数控技术 河南科技大学教案 英文版.docx

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

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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