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在薄板拉深过程中,当毛坯的相对厚度t/D_0较小,拉深系数m较小时,拉深毛坯的法兰变形区在切向压应力的作用下很可能发生失稳起皱现象。毛坯严重起皱后,由于不能通过凸模与凹模之间的间隙而被拉破,造成废品。为了解决制件在拉深过程中的失稳起皱问题,需要在模具上设计压边装置。通常压边装置不外有两种:一种是钢性压边装置;另一种是弹性压边装置。钢性压边装置只能在双动冲床上进行,在此不予讨论。弹性压边装置最常见的是橡胶,弹簧和气垫。前两种由于压边力随冲床行程变化而变化,对于拉深较深的制件不利。而气垫虽然压边力随冲床行程变化很小,但一般较小的冲床都不加装气垫,而且这一装置比较复杂,需要附设气源。下面介绍一种利用液压机的顶出机构进行压边的方法。由于这种方法简单易行,动作可信且通用性好,所以,得到了较为广泛地应用。液压机一般由主缸(上缸)和顶出缸(下缸)两部分组成。一般情况下,顶出缸只作为顶出机构使用。现在将其稍作改进,即可进行拉深压边。如图示,只要在液压机的工作台上装设一个顶出箱,下面用压板螺丝压牢,与工作台成为一体。顶出箱内设一顶出板,该顶出板与顶出缸的活塞固定在一起。顶出箱上面紧固一个辅助工作平台,其上开设燕尾槽,
In the process of sheet drawing, when the relative thickness of the blank is smaller and the drawing coefficient is smaller, the buckling deformation of the blank is likely to occur under the effect of tangential compressive stress. Blank serious wrinkles, because they can not pass through the gap between the punch and die was broken, resulting in waste. In order to solve the problem of instability and wrinkling in the process of drawing, the blank holder should be designed on the die. There are usually two types of blank holder: one is a blank holder and the other is a blank holder. Steel blank holder device can only be carried out on the double-action punch press, will not be discussed here. The most common elastic blank holder is rubber, spring and air cushion. The first two due to the blank holder force changes with the punch stroke changes, for the deeper parts of the detriment. The air cushion while the blank holder force changes with the stroke is very small, but generally smaller punch is not equipped with air cushion, and the device is more complex, the need to attach gas source. The following describes a hydraulic mechanism using the ejection mechanism for crimping method. Because of this method is simple, credible action and good generality, therefore, has been more widely used. Hydraulic machine is generally composed of the master cylinder (upper cylinder) and the top of the cylinder (lower cylinder) composed of two parts. Under normal circumstances, the top of the cylinder as a top body only. Now a little improvement, you can deep drawing blank. As shown in the figure, as long as the top of the table in the hydraulic machine installed under the pressure plate with a screw press firmly with the table into one. Top out of the box with a top plate, the top plate and the top of the cylinder piston fixed together. Top box to fasten an auxiliary work platform, which opened the dovetail groove,