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專 業(yè)：材料成型及控制工程（模具設(shè)計(jì)制造及自動(dòng)化）
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Forming and stamping of sheet metals NC INCREMENTAL SHEET METAL FORMING
Proceedings of International Technology and Innovation Conference 2009
4 Sheet metal forming and blanking
4.1 Principles of die manufacture
4.1.1 Classification of dies
In 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.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 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 conditions 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 several 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 Production steps for the manufacture of an oil sump
Types of dies
The 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 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 sufficiently 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 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 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 automated,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 operation 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 la
Fig.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 spacing 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 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 operations 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 mechanically.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 are 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 bending 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 with 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,wobble 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 nut
4.1.2 Die development
Traditionally the business of die engineering has been influenced by the automotive industry.The following observations about the die development 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 the 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 fundamentally.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 much broader involvement is established well before the actual die development is initiated.
Fig.4.1.6 Time schedule for a mass produced car body panel
The 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 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 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 metal 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 drawing
The data record and the part drawing serve as the basis for all subsequent processing steps.They describe all the details of the parts to be produced. The information given in the
Fig.4.1.7 Timetable for an SE project
part 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 patterns),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 plan and draw development
The 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 sheet metal material,the press to be used,transfer of the parts into the press,the transportation of scrap materials,the undercuts as well as the
sliding 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 first forming stage–if 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,the
forming 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 predicted and analysed interactively on the computer display.
Die design
After 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 possible 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 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 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 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 are designed so that collisions are avoided and a minimum clearance of about 20 mm is set between all the moving parts.
金屬板料的成形及沖裁數(shù)控漸進(jìn)成形研究
技術(shù)與創(chuàng)新國(guó)際會(huì)議論文集2009
4 金屬板料的成形及沖裁
4. 模具制造原理
4.1.1模具的分類
在金屬成形的過程中，工件的幾何形狀完全或部分建立在模具幾何形狀的基礎(chǔ)上的。與機(jī)械加工相比，在成形時(shí)明顯更大的壓力是必要的。由于零件的復(fù)雜性，往往不是只進(jìn)行一次操作就能成形的。根據(jù)零件的幾何形狀，通過由一個(gè)或幾個(gè)生產(chǎn)過程例如成形或沖裁的幾個(gè)操作步驟進(jìn)行生產(chǎn)。一個(gè)操作也可以同時(shí)完成幾個(gè)過程。
在設(shè)計(jì)階段，合理的生產(chǎn)步驟、生產(chǎn)次序以及生產(chǎn)工序數(shù)都由生產(chǎn)計(jì)劃來決定（如圖4.1.1）。在這個(gè)計(jì)劃中，應(yīng)該對(duì)機(jī)器的可利用性、零件的計(jì)劃生產(chǎn)量和其他限制條件予以考慮。
其目的是在保證高水平的操作可靠性的同時(shí)最大限度地減少需要使用的模具數(shù)量。通過部件設(shè)計(jì)部和生產(chǎn)部之間的緊密合作促使幾個(gè)成形和有關(guān)的沖裁過程能在一個(gè)成形操作中完成，如此一來，僅僅在設(shè)計(jì)階段就可以大大地簡(jiǎn)化部件。
顯然，越是更多的操作集成到一個(gè)單獨(dú)的模具上，模具結(jié)構(gòu)就必然更為復(fù)雜。其后果是成本較高、產(chǎn)量下降和可靠性較低。
圖4.1.1 油底殼的生產(chǎn)步驟
模具類型
模具的類型和模具之間零部件的密切相關(guān)運(yùn)輸是根據(jù)成形步驟、預(yù)算的部件的尺寸、要生產(chǎn)的部件的生產(chǎn)量來確定的。
