沖裁模結(jié)構(gòu)課件

第2章

沖裁模結(jié)構(gòu)與設(shè)計

ChapterTwoblankingdie’s

structureanddesign

1使板料分離的沖壓工藝稱為沖裁。Thestampingtechniquetodividethesheetmataliscalledblanking.Therearevariouskindsofit.suchas,cutdown,punch,pierce,trim,incise,dissectandsoon.

沖裁工藝的種類很多，常用的有切斷、落料、沖孔、切邊、切口、剖切等。沖裁是沖壓工藝的最基本工序之一。blanking

isonebasicprocedureofstampingtechnique。在沖壓加工中應(yīng)用極廣。它既可以直接沖出成品零件，也可以作為彎曲、拉深和擠壓等其它工序的坯料，還可以在已成形的工件上進行再加工（切邊、切口、沖孔等工序）。2本章要點:importantpointsofthischapterl

沖裁工藝。Blankingtechnique.l

典型沖裁模結(jié)構(gòu)。Typicalblankingdie’sconstructerl

沖裁模主要零部件的結(jié)構(gòu)分析與標準的選用。Theconstructeranalysisandstandards’selectionofblankingdie’simportantcomponentsl

沖裁模設(shè)計要點theimportantpointsofblankingdie’sdesign3本章難點：difficultiesofthischapterl

沖裁工藝。Blankingtechnique.l

沖裁模設(shè)計要點theimportantpointsofblankingdie’sdesign42．1沖裁工藝

Blankingtechnique.

2．1．1沖裁基本知識thebasicknowledgeofBlanking

在沖裁工藝中，以落料、沖孔應(yīng)用最多。Themostuseofitispunchingandpiercing.從板料上沖下所需形狀的工件（或毛坯）稱為落料。Runintotherequiredtype’sworkpiecefromthesheetmatal(orroughcast)ispunching.在工件上沖出所需形狀的孔（沖去的為廢料）稱為沖孔。Runintotherequiredform’sworkpiece(thewashedthingisscrap)ispierce

落料和沖孔的變形性質(zhì)完全相同，但在進行模具工作部分設(shè)計時，要分開加以考慮。Punchingandpiercehavethesamedistortionfeature,butwhendoingthemodelworkdesign,weshoulddistinguishthemtoconsiderthem.52．1．1沖裁基本知識thebasicknowledgeofBlanking62．1．1沖裁基本知識thebasicknowledgeofBlanking

根據(jù)沖裁變形機理的不同，沖裁工藝可以分為普通沖裁和精密沖裁兩大類。Accordingtothedifferentdistortionmechanism,blankingtechniquehastwotypesarecommonblankingandexactblanking.普通沖裁:commonblanking是由凸、凹模刃口之間產(chǎn)生剪裂縫的形式實現(xiàn)板料分離。Tomaketheedgeofthemaledieandfemaledieproducetheshearingcrannytoseparatethesheetmatal.精密沖裁:exactblanking是以變形的形式實現(xiàn)板料的分離。Throughthedistortionformtofinishthesheetmatal.前者沖出的工件斷面比較粗糙，精度較低。后者沖出的工件不但斷面比較光潔而且精度也較高，但需要有專門的精沖設(shè)備及精沖模具。Theformer’sworkpiece’sshearingsurfaceismorerough,andthelatterismoreglabrousandtheprecisionishigher,butitneedsspecialpreciseequipmentandmodel.72．1．2沖裁過程分析theprocedureanalysisofblanking凸模1與凹模2具有與工件輪廓一樣的刃口。Maledie1andfemaledie2havethesameedgewithworkprofile.凸、凹模之間存在一定的間隙。Maledieandfemalediemustexistencegap.當(dāng)壓力機滑塊把凸模推下時，便將放在凸、凹模中間的板料沖裁成所需的工件。82．1．2沖裁過程分析theprocedureanalysisofblanking當(dāng)模具間隙正常時，金屬板料的沖裁變形過程大致可分為三個變形階段.Whenthemouldgapisnormal,themetalsheetmatal’sblankingdistortionprocedurehas3phases.（1）彈性變形階段elasticdistortionphase（2）塑性變形階段plasticdistortionphase（3）剪裂階段shearingcrackphase如下圖:910（1）彈性變形階段elasticdistortionphase

