Plasmacutting
Plasmaarccuttingusestheheatofahigh-temperatureplasmaarctolocallymelt(andevaporate)themetalattheincisionoftheworkpiece,andusethemomentumofthehigh-speedplasmatoremovethemoltenmetaltoformtheincisionAkindofprocessingmethod.
NumericalControlTechnology
Inindustrialproduction,metalthermalcuttinggenerallyincludesgascutting,plasmacutting,andlasercutting.Comparedwithgascutting,plasmacuttinghasawidercuttingrangeandhigherefficiency.Thefineplasmacuttingtechnologyisclosetothequalityoflasercuttingintermsofthecuttingsurfacequalityofmaterials,butthecostismuchlowerthanthatoflasercutting.Ithasshowngreatadvantagesinsavingmaterialsandimprovinglaborproductivity.Thishaspromotedthedevelopmentofplasmacuttingtechnologyfrommanualorsemi-automatictonumericalcontrol,andhasbecomeoneofthemaindirectionsofthedevelopmentofnumericalcontrolcuttingtechnology.CNCplasmacuttingtechnologyisahighandnewtechnologythatintegratesCNCtechnology,plasmacuttingtechnology,andinverterpowersupplytechnology.Itsdevelopmentisbasedonthecommonprogressofcomputercontrol,plasmaarccharacteristicsresearch,powerelectronicsandotherdisciplines.mycountry'sCNCcuttingtechnologystartedinthe1980s,andCNCplasmacuttingtechnologystartedevenlater.However,inrecentyears,somedomesticuniversities,scientificresearchunits,andmanufacturershaveconductedresearchonCNCplasmacuttingtechnology,andhavegraduallydevelopedandproducedvariousspecificationsofCNCplasmacuttingequipment,narrowingthegapwithforeignadvancedtechnology
Typeintroduction
Ordinarycutting
Accordingtothemainworkinggasused,itismainlydividedintoargonplasmaarccuttingandoxygenplasmaarccutting.Thereareseveraltypesofoxygenplasmaarccuttingandairplasmaarccutting.Thecuttingcurrentisgenerallybelow100A,andthecuttingthicknessislessthan30mm.
Re-constraintcutting
Accordingtothere-constraintmethodofplasmaarc,itismainlydividedintowaterre-compressedplasmaarccutting,magneticfieldre-constrainedplasmaarccuttingandsoon.Astheplasmaarciscompressedagain,itscurrentdensityandtheenergyofthecuttingarcarefurtherconcentrated,therebyimprovingthecuttingspeedandprocessingquality.
Finecutting
Thecurrentdensityofplasmaarcisveryhigh,usuallyseveraltimesthatofordinaryplasmaarc.Duetotheintroductionoftechnologiessuchasrotatingmagneticfield,thestabilityofthearcisalsoimproved.Improve,therefore,itscuttingaccuracyisquitehigh.Thesurfacequalityoffineplasmacuttingabroadhasreachedthelowerlimitoflasercutting,anditscostisonlyone-thirdofthatoflasercutting.
PrincipleofAirMachine
Composedofanelectriccontrolsystemandanozzle.Theelectriccontrolsystemgeneratesanelectricarcthatiscompressedbycompressedairandsprayedoutfromthenozzle,whichisabitlikethenatureofdioxygenwelding.Thesubsequentarchasahightemperatureoftensofthousandsofdegrees.Inthisway,itcancutnon-ferrousmetalssuchascopper,stainlesssteel,aluminum,etc.,andtheincisionisnarrow.Thetemperatureofthecompressedarcisveryhigh.Usecompressedairtoblowthearcoutofasmallhole.Thearcisionizedair
plasma:asthetemperaturerises,Thegeneralsubstanceisshownassolid,liquidandgasinturn.Theyarecollectivelyreferredtoasthethreestatesofmatter.Whenthetemperatureofthegasrisesfurther,manyorevenallofthemoleculesoratomswilldissociateintoelectronsandpositiveionsduetoviolentcollisionswitheachother.Atthistime,thematterwillenteranewstate,thatis,astatemainlycomposedofelectronsandpositiveions(orpositivelychargednuclei).Thisstateofmatteriscalledplasma,anditcanbecalledthefourthstateofmatter.
