Carding.docx
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Carding.docx
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Carding
Carding
Introduction
Openedandcleanedmaterialsarriveatthecardingstageintheformofsmalltuftscomposedofentangledfibers.Thepurposeofthecardingstageistodisentanglethesetuftsintoacollectionofindividualfibers,thecollectionbeingintheformofaweboffibers,andthentoconsolidatethiscollectionintoasliveroftherequiredcount.Cardingistheactionofreducingtuftsofentangledfibersintoafilmywebofindividualfibersbyworkingthetuftsbetweencloselyspacedsurfacesclothedwithopposingsharppoints.Machinesusedtocarryoutthisworkarecalledcards.
Therearefourmaincardingobjectives,theyare:
(1)Toseparatefibertuftsintoindividualfiberwithaminimumoffiberbreakage;
(2)Toremoveimpuritiesandfiberentanglements;(3)Tomixthefibersintimatelytoprovideauniformdistribution;and(4)Toformabulkysliverofoverlapping,partiallyalignedfibers.
Chutefeedingsystem
Thefibersfromblendingandopeningaredeliveredtothecardintheformofapickerlaporfromachute-fedhopper.Intheearly1960sintheworld,themethodoffeedingfibrousstocktothecardunderwentachangefrompickerlapfeedingtochutefeeding.
Thetransitiontothechutefeedingsystemoccurredrapidlybecauseofseveralbenefitsincludingtheeliminationofthestrenuousmanualtaskofhandlingtheheavylaps,reducedwasteassociatedwithlayinglapsontothecard,andhighproductionrates.Onenegativeaspectofthechutefeedingsystemisthefactthatweightcontrolbyweighingislostwhenthepickerisreplaced.Allofthepickerlapswereweighted,thusgivingacompletercontroloflong-termproductweight.
Thetypicalfiberstockflowarrangementistohaveamachinecalledafineopenerorcardfeederasthefinalmachineunitthatprocessesthestockbeforeitistransportedbymeansofastocktransportfantotheductsystemthatdeliversthestocktothechutes.Thepurposeofthefineopeneristofullyopenthefiberssoitcanslowconsistentlytoandthroughthechutes.Onefineopenerwithtransportfanwilltypicallyfeedstocktoalineof6to10cards.
Thetuftsaretransportedpneumaticallytoeachcardviadistributionducting.Eachcardhasachutefeedsystemconnectedtotheducting.Thefunctionofthechuteistoformamatorfleeceoffiberstobefedintothecard.Therearevariousdesignsofchutefeeds,buttheirworkingprinciplesarebasicallysimilar.Oneimportantchangeforimprovementofthechuteswastheuseofadoublecompartmentinthechutethatseparatedthematformingchamberinthelowerpositionofthechutefromthepressurechangesthatoccurinthetransportductthatisassociatedwiththeupperportionofthechute.Inthismannerthemassofstockinthelowercompartmentcanbemaintainedquiteconsistently.
Diagramofafineopener:
1Condenser,2Dustcage,3Fan,4finnedroller,5Feedingunit,6Lightbarrier,7Feedrollers,8Openingroller,9Grid,10Cleanerunit,11Saw-toothroller,12Pressureroller,13Innerfeedlattice,14Feedrollers,15Moteknife,16Cardingsegment
Rieter’sAerofeedsystemoftransportductstochutes:
1thefineopener,2thestocktransportfan,3pneumaticduct
DiagramoftheFBK533cardchute.1Distributionduct,2Dustextractionduct,3Upperairoutlet,4Materialreservetrunk,5Fan,6Feedroller,7Openingroller,8Controlunit,9Nominalpressureadjustment,11Pressuretransducer,12Feedtrunk,13Lowerairoutlet,14Deliveryrollers,15Cardfeedroller
Diagramofthemainpartsofthetypicalshortstaplecard.
ThefigureshowstheTruetzchlerModel533ExactafeedFBKchute.Thepurposeofthefaninthechuteistokeepaconsistentairpressureonthefibrousstockinthelowermatformingcompartment.Thewhite-filledarrowsinthediagramtracetheairflowcausedbythefan.Gridsinthefrontandbackwallsnearthebottomofthecompartmentallowtheexcessairtoflowuptotheintakeofthecirculatingfan.Thefeedrollerintheupperchutechamberiscausedtoactuatebyapressuresensorlocatedinthelowercompartment.Whenthefeedrollerisnotturning,nostockgetsdeliveredtothemat-formingcompartment.Inthismannerthemassofstockinthelowercompartmentcanbemaintainedquiteconsistently.Theairescapegrids,covertheentirewidthofthelowerchute,anarrangementwhichcausesthestockmasstobepositioneduniformlyfromsidetoside.Ifthestockiswellopenedasitentersthetransportduct,thischutedesignwilldeliveraverysatisfactorymattothecardfeedtable.Thedeliveryrollersatthebottomofthechutearedrivenbyachainlinkagewiththecardfeedroller.Thestockinthechuteiscompressedbyairpressureoranoscillatingperforatedwallplate.Thedeliveryrollersalsoapplysomeadditionalpressurethestockasitisbeingforcedoutofthechute.Therefore,thereisanexpansionofthematasitisreleasedontothecardfeedtable.Theturningofthefeedrollerofthecardtendstopullthematovertableandunderitselfasthematisfedtothecardtaker-in.Becauseoftheseactions,itiscriticalthatthesurfacespeedsofthechutedeliveryrollersandthecardfeedrollerbesetataratiothatwillpreventpressurefrombeingbuiltuponthemat,andpreventthematfrombeingdraftedenoughtocauseshort-termmassvariation.