當(dāng)凸模開始接觸板料并下壓時，凸模與凹模刃口周圍的板料產(chǎn)生應(yīng)力集中現(xiàn)象，使材料產(chǎn)生彈性壓縮、彎曲、拉伸等復(fù)雜的變形。Whenthemalediestartstotouchwithsheetmatalandpressitlowly,thesheetmatalwhicharoundthemaledieandfemaledie’sedgeproducethestresscentralphenomena,makethematerialproducetheelasticcompression,bend,extendandsoonthesecomplexdistortion.板料略有擠入凹模洞口的現(xiàn)象。此時，凸模下的材料略有彎曲，凹模上的材料則向上翹。間隙愈大，彎曲和上翹愈嚴重。隨著凸模繼續(xù)壓入，直到材料內(nèi)的應(yīng)力達到彈性極限。11（2）塑性變形階段plasticdistortionphase當(dāng)凸模繼續(xù)壓入，板料內(nèi)的應(yīng)力達到屈服點，板料與凸模和凹模的接觸處產(chǎn)生塑性剪切變形。Whenthemaledieisgoneonpressfitting,thestressinthesheetmetalwillgettotheyieldpoint,andthetangencyplaceofsheetmetalandmalediewithcavityplatewillhaveplasticsheerdeformation.隨著凸模的下壓，應(yīng)力不斷加大，直到分離變形區(qū)的應(yīng)力達到抗剪強度，塑性變形階段結(jié)束。

Withthemalediebeingpresseddown,thestressgoesonaggrandizing.Theplasticsheerdeformationplacewon’tbefinishedwithseparatedeformedzoneofstressgetstotheshearingstrength.12（3）剪裂階段shearingcrackphase當(dāng)板料的應(yīng)力達到抗剪強度后，凸模再向下壓，則在板料與凸模和凹模的刃口接觸處分別產(chǎn)生裂紋。Aftersheetmatalstressgetstotheshearingintension,themaledieisgoneonbeingpresseddownandthefissurewillbebegotatthetangencyplaceofsheetmetalandmaledie’swithcavityplate’sblademouthapart.隨著凸模下壓，裂紋逐漸擴大并向材料內(nèi)延伸。Withthemalediebeingpresseddown,fissureiscometoenlargeandextendedtotheinsideofmaterials.當(dāng)上、下裂紋重合時，板料便被分離。Whensurfissrueandlay-fissurecoinage,sheetmatalwillbeasundered.凸模再下壓，將已分離的材料克服摩擦阻力從板料中推出，完成沖裁過程。Andwithmalediebeingfrictionalressistanceandwillbepushedoutofthesheetmatalandthentheblankingcoursewillbefinished.132．1．2沖裁過程分析theprocedureanalysisofblanking在正常的沖裁工作條件下，由凸模刃口出發(fā)的剪裂縫與由凹模刃口出發(fā)的剪裂縫是重合的。這時可以得到如圖2.4所示的沖裁件斷面，它具有明顯的四個特征區(qū)。Atthenormalconditionsofblankingwork,theshearfractureslotsarecoinage,whichstartoffthemaledieandcavityplateblademouth.Now,theblankingpiece’sseverpanelisbeingobtainde.Lookatthepicture2-4.Ithasfourevidentearmarkzone’s.（1）圓角帶；circleanglezone（2）光亮帶；euphoticzone（3）斷裂帶；fracturezone（4）毛刺。burr

14152．1．2沖裁過程分析theprocedureanalysisofblanking圓角帶1又稱塌角circleanglezone1,hasanalternatenamefallenangle.材料塑性愈好，凸、凹模之間間隙愈大，形成的塌角也就愈大。Theplasticofmaterialisbetter,andthegapbetweenmaledieandcavityplateisbigger,thefallendownanglewillbebigger.光亮帶2euphoticzone2光亮帶垂直于底面。材料塑性愈好，凸模和凹模之間的間隙（圖中Z／2為單邊間隙）愈小，光亮帶的高度愈高。Theeuphoticzoneandthebottonsideareuprightness.Thematerialplasticisbetter,thegap(thegapinz/2isasinglesideone)betweenmaledieandcavityplateissmaller,andthehightofeuphoticzonewillbehigher.162．1．2沖裁過程分析theprocedureanalysisofblanking斷裂帶3fracturedzone3