Currentdomesticsituation
FlamecuttingandplasmacuttingarethemostcommonapplicationsforplateblankinginChinesefactories.Theequipmentusedincludesmanualblanking,profilingmachineblanking,andsemi-automaticcutting.MachineblankingandCNCcuttingmachineblanking,etc.Comparedwithothercuttingmethods,manualcuttingismorerandom,flexibleandconvenient,anddoesnotrequirespecialsupportingcuttingequipment.However,theshortcomingsofmanualcuttingarealsoobvious.Thecuttingqualityispoor,thesizeerrorislarge,thematerialwasteislarge,theworkloadofthesubsequentprocessingproceduresislarge,andtheworkingconditionsareharsh.Cuttingwithaprofilingmachinecangreatlyimprovethequalityoftheblankingworkpiece,butitmustbepre-processedwithamastermoldsuitablefortheworkpiece,whichisnotsuitableforsingle-piece,small-batchandlarge-scaleblanking.Althoughthesemi-automaticcuttingmachinereducesthelaborintensityofworkers,itsfunctionissimpleandonlysuitableforcuttingofoneshape.Theabovethreecuttingmethodsarestillwidelyusedinsmallandmedium-sizedenterprisesinmycountryandeveninsomelarge-scaleenterprisesduetothelowerequipmentcostandsimpleoperationcomparedwithCNCcutting.
Withthevigorousdevelopmentofthedomesticeconomicsituationandtheaccelerationofthetrendofreplacingcastingwithwelding,theadvantagesofCNCcuttingaregraduallybecomingIthasimprovedandimprovedthelaborenvironmentofworkers,andlaborefficiencyhasbeenfurtherimproved.Atpresent,theCNCcuttingmachinesusedinChina'smetalprocessingindustryaremainlyflameandordinaryplasmacuttingmachines,butpureflamecuttingcannolongermeettheneedsofmodernproduction.Atpresent,mostoftheCNCcuttingmachinesindemandinthemarketareCNCplasmacuttingmachines.Thistypeofcuttingmachinecanmeettheneedsofcuttingmetalplatesofdifferentmaterialsanddifferentthicknessesandprocessingmetalparts,sothedemandwillbeincreasing.However,thegapwithforeigncountriesisstillveryobvious.Themainmanifestationsare:90%ofthemetalprocessingindustryindevelopedcountriesiscuttingbyCNCcuttingmachines,andonly10%iscuttingbyhand;whilethecuttingofCNCcuttingmachinesinChinaonlyaccountsfor10%ofthetotalcutting.%,amongwhichtheproportionofCNCplasmacuttingissmaller.Thereasonisthatthehigherequipmentcost,complexityandmaintenanceandoperationrestrictthefurtherpopularizationofCNCcuttinginourcountry.Therefore,domesticCNCcuttingmachinemanufacturershaveintroducedforeigncontrolThesystemtechnologywasappliedtothecuttingfieldaftersecondarydevelopment,andaCNCcuttingmachinesuitableforChina'snationalconditionswasdesigned.ThespecialCNCcuttingequipmentdevelopedandproducedbysomemanufacturershasreachedorsurpassedsimilarforeignproductsintechnology.
TheannualmarketdemandforCNCcuttingmachinesinChinaisabout30,000-35,000,andtheproductsaremainlyCNCplasmacuttingmachines.Incomparison,theannualsalesofprofilingcuttingmachinesareseveralthousand,semi-automaticcuttingmachinesItsellstensofthousandsofunitseveryyear.ItcanbeseenthatthedevelopmentpotentialofChina'sCNCcuttingmarket,especiallytheCNCplasmacuttingmarket,ishuge.
