Impact Printers.docx
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Impact Printers.docx
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ImpactPrinters
ImpactPrinters
Impactprintersrefertoaclassofprintersthatworkbybangingaheadorneedleagainstaninkribbontomakeamarkonthepaper,inasenseimpactingthepaperwithaninkpen.Thisincludesdot-matrixprinters,daisy-wheelprinters,andlineprinters.Itformscharactersorimagesbystrikingamechanismsuchasaprinthammerorwheelagainstaninkedribbon,leavinganimageonpaper.Impactprintersaredyingout.
Impactprintersproduceoutputbystrikingaribbonwithahammer.Whentheribbonishitamarkismadeonthepaperbehindit.
Impactprintersaretheoldesttypeofprintertechnology.Becauseofthehammeringactionimpactprintersarenoisywhentheyareprinting.
∙Cost:
Impactprintersarecheaptobuyandverycheaptorun.
∙Duplication:
Ifcarbonpaperisputintotheprinterthenanimpactprintercanprintmorethanonecopyofadocumentatatime.Thisfeatureisoftenusedbycompanieswhentheyprintinvoices,billsetc.Thecompanycankeeponecopythemselvesandsendtheothercopytothecustomer.
Dot-MatrixPrinters
Thetechnologybehinddot-matrixprintingisquitesimple.Thepaperispressedagainstarubber-coatedcylinderandisintermittentlypulledforwardasprintingprogresses.Theelectromagnetically-drivenprintheadmovesacrossthepaperandstrikestheprinterribbonsituatedbetweenthepaperandprintheadpin.Theimpactoftheprintheadagainsttheprinterribbonimprintsinkdotsonthepaperwhichformhuman-readablecharacters.
Dot-matrixprintersvaryinprintresolutionandoverallqualitywitheither9or24-pinprintheads.Themorepinsperinch,thehighertheprintresolution.Mostdot-matrixprintershaveamaximumresolutionaround240dpi(dotsperinch).Whilethisresolutionisnotashighasthosepossibleinlaserorinkjetprinters,thereisonedistinctadvantagetodot-matrixoranyformofimpactprinting.Becausetheprintheadmuststrikethesurfaceofthepaperwithenoughforcetotransferinkfromaribbonontothepage,itisidealforenvironmentsthatmustproducecarboncopiesthroughtheuseofspecialmulti-partdocuments.Thesedocumentshavecarbonorotherpressure-sensitivematerialontheundersideandcreateamarkonthesheetunderneathwhenpressureisapplied.Thereforesincepressureisappliedtothepaperbytheprintheadthecarbonpaperwouldthenimprintthesametextonthepaperbehindit,almostorexactlylikeareceipt.
∙Dotmatrixprintersarecheaptopurchaseandhavelowoperatingcosts.
∙Mostcanrunineitherdraftmode(quickbutverylowquality)orNearLetterQualitymode(slowerbutbetterquality).
∙Thedisadvantagesofdotmatrixprintersarethattheoutputqualityispoor,ittakesalongtimetoprintadocumentandthenoisecanbeannoying.
Howdoesadotmatrixprinterproduceoutput?
∙Producesanimagebystrikingthepaperthrougharibbon.
∙Itsprintheadconsistsofasmallnumberofpinsvaryingbetween9and24.
∙Astheprintheadmovesacrossthepageoneormorepinsstriketheribbonandmakeadotonthepaper.
Daisy-wheelPrinters
ThetechnologicalconceptbehindDaisy-wheelprintersisquitesimilartothatofamanualtypewriter.Theseprintershaveprintheadscomposedofmetallicorplasticwheelscutintopetals.Eachpetalhastheformofaletterincapitalandlower-case,number,orpunctuationmarkonit.Whenthepetalisstruckagainsttheprinterribbon,theresultingshapeforcesinkontothepaper.Daisy-wheelprintersareloudandslow.Theycannotprintgraphics,andcannotchangefontsunlesstheprintwheelisphysicallyreplaced.Withtheadventoflaserprinters,daisy-wheelprintersaregenerallynotusedinmoderncomputingenvironments.Theyhavebecomeobsolete.
HowdoesaDaisywheelprinterproduceoutput?
∙Thecharacterpatternsareallarrangedaroundtheedgeofawheel.
∙Whenaletteristobeprintedthewheelrotatessothatthecorrectletterislinedupwiththeribbon.
∙Thewheelisthenpressedagainsttheribbontoprintthecharacteronthepaper.
Daisywheelprintersareveryslowandnoisy.Itisnotpossibletoprintgraphicsusingadaisywheelprinter.
LinePrinters
Anothertypeofimpactprinter,somewhatsimilartothedaisy-wheel,isthelineprinter.Themaindifferenceisthatinsteadofaprintwheel,lineprintershaveamechanismthatallowsmultiplecharacterstobesimultaneouslyprintedonthesameline.Themechanismmayusealargespinningprintdrumoraloopedprintchain.Asthedrumorchainarerotatedoverthepaper'ssurface,electromechanicalhammersbehindthepaperpushthepaper(alongwitharibbon)ontothesurfaceofthedrumorchain,markingthepaperwiththeshapeofthecharacteronthedrumorchain.Lineprintersaremuchfasterthandot-matrixordaisy-wheelprinters;however,theytendtobequiteloud,havelimitedmulti-fontcapability,andoftenproducelowerprintqualitythanmorerecentprintingtechnologies.Sincelineprintersareusedfortheirspeed,theyusespecialtractor-fedpaperwithpre-punchedholesalongeachside.Thisarrangementmakescontinuousunattendedhigh-speedprintingpossible,withstopsonlyrequiredwhenaboxofpaperrunsout.Thistypeofprinterisnotusedwithsmallorpersonalcomputers,butisusedwithlargecomputers.Becauseofitshighspeeditisidealforcompanieswherealotofprintinghastobedone.