斷裂帶表面粗糙，并帶有斜度。凸模和凹模的間隙愈大，則斷裂帶高度愈大且斜度也增大。Fracturedzonehasacruditysurfacewithapitch.Thegapbetweenmaledieandcavityplateisbigger,theheightoffracturedzonewillbehigherandthepitchwillbebigger.毛刺4burr4緊挨著剪裂帶的邊緣，是由于裂紋的產(chǎn)生不是正對著凸模和凹模的刃口而是在靠近刃口的側(cè)面。Thatnexttotheedgeofshearfracturezone,iscausefbyfissuregeneration,whichiscloseduptheflankofblademouthbutnotagainstthemaledie’sandcavity’sblademouth.17計算凸模和凹模尺寸的依據(jù)：thegistofcalculationmaledieandfemaledie’ssize對于沖孔件的孔，決定與軸類零件配合性質(zhì)的是它的最小尺寸，即其光亮柱體部分尺寸；對于落料件，決定與孔類零件配合性質(zhì)的是它的最大尺寸，也是它的光亮柱體部分尺寸。Asfortheholeoftherushventpiece,itsleastsizedependsonthecoordinationcyoftheaxlegenusdetails,thatisthedimensionoflustrepolepart;Asforblankingpiece,itsmacrosizedependsonthecoordinationcyofventgenusdetails,thatisthedimensionoflustrepole,too.于是，可以得出如下重要的關(guān)系式:落料尺寸=凹模尺寸punchingsize=femalediesize沖孔尺寸=凸模尺寸piercesize=malediesize182．1．3沖裁件的質(zhì)量分析blankingpiece’squalityanalysis1．尺寸精度；sizeprecision2．?dāng)嗝尜|(zhì)量；breakingsurface’squality3．毛刺。burr191．尺寸精度sizeprecision沖裁件的尺寸精度與許多因素有關(guān)，如沖模的制造精度、材料性質(zhì)、沖裁間隙和沖裁件的形狀等。Thesizeprecisionofblankingpieceisinrelationtolotsoffactors,forexample:（1）沖模的制造精度；die’sconstructiveprecision（2）材料性質(zhì)；materialquality（3）沖裁間隙；blankinggap（4）沖裁件的形狀。blankingpiece’sshape20（1）沖模的制造精度die’sconstructiveprecision沖模的制造精度對沖裁件的尺寸精度有直接影響。沖模的精度愈高，沖裁件的精度亦愈高。Thedie’sconstructiveprecisionhaseffectonblankingpiece’ssizeprecisiondirectly.21（2）材料性質(zhì)materialquality對于比較軟的材料，彈性變形量較小，沖裁后的回彈值也少，因而零件精度較高。而硬的材料，情況正好與此相反。Tothesoftermaterial,elasticdistortionquantityissmaller,andthere-flipvalueissmall,sothecomponentprecisionishigher.22（3）沖裁間隙blankinggap如間隙過大，對于落料件，其尺寸將會小于凹模尺寸，對于沖孔件，其尺寸將會大于凸模尺寸。Ifthegapistoobiggerasforfallenmaterialpiece,itssidewillbesmallerthancavitysize;asforrushventpiece,itssidewillgreaterthanmaledie’s.如間隙過小，對于落料件，其尺寸將會大于凹模尺寸，對于沖孔件，其尺寸將會小于凸模尺寸。Ifthegapistoosmaller,asforfallenmaterialpiec,itssidewillbegreaterthancavitysize;asforrushventpiece,itssidewillsmallerthanmaledie’s.23（4）沖裁件的形狀blankingpiece’sshape沖裁件的形狀越簡單其精度越高。Theeasiertheshapeis,thehighertheprecisionis.242．?dāng)嗝尜|(zhì)量breakingsurfacequality對于斷面質(zhì)量，起決定作用的是沖裁間隙。Toit,it’suptotheblankinggap.在具有合理間隙的沖裁條件下裂紋重合。Undertheconditionofthepropergap’sblanking,thecrackwillbesuperposition.所得沖裁件斷面有一個微小的塌角（theangleofdent），并有正常的既光亮又與板平面垂直的光亮帶(euphoticzone)，其斷裂帶雖然粗糙但比較平坦，雖有斜度但并不大，所產(chǎn)生的毛刺也是不明顯的。25