Cuttingpowersupply
ItwasoriginallyappliedinChina.Manyhigh-leakagetransformersandsecondary-siderectifiercuttingmachinepowersupplieshavebeengraduallyreplacedbyinverterplasmacuttingpowersupplies.Mostdomesticplasmapowersuppliesareusedformanualcuttingandequippedwithtrolleycuttingmachines.Inrecentyears,duetoimprovedperformance,TheinverterplasmacuttingpowersupplyadoptsadvancedIGBTinvertertechnology.Ithastheadvantagesofsmallsize,lightweight,lownoise,lowpowerconsumptionandconvenientcarrying.Simpleoperation,fastcuttingspeed,narrowandsmoothcut,andsmalldeformationoftheworkpiece.Safetouseandhighreliability.Itisequippedwithautomaticprotectionfunctionssuchasovervoltage,undervoltage,overcurrentandoverheating.Itisgraduallyreplacingtraditionaloxyacetylenecutting
Currentsituationanddevelopment
ComputertechnologyTherapiddevelopmentofCNCtechnologyhaspromotedtheupgradingofCNCtechnology,andthishasalsoincreasinglyimprovedthehigh-precision,high-speed,andhigh-efficiencyfunctionsofCNCplasmacutting.CNCsystemmanufacturersinEurope,theUnitedStates,andJapan,whichrepresenttheworld’sadvancedlevel,usetherichsoftwareofindustrialcomputersThenewgenerationofCNCsystemdevelopedbyhardwareresourceshasanopenarchitecture,thatis,thedevelopmentofCNCsystemcanbeonaunifiedoperatingplatform,facingendusers,bychanging,addingortailoringstructuralobjects(numericalcontrolfunctions)toformserialization,andConvenientlyconnectusersThespecialapplicationsandtechnicalknow-howareintegratedintothecontrolsystemtoquicklyrealizethedevelopmentofdifferentvarietiesanddifferentgradesofproducts.TheopenarchitecturemakestheCNCsystembetterversatility,flexibility,adaptability,andexpandability.Thedirectionofdevelopment.
Currently,theopensystemhastwobasicstructures:
CNC+industrialcomputermotherboard
InsertanindustrialcomputermotherboardintothetraditionalIntheCNCmachine,theindustrialcontrolboardismainlyusedforreal-timecontrol,andtheCNCismainlyusedforreal-timecontrolbasedoncoordinateaxismovement.
Industrialcomputer+motioncontrolboard
Insertthemotioncontrolboardintothestandardslotoftheindustrialcomputerforreal-timecontrol,andtheindustrialcomputerismainlyusedfornon-Real-timecontrol.
TheCNCsystemsofCNCplasmacuttingmachinesproducedinmycountryaremostlydevelopedindependentlybasedontheintroductionofforeignCNCtechnology,andgraduallyformedaCNCsystemthatismoreadaptabletodomesticusers.Generallyspeaking,thenumericalcontrolsystemhasthebasicfunctionsofsimilarforeignsystems,butcomparedwithforeignadvancednumericalcontrolsystems,itstillhaserrorrecords,networkedproduction,andfullyautomatedproduction.Biggap.
Anti-interferencemeasures
Thecuttingpowersupplyhasstrongelectromagneticinterference,whichrequiresthecomputercontrolsystemtohaveahighanti-interferenceability,whichcanresistthehighfrequencyofplasmaignition.Interferencecanalsoresisttheinterferenceofhigh-currentplasmaarcatwork,andalsoresistothersourcesofinterferenceattheworksite.Throughtheanti-interferencedesign,thereliabilityoftheCNCplasmacuttingsystemisimproved,anditsfailurerateisalsoreduced.
Domesticandforeigntrends
ForeignmanufacturersofCNCcuttingmachinesaremainlyconcentratedinGermany,theUnitedStatesandJapan.Fromthepointofviewofmechanicalstructure,itsdevelopmenthasgonethroughthreestagesofcrosstype(lighttype),doortype(small),andgantrytype(large),withawidevarietyofcorrespondingmodels.ManufacturersthatcanrepresentthehighestlevelofCNCplasmacuttingtechnologyaremainlyconcentratedinGermany.Forexample,thecuttingaccuracyofthefineplasmacuttingmachineofGermanESABhasreachedthelowerlimitoflasercutting.Atpresent,foreignmanufacturershaveinstalledaspecialcuttingmanipulatoronthegantrycuttingmachine.Agantry-typespecialcuttingtoolwithafive-axiscontrolsystemwasdeveloped.Thesystemcancutvarioustrajectoriesinspaceanduseaspecialtrackingprobetocontrolthecuttingtrajectoryduringthecuttingprocess.Incontrast,althoughthecross-type,door-type,andgantry-typeareproducedinChina,thebreadthisnotenough.Themanufacturer'sproductmodelisrelativelysingle,andthereisnogantry-typespecialprofilecuttingmachineproduct.
