模具专业外文文献翻译外文翻译冲模及复合模设计.doc
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1、Stamping and Punching DiesCompound Die Design A compound die performs only cutting operations (usually blanking and piercing) which are completed during a single press stroke. A characteristic of compound dies is the inverted position of the blanking die and blanking punch which also functions as th
2、e piercing die. The die is fastened to the upper shoe and the blanking punch having a tapered hole in it and in the lower shoe for slug disposal is mounted on the lower shoe. The guide pins, or posts, are mounted in the lower shoes. The upper shoes contains bushing which slide on the guide pins. The
3、 assembly of the lower and upper shoes with guide pins and bushing is a die set. Die sets in many sizes and designs are commercially available. On the upstroke of the press slide, the knock out rod of the press strikes the ejector plate, forcing the ejector tie rod and shedder downward, thus pushing
4、 the finished work piece out of the blanking die. Four special shoulder screws (stripper bolts), commercially available, guide the stripper in its travel and retain it against the preload of its springs. The blanking die as well as the punch pad is screwed and doweled to the upper shoe. 1、 Bending D
5、ie Bending 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. Metal flow takes place within the plastic range of the lengthwise direction of the bend retains a p
6、ermanent 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 does 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 b
7、end metal where all strain is zero. 2、 Bending Methods Metal sheet or strip, supported by a V bending, produces a bend having an included angle which may be acute, obtuse, or of 90. Friction between a spring-loaded knurled pin in the Vee of a die and the part will prevent or reduce side creep of the
8、 part during its bending. Other methods are Z-bending edge bending and U-bending etc. 3、 Drawing Die Drawing is a process of changing a flat, precut metal blank into a hollow vessel without excessive wrinkling, thinning, or fracturing. The various forms produced may be cylindrical or box-shaped with
9、 straight or tapered sides or sides or a combination of straight, tapered, or curved sides. The size of the parts may vary from 0.25mm diameter or smaller, to aircraft or automotive parts large enough to require the use of mechanical handing equipment. 4、 Single-action Die The simplest type of draw
10、dies is one with only a punch and die. One type of drawing die use in a single-action press is shown in Fig.3-4. This die is plain single-action type where the punch pushes the metal blank into the die, using a spring-loaded pressure pad to control the metal flow. The punch has an air vent to elimin
11、ate suction which would hold the cup on the punch and damage the cup when it is stripped from the punch by the pressure pad. The sketch shows the pressure pad fitting the stop pin, which acts as a spacer that an even and proper pressure is exerted on the blank at all times. If the spring pressure pa
12、d is used without the stop pin, the more the springs are depressed, the greater the pressure exerted on the blank, thereby limiting the depth of drawing. Because of limited pressures obtainable, this type of die should be used with light- gage stock and shallow depths. Mold Cavities and Cores The ca
13、vity and core give the molding its external shapes respectively, the impression imparting the whole of the form to the molding. When then proceeded to indicate alternative ways by which the cavity and core could be incorporated into the mold and we found that these alternatives fell under two main h
14、eadings, namely the integer method and the insert method. Another method by which the cavity can be incorporated is by means of split inserts or splits. When the cavity or core is machined from a large plate or block of steel, or is cast in one piece, and used without bolstering as one of the mold p
15、lates, it is termed an integer cavity plate or integer core plate. This design is preferred for single-impression molds because of characteristics of the strength, smaller size and lower cost. It is not used as much for multi-impression molds as there are other factors such as alignment which must b
16、e taken into consideration. Of the many manufacturing processes available for preparing molds only two are normally used in this case. There are a direct machining operation on a rough steel forging or blank using the conventional machine tool, or the precision investment casting technique in which
17、a master pattern is made of the cavity and core. The pattern is then used to prepare a casting of the cavit y or core by or special process. A 4.25% nickel-chrome-molybdenum steel (BS 970-835 M30) is normally specified for integer mold plates which are to be made by the direct machini ng method. The
18、 precision investment casting method usually utilizes a high-chrome steel. For molds containing intricate impressions, and for multi-impression molds, it is not satisfactory to attempt to machine the cavity and core plates from single blocks of steel as with integer molds. The machining sequences an
19、d operation would be altogether too complicated and costly. The inset-bolster assembly method is therefore used instead. The method consists in machining the impression out of small blocks of steel. These small blocks of steel are known, after machining, as inserts, and the one which forms the male
20、part is termed the core insert and, conversely, the one which forms the female part the cavity inserts. These are then inserted and securely fitted into holes in a substantial block or plate of steel called a bolster. These holes are either sunk part way or are machined right through the bolster pla
21、te. In the latter case there will be a plate fastened behind the bolster and this secures the insert in posit ion. Both the integer and the insert-bolster methods have their advantages depending upon the size, the shape of the molding, the complexity of the mold, whether the single impression or a m
22、ulti-impression mold is desire, the cost of making the mold, etc. It can therefore be said that in general, once the characteristics of the mold required to do a particular job which have been weighed up, the decision as to which design to adopt can be made. Some of these considerations have already
23、 been discussed under various broad headings, such as cost, but to enable the reader to weigh them up more easily, when faced with a particular problem, the comparison of the relative advantages of each system is discussed under a number of headings. Unquestionably, for single impression molds integ
24、er design is to be preferred irrespective of whether the component form is a simple or a complex one. The resulting mold will be stronger, smaller, less costly, and generally incorporate a less elaborate cooling system than the insert -bolster design. It should be borne in mind that local inserts ca
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