数控技术 河南科技大学教案 英文版.docx
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数控技术 河南科技大学教案 英文版.docx
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数控技术河南科技大学教案英文版
河南科技大学教案首页
课程名称 数控技术(双语) 任课教师 韩建海
Chapter2 NCPartProgramming 计划学时 8
教学目的和要求:
Bylearningthecontentsofthischapter,studentswillgraspthebasicsofNCprogramming;masterthemanualprogrammingmethodsandtechniquesofNCmillingmachine,NClathe,NCmachiningcenters;understandthenumericalcontrolprogramminglanguage,processandmethodsofgraphicalprogramming.
重点:
1.BasicknowledgeofCNCprogramming:
programmingcontentandsteps,programmingmethods,NCMachiningProcess
2.Manualprogramming:
Gcode,Mcodeandothercode,holemachiningprogramming,turningprogramming,contourmillingprogramming.
难点:
1.Thecharacteristicsandskillsof NCTurningandNCMillingprogramming.
思考题:
1.Glossary:
NCprogramming,workcoordinates,toolcoordinates,partcoordinatesystem,theabsolutecoordinatesystem,therelativecoordinatesystem
2.WhataretherequirementsofISOstandardontheCNCmachinetoolcoordinatesystem?
3.Whatarethebasepointsandnodepoints?
4.WhatarethecharacteristicsofNCTurningprogramming?
内容提要
ThischapterwillelaboratetheCNCmachiningprocessanalysisandthetypicalprocessingmethods;themethodsofestablishment,structureandcommonlyusedalgorithmsofNCprogram;andmakeabriefoftheautomaticprogramming.
Chapter2 NCPartProgramming
2.1 INTRODUCTION
Theprogramofinstructionsisthedetailedstep--by--stepcommandsthatdirecttheactionsoftheprocessing equipment.In machinetoolapplications,theprogramofinstructionsiscalledapartprogram,andthepersonwhopreparestheprogramiscalledapartprogramNumericalcontrol(NC)isaformofautomaticallyoperatingamachinetoolbasedoncodedalphanumericdata.Acompletesetofcodedinstructionsforexecutinganoperationiscalledaprogram.Theprogramistranslatedintocorrespondingelectricalsignalsforinputtoservomotorsthatrunthemachine.
Wecallthewholeprocessfrompartgraphicstofinishingcontrolmediumtheprogrammingofnumericalcontrolmanufacturing,orcallitNCProgramming.Whenusingnumerical’controlmachinetooltomanufactureparts,theprogrammingisveryimportant.Theprogramisnotonlycorrectandfastbutalsoeffectiveandeconomic.
2.1.1TheContentsandStepsofNumericalControlProgramming
BeforeNCprogramming,theprogrammershouldunderstandthenumericalcontrolmachinespecifications,characteristics,thefunctionsandprogramminginstructionformatofthe CNCsystem,etc.Whenprogramming,heshouldanalyzethepart’stechnicalrequirements,geometricalshapedimensionsandtechnologicalrequirements.Thenhecandeterminethemanufacturingmethodandcalculatenumericalvalue,getcutterposition,Accordingtopartdimension,cutterpositionvalue,cuttingparameters(spindlespeed,feed-rate,cuttingdepth)andauxiliaryfunctions(ATC,CW,CCW,coolantonandoff),theprogrammercanprogram.TheprogramcanbeinputtedintoCNCsystemandtheCNCsystemcontrolsCNCmachinetoolstomanufactureautomatically.
Generallyspeaking,themainstepsofNCprogrammingareanalyzingpartgraphics,determiningthemanufacturingtechnologicalprocess,calculating,numericalvalue,programming,verifyingtheprogramandinputtingtheprogramintoCNCsystem.Figure2.1illustratestheprogrammingsteps.
(1)Analyzingpartgraphicsanddeterminingthemanufacturingtechnologicalprocess
Thisstepincludesanalyzingthepartgraphics,understandingthemachiningcontentsandrequirements,thendeterminingtechnologicalprocesses,machiningplans,machiningsequence,machiningroutes,fixingmethods,cuttingparametersandselectingcuttingtools,etc.Besidesthese,thenumericalcontrolmachinecodesshouldbeunderstoodclearlyandthenumericalcontrolmachinefunctionsshouldbeexploitedfully.
(2)Correctlyselectingprogramoriginandcoordinatesystem
Innumericalcontrolmachinetoolsmanufacturing,correctlyselectingprogramoriginandcoordinatesystemisveryimportant.OnNCprogramming,theprogramcoordinatesystemisthestandardC00rdlnatesystemascertained0ntheworkpiece.
(3)Calculatingnumericalvalues
Afterfinishingthetechnologicalprocess,thenextstepistogetthetoolpathaccordingtopartgeometricdimensionandthemethodofcutterradiuscompensation,SOwewillobtainthecutterposition.
(4)Writingpartprograms
Afterdeterminingmachiningroute,technologicalprocessandthecoordinatevalueoftoolpath,step-by-step,theprogrammercanwritetheprograminaccordancewiththespecifiedfunctioncodesandprogramformatofCNCsystem.