大型鈑金零件的生產(chǎn)幾乎完全采用單套模具來實(shí)現(xiàn)的。典型零件可在汽車制造、國(guó)內(nèi)家電業(yè)以及散熱器的生產(chǎn)中找到。適當(dāng)?shù)霓D(zhuǎn)移系統(tǒng)，例如真空抽吸系統(tǒng)，可以使雙動(dòng)模安裝在一個(gè)足夠大的安裝面上。例如，用這種方式可以使汽車左右車門在一個(gè)工作行程中一起成形。（參考圖4.4.34）。
尺寸大的單套模具需安裝在大型壓力機(jī)上。部件從一個(gè)成形點(diǎn)到另一個(gè)成形點(diǎn)的運(yùn)輸是機(jī)械化地執(zhí)行的。工人或機(jī)器人可以使用與單工序壓力機(jī)一前一后安裝的沖壓線(對(duì)比圖4.4.20與 4.4.22)，同時(shí)，在大型多工位壓力機(jī)上，系統(tǒng)還配備了夾鉗軌（如圖4.4.29）或交叉抽吸系統(tǒng)（如圖4.4.34）來運(yùn)輸部件。
多工位轉(zhuǎn)換模是用于小型和中型零件的大批量生產(chǎn)（如圖4.1.2）。它們由幾個(gè)安裝在同一個(gè)基準(zhǔn)平面上的單工序模具組成。金屬板料的送進(jìn)主要以機(jī)械手運(yùn)送的方式，也可以人工地從一個(gè)模具運(yùn)到另一個(gè)模具。如果這部分的運(yùn)輸自動(dòng)化，那么此時(shí)的壓力就稱為轉(zhuǎn)換壓力。在大板料轉(zhuǎn)換沖壓線上，最大的多工位轉(zhuǎn)換模要與單工序模具配合使用（參考圖4.4.32）。
級(jí)進(jìn)模，也稱為漸進(jìn)沖裁模，鈑金件是分階段沖裁的； 一般來說，沒有實(shí)實(shí)在在的成形操作。鈑金是以金屬圈或金屬條的形式送進(jìn)的。通過使用尺寸適宜的金屬板料和優(yōu)化的材料利用率可以達(dá)到對(duì)板料的合理利用（對(duì)比圖Fig.4.5.2與圖4.5.5）。工件一直固定在載體上，直到最后一次操作。沖裁完成后，整個(gè)條料按照工序流動(dòng)方向移動(dòng)時(shí)，該部件隨著轉(zhuǎn)移。移動(dòng)的長(zhǎng)度等于模具間中心線的距離，它也被稱為步距。切邊，通過使用非常精確的進(jìn)給裝置或試點(diǎn)引腳確保相關(guān)進(jìn)給零件精度。在最后一個(gè)工位，即最后一道工序，已成形的部分于載體斷開。例如電動(dòng)機(jī)金屬轉(zhuǎn)子和定子的生產(chǎn)就是漸進(jìn)沖裁模的一個(gè)應(yīng)用領(lǐng)域（如圖.4.6.11和4.6.20）。
圖4.1.2轉(zhuǎn)移成套模具在機(jī)動(dòng)裝置中的自動(dòng)變速器上生產(chǎn)應(yīng)用
較小的成形部件使用復(fù)合級(jí)進(jìn)模通過幾個(gè)連續(xù)的操作即可完成后生產(chǎn)。與級(jí)進(jìn)模相比，不僅可以完成沖裁，而且能完成成形操作。然而，工件還是與載體相連一直到最后一步操作（如圖4.1.3和對(duì)比圖4.7.2）。由于零件的高度，鋼帶必須提高時(shí)，通常使用起重邊緣或類似的起重設(shè)備，以便實(shí)現(xiàn)條料金屬的機(jī)械化運(yùn)輸。由于其幾何尺寸而不能用一個(gè)金屬條料生產(chǎn)出來的沖壓金屬零件選擇性地在轉(zhuǎn)移設(shè)置上生產(chǎn)。
圖4.1.3 用一個(gè)條料在復(fù)合級(jí)進(jìn)模上生產(chǎn)的汽車加強(qiáng)筋
接下來時(shí)已經(jīng)提到過的模具，一系列特殊模具適用于個(gè)別特殊運(yùn)用。按規(guī)定，這些模具是單獨(dú)使用的。但是，特殊的操作使得特殊的模具集成到一個(gè)工序上成為可能。因此，例如，使用翻邊模幾個(gè)金屬部件組合在一起能積極通過某些區(qū)域的彎曲（如圖4，1，4和對(duì)比圖2，1，34）。在此期間加強(qiáng)部分，膠水或其他組件的運(yùn)作可實(shí)施。
其他的特殊模具使特殊的連接部件直接定位在壓力機(jī)上。裝配和定位部件，例如，引進(jìn)與壓力周期同步的沖頭到指定的位置以便沖頭與鈑金零件（如圖4.1.5）。如果有足夠的可用空間，成形和沖裁操作可以在同一模具上完成。
更一步的例子包括彎曲，滾壓成形，沖壓，精密沖裁，震動(dòng)沖裁和焊接操作（對(duì)比圖4.7.14和圖4.7.15）。
如圖4.1.4卷邊模
如圖4.1.5帶有整體沖壓螺母的沖壓件
4.1.2 模具開發(fā)
汽車行業(yè)的發(fā)展已經(jīng)必然地影響了模具工程的發(fā)展。以下對(duì)與模具開發(fā)的研究主要是關(guān)于車身覆蓋件模具結(jié)構(gòu)的。然而，用一個(gè)基本的環(huán)境獲得實(shí)質(zhì)的結(jié)論，以便于它們適用于包括鈑金成形模和沖裁模的制造在內(nèi)的所有領(lǐng)域。
為汽車覆蓋件的大批量生產(chǎn)定時(shí)生產(chǎn)周期
