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风扇轴套环零部件拉伸级进模具设计【12张CAD图纸+毕业答辩论文】【冲压模具】

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关键词：: 风扇轴套零部件拉伸模具设计原创全套 cad 图纸毕业答辩论文冲压模具

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摘要

随着人们的生活水平不断提高，对生活质量的要求也越来越高，各种电器不断进入人们的生活当中，以满足人们对不断提高的生活需求。

风扇轴套是日常生活中常见到的一种机械零件，通过拉伸、冲裁等工序将零件加工出来。级进模是一种很常用而且工作效率也很高的冲压模，冲压模具是现在加工盘盖类、轴套类零件最常用的方法，此种加工方法广泛应用于机械零件、仪表仪器、日常生活、军工产品、车船、交通工具等，冲压模加工具有以下优点：成品零件力学性能好、材料利用率高、能够加工其它加工方法所难以加工复杂零件、容易实现自动化，而且加工效率高，适合于大批量生产且成本低；另外原材料一般不需要加热等处理，也节约了加工成本，但是要对其进行排样。它所具有的优点是其它加工方法所不具有的。级进模是冲压模的一种，其加工效率比复合膜低但是比一般的单工序冲压模高，结构相对复杂：比复合膜的结构简单，但是比单工序模的结构复杂。级进模的结构一般由导料定位装置、多付拉伸模、冲裁模等主要部件组成。在外加压力机的情况下就可以对板料进行冲裁、冲压，拉伸等加工工序的操作。

关键词：机械零件；复杂零件；级进模；板料；压力机

Abstract

As people life level increases the demand for the quality of life, more and more is also high, various electric constantly into people's life, to meet people to improve life demand.

Fan collar is see daily life in a mechanical parts, through blanking process such as tensile, will parts processing out. Progressive die is a very common and high efficiency also punch mould and stamping mould is now processing plate cover class and the sleeves kind parts is the most commonly used method, the processing method is widely used in mechanical parts, instrument, daily life, military products, vehicle traffic tools, stamping mould processing has the following advantages: finished parts mechanics performance is good, material utilization rate, processing method that can process other it is difficult for processing complex parts, easy to realize automation and the processing efficiency high, suitable for mass production and cost is low; Additional materials generally do not need to heating processing, also save the processing cost, but in its arrangement. The advantage is that it has other processing methods with. Progressive metal stamping progressive die is a kind of, its processing efficiency than composite film than the average low but progressive metal stamping single process structures are relatively high, than composite membrane complex: simple structure, but better than the single procedure mode complex structure. The structure of the progressive die by conducting knew a device general tensile modulus, and pay extra punch die and other major parts. The situation in plus press of sheet metal for cutting, stamping, processes such as drawing of the operation.

Keywords: mechanical parts； Complex parts； Progressive die； Sheet； press

引言5

１风扇轴套零件的设计7

1.1 分析零件的使用要求7

1.2 零件的设计图7

1.2.1 分析其结构及工艺的特点8

2 选用合理的排样方式9

2.1 计算坯料的直径9

2.2 确定加工方案9

2.3 选择板料10

3 确定拉伸系数及凹凸模的相关尺寸11

3.1 计算拉伸系数11

3.1.1 判断能否一次将制件拉伸成形：11

3.1.2 确定各次拉伸的拉伸系数，及其圆筒直径12

3.2 确定凹凸模的圆角半径14

3.3 核算坯料直径及计算各次拉伸高度14

3.3.1 重新计算坯料直径并计算拉伸高度14

3.3.2 计算首次拉伸高度14

3.3.3 计算后续拉伸的高度14

3.4 确定凸凹模尺寸15

3.4.1 确定各伸模的具体尺寸15

3.4.2 算冲底孔、落料模具工作部分的具体尺寸17

4 计算冲压力及选用冲压设备18

4.1计算压边力18

4.2 计算拉伸力19

4.2.1 计算各次拉伸的拉伸力19

4.2.2 计算拉伸的拉伸功19

4.3 计算所需的冲裁力20

4.3.1 计算侧刃冲裁的冲裁力20

4.3.2 冲工艺槽孔20

4.3.3 冲底孔、落料20

4.4 计算卸料力、推件力20

4.5 初步选用压力机22

5 计算压力中心23

5.1 冲压件的压力中心23

5.2 模具的压力中心23

6 模具的总体结构设计24

6.1 确定模具的定位方式和送料方式24

6.2 卸料与出件方式25

6.2.1 确定卸料方式25

6.2.2 确定顶件方式25

7 确定模具的主要部件26

7.1 垫板的设计26

7.2 设计凹凸模26

7.2.1 校核凹凸模强度及凹模厚度27

7.2.2 确定凹模尺寸28

7.2.3 橡胶的厚度28

7.2.4 墩平装置29

7.3 选定并校核螺钉的强度30

7.3.1 紧固螺钉30

7.3.2 选择卸料螺钉30

7.4 根据模具尺寸选用模架31

7.4.1 选用模架形式31

7.4.2 选用并确定模架31

7.5 选用模柄32

8 确定压力机32

9. 模具零件的材料及其加工工艺34

9.1 选用模具材料34

9.2 模具主要部件的加工工艺35

9.2.1 模具凹、凸模的加工工艺35

9.2.2 凸模固定板的加工工艺36

9.2.3 模架的加工36

9.3 模具的装配37

9.4 模具的总装配37

9.5 模具的经济性分析39

10 结论40

谢辞41

参考文献：42

引言

冲压模具的种类很多，按照工序分有：单工序模、级进模、复合膜；按照冲裁件的精度分有：普通冲裁模、精密冲裁模；按照其尺寸分类有：小型模具、中型模具、大型模具；按照导向形式分有：无导向模具、有导向模具。还有根据模架的不同形式的分类等，或者是以上模具的派生性，根据不同需要而设计的各种形式。

