第二章冲裁模的结构与设计

一、课题:Task第二章冲裁模的结构与设计ChapterTwoBlankingdie’sstructureanddesign二、目的要求:Intentionandrequest1．掌握了解冲裁模的冲裁工艺及基本知识。2．清楚了解冲裁过程分析并能够掌握冲裁件的质量分析。3．掌握冲裁间隙的计算、分析及应用。三、重点、难点和突破的方法:Importantpoints、difficultypointsandbreachmethods冲裁工艺。Blankingtechnique.典型冲裁模结构。Typicalblankingdie’sconstructer.冲裁模主要零部件的结构分析与标准的选用。Theconstructeranalysisandstandards’selectionofblankingdie’simportantcomponents.冲裁模设计要点theimportantpointsofblankingdie’sdesign.四、复习提问：Reviewandquestion1、模具间隙正常时，金属板料的冲裁变形过程大致可分为哪三个变形阶段？Wherehas3phasesthemetalsheetmatal’sblankingdistortionprocedure，whenthemouldgapisnormal.2、在正常的冲裁工作条件下，冲裁件断面具有哪四个明显特征区？Wherehasfourevidentearmarkzone’sblankingpiece’ssever,Atthenormalconditionsofblankingwork.五、教具：Teachingaid多媒体multimedia六、作业：Homework习题2.1Exercise2.1七、授课讲义：Classroomteaching第二章冲裁模的结构与设计ChapterTwoBlankingdie’sstructureanddesign使板料分离的冲压工艺称为冲裁。Thestampingtechniquetodividethesheetmataliscalledblanking.Therearevariouskindsofit.suchas,cutdown,punch,pierce,trim,incise,dissectandsoon.冲裁工艺的种类很多，常用的有切断、落料、冲孔、切边、切口、剖切等。Cut、Blanking、Punch、Cuttingedge、Slittingandsoon。冲裁是冲压工艺的最基本工序之一。blankingisonebasicprocedureofstampingtechnique。在冲压加工中应用极广。它既可以直接冲出成品零件，也可以作为弯曲、拉深和挤压等其它工序的坯料，还可以在已成形的工件上进行再加工（切边、切口、冲孔等工序）。2．1冲裁工艺Blankingtechnique.2．1．1冲裁基本知识thebasicknowledgeofBlanking在冲裁工艺中，以落料、冲孔应用最多。Themostuseofitispunchingandpiercing.从板料上冲下所需形状的工件（或毛坯）称为落料。Runintotherequiredtype’sworkpiecefromthesheetmatal(orroughcast)ispunching.在工件上冲出所需形状的孔（冲去的为废料）称为冲孔。Runintotherequiredform’sworkpiece(thewashedthingisscrap)ispierce落料和冲孔的变形性质完全相同，但在进行模具工作部分设计时，要分开加以考虑。Punchingandpiercehavethesamedistortionfeature,butwhendoingthemodelworkdesign,weshoulddistinguishthemtoconsiderthem根据冲裁变形机理的不同，冲裁工艺可以分为普通冲裁和精密冲裁两大类。Accordingtothedifferentdistortionmechanism,blankingtechniquehastwotypesarecommonblankingandexactblanking.普通冲裁:commonblanking是由凸、凹模刃口之间产生剪裂缝的形式实现板料分离。Tomaketheedgeofthemaledieandfemaledieproducetheshearingcrannytoseparatethesheetmatal.精密冲裁:exactblanking是以变形的形式实现板料的分离。Throughthedistortionformtofinishthesheetmatal.前者冲出的工件断面比较粗糙，精度较低。后者冲出的工件不但断面比较光洁而且精度也较高，但需要有专门的精冲设备及精冲模具。Theformer’sworkpiece’sshearingsurfaceismorerough,andthelatterismoreglabrousandtheprecisionishigher,butitneedsspecialpreciseequipmentandmodel.2．1．2冲裁过程分析theprocedureanalysisofblanking凸模1与凹模2具有与工件轮廓一样的刃口。Maledie1andfemaledie2havethesameedgewithworkprofile.凸、凹模之间存在一定的间隙。Maledieandfemalediemustexistencegap.当压力机滑块把凸模推下时，便将放在凸、凹模中间的板料冲裁成所需的工件。