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1、 英 文 翻 译4 Sheet metal forming and blanking4.1 Principles of die manufacture4.1.1 Classification of diesIn metalforming,the geometry of the workpiece is established entirely or partially by the geometry of the die.In contrast to machining processes,ignificantly greater forces are necessary in forming
2、.Due to the complexity of the parts,forming is often not carried out in a single operation.Depending on the geometry of the part,production is carried out in several operational steps via one or several production processes such as forming or blanking.One operation can also include several processes
3、 simultaneously(cf.Sect.2.1.4).During the design phase,the necessary manufacturing methods as well as the sequence and number of production steps are established in a processing plan(Fig.4.1.1).In this plan,the availability of machines,the planned production volumes of the part and other boundary co
4、nditions are taken into account.The aim is to minimize the number of dies to be used while keeping up a high level of operational reliability.The parts are greatly simplified right from their design stage by close collaboration between the Part Design and Production Departments in order to enable se
5、veral forming and related blanking processes to be carried out in one forming station.Obviously,the more operations which are integrated into a single die,the more complex the structure of the die becomes.The consequences are higher costs,a decrease in output and a lower reliability.Fig.4.1.1 Produc
6、tion steps for the manufacture of an oil sumpTypes of diesThe type of die and the closely related transportation of the part between dies is determined in accordance with the forming procedure,the size of the part in question and the production volume of parts to be produced.The production of large
7、sheet metal parts is carried out almost exclusively using single sets of dies.Typical parts can be found in automotive manufacture,the domestic appliance industry and radiator production.Suitable transfer systems,for example vacuum suction systems,allow the installation of double-action dies in a su
8、fficiently large mounting area.In this way,for example,the right and left doors of a car can be formed jointly in one working stroke(cf.Fig.4.4.34).Large size single dies are installed in large presses.The transportation of the parts from one forming station to another is carried out mechanically.In
9、 a press line with single presses installed one behind the other,feeders or robots can be used(cf.Fig.4.4.20 to 4.4.22),whilst in large-panel transfer presses,systems equipped with gripper rails(cf.Fig.4.4.29)or crossbar suction systems(cf.Fig.4.4.34)are used to transfer the parts. Transfer dies are
10、 used for the production of high volumes of smaller and medium size parts(Fig.4.1.2).They consist of several single dies,which are mounted on a common base plate.The sheet metal is fed through mostly in blank form and also transported individually from die to die.If this part transportation is autom
11、ated,the press is called a transfer press.The largest transfer dies are used together with single dies in large-panel transfer presses(cf.Fig.4.4.32). In progressive dies,also known as progressive blanking dies,sheet metal parts are blanked in several stages;generally speaking no actual forming oper
12、ation takes place.The sheet metal is fed from a coil or in the form of metal strips.Using an appropriate arrangement of the blanks within the available width of the sheet metal,an optimal material usage is ensured(cf.Fig.4.5.2 to 4.5.5). The workpiece remains fixed to the strip skeleton up until the