冲压工艺是使用压力机通过冲压模具使材料分离或者是产生塑性变形的、以获得一定形状和尺寸的制品的一种少、无切削加工工艺。因为一般是在常温或者较低的温度下对材料进行加工的，因而也称为冷冲压工艺。也是加工厚度较薄的板状金属材料最常用的加工方法，因此也称为板料成型。主要是应用在金属方面，在非金属领域的使用相对较少。在生产刚开始的时候，虽然设备、模具、厂房等投入成本的很大，但是与其它加工方法（比如锻造、铸造、焊接、铆接、机械切削加工等）相比，有很多优点：制件性能稳定，强度好，材料利用率高，加工效率高等，特别是在大批量生产中更能体现出冲压加工的优越性。冲压工艺主要包括冲裁、拉伸、弯曲、涨形、翻边、扩口、缩口等，本次我研究的课题中的级进模就属于冲压模的一种。

自从计算机在模具行业中的应用以来，人们终止了以前单靠经验和机械绘图来完成模具的设计的历史。计算机辅助设计（CAD）的出现，很大程度地降低了模具设计的成本，也大大地缩短了设计周期、提高了模具设计的质量。促进了模具行业的发展。以及随后发展起来的计算机辅助制造（CAM）、计算机辅助分析工程（CAE），Pro/E、UG等3D软件的应用，特别是现在CAD/CAM/CAE集成软件的应用，在模具设计中发挥着越来越重要的作用。

我国的模具行业在最近的几年才迅速发展起来的，相对其它国家而言，起步很晚，虽然发展很快，目前我国在模具制造中已经取得了很大的成就，甚至在一些方面也达到了世界顶级水平，比如我国精冲模方面的多工位与多功能冲压模具已经达到世界先进水平，不但已经取代进口，还有部分出口到发达国家。

