当这种压缩变得太大以致材料保持平坦时，它开始折叠或起皱。为了防止这种情况，允许材料在拉环和压力垫之间的受控间隙中流动。绘制外壳失败的两个主要原因是超过空白（或外壳）直径减小的百分比和不正确的拉环半径。
当从坯料直径到第一拉伸直径和从拉伸外壳直径到更小的外壳直径拉伸时，内向金属将流动的距离是有限的。这表示为抽取减少的百分比。减少的最大百分比受到向内的材料流的限制，这导致金属进入压缩，这又导致阻力流动。太多的阻力将导致壳体顶部附近的裂缝，这是最紧张的区域。论文网
还原的百分比随金属厚度而变化。例如，对于深拉拔钢坯，减少到第一拉伸壳直径的百分比从0。015英寸的32％变化。厚料至48％，为0。125英寸。厚料。
拉环上有一个最小和最大的拉伸半径，用于控制材料的流动。对于深冲钢零件，正确的半径从5/32-in不等。最小为1/4英寸，最大为0。015英寸。股票和11/32-in。最小为15/32英寸，最大为0。125英寸。股票。
如果半径太小，金属将不能很好地流动，这增加了流动阻力，造成杯盖附近的过度变薄或断裂。如果半径太大，金属在离开拉环和压力垫之间的夹紧点之后，并且在其形成到杯的垂直壁之前会起皱。
正常的趋势是使半径太小，因为“在模具试验期间使半径更大，并且难以制造较小的半径”。结果是，不必要的压力放在杯子上，这导致过度的变薄或压裂。很多时候，第一个牵引车站的缩减比例不合适或不正确的拉伸半径问题不会出现在第一个牵引车站，但是在后来的一个重新设计的车站，结果是花了相当多的时间来修复错误的车站。
外文原文二
Progressive die stamping is a cost-effective and safe method of producing components。 Careful design and construction of dies will ensure optimum performance。By Arnold Miedema
Capitol Concept & Engineering Corp。, Wyoming, MI
A progressive die performs a series of fundamental sheet metal operations at two or more stations in the die during each press stroke。 These simultaneous operations produce a part from a strip of material that moves through the die。 Each working station performs one or more die operations, but the strip must move from the first station through each succeeding station to produce a complete part。 Carriers, consisting of one or more strips of material left between the parts, provide movement of the parts from one die station to the next。 These carrier strips are separated from the parts in the last die station。
There are 5 elements that should be addressed when designing and building a progressive die to maximize its performance:
•Interpreting the part print,
•Starting material into the die,
•Part lifters and part feeding,
•Upper pressure pads, and
•Drawn shells。
Interpreting the Part Print
The first step in the proper design of a progressive die is to correctly analyze the part print。 The tool designer must interpret the print to determine the function of the part by looking for such things as the type of material, critical surfaces, hole size and location, burr location, grain direction requirements, surface finish and other factors。
The die designer must understand the part well, particularly if it has irregular shapes and contours。 However, modern computer-drawn prints make this more difficult because computer-drawn part data can be downloaded directly to the die-design computer。 As a result, the designer may not become thoroughly familiar with important part features。
Also, many computer-drawn parts are more difficult to understand, because often, only one surface is shown and it may be the inside or outside surface。 Computer drawings often show all lines, including hidden features, as solid lines instead of dotted lines。 This leads to interpretation errors, which in turn leads to errors in the building of the die。 冲压渐进模具英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_83427.html