13、 laFig.4.1.2 Transfer die set for the production of an automatic transmission for an automotive application-st operation.The parts are transferred when the entire strip is shifted further in the work flow direction after the blanking operation.The length of the shift is equal to the center line spac
14、ing of the dies and it is also called the step width.Side shears,very precise feeding devices or pilot pins ensure feed-related part accuracy.In the final production operation,the finished part,i.e.the last part in the sequence,is disconnected from the skeleton.A field of application for progressive
15、 blanking tools is,for example,in the production of metal rotors or stator blanks for electric motors(cf.Fig.4.6.11 and 4.6.20). In progressive compound dies smaller formed parts are produced in several sequential operations.In contrast to progressive dies,not only blanking but also forming operatio
16、ns are performed.However, the workpiece also remains in the skeleton up to the last operation(Fig.4.1.3 and cf.Fig.4.7.2).Due to the height of the parts,the metal strip must be raised up,generally using lifting edges or similar lifting devices in order to allow the strip metal to be transported mech
17、anically.Pressed metal parts which cannot be produced within a metal strip because of their geometrical dimensions are alternatively produced on transfer sets. Fig.4.1.3 Reinforcing part of a car produced in a strip by a compound die set Next to the dies already mentioned,a series of special dies ar
18、e available for special individual applications.These dies are,as a rule,used separately.Special operations make it possible,however,for special dies to be integrated into an operational Sequence.Thus,for example,in flanging dies several metal parts can be joined together positively through the bend
19、ing of certain metal sections(Fig.4.1.4and cf.Fig.2.1.34).During this operation reinforcing parts,glue or other components can be introduced. Other special dies locate special connecting elements directly into the press.Sorting and positioning elements,for example,bring stamping nuts synchronised wi
20、th the press cycles into the correct position so that the punch heads can join them with the sheet metal part(Fig.4.1.5).If there is sufficient space available,forming and blanking operations can be carried out on the same die. Further examples include bending,collar-forming,stamping,fine blanking,w
21、obble blanking and welding operations(cf.Fig.4.7.14 and4.7.15).Fig.4.1.4 A hemming die Fig.4.1.5 A pressed part with an integrated punched nut4.1.2 Die developmentTraditionally the business of die engineering has been influenced by the automotive industry.The following observations about the die dev
22、elopment are mostly related to body panel die construction.Essential statements are,however,made in a fundamental context,so that they are applicable to all areas involved with the production of sheet-metal forming and blanking dies.Timing cycle for a mass produced car body panel Until the end of th
23、e 1980s some car models were still being produced for six to eight years more or less unchanged or in slightly modified form.Today,however,production time cycles are set for only five years or less(Fig.4.1.6).Following the new different model policy,the demands ondie makers have also changed fundame
24、ntally.Comprehensive contracts of much greater scope such as Simultaneous Engineering(SE)contracts are becoming increasingly common.As a result,the die maker is often involved at the initial development phase of the metal part as well as in the planning phase for the production process.Therefore,a m