2．?dāng)嗝尜|(zhì)量breakingsurfacequality26

2．?dāng)嗝尜|(zhì)量breakingsurfacequality當(dāng)間隙過大或過小時，就會使上、下裂紋不能重合。Whenthegapistoobigorsmall,itwillstoptheupperandlowercrackfromsuperposition.（1）間隙過大：thegapistoobig

凸模產(chǎn)生的裂紋相對于凹模產(chǎn)生的裂紋向里移動一個距離。themaledie’sgap

opposite

femaledie’sgapmoveonedistanceoutward.

板料受拉伸、彎曲的作用加大，使剪切斷面塌角加大，光亮帶的高度縮短，斷裂帶的高度增加，錐度也加大，有明顯的拉斷毛刺，沖裁件平面可能產(chǎn)生穹彎現(xiàn)象。

27

2．?dāng)嗝尜|(zhì)量breakingsurfacequality（2）間隙過?。簍hegapistoosmall會使凸模產(chǎn)生的裂紋向外移動一個距離。Itwillmakethemaledie’sgapmoveonedistance.上、下裂紋不重合，產(chǎn)生第二次剪切，由凸模和凹模刃口所產(chǎn)生的裂從而在剪切面上形成了略帶倒錐的第二個光亮帶。在第二個光亮帶下面存在著潛伏的裂紋。由于間隙過小，板料與模具的擠壓作用加大，在最后被分離時，沖裁件上有較尖銳的擠出毛刺。283．毛刺burr沖裁過程的分析可知，沖裁件產(chǎn)生微小的毛刺是不可避免的。Accordingtotheblankingprocedure,itcan’tavoidtheblankingpieceproduceburr.若產(chǎn)品要求不允許存在微小毛刺，則在沖裁后應(yīng)增加去除毛刺的輔助工序。正常沖裁中允許的毛刺高度見表2.2。

Iftheproduct’srequirementisnotallowedtoexistthesmallburr,soweshouldaddtheassistantworkingproceduretoremovetheburr.Theheightofburroftheusualblankingisinthetable2.2.293．毛刺burr若沖裁過程不正常，毛刺就會明顯增大，這是不允許的。產(chǎn)生毛刺的原因主要有兩個，其一是沖裁間隙不合理。Iftheprocedureisnotnormal,theburrwillbecomebigger,it’snotpermitted.Thereare2reasonsofcausingburr,oneofitistheimproperblankinggap.（1）間隙過大，會產(chǎn)生明顯的拉斷毛刺。（2）間隙過小，會產(chǎn)生尖銳的擠出毛刺。(1)Thegapistoobigthatwillsnaptheburrobviously;(2)it’stoosmallthatwillpileouttheburrstridently.303．毛刺burr產(chǎn)生毛刺的原因其二是凸?；虬寄Ｄモg后，其刃口處形成圓角，這是產(chǎn)生毛刺的主要原因。Thesecondreasonisthatproducethecircleangleattheedgeafterabradedthemaledieandthefemaledie.Andthisisthemainreason.當(dāng)凸模和凹模刃口帶有圓角后，沖裁時材料中就減少了應(yīng)力集中現(xiàn)象而增大了變形區(qū)域，產(chǎn)生的裂紋偏離刃口，凸模和凹模間金屬在剪切斷裂前有很大的拉伸，這就使沖裁斷面上產(chǎn)生了明顯的毛刺。

312．1．3沖裁件的質(zhì)量分析blankingpiece’squalityanalysis綜上所述用普通沖裁方法所能得到的沖裁件，其尺寸精度與斷面質(zhì)量都不太高。金屬沖裁件所能達到的經(jīng)濟精度為ITl4~ITl0級，要求高的可達到ITl0~IT8級。厚料比薄料更差。若要進一步提高沖裁件的質(zhì)量，則要在沖裁后加整修工序或采用精密沖裁法。Tosumuptheabovearguments,usecommonblankingmethodgainedblankingware,itssizeprecisionandcutsurfacequalityareallnotvery.Metalblankingware’seconomyaccuracyarecertainlyattainableIT14-IT10.