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内容简介：: 编号：毕业设计(论文)任务书题目：风扇轴套环零部件拉伸级进模设计院（系）：应用科技学院专业：机械设计制造及其自动化学生姓名：郑喜华学号： 0701120229 指导教师单位：应用科技学院姓名：曹泰山职称：讲师题目类型：理论研究实验研究工程设计工程技术研究软件开发2011年 1 月 15 日一、毕业设计（论文）的内容、要求内容1、查找相关的资料并阅读消化，明确设计要求，分析该粉料送进装置的设计可能性和经济性等因素。对零件图纸进行结构和工艺分析，设计成型工艺；2、进行市场调查，了解现有粉料送进装置的结构与工作原理，做好设计前的准备工作。3、完成粉料送进装置的结构的总体尺寸设计和结构草图的绘制，模具结构总装图和零件工作图的设计绘制等；4、编制主要零件的制造工艺；合理选用零件的材料，绘制零件图，标注技术要求。5、合理选择相关组件，进行传动系统的设计。要求1、保证粉料送进装置机构的运动达到预期的要求，要求结构紧凑、合理。完成装配图的绘制。进行相关的理论计算。2、完成装配图的绘制。进行相关的理论计算。确定该装置的形状特点并对其进行经济分析。3、尽量选用标准件，常用件、降低成本。二、毕业设计（论文）应完成的工作1、完成装置的结构总体方案设计2、合理选用标准件，完成零件间的配给选用及相关的设计计算。3、用1号图纸手绘粉料送进装置的装配图，采用CAD软件绘制零件图，绘图量达到学院的要求。4、完成二万字左右的毕业设计说明书（论文）；在毕业设计说明书（论文）中必须包括300-500个单词详细的英文摘要；5、独立完成与课题相关，不少于四万字符的指定英文资料翻译（附英文原文）；6、完成导师所指定的其它工作。并附有开题报告一份。三、应收集的资料及主要参考文献1、孙恒编 .机械原理 . 北京 . 高教出版社 . 2002.4 2、大连理工大学 . 机械制图 . 高教出版社 . 2004.9 3、濮良贵 . 机械设计 . 高教出版社 . 2002.1 4、王选逵 . 机械制造工艺学 . 机械工业出版社 . 1998.11 5、周开勤 . 机械零件手册 . 高教出版社 . 2001.76、朱张娇 . 工程材料 . 清华大学出版社 . 2004.77、廖念慈 . 互换性与技术测量 . 计量出版社 . 2001.1 8、ROBERT.NORTON . Design of Machinery . CHIAN MACHINE PRESS . 2001.4 .四、试验、测试、试制加工所需主要仪器设备及条件1、计算机一台进度计划表序号起止日期从2011.1.15开始计划完成内容实际完成内容检查日期检查人签名12011.1.5毕业设计动员并选题2206交开题报告32011.3.1-3.11完成开题并做调研，进行翻译42011.3.11-3.21完成结构设计52011.3.21-4.1绘制结构草图62011.4.1-4.11完成相关计算72011.4.11-4.21完成英文翻译82011.4.21-5.1绘制零件图92011.5.1-5.11绘制装配图102011.5.11-5.21撰写论文112011.5.21-6.1完成毕业设计1220.5到2011.6.5结束修改并打印论文任务下达时间： 2011年 1 月 15 日编号：毕业设计(论文)外文翻译（原文）学院：应用科技学院专业：机械设计制造及其自动化学生姓名：郑喜华学号： 0701120229 指导教师单位：姓名：曹泰山职称：讲师 2011年 5 月 102 日编号：毕业设计(论文)外文翻译（译文）院（系）：应用科技学院专业：机械设计制造及其自动化学生姓名：郑喜华学号： 0701120229 指导教师单位：姓名：曹泰山职称：讲师 2011年 5 月 12 日桂林电子科技大学Int J Adv Manuf Technol (2002) 19:253259 2002 Springer-Verlag London LimitedAn Analysis of Draw-Wall Wrinkling in a Stamping Die DesignF.-K. Chen and Y.-C. LiaoDepartment of Mechanical Engineering, National Taiwan University, Taipei, TaiwanWrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsupported.In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finiteelement simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design.Keywords: Draw-wall wrinkle; Stamping die; Stepped rectangular cup; Tapered square cups1. IntroductionWrinkling is one of the major defects that occur in the sheet metal forming process. For both functional and visual reasons,wrinkles are usually not acceptable in a finished part. There are three types of wrinkle which frequently occur in the sheet metal forming process: flange wrinkling, wall wrinkling, and elastic buckling of the undeformed area owing to residual elastic compressive stresses. In the forming operation of stamping a complex shape, draw-wall wrinkling means the occurrence of wrinkles in the die cavity. Since the sheet metal in the wall area is relatively unsupported by the tool, the elimination of wall wrinkles is more difficult than the suppression of flange wrinkles. It is well known that additional stretching of the material in the unsupported wall area may prevent wrinkling,and this can be achieved in practice by increasing the blankholder force; but the application of excessive tensile stresses leads to failure by tearing. Hence, the blank-holder force must lie within a narrow range, above that necessary to suppress wrinkles on the one hand, and below that which produces fracture on the other. This narrow range of blank-holder force is difficult to determine. For wrinkles occurring in the central area of a stamped part with a complex shape, a workable range of blank-holder force does not even exist.In order to examine the mechanics of the formation of wrinkles, Yoshida et al. 1 developed a test in which a thin plate was non-uniformly stretched along one of its diagonals.They also proposed an approximate theoretical model in which the onset of wrinkling is due to elastic buckling resulting from the compressive lateral stresses developed in the non-uniform stress field. Yu et al. 2,3 investigated the wrinkling problem both experimentally and analytically. They found that wrinkling could occur having two circumferential waves according to their theoretical analysis, whereas the experimental results indicated four to six wrinkles. Narayanasamy and Sowerby 4examined the wrinkling of sheet metal when drawing it through a conical die using flat-bottomed and hemispherical-ended punches. They also attempted to rank the properties that appeared to suppress wrinkling.These efforts are focused on the wrinkling problems associated with the forming operations of simple shapes only, such as a circular cup. In the early 1990s, the successful application of the 3D dynamic/explicit finite-element method to the sheetmetal forming process made it possible to analyse the wrinkling problem involved in stamping complex shapes. In the present study, the 3D finite-element method was employed to analyse the effects of the process parameters on the metal flow causing wrinkles at the draw wall in the stamping of a tapered square cup, and of a stepped rectangular part.A tapered square cup, as shown in Fig. 1(a), has an inclined draw wall on each side of the cup, similar to that existing in a conical cup. During the stamping process, the sheet metal on the draw wall is relatively unsupported, and is therefore prone to wrinkling. In the present study, the effect of various process parameters on the wrinkling was investigated. In the case of a stepped rectangular part, as shown in Fig. 1(b),another type of wrinkling is observed. In order to estimate the effectiveness of the analysis, an actual production part with stepped geometry was examined in the present study. The cause of the wrinkling was determined using finite-element analysis, and an optimum die design was proposed to eliminate the wrinkles. The die design obtained from finite-element analysis was validated by observations on an actual production part.Sketches of (a) a tapered square cup. Sketches of(b) a stepped rectangular cup.Fig. 1.2. Finite-Element ModelThe tooling geometry, including the punch, die and blankholder,were designed using the CAD program PRO/ENGINEER. Both the 3-node and 4-node shell elements were adopted to generate the mesh systems for the above tooling using the same CAD program. For the finite-element simulation,the tooling is considered to be rigid, and the corresponding meshes are used only to define the tooling geometry and are not for stress analysis. The same CAD program using 4-node shell elements was employed to construct the mesh system for the sheet blank. Figure 2 shows the mesh system for the complete set of tooling and the sheet-blank used in the stamping of a tapered square cup. Owing to the