Inrecentyears,duetohigherandhigherrequirementsforcuttingqualityandlaborenvironment,foreignadvancedplasmacuttingtechnologiessuchaslarge-scaleunderwaterplasmacuttingandfineplasmacuttinghavedevelopedrapidly.Themarketdemandforcorrespondingproductsinourcountryisalsoincreasingyearbyyear.Inmycountry'splasmacuttingequipmentproductionindustry,duetothelackofamechanismfortheconversionofplasmacuttingtheoryresearchandproductionpractice,newtechnologiesarenotwidelyusedandnewproductdevelopmentisnotfast,whichrestrictsthefurtherdevelopmentandapplicationofplasmacuttingtechnology.
ItisforeseeablethatthemarketdemandforCNCcuttingmachinesinmycountrywillstillbedominatedbyCNCplasmacuttingmachines.Atthesametime,themarketdemandforlarge-scaleunderwaterplasmacutting,fineplasmacuttingandotheradvancedcuttingequipmentwidelyusedinforeigncountriesisincreasingyearbyyear.
FromtheperspectiveofthedevelopmenttrendoftheforeignCNCplasmacuttingindustry,intelligentprecisioncuttingwillbecomethefuturedevelopmentdirectionofthecuttingindustry.mycountry'ssteeloutputhasalreadyreached100milliontons,coupledwiththevigorousdevelopmentofthemanufacturingindustry,thiswillsurelypromotethesounddevelopmentofdomesticCNCplasmacuttingtechnology.Generallyspeaking,mycountry'sCNCplasmacuttinghasreachedthelevelofsimilarforeignproductsinbasicfunctions,butthereisstillalongwaytogotofullymeetorexceedtheforeignlevel.Domesticenterprisesandscientificresearchunitsshouldincreasescientificresearch,attachimportancetohorizontalcooperationbetweenenterprises,formcomplementaryadvantages,andstriveforfurtherimprovementinthefollowingaspects:
a.Thecorrelationbetweenplasmatheoreticalresearchandproductionshouldbestrengthened;
b.Plasmapowersupplyshouldfurtherimproveitsstability;
c.ActivelydevelopeconomicalandreliableCNCplasmacuttingequipmentsuitableformycountry'snationalconditions;
d.Theman-machinedialogueinterfaceisfriendly,suitableforcuttingandcuttingworkerstooperate;
e.Networkinterconnectionfunction.
Cuttingquality
CNCplasmacuttingmachineisakindofadvancedmechatronicsequipmentusedforblankingandcuttingofsheetmetal.Ithasbeenwidelyusedinshipbuilding,machinerymanufacturingandotherindustries..TherearemanyfactorsthataffectthecuttingqualityofaCNCplasmacuttingmachine.Inadditiontothedesignparametersofthecuttingmachine,itisalsorelatedtooperationcontrolandcuttingtechnology.Inordertoimprovethecuttingquality,wecarriedoutacomprehensivecuttingtest,analyzedandsortedoutthetestdata,andobtainedsomeofthebestworkingparametersoftheCNCplasmacuttingmachine.Thedescriptionisasfollows:
1.ThecharacteristicsandqualityevaluationofCNCplasmacutting
TheCNCplasmacuttingmachinecancutallkindsofcomplicatedshapes,andithasfastcuttingspeed,Highefficiency,goodcuttingsurfacequality,accuratecuttingsize,andsmallthermaldeformationoftheworkpiece.Thecutpartscanbeweldedandapplieddirectlywithoutmachining.However,theCNCplasmacuttingmachineusesplasmaarctocut.Comparedwithoxygencutting,itstillhascertaindefects,mainlyreflectedinthelargerinclinationofthecuttingsurface,andthefinishisnotasgoodasoxygencutting.
