授课时间： 2007.4.3 授课形式：讲授 授课地点：国杰110 授课时数：2 新课内容： Lesson 8 Blanking Technique 教学目标： 重点掌握冲压工艺的操作、冲压力、间隙等的相关知识，熟练掌握主要专业词汇。 教学重点、难点及处理措施： 教学重点是专业词汇的理解识记、文章词句的理解； 教学难点在常用专业词汇的熟练识记和应用，注意文章翻译中的句序； 处理措施：可以采用加强练习、教师解释的方式帮助学生解决学习中的问题。 教学过程： 教学中主要采用教师讲解和学生的参与的方式进行。在教学中，对学生进行提问，加深学生的理解。 教学手段： 以讲授和板书为主，辅以学生的自学。 作业： 复习所学课程，识记生词。
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Lesson 8 Blanking Technique 第八课 冲裁工艺
课文讲授，主要以教师翻译讲解和学生的参与理解翻译为主，在文章的学习中，识记专业词汇。
授课时间为45’×2
Cutting (Shearing) Operations 剪切加工
In the following discussion, certain die terminology will be used frequently, Figure 8-1 presents the terms most commonly encountered. 译文
下面的讨论中，会频繁使用特定的模具术语，图8-1表示的是最长用的名称。 分析
terminology术语
图8-1 简单模具的常用组件 图8-2 模具剪切力
Shear Action in Die Cutting Operations 模具切削加工剪切操作
The cutting of metal between die components is a shearing process in which the metal is stressed in shear between two cutting edges to the point of fracture, or beyond its ultimate strength. 译文
模具零件之间金属剪切是一个金属受到剪切边压力作用达到断裂值或超过临界强度的剪切过程。 分析
Component 断裂 ultimate strength临界强度
The metal is subjected to both tensile and compressive stresses( Figure 8-2 ); stretching beyond the elastic limit occurs, then plastic deformation, reduction in area, and finally, fracturing starts through cleavage planes in the reduced area and becomes complete. 译文
金属受到张力和压力的共同作用（图8-2）；拉力超过弹性极限，产生弹性变形，断面收缩，最后在断面收缩处从解理面产生断裂，并且完全断裂。 分析
tensile and compressive stresses张力和压力elastic limit弹性极限 reduction in are断面收缩 cleavage plane解理面
The fundamental steps in shearing or cutting are shown in Figure 8-3.The pressure applied by the punch on the metal tends to deform it into the die opening. When the elastic limit is
exceeded by further loading, a portion of the metal will be forced into the die opening in the form of an embossed pad on the lower face of the material. A corresponding depression results on the
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upper face, as indicated at Figure 8-3a. As the load is further increased, the punch will penetrate the metal to a certain depth and force an equal portion of metal thickness into the die, as indicated at Figure 8-3b. This penetration occurs before fracturing starts and reduces the cross-sectional area of metal through which the cut is being made. Fracture will start in the reduced area at both upper and lower cutting edges, as indicated at Figure 8-3c. If the clearance is suitable for the material being cut, these fractures will spread toward each other and eventually meet, causing complete separation. Further travel of the punch will carry the cut portion through the stock and into the die opening. 译文
图8-3表示的是在剪切或切削中最基本的步骤。在金属上凸模产生的压力有将金属压入模腔的趋势。当增加载荷超过弹性极限时，金属的一部分在材料下面就会以以压入垫板的形式被压入模腔。上面就会有相应的凹坑，如图8-3a所示。随着载荷的进一步增加，凸模将穿透金属到一定深度，并迫使同样的金属厚度进入模具，如图8-3b所示。穿透发生在断裂之前，并且减少金属横截面面积，形成切口。断裂开始于上下剪切边的面积缩减区，如图8-3c所示。对于所需要剪切的材料，若间隙适当时，这些断口将相互扩展最终相遇，从而引起材料完全分离。加深凸模进程会切削部分穿过模座并进入模腔。 分析
elastic limit弹性极限 die opening模腔 penetrate穿透 fracture 断裂 cross-sectional area横截面面积
图8-3 金属剪切过程 弹性变形/厚度减小/断裂
Center of Pressure 压力中心
If the contour to be blanked is irregularly shaped, the summation of shearing forces on one side of the center of the rain may greatly exceed the forces on the other side. Such irregularity results in a bending moment in the press ram, and undesirable deflections and misalignment. It is therefore necessary to find a point about which the summation of shearing forces will be
symmetrical. This point is called the center of pressure, and is the center of gravity of the line that is the perimeter of the blank. It is not the center of gravity of the area.