Non-ImpactPrinters
Thisreferstoasettypeofprinterswhichoperatewithoutstrikingthepaperortheribbon.Thesetypesofprintersarequieterthantheimpactprinters.TherearetwomaintypesofNon-Impactprinters,laserprintersandinkjetprinters.However,thethermalprinterisalsoconsideredasaNon-Impactprinter.
LaserPrinters
Aphotoconductivedrumisinitiallychargedandthenahighintensitylaserbeamisusedtodischargeselectedareasonthedrum.Thesedischargedareascorrespondtothewhiteareasoftheprinteddocument.Tonerisattractedtopartsofthedrumwithahighcharge.Thedrumrotatesandtransfersthetonertothepaperwhichhasanevengreaterelectricalcharge.Finallyaheaterfixesthetonerontothepaper.LaserPrintersusealaserbeamanddrypowderedinktoproduceafinedotmatrixpattern.Theyproducesharp,crispimagesofbothtextandgraphics,providingresolutionsfrom300dpiupto1200dpi.Theyarequitefast.Theyareusedinbothsmallpersonalcomputersandmainframes.Thestandardofprintisverygoodandlaserprinterscanalsoproduceverygoodqualityprintedgraph.
Laserprintershavebuilt-inRAMchipstostoredocuments
outputfromthecomputer.Ifyouareworkingindesktoppublishingandprintingcomplicateddocumentswithcolorandmanygraphics,youwillneedaprinterwithalotofRAM.LaserprintersalsohavetheirownROMchipstostorefontsandtheirownsmalldedicatedprocessor.
Howdoesalaserprinterproduceoutput?
∙Laserprintersarecalledpageprintersbecausetheyprintawholepageatatime.
∙Alaserbeamisusedtodrawtheimagetobeprintedontoalightsensitivedrum.
∙Aftertheimagehasbeendrawnonthedrum,finepowderinkcalledtonerisputontoit.Thetoneronlystickswherethelaserhasdrawntheimage.
∙Thepaperthenpassesoverthedrumandthetoneristransferredontothepaper.
Laserprintersproduceveryhighqualityoutput,areveryquietandveryfast.Typicalhomelaserprinterscanprint8pagesperminute(ppm).Someindustrialversionsprintover40ppmandcanprintonbothsidesofapieceofpaperatthesametime.Themaindisadvantageofthistypeofprinteristhehighcost.
InkJet
Likelaseranddot-matrixprinters,ink-jetprintersalsoformimageswithlittledots.Charactersareformedasaresultofelectricallychargedorheatedinkbeingsprayedinfinejetsontothepaper.Individualnozzlesintheprintingheadproducehighresolution(upto400dotsperinchor400dpi)dotmatrixcharacters.Inkjetprintersusecolourcartridgeswhichcombinered,yellowandblueinkstocreatecolourtones.Thismethodofprintingcangenerateupto200cpsandallowsforgoodquality,cheapcolourprinting.
Aninkjetprinter
Colourcartridgeshowinginkjetnozzles
Howdoesaninkjetprinterproduceoutput?
∙Inkisheldincartridges.Colourprintersusuallyuse4cartridges:
Cyan,magenta,yellowandblack.
∙Dropletsofinkareheatedandforcedontothepage
∙Theyformacharacterorshapefrompatternsofdots.(dpi)
Typicallyinkjetprinterscanproduce360or720dotsperinch(dpi)butthesedotsarelargerthanthosethatalaserprintermakessothequalityalthoughverygoodisnotquiteasperfect.Ink-jetprinterscanworkinblackandwhiteorcolour.Blackandwhiteversionscostfrom£50andcolouronesfromabout£70.Theyareslowerthanlaserprinters(3ppm+)andcostmoretorun.
ThermalPrinters
Charactersareformedbyheatedelementsbeingplacedincontactwithspecialheatsensitivepaperformingdarkeneddotswhentheelementsreachacriticaltemperature.Thermalprinterpapertendstodarkenovertimeduetoexposuretosunlightandheat.Thestandardofprintproducedispoor.Thermalprintersarewidelyusedinbatterypoweredequipmentsuchasportablecalculatorsandalsousedinprinters.
Howdoesathermalprinterproduceoutput?
∙ThermalprintersarenolongerusedasprintersforPCs.Theyarehoweverstillusedinsomecomputercontrolsystems,tillsandinmanyfaxmachines..Thequalityisreasonableandgraphicscanbeprinted.
∙Theseprintersprintonspecialheatsensitivepaper,whichisexpensive.
∙Theimageisproducedfromsmallblackdots,whicharemadeonthepaperbyheatingitup
Plotter
Aplottercanbeusedtoproduce
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