ThemaincriteriaforevaluatingthequalityofCNCplasmacuttingare:theinclinationofthecuttingsurface,thedepthofthecutpattern,andtheamountofdross.Theinclinationofahigh-qualitycuttingsurfaceshouldbelessthan30,thecuttingdepthshouldbelessthan0.15mm,andthereislessdross,whichiseasytoremove.
Undertheconditionsofstablevoltageandcurrent,inadditiontothequalityoftheelectrodeandthenozzleitself,thefactorsthataffectthecuttingqualityaremainlyduetotworeasons:oneistheheightandstabilityofthecuttingnozzle;theotheristhecuttingspeedMatchwithworkingpressure.
Whentheheightofthecuttingnozzlefromthesteelplateiscontrolledbyanarcvoltageheightregulator,itsdynamicpositioningaccuracycanreach±0.013mm.Therefore,theheightofthecuttingnozzleandthesteelplatecanbekeptunchanged,sotheinclinationofthecuttingsurfaceissmallanduniform,andthesmoothnessisgood.Whenadjustingtheheightofthecuttingnozzlefromthesteelplatebyhand,thesteelplatetobecutshouldbeplacedasflataspossibletoreducethenumberoftimesoftorchadjustmentandensurethestabilityofthetorchcuttingprocess.Inthispaper,manualadjustmentisusedtocontroltheheightofthecuttingnozzlefromthesteelplateto6-8mm.Throughaseriesofcuttingtests,therelationshipbetweencuttingspeed(mouth),workingairpressure(P)andcuttingqualityisexplained.
2.Testmethod
ThetestequipmentisCNC-3000CNCplasmacuttingmachineproducedbyNandaiUniversityLanguangElectromechanicalEquipmentCo.,Ltd.,equippedwithLG-100K,LG-120K,LG-160KandLG-200Kfourtypesofairplasmacuttingmachineswithdifferentpowers,oneeach,eachmodelhassixsetsofelectrodesandnozzles.
InstallthecuttingtorchesofthefourairplasmacuttingmachinesonthecuttingtrolleyoftheCNCcuttingmachineinsequence.Eachtypeofairplasmacuttingmachinemustcompletethewholeprocessofalltestsseparately,thatis,usedifferentcuttingspeedsanddifferentairpressurestocutA3steelplatesofdifferentthicknesses(cooledwithtapwater).Cuttingiscarriedoutgraduallyfromlowairpressuretohighairpressure,fromlowspeedtohighspeed.Theairpressureiscontrolledbythefiltercontrolvalve,andthecuttingspeediscontrolledbytheCNCcuttingmachine.Thecuttingpartisasquarepartof100mmxl00mm.
3.Testresultsandanalysis
Thetestresultsoftwodifferentthicknesssteelplatesof6mmand10mmwithLG-IOOKairplasmacuttingmachineareshowninTable1.Duetotoomuchtestdata,thetestdataforcuttingsteelplatesofotherthicknesseswiththismachine,andthetestdataforcuttingwithLG-120K,LG-160K,andLG-200Kmachinesarenotlistedonebyone.Thediagramwillbeusedbelow.Waytoexpressit.
TablelLG-100Kairplasmacuttingmachinecuttingtestresults
FromtheresultsofTable1,itcanbeseenthatH{,whenthecuttingspeedistoohighandtheairpressureistoolow,theinclineofthecuttingsurfaceDegreeisgreat.Thisisbecausethespeedistoofastandthearccolumnisseverelytiltedbackwardsandtheslitcannotkeepup.Therefore,thesizeofthepartstobecut,thesizeofthelowerplaneislarge,especiallywhencuttingrightangles...thebottomofthecornerisslitintoacirculararcshape,notarightangleshape.Ifthecuttingspeedistoolowandtheairpressureistoohigh,thedrosswillbeserious,difficulttoremove,andthefinishwillbepoor.Ifthecuttingspeedisappropriate,theworkingairpressureistoohigh.Thestiffnessandroundnessofthearccolumnaredamaged,thecuttingabilityisreduced,andthecuttingfinishispoor.Therefore,tocutsteelplatesofdifferentthicknesses,differentcuttingpower,cuttingspeedandworkingairpressureneedtobeselectedreasonablytogetthebestcuttingeffect.
