《數(shù)控應(yīng)用專業(yè)英語》課件第6章

6REFERENCEPOSITION

General·Referenceposition

Thereferencepositionisafixedpositiononamachinetooltowhichthetoolcaneasilybemovedbythereferencepositionreturnfunction.Forexample,thereferencepositionisusedasapositionatwhichtoolsareautomaticallychanged.Uptofourreferencepositionscanbespecifiedbysettingcoordinatesinthemachinecoordinatesysteminparameters.Fig.6.1(a)Machinezeropointandreferencepositions

·Referencepositionreturnandmovementfromthereferenceposition

Toolsareautomaticallymovedtothereferencepositionviaanintermediatepositionalongaspecifiedaxis.Or,toolsareautomaticallymovedfromthereferencepositiontoaspecifiedpositionviaanintermediatepositionalongaspecifiedaxis.Whenreferencepositionreturniscompleted,thelampforindicatingthecompletionofreturngoeson.

·Referencepositionreturncheck

Thereferencepositionreturncheck(G27)isthefunctionwhichcheckswhetherthetoolhascorrectlyreturnedtothereferencepositionasspecifiedintheprogram.Ifthetoolhascorrectlyreturnedtothereferencepositionalongaspecifiedaxis,thelampfortheaxisgoeson.Fig.6.1(b)ReferencepositionreturnandreturnformthereferencepositionFormat·Referencepositionreturn

G28IP-;referencepositionreturn

G30P2IP-;2ndreferencepositionreturn(P2canbeomitted.)

G30P3IP-;3rdreferencepositionreturn

G30P4IP-;4threferencepositionreturn

IP-:commandspecifyingtheintermediateposition(absolute/incrementalcommand).·ReturnfromreferencepositionG29IP-;

IP-:commandspecifyingthedestinationofreturnfromreferenceposition(absolute/incrementalcommand).·ReferencepositionreturncheckG29IP-;

IP-:commandspecifyingthereferenceposition(absolute/incrementalcommand).Explanations·Referencepositionreturn(G28)

Positioningtotheintermediateorreferencepositionsareperformedattherapidtraverserateofeachaxis.

Therefore,forsafety,thecuttercompensation,andtoollengthcompensationshouldbecancelledbeforeexecutingthiscommand.

ThecoordinatesfortheintermediatepositionarestoredintheCNConlyfortheaxesforwhichavalueisspecifiedinaG28block.Fortheotheraxes,thepreviouslyspecifiedcoordinatesareused.

Example:

N1G28X40.0;Intermediateposition(X40.0)

N2G28Y60.0;Intermediateposition(X40.0,Y60.0)·2nd,3rd,and4threferencepositionreturn(G30)

Inasystemwithoutanabsolutepositiondetector,thefirst,third,andfourthreferencepositionreturnfunctionscanbeusedonlyafterthereferencepositionreturn(G28)ormanualreferencepositionreturnismade.TheG30commandisgenerallyusedwhentheautomatictoolchanger(ATC)positiondiffersfromthereferenceposition.·Returnfromthereferenceposition(G29)

Ingeneral,itiscommandedimmediatelyfollowingtheG28commandorG30.Forincrementalprogramming,thecommandvaluespecifiestheincrementalvaluefromtheintermediatepoint.

Positioningtotheintermediateorreferencepointsareperformedattherapidtraverserateofeachaxis.

WhentheworkpiececoordinatesystemischangedafterthetoolreachesthereferencepositionthroughtheintermediatepointbytheG28command,theintermediatepointalsoshiftstoanewcoordinatesystem.

IfG29isthencommanded,thetoolmovestothecommandedpositionthroughtheintermediatepointwhichhasbeenshiftedtothenewcoordinatesystem.

ThesameoperationsareperformedalsoforG30commands.·Referencepositionreturncheck(G27)

G27commandpositionsthetoolatrapidtraverserate.Ifthetoolreachesthereferenceposition,thereferencepositionreturnlamplightsup.

However,ifthepositionreachedbythetoolisnotthereferenceposition,analarmisdisplayed.·Settingofthereferencepositionreturnfeedrate

Beforeamachinecoordinatesystemisestablishedwiththefirstreferencepositionreturnafterpoweron,themanualandautomaticreferencepositionreturnfeedrateandautomaticrapidtraverserateconformtothesettingofparameterNo.1428foreachaxis.Evenafteramachinecoordinatesystemisestablisheduponthecompletionofreferencepositionreturn,themanualreferencepositionreturnfeedrateconformstothesettingoftheparameter.NOTE

(ⅰ)Tothisfeedrate,arapidtraverseoverride(F0,25,50,100%)isapplied,forwhichthesettingis100%.

(ⅱ)Afteramachinecoordinatesystemhasbeenestablisheduponthecompletionofreferencepositionreturn,theautomaticreferencepositionreturnfeedratewillconformtotheordinaryrapidtraverserate.

(ⅲ)ForthemanualrapidtraverserateusedbeforeamachinecoordinatesystemisestablisheduponthecompletionofreferencepositionreturnajogfeedrateormanualrapidtraverseratecanbeselectedusingRPD.Restrictions·Statusthemachinelockbeingturnedon

Thelampforindicatingthecompletionofreturndoesnotgoonwhenthemachinelockisturnedon,evenwhenthetoolhasautomaticallyreturnedtothereferenceposition.Inthiscase,itisnotcheckedwhetherthetoolhasreturnedtothereferencepositionevenwhenaG27commandisspecified.·Firstreturntothereferencepositionafterthepowerhas

beenturnedon(withoutanabsolutepositiondetector)

WhentheG28commandisspecifiedwhenmanualreturntothereferencepositionhasnotbeenperformedafterthepowerhasbeenturnedon,themovementfromtheintermediatepointisthesameasinmanualreturntothereferenceposition.

Inthiscase,thetoolmovesinthedirectionforreferencepositionreturnspecifiedinparameterZMIx.Thereforethespecifiedintermediatepositionmustbeapositiontowhichreferencepositionreturnispossible.

·Referencepositionreturncheckinanoffsetmode

Inanoffsetmode,thepositiontobereachedbythetoolwiththeG27commandisthepositionobtainedbyaddingtheoffsetvalue.Therefore,ifthepositionwiththeoffsetvalueaddedisnotthereferenceposition,thelampdoesnotlightup,analarmisdisplayedinstead.Usually,canceloffsetsbeforeG27iscommanded.·Lightingthelampwhentheprogrammedpositiondoesnotcoincidewiththereferenceposition

Whenthemachinetoolsystemisani