直到20世紀(jì)80年代末，部分車型以6至8年大致維持不變或略加修改的形式而仍然處于制作中。然而今天，生產(chǎn)周期只有5年或更少（如圖4.1.6）。隨著不同的新設(shè)計(jì)工藝的發(fā)展，客戶對(duì)模具制造商的要求也發(fā)生了根本變化。更大范圍的綜合合同，如同步工程（SE）合同已變得越來越普遍。結(jié)果是，模具制造商往往僅處于金屬零件的最初的發(fā)展階段，以及生產(chǎn)過程的規(guī)劃階段。因此，在實(shí)際模具開發(fā)和啟動(dòng)之前應(yīng)該拓展更廣泛、長(zhǎng)遠(yuǎn)的業(yè)務(wù)。
圖4.1.6 汽車覆蓋件的大批量生產(chǎn)的時(shí)間表
同步工程項(xiàng)目時(shí)間表
在車身覆蓋件的生產(chǎn)過程中，只有極少部分時(shí)間用于模具的制造。對(duì)于大型模具，大約有十個(gè)月的準(zhǔn)備期，其中包括模具的設(shè)計(jì)與調(diào)試。對(duì)于復(fù)雜的同步工程項(xiàng)目中，必須在1.5至2年內(nèi)完成，必須能完成同步任務(wù)。此外，在模具交付前后必須具有更多的產(chǎn)品資料說明。這些短期的準(zhǔn)備需要優(yōu)化的設(shè)計(jì)、特別的技能、可利用空間以及最新技術(shù)的使用和通訊系統(tǒng)。該時(shí)間表顯示，用于生產(chǎn)鈑金件的模具的制造期間的個(gè)人工作內(nèi)容（如圖4.1.7）。大型模具的生產(chǎn)計(jì)劃或多或少都相似，以便于這個(gè)時(shí)間表可以被認(rèn)為是普遍有效的。
圖4.1.7 同步工程項(xiàng)目時(shí)間表
數(shù)據(jù)采集和零件圖
數(shù)據(jù)采集和零件圖是所有工序步驟的基礎(chǔ)。它們描述了要生產(chǎn)部件的所有細(xì)節(jié)。在零件圖提供的信息包括：零件識(shí)別，部件的編號(hào)，板材厚度，板材的質(zhì)量，成品零件的公差等（參考圖4.7.17）。
為了避免實(shí)體模型（主模型）的制作，CAD圖形應(yīng)通過線、面或體積模型來完整地描述工件的幾何形狀。一般地，必須盡可能早地繪制好具有完全封閉曲面的高質(zhì)量片體數(shù)模來滿足所有產(chǎn)品負(fù)責(zé)人的使用要求。
工藝方案和制圖計(jì)劃
工藝方案，即生產(chǎn)鈑金件應(yīng)遵循的操作順序，是根據(jù)以往生產(chǎn)出的零件的經(jīng)驗(yàn)數(shù)據(jù)制定的（參考圖4.1.1）。在此階段，必須提前及時(shí)考慮到各種邊界條件：金屬板材料，所需壓力，零件的加工硬化，廢料的排出，廢料刀以及導(dǎo)料銷的安裝和調(diào)試。
制圖計(jì)劃，即計(jì)算機(jī)輔助設(shè)計(jì)和第一個(gè)成形階段的部件的壓料圈的布局（如果第二個(gè)成形階段也需要）,要求相當(dāng)有經(jīng)驗(yàn)的人來制定（如圖4.1.8）。為了識(shí)別和避免難繪制的區(qū)域，有必要來制造制圖計(jì)劃的實(shí)體分析模型。通過這一模型，可對(duì)所繪制的部件的成形條件進(jìn)行審查和準(zhǔn)確的修改說明，并且這些內(nèi)容最終包含在數(shù)據(jù)采集里（如圖4.1.9）。
智能模擬方法正在一定程度上取代著這一進(jìn)程，通過智能模擬，已成形件的潛在缺陷可以在電腦顯示其綜合預(yù)測(cè)和分析。
圖4.1.8 CAD對(duì)制圖計(jì)劃的數(shù)字分析
圖4.1.9 CAD制圖計(jì)劃實(shí)體分析模型
模具設(shè)計(jì)
工藝方案、制圖計(jì)劃以及沖壓力設(shè)定好后，就可以開始模具的設(shè)計(jì)了。一般規(guī)定，在這個(gè)階段，必須考慮客戶要求的標(biāo)準(zhǔn)和制造規(guī)格。因此，可能獲得一個(gè)統(tǒng)一的模具設(shè)計(jì)標(biāo)準(zhǔn)，并可能考慮客戶關(guān)于存放標(biāo)準(zhǔn)、更換和易磨損部件的特殊要求。許多模具需要通過設(shè)計(jì)來使他們可以安裝在不同類型的壓力機(jī)。
模具往往即可以安裝在一臺(tái)壓力機(jī)上，也可以安裝在兩個(gè)不同的獨(dú)立的后勤壓力機(jī)上。在這種情況下，必須考慮模具鎖模部分，壓腳及廢料板在不同壓力機(jī)上的分布情況。此外，必須指出，拉絲模在單動(dòng)壓力機(jī)的工作時(shí)可能會(huì)在雙動(dòng)壓力機(jī)上安裝（對(duì)比章節(jié)3.1.3和圖4.1.16）。
在模具的設(shè)計(jì)和其尺寸的確定階段，考慮夾鉗和橫木轉(zhuǎn)移部件的運(yùn)動(dòng)的靈活性尤為重要（參考章節(jié)4.1.6）。這些描述了，在一個(gè)完整的工作行程中，壓力傳輸系統(tǒng)組件和模具零部件之間的相對(duì)運(yùn)動(dòng)。壓力機(jī)滑行裝置的上行、夾鉗軌的打開和閉合運(yùn)動(dòng)以及整個(gè)傳輸系統(tǒng)的縱向運(yùn)動(dòng)都是有條不紊的進(jìn)行的。模具通過設(shè)計(jì)來避免發(fā)生碰撞，并且所有運(yùn)動(dòng)部件之間設(shè)置最小約20毫米的間隙。
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