FromthedatainTable1,itcanalsobeseenthatⅡndifferentsteelplatethicknesseshavedifferentoptimalcuttingspeedsandworkingairpressures.Weanalyzedandsortedoutthetestdataoffourdifferenttypesofmodels,andplottedthebestcuttingspeedandTastheairpressureparametercurvegraphsofdifferentpowerplasmacuttingmachinesforcuttingsteelplatesofdifferentthicknesses,asshowninFigure1.Fig.1Correspondingdiagramofthebestcuttingparametersofdifferentpowercuttingmachines
Accordingtothetestresultsoffourdifferentpowermodels,thebestcuttingparametersofdifferentpowercuttingmachinesforcuttingsteelplatesofdifferentthicknessesareobtainedasshowninTable2.Shown.Accordingtothesedata,wehavecarriedoutpracticalapplicationcuttinginsomemanufacturers,andtheeffectisverygood?Thecuttingqualityisgreatlyimproved.
Maintenancemethod
1.Ensurethecorrectpressureandflowofplasma
Thecorrectpressureandflowofplasmaareveryimportanttotheservicelifeofconsumables.Iftheairpressureistoohigh,thelifeoftheelectrodewillbegreatlyreduced;iftheairpressureistoolow,thelifeofthenozzlewillbeaffected.Refertotheinstructionmanualoftheplasmacuttingmachinewhensetting.
2.Useareasonablecuttingdistance
Thecuttingdistanceisthedistancebetweenthecuttingnozzleandthesurfaceoftheworkpiece.Thisdistanceshouldbekeptasconstantaspossible,generallyaround3-8MM.Ifthepoweristoolarge,thecuttingandpenetrationabilitywillbereduced,andtheelectrodewillberelativelyconsumed,whichwillreducetheelectrodelife;ifitistooclose,itwillbesimplerandveryexpensivenozzles.Thelifeofthenozzlewillbedoubled,evenwhenitisinstalled.Burnout;whenperforating,trytousetwicethedistanceofthenormalcuttingdistanceorusethemaximumheightthattheplasmaarccandeliver.
3.Theperforationthicknessandcuttingthicknessshouldbewithintheallowablerangeofthemachinesystem
Theplasmacuttingmachinecannotperforatethesteelplatethatexceedstheworkingthickness.Theusualperforationthicknessisthenormalcuttingthickness1/2of.Trytocutwithintheratednormalcuttingthicknessrangeoftheplasmacuttingmachine,andtrynottocutatthelimitcuttingthickness.Thenormalcuttingthicknessofthedomesticcuttingmachineisgenerally60%ofthemaximumcuttingthicknessmarkedbytheproduction,andtrytocutwithinthisthicknessrange.Canbestprotectthecuttingnozzle.
4.Donotoverloadthenozzle
Letthenozzleoverload(thatis,exceedtheworkingcurrentofthenozzle),whichwillquicklydamagethenozzle.Thecurrentintensityshouldbe95%oftheworkingcurrentofthenozzle.Forexample:thecurrentintensityofa100Anozzleshouldbesetto95A.
5.Keeptheplasmagasdryandclean
Theplasmasystemneedsdryandcleanplasmagastoworkproperly.Dirtygasisusuallyaprobleminthegascompressionsystem,whichshortenstheservicelifeofconsumablepartsandcausesabnormaldamage.Themethodtotestthegasqualityistosetthecuttingtorchintheteststate,andplaceamirrorbelowittoconsumethegasinthecuttingtorch.Ifmoistureandmistappearonthemirror,youneedtofindoutthereason.