中英文文献翻译小孔钻在工程塑料片材方面及其精度估算Word文档格式.docx
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中英文文献翻译小孔钻在工程塑料片材方面及其精度估算Word文档格式.docx
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mm,inrecentmachiningtechnologyaswell.Inthisreport,1-mmdiameterholesaredrilledontwoengineeringplasticssheetsandtheirdrillingaccuracyisdiscussed.
Keywords:
Smalldiameterhole;
Drilling;
Engineeringplastics;
Machiningaccuracy
1.Introduction
Processingofsmalldiameterholesisdoneinvariousmaterials,correspondingtothetrendofdownsizingorhighaccuracyinpartsincorporatedintoelectronicequipments,medicalinstrumentsortextilemachineries.Manytechniquesareputtopracticaluse,includingdrilling,ultrasonicmachining,electricdischargemachining,electrolyticmachining,laserbeammachining,electronbeammachining,fluidorabrasivejetmachining,andchemicalblanking.Dependingontheworkpiecematerial,themachiningaccuracy,andthelotsize,thebestprocessformakingholesofsmalldiametermaybeappropriatelyselected.Withinthesevariousmachiningprocesses,thedrillingprocesscanreadilydealwithawidevarietyofmachiningconditions.
However,therearesomedifficultproblemsindrillingholessmallerthan1
mmindiameter.Forexample,alargeloadcannotbeputonsmalldrills,owingtotheirlowstrengthandrigidity.Thus,thefeedrateperunitdrillrotationmustbesetsmall.Theremovalofdrilledchipsisdifficultowingtothesmalldrillflutearea.
Inmanycases,engineeringplasticsareusedinmakingvariousmachinepartsbecausetheyarelightandhavesuperiorspecificstrength(thatis,theratiooftensilestrengthtodensity)comparedwithcarbonsteel.Also,thematerialcostofengineeringplasticsiscompetitiveandtheirmachinabilityisfairlygood.
Withthesepointsasbackground,theorthogonalcuttingofengineeringplasticswasinvestigated[1]anditwassuggestedherethatthevisco–elasticpropertiesofengineeringplasticshavesomeeffectsonthemagnitudeofcuttingforceandthesurfaceroughnessofmachinedsurfaces.Thereisareviewpaper[2]regardingthemachiningofengineeringplastics.Inthisreviewpaper,drillingprocesswasalsotreated.Itwaspointedoutthattheheatingupoftheworkpieceduetobuild-upofswarfondrillflutesisanobstacletothedrillingprocessofengineeringplastics.Recently,someexperimentshavebeenattemptedondrillingglass–fiber-reinforcedengineeringplasticssheets[3]and[4],andthethrustforceandtorqueduringdrillinghavebeenmeasured.Inthesepapers,itwasreportedthatthedelaminationphenomenondecreasesthedrilledholeintegrity,whenholesofabout5-mmdiameteraredrilled.However,theinvestigationontheaccuracyinsmallholedrillingofengineeringplasticsisleftpending.
Theninthispaper,smalldiameterholesof1
mmaredrilledintwotypicalengineeringplasticssheets,andtheeffectofspindlespeedandfeedrateontheaccuracy(radiuserror)isestimated.
2.Workpiecematerials
Twotypicalengineeringplasticssheets,polyacetal(POM)andpolyetherimide(PEI),weredrilled.ThematerialspropertiesarelistedinTable1.
Table1.
Materialpropertiesofworkpieceengineeringplastics
Performance
Unit
POM
PEI
Specificgravity
1.41
1.27
Rateofwater
%
0.22
0.25
Meltingpoint
°
C
165
210
Coefficientoflinearthermalexpansion
cm/cm/°
9×
10−5
5.6×
Tensilestrength
MPa
61
124
Tensileextension(Yieldingpoint)
40
23
Bendingstrength
89
157
Bendingelasticity
GPa
2.60
3.07
Compressivestrength
103
118
Izoteimpactvalue
J/m
74
42
Rockwellhardness
Mscale
119
127
Polyacetalisacrystallizedengineeringplasticsmaterial.Themainrawmaterialsareacetalco-polymerandhomo-polymer.POMhasgoodfatiguepropertiesandmachinability.Manycams,guidesandlinersaremadeofPOM.Veryhighaccuracyisneededinthesemachinedparts.PEIisanamorphousengineeringplastichavingsuperiorthermalresistancecharacteristics.Specialelectricalparts,forexample,electricinsulators,connectors,aremadeofPEI,whichissuperiorinmechanicalstrengthbutinferiorinmachinabilitytoPOM.
Theworkpiecesizewas:
length100
mm,width50
mmandthickness0.8
mm.
3.Experimentalapparatusandprocedure
Thedrillingmachineusedisforsmalldiameterholes,andisequippedwithanautomaticfe
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