symmetric conditions, only a quarter of the square cup is analysed. In the simulation, the sheet blank is put on the blank-holder and the die is moved down to clamp the sheet blank against the blank-holder. The punch is then moved up to draw the sheet metal into the die cavity.In order to perform an accurate finite-element analysis, the actual stressstrain relationship of the sheet metal is required as part of the input data.In the present study, sheet metal with deep-drawing quality is used in the simulations.A tensile test has been conducted for the specimens cut along planes coinciding with the rolling direction (0) and at angles of 45and 90to the rolling direction.The average flow stress ,calculated from the equation =（0+245+90）/4, for each measured true strain,as shown in Fig.3, is used for the simulations for the stampings of the tapered square cup and also for the stepped rectangular cup. All the simulations performed in the present study were run on an SGI Indigo 2 workstation using the finite-element program PAMFSTAMP. To complete the set of input data required for the simulations, the punch speed is set to 10 m s_1 and a coefficient of Coulomb friction equal to 0.1 is assumed.Fig. 2. Finite-element mesh.Fig. 3. The stressstrain relationship for the sheet metal.3. Wrinkling in a Tapered Square CupA sketch indicating some relevant dimensions of the tapered square cup is shown in Fig. 1(a). As seen in Fig. 1(a), the length of each side of the square punch head (2Wp), the die cavity opening (2Wd), and the drawing height (H) are considered as the crucial dimensions that affect the wrinkling.Half of the difference between the dimensions of the die cavity opening and the punch head is termed the die gap (G) in the present study, i.e. G = Wd-Wp. The extent of the relatively unsupported sheet metal at the draw wall is presumably due to the die gap, and the wrinkles are supposed to be suppressed by increasing the blank-holder force. The effects of both the die gap and the blank-holder force in relation to the occurrence of wrinkling in the stamping of a tapered square cup are investigated in the following sections.3.1 Effect of Die GapIn order to examine the effect of die gap on the wrinkling, the stamping of a tapered square cup with three different die gaps of 20 mm, 30 mm, and 50 mm was simulated. In each simulation, the die cavity opening is fixed at 200 mm, and the cup is drawn to the same height of 100 mm. The sheet metal used in all three simulations is a 380 mm 380 mm square sheet with thickness of 0.7 mm, the stressstrain curve for the material is shown in Fig. 3.Fig. 4. Wrinkling in a tapered square cup (G =50 mm).The simulation results show that wrinkling occurred in all three tapered square cups, and the simulated shape of the drawn cup for a die gap of 50 mm is shown in Fig. 4. It is seen in Fig. 4 that the wrinkling is distributed on the draw wall and is particularly obvious at the corner between adjacent walls. It is suggested that the wrinkling is due to the large unsupported area at the draw wall during the stamping process,also,the side length of the punch head and the die cavity openingare different owing to the die gap. The sheet metal stretched between the punch head and the die cavity shoulder becomes unstable owing to the presence of compressive transverse stresses. The unconstrained stretching of the sheet metal under compression seems to be the main cause for the wrinkling at the draw wall. In order to compare the results for the three different die gaps, the ratio of the two principal strains is introduced, being min/max, where max and min are the major and the minor principal strains, respectively. Hosford and Caddell 5 have shown that if the absolute value of is greater than a critical value, wrinkling is supposed to occur, and the larger the absolute value of , the greater is the possibility of wrinkling.The values along the cross-section MN at the same drawing height for the three simulated shapes with different die gaps, as marked in Fig. 4, are plotted in Fig. 5. It is noted from Fig. 5 that severe wrinkles are located close to the corner and fewer wrinkles occur in the middle of the draw wall for all three different die gaps. It is also noted that the bigger the die gap, the larger is the absolute value of . Consequently,increasing the die gap will increase the possibility of wrinkling occurring at the draw wall of the tapered square cup.3.2 Effect of the Blank-Holder ForceIt is well known that increasing the blank-holder force can help to eliminate wrinkling in the stamping process. In order to study the effectiveness of increased blank-holder force, the stamping of a tapered square cup with die gap of 50 mm,which is associated with severe wrinkling as stated above, was simulated with different values of blank-holder force. The blank-holder force was increased from 100 kN to 600 kN,which yielded a blank-holder pressure of 0.33 MPa and 1.98 MPa, respectively. The remaining simulation conditions are maintained the same as those specified in the previous section.（An intermediate blank-holder force of 300 kN was also used in the simulation.）The simulation results show that an increase in the blankholder force does not help to eliminate the wrinkling that occurs at the draw wall.The values along the cross-section compared with one another for the stamping processes with blank-holder force of 100 kN and 600 kN. The simulation results indicate that the _ values along the cross-section MN are almost identical in both cases. In order to examine the difference of the wrinkle shape for the two different blank-holder forces, five cross-sections of the draw wall at different heights from the bottom to the line MN, as marked in Fig. 4, are plotted in Fig. 6 for both cases.It is noted from Fig. 6 that the waviness of the cross-sections for both cases is similar. This indicates that the blank-holder force does not affect the occurrence of wrinkling in the stamping of a tapered square cup, because the formation of wrinkles is mainly due to the large unsupported area at the draw wall where large compressive transverse stresses exist. The blankholder force has no influence on the instability mode of the material between the punch head and the die cavity shoulder.Distance(mm)Fig. 5. -value along the cross-section MN for different die gaps.Fig. 6. Cross-section lines at different heights of the draw wall fordifferent blank-holder forces. (a) 100 kN. (b) 600 kN.4. Stepped Rectangular CupIn the stamping of a stepped rectangular cup, wrinkling occurs at the draw wall even though the die gaps are