of forming .The neutral axis is the plane area in bent metal where all strains are zero .Bend Radii. Minimum bendradii 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.Bend Allowances. Since bent metal is longer after bending , its increased length , generally of concern to the product designer , may also have to be considered by the die designer if the length tolerance of the bent part is critical .The length of bent metal may be calculated from the equation:B=A 2 (Ri+Kt)/360Where Bbend allowance, in (mm) (along neutral axis);Abend angle, deg;R i inside radius of bend, in (mm);t metal thickness ,in (mm);K0.33 when Ri is less than 2t and is 0.5 when Ri is more than 2t.Bending Methods . Two bending methods are commonly made use of in press tools. Metal sheet or strip by a V block is forced by a wedge-shaped punch into the block .This method, termed V bending, produces a bend having an included angle which may beacute, obtuse, or90. Friction between a spring-loaded knurled pin in the vee of a die and the part will prevent or reduce side creep of the part during its bending.Edge bending 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 movenment during downward travel of the punch .Bending Force. The force required for V bending is as follows:P=KLSt/WForce 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 . After bending pressure on metal is released , the elastic stress also are released , which causes metal movement resulting in a decrease in the bend angle ( as well as an increase in the included angle between the bent portions ) . Such a metal movement , termed springback , varies in steel from 0.5 to 5 ,depending upon its hardness ,phosphor bronze may springback , varies in steel from 10 to 15.V-bending dies customarily compensate for springback with V blocks and wedge-shaped punches having included angles somewhat less than that required in the part. The part is bent through a greater angle than that required but it springs back to the desired angle.Parts produced in other types of bending dies are also overbent though an angle equal to the springback angle with an undercut or relieved punch.中文翻译冲孔模设计在一个压力机行程中，在原材料上冲裁出两个孔的一个完整的冲压模具。一家大制造商将其分类并标准化为单工位冲孔模。任意一副完整的冲压模具，都是由一对（或多对）生产冲压零件的配合零件组成的，同时还包括模具上的固定支承零件和传力连接零件。压力加工术语上通常把所有冲压模具上的凹件定义为凹模。导柱安装在下模座上。上模座安装与导柱滑动配合的导套。上、下模座连同导柱、导套组成的部件称为模架。市场上有多种模架尺寸和设计形式供选用。安装在上模座上的凸模固定板固定了两个圆形凸模，这两个圆形凸模（模具中的凸出部分）通过嵌入在卸料板上的模套进行导向。安装在一个细小凸模外围的护套可以防止凸模在压力机滑动的压力作用下弯曲。在冲裁完工件后，两个凸模还要伸入凹模衬套一小段距离。凹模是由两个嵌入在凹模板内的衬套组成。由于冲孔模应冲出所要求的孔径，所以凹模的衬套内径应稍大于凸模一个间隙值。当废料或工件粘在上行的凸模上时，必须从凸模上卸掉废料。弹簧驱动的卸料板相对凹模板运动，将原材料卸下，直到凸模从冲过的孔内抽出。被冲孔的工件用定位板定位，定位板是与重建外形轮廓相符的平板。在滑块下行之前，毛坯要在凹模内通过定位销、定位板或其它类型的定位装置定位。弯曲模设计弯曲是沿平板料或条料位于中性面内的中心线（通常为沿长度方向）发生的均匀变形。由于金属流动发生在金属的塑性变形范围内，因此当加载荷去除后将会保留一个永久性的弯曲变形，弯曲件内表面呈现压缩变形。普通弯曲变形不可能在被弯曲的金属材料上准确地再现凸、凹模形状再现是成性工序中的一种。中性层是在弯曲材料上变形为零的平面。弯曲半径。最小弯曲半径因材料而异，通常情况下，退火状态的金属材料能被弯曲与材料厚度相等的半径而不会发生弯裂现象。弯曲件的展开长度。由于弯曲后被弯金属会变长，一般产品设计者应考虑其增加的长度，如果弯曲件的长度公差非常关键，那么对于模具设计者也必须考虑其长度的变化。弯曲金属的长