Opened,mixed,andcleanedfibertuftsaretransportedbyairductsfromthefinalstageoftheOpeningRoomprocessestoachutethatpreparesafibermatforfeedingthecard.Figureshowsthemainpartsofthetypicalshortstaplecard.
Cards
Thecardisthefirstmachineintheyarnmanufacturingprocessthatisdesignedtoproduceacontinuousstrandoffibers.Thepurposeofthecardistoseparatefibersindividually,arrangetheminasomewhatlongitudinaldirection,removecontamination,reassemblethefibersintoacontinuousstrandofuniformweightandquality,andcoilthestrand(sliver)intoacan.
Diagramoftrevolvingcard.
Revolvingflatcardsareusedintheprocessingofcotton.Arevolvingflatcardconsistsofalargerotatingcylindercoveredwithwirepinsorteethandaseriesofflats.Theflatsformanendlessbeltthatrotatesabovethecardcylinder.Thecylinderandtheflatsrotateinthesamedirectionbutatdifferentspeedstoteasethefibersintoathin,filmyweb.Thisisknownascarding.Intheprocess,shortfibersandtrashareremovedanddepositedontheflats.Thefibers,whichremainonthecardcylinder,arepartiallyaligned,sotheirlongitudinalaxesaresomewhatparalleltoeachotherandthelengthofthecardweb.Thethinwebispulledoffthecylinderandgatheredintoasoftmass,whichispulledthroughacone-shapedcondenser,ortrumpet,toproducearopelikestrandcalledasliver.Acottoncardsliverhasnotwistandonlyalittlestrength,providedbytheentanglingoffibers.Thestrengthisadequatetoallowtheslivertobedoffed(removed)intoacanorplacedonaconveyorfortransfertothenextprocessingstep,which,forring-spunandmostrotor-spunyarns,isdrawingordrafting.
Worstedandwoolencardsmaybereferredtoasrollercards.Thesecardsappeartobeanarrangementoflargetandemcylinderswithseveralpairsoflargeandsmallrollerspositionedovereachcylinderandahopperweigh-panfeedertothecard.Werefertothesearrangementsascardingsets.Thefirstcylinderintheset,usuallythesmallestinsize,istermedthebreast,andeachoftheothersaswift.Eachlargeandsmallrollerpositionedoverthebreastorswiftiscalled,respectively,aworkerandastripper.Theworker/stripperunits,incombinationwiththeswift,giveacardingaction,whichturnsthetuftsintomicrotuftletsandfinally,individualfibers.Fibersareremovedfromtheswifttoformthedofferweb.Ontheworstedcard,thedofferwebisremovedeitherbyahigh-speedoscillationcomb(flycomb)orbyredirectingrollersandisthenconsolidatedintoasliver.Whereas,withthewoolensystem,thedofferwebisconvertedintoslubbings.
CardingActions
Cardingistheactionbyworkingthetuftsbetweencloselyspacedsurfacesclothedwithopposingsharppoints.Cardingactionsaredeterminedbythefollowingfactors:
(1)Therelativedirectionofmovementoftherollersurfaces;theymayeithermoveinthesamedirection,orinoppositedirections;
(2)Thedirectionofinclinationofthecardclothingpins,thismaybepointsleadingorbacksleading(seeFig.2-1);(3)Therelativesurfacespeedsofthepointsofthecardclothing;and(4)Thedistancebetweenpointsontheadjacentrollers,thisdistanceiscalledthesetting.
Fig.2-1Theinclinationofthecardclothingpins
Thearrangementsofthefactorsresultinthreebasiccardingactions:
(1)Cardingorworkingaction
Whenitisusedtoopenanddisentanglethefibersitiscalledworkingorcarding.Todisentanglethefibersofthetuftsnowattachedtothefaster-movingsurface,astationaryormuchslowermovingsurface,coveredinsharppoints,isrequiredtobeincloseproximitywiththefastersurface.Themotionoftheslowersurfacemaybeinthesameoropposingdirection,butthesharppointswouldbeangledtoopposethoseoffaster-movingsurface.Thus,point-to-pointgivesthecardingaction.ThetwowaysinwhichthisactionmaybeachievedbetweentwomovingsurfacesareshowninFig.2-2,withtheflowoffibersindicated.
(2)Strippingaction
Thisactionisusedtoconveyallthefibersfromonesurfacetoanother,normallyusingaclosesetting.Usually,apoint-to-backactiongivesthestrippingaction.Smalltuftsattachedtothesharppointsofthebeatercanbeeasilyremovedbyasecondpin-coveredbeaterrotatinginthe
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