not so significant.Figure 1(b) shows a sketch of a punch shape used for stamping a stepped rectangular cup in which the draw wall C is followed by a step DE. An actual production part that has this type of geometry was examined in the present study. The material used for this production part was 0.7 mm thick, and the stressstrain relation obtained from tensile tests is shown in Fig. 3.The procedure in the press shop for the production of this stamping part consists of deep drawing followed by trimming.In the deep drawing process, no draw bead is employed on the die surface to facilitate the metal flow. However, owing to the small punch corner radius and complex geometry, a split occurred at the top edge of the punch and wrinkles were found to occur at the draw wall of the actual production part,as shown in Fig. 7. It is seen from Fig. 7 that wrinkles are distributed on the draw wall, but are more severe at the corner edges of the step, as marked by AD and BE in Fig. 1(b).The metal is torn apart along the whole top edge of the punch,as shown in Fig. 7, to form a split.Fig. 7. Split and wrinkles in the production part.Fig. 8. Simulated shape for the production part with split and wrinkles.In order to provide a further understanding of the deformation of the sheet-blank during the stamping process, a finiteelement analysis was conducted. The finite-element simulation was first performed for the original design. The simulated shape of the part is shown from Fig. 8. It is noted from Fig.8 that the mesh at the top edge of the part is stretched significantly, and that wrinkles are distributed at the draw wall,similar to those observed in the actual part.The small punch radius, such as the radius along the edge AB, and the radius of the punch corner A, as marked in Fig.1(b), are considered to be the major reasons for the wall breakage. However, according to the results of the finiteelement analysis, splitting can be avoided by increasing the above-mentioned radii. This concept was validated by the actual production part manufactured with larger corner radii.Several attempts were also made to eliminate the wrinkling.First, the blank-holder force was increased to twice the original value. However, just as for the results obtained in the previous section for the drawing of tapered square cup, the effect of blank-holder force on the elimination of wrinkling was not found to be significant. The same results are also obtained by increasing the friction or increasing the blank size. We conclude that this kind of wrinkling cannot be suppressed by increasing the stretching force.Since wrinkles are formed because of excessive metal flow in certain regions, where the sheet is subjected to large compressive stresses, a straightforward method of eliminating the wrinkles is to add drawbars in the wrinkled area to absorb the redundant material. The drawbars should be added parallel to the direction of the wrinkles so that the redundant metal can be absorbed effectively. Based on this concept, two drawbars are added to the adjacent walls, as shown in Fig. 9, to absorb the excessive material. The simulation results show that the wrinkles at the corner of the step are absorbed by the drawbars as expected, however some wrinkles still appear at the remaining wall. This indicates the need to put more drawbars at the draw wall to absorb all the excess material. This is, however,not permissible from considerations of the part design. Fig. 9. Drawbars added to the draw walls.One of the advantages of using finite-element analysis for the stamping process is that the deformed shape of the sheet blank can be monitored throughout the stamping process, which is not possible in the actual production process. A close look at the metal flow during the stamping process reveals that the sheet blank is first drawn into the die cavity by the punch head and the wrinkles are not formed until the sheet blank touches the step edge DE marked in Fig. 1(b). The wrinkled shape is shown in Fig. 10. This provides valuable information for a possible modification of die design.Fig. 10. Wrinkle formed when the sheet blank touches the steppededge.Fig. 11. Cut-off of the stepped corner.Fig. 12. Simulated shape for the modified die design.An initial surmise for the cause of the occurrence of wrinkling is the uneven stretch of the sheet metal between the punch corner radius A and the step corner radius D, as indicated in Fig. 1(b). Therefore a modification of die design was carried out in which the step corner was cut off, as shown in Fig.11, so that the stretch condition is changed favourably, which allows more stretch to be applied by increasing the step edges.However, wrinkles were still found at the draw wall of the cup. This result implies that wrinkles are introduced because of the uneven stretch between the whole punch head edge and the whole step edge, not merely between the punch corner and the step corner. In order to verify this idea, two modifications of the die design were suggested: one is to cut the whole step off, and the other is to add one more drawing operation, that is, to draw the desired shape using two drawing operations.The simulated shape for the former method is shown in Fig.12. Since the lower step is cut off, the drawing process is quite similar to that of a rectangular cup drawing, as shown in Fig. 12. It is seen in Fig. 12 that the wrinkles were eliminated.In the two-operation drawing process, the sheet blank was first drawn to the deeper step, as shown in Fig. 13(a). Subsequently,the lower step was formed in the second drawing operation, and the desired shape was then obtained, as shown in Fig. 13(b). It is seen clearly in Fig. 13(b) that the stepped rectangular cup can be manufactured without wrinkling, by a two-operation drawing process. It should also be noted that in the two-operation drawing process, if an opposite sequence is applied, that is, the lower step is formed first and is followed by the drawing of the deeper step, the edge of the deeper step,as shown by AB in Fig. 1(b), is prone to tearing because themetal cannot easily flow over the lower step into the die cavity.The finite-element simulations have indicated that the die design for stamping the desired stepped rectangular cup using one single draw operation is barely achieved. However, the manufacturing cost is expected to be much higher for the twooperation drawing process owing to the additional die cost and operation cost. In order to maintain a lower manufacturing cost, the part design engineer made suitable shape changes, and modified the die design according to