(5)Fabricatingcontrolmedium
TheProgramiscoded0nasuitablemediumforsubmissiontothemachinecontrolunit.formanyyears,thecommonmediumwas1-inchwidePunchedtape,usingastandardformatthatcouldbeinterpretedbythemachinecontrolunit.Today,punchedtapehaslargelybeenreplacedbynewerstoragetechnologiesinmodernshops.Thesetechnologiesincludemagnetictape,diskette,andelectronictransferofpartprogramsfromacomputer.
(6)Verifyingpartprograms
Beforetheprogramisusedinrealproduction,wemustchecktheprogram.Wedetecttoolpatherrorsthatcouldruinthepart,damagethefixtures,breakthecuttingtoolorcrashthemachine,etc.Insomecases,wetesttheprogramthroughmanufacturingapartonamachine.Onthebasisofdetectingresult,theprogramisneededtobemodifiedandtobeadjusteduntiltheprogramsatisfiesthemachiningrequirementscompletely.
Thestepsabove-mentionedareprogrammedmanually.Thisprogrammingmethodiscalledmanualpartprogramming.Andwealsoknowthataprogrammernotonlymusthavetheknowledgeofthestructureofmachinetools,thefunctionsandstandardsofCNCsystem,butalsohavetheknowledgeoftechnologicalprocess,suchasfixtures,cuttingtoolsandcut-tingparameters,etc.
2.1.2TheMethodsofNCProgramming
Partprogrammingcanbeaccomplishedusingavarietyofproceduresrangingfrommanualmethodtohighlyautomatedmethod.
(1)Manualpartprogramming
Theprogrammingiscalledmanualpartprogrammingwhichwholepartprogrammingiscompletedmanually(includingcalculatingnumericalvalueonacomputer).
Inmanymechanicalmanufacturingtrades,therearealargenumberofuncomplicatedpartsthatareconstitutedonlybythesimplegeometricelementsofstraightlinesandcircles.Thenumericalvaluesofthepartsarecalculatedsimply.Theblocksofaprogramaren’tlot.Andcheckingtheprogramiseasy.Thesepartprogramscanbecompletedmanually.Somanualprogrammingisstillaverycommonprogrammingmethodathomeandabroad.
Butmanualprogramminghasdifficultyorimpossibilitytoprogramcomplicatedpartsthathavenon-circularcurvesandsurfaces.Sowemustusetheautomaticpartprogrammingtoprogram.
(2)Automaticprogramming
Automaticprogrammingisalsocalledcomputer-aidedProgramming.Mostorallofthe programmingiscompletedbyacomputer,suchascalculatingnumericalvalues,writingprograms,fabricatingthecontrolmedium,etc.Automaticprogramminglightensprogrammerintensityoflabor,shortenstheprogrammingtimeandimprovestheprogrammingquality.Atthesametime,itsolvesthecomplicatedpartprogrammingwhichisimpossibletoprogramby manualprogramming.Themorepartsarecomplicatedshapeandtechnologicalprocess,the moresuperiorityofautomaticprogrammingclearis.
Therearemanymethodsofautomaticpartprogramming.Accordingtothedifferencesofinputprogrammingmessageandhandlingstylesbyacomputer,theyaredividedintoautomaticallyprogrammedtool(APT)basedonautomaticprogramminglanguageandpartprogrammingusingCAD/CAM(computer-aideddesign/computeraidedmanufacturing)based oninteractivegraphicssystem.ACAD/CAMsystemisacomputerinteractivegraphicssys-temequippedwithsoftwaretoaccomplishcertaintasksindesignandmanufacturing.
2.1.3TheBasisofNCPartProgramming
2.1.3.1TheGeometricBasisofNCPartProgramming
(1)NCCoordinatesystems
ThelocationofaCNCMachinetoolsatanytimeiscontrolledbyasystemofXYZcoordinatescalledCartesiancoordinates.Thissystemiscomposedofthreedirectionallines,calledaxes,mutuallyintersectingatanangleof90.Thepointofintersectionisknownastheorigin.
Thoseaxissystemstandardsinclude:
(i)Primarymachineaxesofmovement:
shouldfollowtheright-handrule.SeeFigure2.2.
(ii)SpindlemovementisprimarilyalongtheZax-is.Movementintotheworkpieceisalongthe-Zaxisandmovementawayfromtheworkpieceisalongthe+Zaxis.
(iii)Inamajorityofmillingmachines,motionalongtheXaxisisthelongesttravelperpendiculartoZ.TheXaxisisparalleltotheworkholdingandisinthehorizontalplane.The+XaxismovestotherightalongaplaneO{theworkastheoperatorlooksatthatplane.
(iv)Withregardtomillingmachines,motionalongtheYaxisistheshortesttravelperpendiculartoZ.TheYaxisisinthesameplaneastheXaxis.Lookingattheplane,theoperatorwillnotethattheYaxisisperpendiculartotheXaxis.
MostCNCmillingmachinescanperformsimultaneousmotionsalongtheX,Y,andZaxesandarecalledthree-axismachines.SeeFigures2.3andFigure2.4.
MorecomplexCNCmachineshavethecapabilityofexecutingadditionalrotarymotions asfollows:
●RotationaboutanaxisparalleltotheXaxisorA-axisrotation
●RotationaboutanaxisparalleltotheYaxisorB-axisrotation
●RotationaboutanaxisparalleltotheZaxisorC-axisrotation
Rotarymotiondirectionsalsofollowtheright-handrule.SeeFigure2.5andFigure2.6.
(2)Programzeropoint
Theprogrammingzeropointisrela
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