UT404SpectrogramWord文档下载推荐.docx
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UT404SpectrogramWord文档下载推荐.docx
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Themaincrest,i.e.thetopofthemain„hill“ofthespectrogramisapproximately
2.8timestheaveragefiberlengthinmm.
Amongthenaturalrandomvariationspresentinthetestmaterial,therecanbeundesiredsystematicvariations,whichmakethespectrogramappeardifferentthannormal.Theyappearas“chimney”peaksor“hill”crestsinthespectrogram.
4.2Periodicfaults(chimneys)
Exampleofachimney:
Spectrogramwitha20mchimney,i.e.20mperiodicfault(combedcotton,16Tex)
Cut-lengthmassdiagramofthesamematerialthantheabovespectrogram,showingthe20mperiodicmassvariation
Theidealizedbasewave(=sinewave)oftheperiodicityandanamplifiedillustrationofhowthetestmaterial’scorrespondingmassvariationwouldlookaredrawnalongsidethediagram.
TheuseoftheSpectrogramistocheckthetestmaterialforanyabnormallyhighperiodicorsystematicmassvariations.Inmostcases,thosevariationsareduetodirty,defectiveorwronglysetpreparationandspinningmachinery.
Thesourceoftheperiodicfaultcanbelocatedinapreviousmaterialprocessingstage,i.e.inamachineofanearlierpassagethantheonethesamplesweretakenfrom.Inthatcase,thefaultwillbeinalongerwavelengthrange,suchasintheaboveexample.
4.2.1Distinguishingdisturbingperiodicfaultsfromtolerablefaults
Generally,theenduseofayarnorfibercompoundhastobeknowninordertodeterminewhichsizesandwavelengthsofperiodicyarnfaultswillbenoticableordisturbing.
Nevertheless,therearesomecommonlyusedrulesfordistinguishingsevereordisturbingmaterialfaultsfromtolerablefaults:
1)Forwavelengthsshorterthan~2m:
Aperiod(chimney)50%higherormorethanitssurroundingscanberegardedasdisturbing.
2)Forwavelengthslongerthan~2m:
Aperiod(chimney)doubleashighormorethanitssurroundingscanberegardedasdisturbing
Examples:
Disturbingperiodicfaults
UT4-SXwillautomaticallymarkdisturbingchimneysaswellasdraftfaultsredasexceptions.Thelimits(accordingtowhichachimneyismarkedasdisturbingornot)
canbedefinedintherespectiveUT4limitsettings.
Otherperiodicfaultsmayappeardisturbinginthespectrogrambutwillnotaffecttheendproductdirectly,suchaschimneysincardslivers.
Nevertheless,itisimportanttopayattentiontothosecasesaswell,sincethefaultscanbeasignofdeteriorationofmachinery.Onemaysavecostsbyinterveningintimetoavoidanydamagetotherespectivemachineryparts.
4.2.2MultiplePeriods
Inverymanycases,asingleperiodicmaterialfaultproducesmultiplechimneys.
Multiplechimneysaretheresultofaperiodicyarnmassvariationwhichisnotevenlyshaped,i.e.notsine-shaped.
Amultipleperiodicfaultconsistsofabasewavelengthandofso-calledharmonicwavelengths.Theharmonics和声学areusuallytobefoundatfactor1/2,1/3,1/4,etc.ofthebasewavelength.
Example:
SpectrogramandyarnboardimageofabadOEyarn.
The10cmmoiré
wascausedbyadirtyRotorgroove.
Thereasonfortheappearanceofmultiplechimneysliesinthebehaviorofwavesignals.Mathematically,itiscomplex(Fouriertransformation),butgraphically,itbecomesquiteevident:
λ
λ/3
λ/5
λ+λ/3+λ/5
Illustrationofhowanewwaveshape(inthiscaseasquarewave)iscreatedbyaddingsinewavesofthebasewavelengthλandfurthershorterwavelengths(harmonicsofλ)ofdecreasingamplitudes.
[Ofcourse,therectangularwaveformisnotactuallyprevalentintextilepractice]
4.2.3Examplesofcommonperiodicfaulttypesintextilepractice
Thesignalshapeofeachoftheaboveexamplesiscontainedinthemassdiagram,butmostoftentheshapeishardlyvisibleornotvisibleatall.Inanormaldiagram,thelengthscaleistoolargetoseeshortvariations.Also,thehighamountofrandomdiagrampeakscoverupthewaveshapeoftheperiodicfault.
Insomecases,suchaswithveryshortperiodicpulses(last2examples),thefaultwouldbevisibleinthediagramashighsignalpeaks,andthematerialitselfwouldcontainregularlyappearingthickplaceswhichwouldclearlystandout.
4.2.4Spectrogramcalculations/Findingthesourceofperiodicfaults
Everygenuineperiodicfault(chimney)visibleinthespectrogramhasitsoriginintheproductionmachinery.