25、uch broader involvement is established well before the actual die development is initiated.Fig.4.1.6 Time schedule for a mass produced car body panelThe timetable of an SE project Within the context of the production process for car body panels,only a minimal amount of time is allocated to allow for
26、 the manufacture of the dies.With large scale dies there is a run-up period of about 10 months in which design and die try-out are included.In complex SE projects,which have to be completed in 1.5 to 2 years,parallel tasks must be carried out.Furthermore,additional resources must be provided before
27、and after delivery of the dies.These short periods call for pre-cise planning,specific know-how,available capacity and the use of the latest technological and communications systems.The timetable shows the individual activities during the manufacturing of the dies for the production of the sheet met
28、al parts(Fig.4.1.7).The time phases for large scale dies are more or less similar so that this timetable can be considered to be valid in general.Data record and part drawingThe data record and the part drawing serve as the basis for all subsequent processing steps.They describe all the details of t
29、he parts to be produced. The information given in the Fig.4.1.7 Timetable for an SE projectpart drawing includes: part identification,part numbering,sheet metal thickness,sheet metal quality,tolerances of the finished part etc.(cf.Fig.4.7.17). To avoid the production of physical models(master patter
30、ns),the CAD data should describe the geometry of the part completely by means of line,surface or volume models.As a general rule,high quality surface data with a completely filleted and closed surface geometry must be made available to all the participants in a project as early as possible.Process p
31、lan and draw developmentThe process plan,which means the operational sequence to be followed in the production of the sheet metal component,is developed from the data record of the finished part(cf.Fig.4.1.1).Already at this point in time,various boundary conditions must be taken into account:the sh
32、eet metal material,the press to be used,transfer of the parts into the press,the transportation of scrap materials,the undercuts as well as thesliding pin installations and their adjustment. The draw development,i.e.the computer aided design and layout of the blank holder area of the part in the fir
33、st forming stageif need bealso the second stage,requires a process planner with considerable experience(Fig.4.1.8).In order to recognize and avoid problems in areas which are difficult to draw,it is necessary to manufacture a physical analysis model of the draw development.With this model,theforming
34、 conditions of the drawn part can be reviewed and final modifications introduced,which are eventually incorporated into the data record(Fig.4.1.9). This process is being replaced to some extent by intelligent simulation methods,through which the potential defects of the formed component can be predi
35、cted and analysed interactively on the computer display.Die designAfter release of the process plan and draw development and the press,the design of the die can be started.As a rule,at this stage,the standards and manufacturing specifications required by the client must be considered.Thus,it is poss
36、ible to obtain a unified die design and to consider the particular requests of the customer related to warehousing of standard,replacement and wear parts.Many dies need to be designed so that they can be installed in different types of presses.Dies are frequently installed both in a production press
37、 as well as in two different separate back-up presses.In this context,the layout of the die clamping elements,pressure pins and scrap disposal channels on different presses must be taken into account.Furthermore,it must be noted that drawing dies working in a single-action press may be installed in