the finite-elementSimulation result to cut off the lower step, as shown in Fig.12. With the modified die design, the actual stamping die for production was manufactured and the production part was found to be free from wrinkles, as shown in Fig.14.The part shape also agreed well with that obtained from the finiteelement simulation.Fig. 13. (a) First operation and (b) second operation in the two-operation drawing process.Fig. 14. The defect-free production part.In order to further validate the finite-element simulation results, the thickness distribution along the cross-section GH obtained from the simulation result as indicated in Fig. 14,was compared with those measured from the production part.The comparison is shown in Fig. 15. It can be seen in Fig.15 that the predicted thickness distribution by finite-element simulation agrees well with that measured directly in the production part. This agreement confirms the effectiveness of the finite-element analysis.Fig. 15. The simulated and measured thickness distribution along GH.5. Summary and Concluding RemarksTwo types of wrinkling occurring in stamping processes were investigated using finite-element analysis, and the causes for wrinkling were examined and the methods to eliminate such wrinkles were developed.The first type of wrinkling appears at the draw wall in the stamping of a tapered square cup. The occurrence of wrinkling is attributed to the large die gap, which is the difference between the side length of the die cavity opening and the side length of the punch head. The large die gap results in a large unsupported area of sheet metal when the metal is drawn into the die cavity and an unfavourable stretch between the punch head and die cavity shoulder. The large unsupported area of sheet metal is therefore prone to wrinkling. The finite-element simulations show that this type of wrinkling cannot be suppressed by increasing the blank-holder force.Another type of wrinkling investigated occurs in an actual stamping part that has a stepped rectangular geometry. It is found that wrinkling occurs at the draw wall above the step even though the die gap is not sufficiently large. The wrinkling is due to the uneven stretch between the punch head and the step edge, according to the finite-element analysis. Several attempts were made in the die design to eliminate the wrinkling,using finite-element simulations, and an optimum design in which the step was cut off is finally established. The modified die design for eliminating wrinkles was validated by the production of a defect-free production part. The good agreement between the simulation results and those observed in the drawn production part demonstrates the accuracy of the finite-element analysis, and the effectiveness of using finite-element simulations as a substitute for the expensive method of actual die try-outs is thereby confirmed.AcknowledgementsThe authors wish to thank the National Science Council of the Republic of China for the grant NSC-862212-E002028 that made this project possible. They also wish to thank KYM for providing the production part.References1. K. Yoshida, H. Hayashi, K. Miyauchi, Y. Yamato, K. Abe, M.Usuda, R. Ishida and Y. Oike, “The effects of mechanical properties of sheet metals on the growth and removing of buckles dueto non-uniform stretching”, Scientific Papers, Institute of Physics and Chemistry Research, 68, pp. 8593, 1974.2. T. X. Yu, W. Johnson and W. J. Stronge, “Stamping and springback of circular plates deformed in hemispherical dies”, International Journal of Mechanical Sciences, 26, pp. 131148, 1984.3. W. J. Stronge, M. P. F. Sutcliffe and T. X. Yu, “Wrinkling of elasto-plastic circular plates during stamping”, Experimental Mechanics, pp. 345353, 1986.4. R. Narayanasamy and R. Sowerby, “Wrinkling of sheet metals when drawing through a conical die”, Journal of Material Processing Technology, 41, pp. 275290, 1994.5. W. F. Hosford and R. M. Caddell, Metal Forming: Mechanics and Metallurgy, 2nd edn, 1993.Process simulation in stamping recent applications for product and process designW. Thomas*, T. Oenoki and T. AltanAbstractProcess simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of FE-simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts.In industrial applications, there are two objectives for conducting FE-simulations of the stamping process; (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FE-simulations are applied. Pam-Stamp, an incremental dynamic-explicit FEM code released by Engineering Systems Intl, matches the second objective well because it can deal with most of the practical stamping parameters. FAST_FORM3D, a one-step FEM code released by Forming Technologies, matches the first objective because it only requires the part geometry and not the complex process information.In a previous study, these two FE codes were applied to complex-shaped parts used in manufacturing automobiles and construction machinery. Their capabilities in predicting formability issues in stamping were evaluated. This paper reviews the results of this study and summarizes the recommended procedures for obtaining accurate and reliable results from FE simulations.In another study, the effect of controlling the blank holder force (BHF) during the deep drawing of hemispherical, dome-bottomed cups was investigated. The standard automotive aluminum-killed, drawing-quality (AKDQ) steel was used as well as high performance materials such as high strength steel, bake hard steel, and aluminum 6111. It was determined that varying the BHF as a function of stroke improved the strain distributions in the domed cups.Author Keywords: Stamping; Process stimulation; Process designArticle Outline1. Introduction2. Product simulation applications3. Die and process simulation applications4. Blank holder force control applications5. Conclusions and future work1. IntroductionThe design process of complex shaped sheet metal stampings such as automotive panels, consists of many stages of decision making and is a very expensive and time consuming process. Currently in industry, many engineering decisions are made based on the knowledge of experienced personnel and these decisions are typically validated during the soft tooling and prototyping stage and during hard die tryouts. Very often the soft and hard tools must be reworked or even redesigned and remanufactured to provide parts with acceptable levels of quality.The best case scenario would consist of the process outlined in Fig. 1. In this design process, the experienced product designer would have immediate feedback using a specially