322．1．4沖裁間隙blankinggap沖裁間隙是指沖裁凸模和凹模之間工作部分的尺寸之差。如圖2.6所示，即blankinggapisthedifferencesizebetweenthemaledieandfemaledie’sworkpart.Lookatthepicture2.6.

Z＝D凹

一D凸如無特殊說明，沖裁間隙一般是指雙邊間隙。Ifithasnototherspecialillustration,blankinggapisthebilateralgap.332．1．4沖裁間隙blankinggap沖裁間隙對沖裁過程有著很大的影響。甚至可以說間隙對沖裁件的質(zhì)量起著決定性的作用。blankinggaphasgreateffectontheblankingprocedure.Andwecansaythatthegaphasthedecisiveeffectontheblankingpiece’squality.除此以外，間隙對模具壽命也有較大的影響。如圖2.7所示是沖裁時作用于模具刃口部分的力。Besidesthat,gapalsohasgreateffectonthedie’susage.Asthepicture2.7hasgivenus.342．1．4沖裁間隙

blankinggap（1）間隙小時：thegapissmall.沖裁過程的擠壓作用加劇，沖裁力F與摩擦力μF增大，使刃口所受壓應(yīng)力增大，造成刃口變形與端面磨損加劇，嚴重時甚至崩刃。加之過小間隙的二次剪切所產(chǎn)生的金屬碎屑因摩擦發(fā)熱粘附在凸模和凹模上又加劇了刃口的磨損。所以，過小間隙會使模具壽命降低。此外，小間隙還使模具制造的難度增加。

Undersizeclearancecanleaddie’slifedown.Andsmallclearancecanleaddifficultyofdie’smanufactureup.352．1．4沖裁間隙blankinggap由沖裁變形過程的分析可知，決定合理間隙值的理論依據(jù)是應(yīng)保證在塑性剪切變形結(jié)束后，由凸模和凹模刃口處所產(chǎn)生的上、下剪切裂紋重合。如圖2.8所示。Accordingtotheblankingdistortionprocedure,thetheorythatdecidethepropergapistomakesuretheedgeofthemaledieandfemaledie’sgapcanbesuperposition.Asthepicture2.8.362．1．4沖裁間隙

blankinggap由圖上的幾何關(guān)系可得：accordingtotherelationshipofthepicture’sgeometry.

Z=2（t–b）tanβ=2t（1–b/t）tanβ式中

t——板料厚度(materialthickness)；b/t——產(chǎn)生裂紋時，凸模壓入板料的相對深度（即光亮帶的相對寬度）；β——最大切應(yīng)力方向與垂線間的夾角。軟鋼(softsteel)β=5o~6o；中硬鋼(mid-hardsteel)β=4o~5o；硬鋼(hardsteel)β=4o。

372．1．4沖裁間隙

blankinggap由上式可以看出，合理間隙值取決于t、b／t、β等三個因素。由于β值的變化不大，所以，影響合理間隙值的大小主要取決于前二個因素，即影響間隙值的主要因素是板料厚度和材料性質(zhì)。Becausetheβvaluehasnotthegreatchange,sotheformer2factorsinfluencethepropergapvalue’ssize,inotherwords,themainfactortoinfluencethegapvaluearethethicknessofthesheetmatalandthequalityofthematerial.板料厚度增大，間隙數(shù)值應(yīng)正比地增大。反之板料愈薄則間隙愈小。

sheetmatal’sthicknessbecomebigger,andthegapvaluealsowillbebiggerwithit.Onthecontrary,ithastheoppositefeature.382．1．4沖裁間隙

blankinggap材料塑性好，光亮帶所占的相對寬度b／t大，間隙數(shù)值就小。而塑性差的硬材料，間隙數(shù)值就大一些。另外，b／t還與板料的厚度有關(guān)。對同一種材料來說，薄料沖裁的b