冲压模具英文文献

冲压模具英文文献内容摘要：

ushion or pressure cylinder. Figure 868 illustrates a backward extrusion die with an unusual punch peration ratio of 5：1 made possible with a modified flatend punch profile. Forward Extrusion Dies. Figure 869 is an example of a typical forward extrusion die in which the metal flows in the same direction as the punch, but at a greater rate owing to change in the crosssectional area. The lower carbide guide ring is added to maintain straightness. The nest above the upper carbide guide ring serves as a guide for the punch during the operation. Figure 870 illustrates another forward extrusion die in which the punch creates the orifice through which the metal flows. The extruding pressure is applied through the punch guide sleeve. Combination Extruding Dies. A typical bination forward and backward extrusion die is shown in Figure 871. In this die, the two –piece pressure anvil acts as a bottom extruding punch and a shedder. The upper extruding punch is guided by a springloaded guide plate into which the guide sleeve is mounted. To maintain concentricity between the punch and die, the punch guide sleeve is centered into the die insert. Punch Design. The most important feature of punch design is end profile. A punch with a flat end face and a corner radius not over ″() can perate three times its diameter in steel, four to six times its diameter in aluminum. A punch with a bulletshaped nose or with a steep angle will cut through the phosphate coat lubricant quicker than a flatend punch. When the lubricant is displaced in extrusion, severe galling and wear of the punch will take palce. The punch must be free of grinding marks and requires a 4181。 in. () finish, lapped in the direction of metal flow. The punch should be made of hardened tool steel or。