design software called one-step FEM to estimate the formability of their design. This would allow the product designer to make necessary changes up front as opposed to down the line after expensive tooling has been manufactured. One-step FEM is particularly suited for product analysis since it does not require binder, addendum, or even most process conditions. Typically this information is not available during the product design phase. One-step FEM is also easy to use and computationally fast, which allows the designer to play “what if” without much time investment.Fig. 1. Proposed design process for sheet metal stampings. Once the product has been designed and validated, the development project would enter the “time zero” phase and be passed onto the die designer. The die designer would validate his/her design with an incremental FEM code and make necessary design changes and perhaps even optimize the process parameters to ensure not just minimum acceptability of part quality, but maximum achievable quality. This increases product quality but also increase process robustness. Incremental FEM is particularly suited for die design analysis since it does require binder, addendum, and process conditions which are either known during die design or desired to be known.The validated die design would then be manufactured directly into the hard production tooling and be validated with physical tryouts during which the prototype parts would be made. Tryout time should be decreased due to the earlier numerical validations. Redesign and remanufacturing of the tooling due to unforeseen forming problems should be a thing of the past. The decrease in tryout time and elimination of redesign/remanufacturing should more than make up for the time used to numerically validate the part, die, and process. Optimization of the stamping process is also of great importance to producers of sheet stampings. By modestly increasing ones investment in presses, equipment, and tooling used in sheet forming, one may increase ones control over the stamping process tremendously. It has been well documented that blank holder force is one of the most sensitive process parameters in sheet forming and therefore can be used to precisely control the deformation process.By controlling the blank holder force as a function of press stroke AND position around the binder periphery, one can improve the strain distribution of the panel providing increased panel strength and stiffness, reduced springback and residual stresses, increased product quality and process robustness. An inexpensive, but industrial quality system is currently being developed at the ERC/NSM using a combination of hydraulics and nitrogen and is shown in Fig. 2. Using BHF control can also allow engineers to design more aggressive panels to take advantage the increased formability window provided by BHF control.Fig. 2. Blank holder force control system and tooling being developed at the ERC/NSM labs.Three separate studies were undertaken to study the various stages of the design process. The next section describes a study of the product design phase in which the one-step FEM code FAST_FORM3D (Forming Technologies) was validated with a laboratory and industrial part and used to predict optimal blank shapes. Section 4 summarizes a study of the die design stage in which an actual industrial panel was used to validate the incremental FEM code Pam-Stamp (Engineering Systems Intl). Section 5 covers a laboratory study of the effect of blank holder force control on the strain distributions in deep drawn, hemispherical, dome-bottomed cups.2. Product simulation applicationsThe objective of this investigation was to validate FAST_FORM3D, to determine FAST_FORM3Ds blank shape prediction capability, and to determine how one-step FEM can be implemented into the product design process. Forming Technologies has provided their one-step FEM code FAST_FORM3D and training to the ERC/NSM for the purpose of benchmarking and research. FAST_FORM3D does not simulate the deformation history. Instead it projects the final part geometry onto a flat plane or developable surface and repositions the nodes and elements until a minimum energy state is reached. This process is computationally faster than incremental simulations like Pam-Stamp, but also makes more assumptions. FAST_FORM3D can evaluate formability and estimate optimal blank geometries and is a strong tool for product designers due to its speed and ease of use particularly during the stage when the die geometry is not available.In order to validate FAST_FORM3D, we compared its blank shape prediction with analytical blank shape prediction methods. The part geometry used was a 5in. deep 12in. by 15in. rectangular pan with a 1in. flange as shown in Fig. 3. Table 1 lists the process conditions used. Romanovskis empirical blank shape method and the slip line field method was used to predict blank shapes for this part which are shown in Fig. 4. Fig. 3. Rectangular pan geometry used for FAST_FORM3D validation.Table 1. Process parameters used for FAST_FORM3D rectangular pan validation Fig. 4. Blank shape design for rectangular pans using hand calculations. (a) Romanovskis empirical method; (b) slip line field analytical method.Fig. 5(a) shows the predicted blank geometries from the Romanovski method, slip line field method, and FAST_FORM3D. The blank shapes agree in the corner area, but differ greatly in the side regions. Fig. 5(b)(c) show the draw-in pattern after the drawing process of the rectangular pan as simulated by Pam-Stamp for each of the predicted blank shapes. The draw-in patterns for all three rectangular pans matched in the corners regions quite well. The slip line field method, though, did not achieve the objective 1in. flange in the side region, while the Romanovski and FAST_FORM3D methods achieved the 1in. flange in the side regions relatively well. Further, only the FAST_FORM3D blank agrees in the corner/side transition regions. Moreover, the FAST_FORM3D blank has a better strain distribution and lower peak strain than Romanovski as can be seen in Fig. 6.Fig. 5. Various blank shape predictions and Pam-Stamp simulation results for the rectangular pan. (a) Three predicted blank shapes; (b) deformed slip line field blank; (c) deformed Romanovski blank; (d) deformed FAST_FORM3D blank.Fig. 6. Comparison of strain distribution of various blank shapes using Pam-Stamp for the rectangular pan. (a) Deformed Romanovski blank; (b) deformed FAST_FORM3D blank.To continue this validation study, an industrial part from the Komatsu Ltd. was chosen and is shown