Anexceptiontothatrulecanbeaperiodicfaultduetomaterialhandling,forexamplethescrapingofarovingbobbinsurface,etc.
Whensearchingtheoriginoftheperiodicity,thefirststepistorememberthatthefaultiscausedbyamovingmachinepart,usuallyarotatingone.Itcanbedirectlytouchingthematerial(rollers,coiling,etc.)orinthemachinedrive(gears,pulleys,etc.)
Ifthepartisrunningsmoothandperfectlyuniform,itwillnotcauseanyperiodicfaults,ofcourse.Ifitisrunningirregularlyand/orhasanunevensurface,thesameunevenpointsoftherotatingpartwillperiodicallyproduceafaultinthematerialpassingoutofitonceperrevolution,i.e.onceperitscircumference.
Spectrogramchimneyresultingfromaneccentricallyrunningtopexitrollerinacottonringspinningdraftingsystemandthetypeofyarnfaultwhichwouldbeproduced
Intheaboveexample,thecircumferenceofthetoprollerwouldhavetobeapproximately
7.7cm÷
π=7.7cm÷
3.14=2.45cm=24.5mm.
Normally,atoprollerinacottondraftingsystemhasaninitialdiameterofaround27mm.Probably,thespinningcontractionand/orrepeatedgrindingoftherollersurfaceareresponsiblefortheslightdifferencebetweenthetheoreticalandtheactualrollerdiameter.
Systematicfaultsearch
Agoodmethodtofindthefaultypartcausingaperiodicmassvariation,visibleasonechimneyoranarrayofchimneysinthespectrogram,isfollowingprocedure:
1.Dividethechimney’swavelength(λ)byπ.π=3.14
-Iftherearemultiplechimneys,checkiftheybelongtogetherbylookingforratiosofλ/2,λ/3,λ/4,etc.Thendividethemainwavelengthλ,thefurthermostrightone,byπ.
2.Checkiftheresultcorrespondstoanydiameterofamovingparttouchingthematerialdirectlyattheoutputofthemachine.
->
Ifthereisapartwithsuchadiameter,thenitisprobablythefaultyelement.
-Iftheresultofλ/πismuchlargerthananydiameterattheoutput,continuewithstep3.
-Ifλ/πissmalleroronlyslightlylargerthananydiameterattheoutput,gotostep4.
3.Dividetheresultλ/πbythedraftingratiospresentinthemachine(s)untilfindingthediameterofaparttouchingthematerialfurtherbackinthemachineorinapreviouspassage.
-Ifnosuchpartcanbefound,continuewithstep4.
4.Lookforapossiblyfaultypartinthemachine’sdrive:
Usingthecorrectgearplan,calculatethegearratiosbackwardsfromthedeliverycylinderofthemachine.
Whenagearratioisfoundthat,whenmultipliedbyλ/π,resultsinthediameterofthedeliverycylinder,thenonehasprobablyfoundthefaultyareainthemachinedrive.
Inamachinewithseveraldeliveriesorspindles,gearfaultswillusuallyproducethesamechimneyheightonallsamplestakenfromamachineatthesametime.
Formula:
or:
Forgearfaults:
Forcertaintypesofmachinessuchascardsorverycomplexgearboxes,itcanbenecessarytouseanauxiliarymethodtofindthefaultsource:
Afaulty(rotating)partcanbesearchedinamachinewhileitisrunning,byflashingontothesuspectedfaultsourcewithastroboscope.
Thisauxiliarymethodisnotgenerallyrecommendedbecauseofthedangerinvolvedwhensearchingafaultonarunningmachine!
Instead,whereavailable,theRPM(rotationsperminute)displaysofthemachineshouldberead.
Auxiliarygeneralformula:
4.2.5Calculationexamplesofperiodicfaultsoriginatingindraftingsystems
5
1)
YarnSpectrogramchimneyatλ≈8.2cm:
Diameterd=λ÷
π=8.2cm÷
3.14=2.61cm≈26mm=diameterofexittoprollerofringframe
2)
YarnSpectrogramchimneyatλ≈3.6m,theotherchimneysareregularfractionsofλ:
a)Diameterd=λ÷
π÷
draftfactor=360cm÷
3.14÷
maindraft(30×
)=3.82cm
->
nosuchpartexistsinthemiddleoftheringframe’sdraftingsystem.
b)3.82cm÷
breakdraft(1.2×
)=3.18cm
nosuchpartexistsattheentryoftheringframe’sdraftingsystemortheexitoftherovingframe’sdraftingsystem.
Solution:
360cm÷
maindraft(30)=12cm=apronlengthLofcrackedapron(theapronlengthisalreadyacircumference).
3)
YarnSpectrogramchimneyatλ≈2.9m:
draftfactor=290cm÷
)=3.08cm
b)3.08cm÷
breakdraft=3.08cm÷
1.2=2.57cm≈26mm=diameteroftopinputrollerofringframe
4)
YarnSpectrogramchimneyatλ≈3.4m:
draftfactor=340cm÷
)=3.61cm
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