当模具间隙正常时，金属板料的冲裁变形过程大致可分为三个变形阶段.Whenthemouldgapisnormal,themetalsheetmatal’sblankingdistortionprocedurehas3phases.（1）弹性变形阶段elasticdistortionphase（2）塑性变形阶段plasticdistortionphase（3）剪裂阶段shearingcrackphase如下图:（1）弹性变形阶段elasticdistortionphase当凸模开始接触板料并下压时，凸模与凹模刃口周围的板料产生应力集中现象，使材料产生弹性压缩、弯曲、拉伸等复杂的变形。Whenthemalediestartstotouchwithsheetmatalandpressitlowly,thesheetmatalwhicharoundthemaledieandfemaledie’sedgeproducethestresscentralphenomena,makethematerialproducetheelasticcompression,bend,extendandsoonthesecomplexdistortion.板料略有挤入凹模洞口的现象。此时，凸模下的材料略有弯曲，凹模上的材料则向上翘。间隙愈大，弯曲和上翘愈严重。随着凸模继续压入，直到材料内的应力达到弹性极限。（2）塑性变形阶段plasticdistortionphase当凸模继续压入，板料内的应力达到屈服点，板料与凸模和凹模的接触处产生塑性剪切变形。Whenthemaledieisgoneonpressfitting,thestressinthesheetmetalwillgettotheyieldpoint,andthetangencyplaceofsheetmetalandmalediewithcavityplatewillhaveplasticsheerdeformation.随着凸模的下压，应力不断加大，直到分离变形区的应力达到抗剪强度，塑性变形阶段结束。Withthemalediebeingpresseddown,thestressgoesonaggrandizing.Theplasticsheerdeformationplacewon’tbefinishedwithseparatedeformedzoneofstressgetstotheshearingstrength.（3）剪裂阶段shearingcrackphase当板料的应力达到抗剪强度后，凸模再向下压，则在板料与凸模和凹模的刃口接触处分别产生裂纹。Aftersheetmatalstressgetstotheshearingintension,themaledieisgoneonbeingpresseddownandthefissurewillbebegotatthetangencyplaceofsheetmetalandmaledie’swithcavityplate’sblademouthapart.随着凸模下压，裂纹逐渐扩大并向材料内延伸。Withthemalediebeingpresseddown,fissureiscometoenlargeandextendedtotheinsideofmaterials.当上、下裂纹重合时，板料便被分离。Whensurfissrueandlay-fissurecoinage,sheetmatalwillbeasundered.凸模再下压，将已分离的材料克服摩擦阻力从板料中推出，完成冲裁过程。Andwithmalediebeingfrictionalressistanceandwillbepushedoutofthesheetmatalandthentheblankingcoursewillbefinished.在正常的冲裁工作条件下，由凸模刃口出发的剪裂缝与由凹模刃口出发的剪裂缝是重合的。这时可以得到如图2.4所示的冲裁件断面，它具有明显的四个特征区。Atthenormalconditionsofblankingwork,theshearfractureslotsarecoinage,whichstartoffthemaledieandcavityplateblademouth.Now,theblankingpiece’sseverpanelisbeingobtainde.Lookatthepicture2-4.Ithasfourevidentearmarkzone’s.（1）圆角带；circleanglezone（2）光亮带；euphoticzone（3）断裂带；fracturezone（4）毛刺。burr2．1．3冲裁件的质量分析blankingpiece’squalityanalysis1．尺寸精度；sizeprecision2．断面质量；breakingsurface’squality3．毛刺。burr2．1．4冲裁间隙blankinggap冲裁间隙是指冲裁凸模和凹模之间工作部分的尺寸之差。如图2.6所示，即blankinggapisthedifferencesizebetweenthemaledieandfemaledie’sworkpart.Lookatthepicture2.6.•Z＝D凹一D凸•如无特殊说明，冲裁间隙一般是指双边间隙。Ifithasnototherspecialillustration,blankinggapisthebilateralgap.小结：本次课主要讲述了冲裁基本知识（thebasicknowledgeofBlanking），冲裁过程分析（theprocedureanalysisofblanking），冲裁间隙blankinggap。重点是（Importantpoints）冲裁间隙blankinggap。