in Fig. 7(a). We predicted an optimal blank geometry with FAST_FORM3D and compared it with the experimentally developed blank shape as shown in Fig. 7(b). As seen, the blanks are similar but have some differences.Fig. 7. FAST_FORM3D simulation results for instrument cover validation. (a) FAST_FORM3Ds formability evaluation; (b) comparison of predicted and experimental blank geometries.Next we simulated the stamping of the FAST_FORM3D blank and the experimental blank using Pam-Stamp. We compared both predicted geometries to the nominal CAD geometry (Fig. 8) and found that the FAST_FORM3D geometry was much more accurate. A nice feature of FAST_FORM3D is that it can show a “failure” contour plot of the part with respect to a failure limit curve which is shown in Fig. 7(a). In conclusion, FAST_FORM3D was successful at predicting optimal blank shapes for a laboratory and industrial parts. This indicates that FAST_FORM3D can be successfully used to assess formability issues of product designs. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.Fig. 8. Comparison of FAST_FORM3D and experimental blank shapes for the instrument cover. (a) Experimentally developed blank shape and the nominal CAD geometry; (b) FAST_FORM3D optimal blank shape and the nominal CAD geometry.3. Die and process simulation applicationsIn order to study the die design process closely, a cooperative study was conducted by Komatsu Ltd. of Japan and the ERC/NSM. A production panel with forming problems was chosen by Komatsu. This panel was the excavators cabin, left-hand inner panel shown in Fig. 9. The geometry was simplified into an experimental laboratory die, while maintaining the main features of the panel. Experiments were conducted at Komatsu using the process conditions shown in Table 2. A forming limit diagram (FLD) was developed for the drawing-quality steel using dome tests and a vision strain measurement system and is shown in Fig. 10. Three blank holder forces (10, 30, and 50ton) were used in the experiments to determine its effect. Incremental simulations of each experimental condition was conducted at the ERC/NSM using Pam-Stamp.Fig. 9. Actual product cabin inner panel.Table 2. Process conditions for the cabin inner investigation Fig. 10. Forming limit diagram for the drawing-quality steel used in the cabin inner investigation.At 10ton, wrinkling occurred in the experimental parts as shown in Fig. 11. At 30ton, the wrinkling was eliminated as shown in Fig. 12. These experimental observations were predicted with Pam-stamp simulations as shown in Fig. 13. The 30ton panel was measured to determine the material draw-in pattern. These measurements are compared with the predicted material draw-in in Fig. 14. Agreement was very good, with a maximum error of only 10mm. A slight neck was observed in the 30ton panel as shown in Fig. 13. At 50ton, an obvious fracture occurred in the panel.Fig. 11. Wrinkling in laboratory cabin inner panel, BHF=10ton.Fig. 12. Deformation stages of the laboratory cabin inner and necking, BHF=30ton. (a) Experimental blank; (b) experimental panel, 60% formed; (c) experimental panel, fully formed; (d) experimental panel, necking detail.Fig. 13. Predication and elimination of wrinkling in the laboratory cabin inner. (a) Predicted geometry, BHF=10ton; (b) predicted geometry, BHF=30ton.Fig. 14. Comparison of predicted and measured material draw-in for lab cabin inner, BHF=30ton.Strains were measured with the vision strain measurement system for each panel, and the results are shown in Fig. 15. The predicted strains from FEM simulations for each panel are shown in Fig. 16. The predictions and measurements agree well regarding the strain distributions, but differ slightly on the effect of BHF. Although the trends are represented, the BHF tends to effect the strains in a more localized manner in the simulations when compared to the measurements. Nevertheless, these strain prediction show that Pam-Stamp correctly predicted the necking and fracture which occurs at 30 and 50ton. The effect of friction on strain distribution was also investigated with simulations and is shown in Fig. 17.Fig. 15. Experimental strain measurements for the laboratory cabin inner. (a) measured strain, BHF=10ton (panel wrinkled); (b) measured strain, BHF=30ton (panel necked); (c) measured strain, BHF =50ton (panel fractured).Fig. 16. FEM strain predictions for the laboratory cabin inner. (a) Predicted strain, BHF=10ton; (b) predicted strain, BHF=30ton; (c) predicted strain, BHF=50ton.Fig. 17. Predicted effect of friction for the laboratory cabin inner, BHF=30ton. (a) Predicted strain, =0.06; (b) predicted strain, =0.10.A summary of the results of the comparisons is included in Table 3. This table shows that the simulations predicted the experimental observations at least as well as the strain measurement system at each of the experimental conditions. This indicates that Pam-Stamp can be used to assess formability issues associated with the die design.Table 3. Summary results of cabin inner study 4. Blank holder force control applicationsThe objective of this investigation was to determine the drawability of various, high performance materials using a hemispherical, dome-bottomed, deep drawn cup (see Fig. 18) and to investigate various time variable blank holder force profiles. The materials that were investigated included AKDQ steel, high strength steel, bake hard steel, and aluminum 6111 (see Table 4). Tensile tests were performed on these materials to determine flow stress and anisotropy characteristics for analysis and for input into the simulations (see Fig. 19 and Table 5).Fig. 18. Dome cup tooling geometry.Table 4. Material used for the dome cup study Fig. 19. Results of tensile tests of aluminum 6111, AKDQ, high strength, and bake hard steels. (a) Fractured tensile specimens; (b) Stress/strain curves.Table 5. Tensile test data for aluminum 6111, AKDQ, high strength, and bake hard steels It is interesting to note that the flow stress curves for bake hard steel and AKDQ steel were very similar except for a 5% reduction in elongation for bake hard. Although, the elongations for high strength steel and aluminum 6111 were similar, the n-value for aluminum 6111 was twice as large. Also, the r-value for AKDQ was much bigger than 1, while bake hard was nearly 1, and aluminum 6111 was much less than 1.The time variable BHF profiles used in this investigation included constant, linearly decreasing, and pulsating (see Fig. 20). The experimental conditions for AKDQ steel were simulated us

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