38、a double-action press(cf.Sect.3.1.3 and Fig.4.1.16).Fig.4.1.8 CAD data record for a draw development In the design and sizing of the die,it is particularly important to consider the freedom of movement of the gripper rail and the crossbar transfer elements(cf.Sect.4.1.6).These describe the relative
39、movements between the components of the press transfer system and the die components during a complete press working stroke.The lifting movement of the press slide,the opening and closing movements of the gripper rails and the lengthwise movement of the whole transfer are all superimposed.The dies a
40、re designed so that collisions are avoided and a minimum clearance of about 20 mm is set between all the moving parts.4 金属板料的成形及冲裁4. 模具制造原理4.1.1模具的分类在金属成形的过程中，工件的几何形状完全或部分建立在模具几何形状的基础上的。与机械加工相比，在成形时明显更大的压力是必要的。由于零件的复杂性，往往不是只进行一次操作就能成形的。根据零件的几何形状，通过由一个或几个生产过程例如成形或冲裁的几个操作步骤进行生产。一个操作也可以同时完成几个过程。 在设计阶段，
41、合理的生产步骤、生产次序以及生产工序数都由生产计划来决定（如图4.1.1）。在这个计划中，应该对机器的可利用性、零件的计划生产量和其他限制条件予以考虑。其目的是在保证高水平的操作可靠性的同时最大限度地减少需要使用的模具数量。通过部件设计部和生产部之间的紧密合作促使几个成形和有关的冲裁过程能在一个成形操作中完成，如此一来，仅仅在设计阶段就可以大大地简化部件。显然，越是更多的操作集成到一个单独的模具上，模具结构就必然更为复杂。其后果是成本较高、产量下降和可靠性较低。图4.1.1 油底壳的生产步骤模具类型模具的类型和模具之间零部件的密切相关运输是根据成形步骤、预算的部件的尺寸、要生产的部件的生产量来
42、确定的。大型钣金零件的生产几乎完全采用单套模具来实现的。典型零件可在汽车制造、国内家电业以及散热器的生产中找到。适当的转移系统，例如真空抽吸系统，可以使双动模安装在一个足够大的安装面上。例如，用这种方式可以使汽车左右车门在一个工作行程中一起成形。（参考图4.4.34）。尺寸大的单套模具需安装在大型压力机上。部件从一个成形点到另一个成形点的运输是机械化地执行的。工人或机器人可以使用与单工序压力机一前一后安装的冲压线(对比图4.4.20与 4.4.22)，同时，在大型多工位压力机上，系统还配备了夹钳轨（如图4.4.29）或交叉抽吸系统（如图4.4.34）来运输部件。多工位转换模是用于小型和中型零件
43、的大批量生产（如图4.1.2）。它们由几个安装在同一个基准平面上的单工序模具组成。金属板料的送进主要以机械手运送的方式，也可以人工地从一个模具运到另一个模具。如果这部分的运输自动化，那么此时的压力就称为转换压力。在大板料转换冲压线上，最大的多工位转换模要与单工序模具配合使用（参考图4.4.32）。级进模，也称为渐进冲裁模，钣金件是分阶段冲裁的； 一般来说，没有实实在在的成形操作。钣金是以金属圈或金属条的形式送进的。通过使用尺寸适宜的金属板料和优化的材料利用率可以达到对板料的合理利用（对比图Fig.4.5.2与图4.5.5）。工件一直固定在载体上，直到最后一次操作。冲裁完成后，整个条料按照工序流
44、动方向移动时，该部件随着转移。移动的长度等于模具间中心线的距离，它也被称为步距。切边，通过使用非常精确的进给装置或试点引脚确保相关进给零件精度。在最后一个工位，即最后一道工序，已成形的部分于载体断开。例如电动机金属转子和定子的生产就是渐进冲裁模的一个应用领域（如图.4.6.11和4.6.20）。图4.1.2转移成套模具在机动装置中的自动变速器上生产应用较小的成形部件使用复合级进模通过几个连续的操作即可完成后生产。与级进模相比，不仅可以完成冲裁，而且能完成成形操作。然而，工件还是与载体相连一直到最后一步操作（如图4.1.3和对比图4.7.2）。由于零件的高度，钢带必须提高时，通常使用起重边缘或类
45、似的起重设备，以便实现条料金属的机械化运输。由于其几何尺寸而不能用一个金属条料生产出来的冲压金属零件选择性地在转移设置上生产。图4.1.3 用一个条料在复合级进模上生产的汽车加强筋接下来时已经提到过的模具，一系列特殊模具适用于个别特殊运用。按规定，这些模具是单独使用的。但是，特殊的操作使得特殊的模具集成到一个工序上成为可能。因此，例如，使用翻边模几个金属部件组合在一起能积极通过某些区域的弯曲（如图4，1，4和对比图2，1，34）。在此期间加强部分，胶水或其他组件的运作可实施。其他的特殊模具使特殊的连接部件直接定位在压力机上。装配和定位部件，例如，引进与压力周期同步的冲头到指定的位置以便冲头与钣
46、金零件（如图4.1.5）。如果有足够的可用空间，成形和冲裁操作可以在同一模具上完成。更一步的例子包括弯曲，滚压成形，冲压，精密冲裁，震动冲裁和焊接操作（对比图4.7.14和图4.7.15）。如图4.1.4卷边模如图4.1.5带有整体冲压螺母的冲压件 4.1.2 模具开发汽车行业的发展已经必然地影响了模具工程的发展。以下对与模具开发的研究主要是关于车身覆盖件模具结构的。然而，用一个基本的环境获得实质的结论，以便于它们适用于包括钣金成形模和冲裁模的制造在内的所有领域。为汽车覆盖件的大批量生产定时生产周期直到20世纪80年代末，部分车型以6至8年大致维持不变或略加修改的形式而仍然处于制作中。然而今天
47、，生产周期只有5年或更少（如图4.1.6）。随着不同的新设计工艺的发展，客户对模具制造商的要求也发生了根本变化。更大范围的综合合同，如同步工程（SE）合同已变得越来越普遍。结果是，模具制造商往往仅处于金属零件的最初的发展阶段，以及生产过程的规划阶段。因此，在实际模具开发和启动之前应该拓展更广泛、长远的业务。图4.1.6 汽车覆盖件的大批量生产的时间表同步工程项目时间表在车身覆盖件的生产过程中，只有极少部分时间用于模具的制造。对于大型模具，大约有十个月的准备期，其中包括模具的设计与调试。对于复杂的同步工程项目中，必须在1.5至2年内完成，必须能完成同步任务。此外，在模具交付前后必须具有更多的产品
48、资料说明。这些短期的准备需要优化的设计、特别的技能、可利用空间以及最新技术的使用和通讯系统。该时间表显示，用于生产钣金件的模具的制造期间的个人工作内容（如图4.1.7）。大型模具的生产计划或多或少都相似，以便于这个时间表可以被认为是普遍有效的。图4.1.7 同步工程项目时间表数据采集和零件图数据采集和零件图是所有工序步骤的基础。它们描述了要生产部件的所有细节。在零件图提供的信息包括：零件识别，部件的编号，板材厚度，板材的质量，成品零件的公差等（参考图4.7.17）。为了避免实体模型（主模型）的制作，CAD图形应通过线、面或体积模型来完整地描述工件的几何形状。一般地，必须尽可能早地绘制好具有完全
49、封闭曲面的高质量片体数模来满足所有产品负责人的使用要求。工艺方案和制图计划工艺方案，即生产钣金件应遵循的操作顺序，是根据以往生产出的零件的经验数据制定的（参考图4.1.1）。在此阶段，必须提前及时考虑到各种边界条件：金属板材料，所需压力，零件的加工硬化，废料的排出，废料刀以及导料销的安装和调试。制图计划，即计算机辅助设计和第一个成形阶段的部件的压料圈的布局（如果第二个成形阶段也需要）,要求相当有经验的人来制定（如图4.1.8）。为了识别和避免难绘制的区域，有必要来制造制图计划的实体分析模型。通过这一模型，可对所绘制的部件的成形条件进行审查和准确的修改说明，并且这些内容最终包含在数据采集里（如图4.1.9）。智能模拟方法正在一定程度上取代着这一进程，通过