The press tool will be designed so that the center of pressure will be on the axis of the press ram when the tool is mounted in the press. 译文
如果毛坯外形是不规则的外形，则一侧重心上的剪切力总合可能会远远超过另一侧的力。这些不规则会导致受压时的弯曲，不理想的偏差和不准。因此必须找到剪切力的总数对称的点。这个点就称为压力中心，而且是毛坯圆周线上重力的中心。不是面积的重力中心。
设计压力工具以使得工具加压时压力中心在压力机轴线上。 分析
Contour 外形 irregularly 不规则地 symmetrical对称的 symmetrical圆周 gravity重力 press ram压力机
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Clearances 间隙
Clearance is the space between the mating members of a die set. Proper Clearances
between cutting edges enable the fractures to meet. The fractured portion of the sheared edge will have a clean appearance. For optimum finish of a cut edge, proper clearance is necessary and is a function of the type, thickness, and temper of the work material. Clearance, penetration, and fracture are shown schematically in Figure 8-4. In Figure 8-5, characteristics of the cut edge on stock and blank, with normal clearance, are shown schematically. The upper corner of the cut edge of the stock ( indicated by A') and the lower comer of the blank (indicated by A'-1 ) will have a radius where the punch and die edges, respectively, make contact with the material. This radiusing is due to the plastic deformation taking place, and will be more pronounced when
cutting soil metals. Excessive clearance will cause a large radius at these comers, as well as a burr on opposite comers. 译文
间隙模具装置匹配件之间的空隙。在切削边之间的合适间隙可以使得断裂相符。剪切边断裂部分会有一个光滑的表面。对于剪切边的最佳光洁度，合理的间隙是必要的而且是样式的功能、厚度和工件材料的回火。间隙、穿透和断裂如图8-4所示。在图8-5中表示了具有一般间隙的材料和毛坯上剪切的特点。余料剪切边的上面角（标记为A'）以及毛坯下面的角（标记为 A'-1 )将会有一个倒圆，这是凸模和模具边各自与材料接触产生的。这个圆角半径是由于材料发生塑性变形而引起的，并且在冲裁比较软的金属材料时圆角半径就会更明显。过大的间隙会引起大的圆角，并且在对应角上产生毛刺。 分析
Clearance间隙 finish光洁度 temper回火 radius 倒圆 burr 毛刺
Cutting Forces 剪切力
The force required to cut (shear) the work material can be calculated by using the following 译文
剪切工件材料所需的力可以用下式计算：
图8-5 模具剪切金属的剪切边特点；
过度间隙的影响（过大间隙/不足间隙/一般间隙）图8-4 凸凹模间隙；凸模进入和冲裁断裂
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Stripping Forces卸料力
The force required to strip the work material off punches can be calculated by using the following formulas: 译文
工件材料卸离凸模所需力可以用下式计算： Press Tonnage 压力吨位
This is a total of forces required to cut and form the part with a 30% safety factor added. In many cases, you will have to add stripping force if stripping is being done with a spring-loaded stripper, because the press has to compress the springs while cutting the material. Likewise, any spring pressure for forming, draw pads, and the like, will have to be added.
The force needed to punch a 2\having a shear strength of 60000 psi (413,7 N/mm2) . 译文
这是剪切和工件成型所需的总力，并增加了30%的安全因素。在任何情况下，如果使用弹簧加载卸料板卸料必须加上卸料力，因为当剪切材料时压力要压上弹簧。同时，任何为了成型、起模板和类似的所用到的弹簧压力也要加上。
凸模需要压力2？？，3.18mm厚？？的孔剪切强度要达到60000pis. 分析
spring-loaded stripper弹簧加载卸料板 draw pad起模板
课后练习(Practice)
Doing the exercise after the article-“question”, give the answer and translate your answer to others. Questions
1.What is the center of pressure?
This point is called the center of pressure, and is the center of gravity of the line that is the perimeter of the blank. It is not the center of gravity of the area. 2.Describe shear action in die cutting operations.
3.What is the fundamental steps in shearing or cutting?
The fundamental steps in shearing or cutting are shown in Figure 8-3.The pressure
applied by the punch on the metal tends to deform it into the die opening. When the elastic limit is exceeded by further loading, a portion of the metal will be forced into the die
opening in the form of an embossed pad on the lower face of the material. A corresponding depression results on the upper face, as indicated at Figure 8-3a. As the load is further increased, the punch will penetrate the metal to a certain depth and force an equal portion
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