自动化课后答案ch16 transfer lines3esi.docx
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自动化课后答案ch16 transfer lines3esi.docx
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自动化课后答案ch16transferlines3esi
Chapter16
AUTOMATEDPRODUCTIONLINES
REVIEWQUESTIONS
16.1Namethreeofthefourconditionsunderwhichautomatedproductionlinesareappropriate.
Answer:
Thefourconditionslistedinthetextare
(1)highproductdemand,
(2)stableproductdesign,(3)longproductlife,and(4)multipleoperationsarerequiredtoproducetheproduct.
16.2Whatisanautomatedproductionline?
Answer:
Asdefinedinthetext,anautomatedproductionlineconsistsofmultipleworkstationsthatareautomatedandlinkedtogetherbyaworkhandlingsystemthattransferspartsfromonestationtothenext.
16.3Whatisapalletfixture,asthetermisusedinthecontextofanautomatedproductionline?
Answer:
Asdefinedinthetext,apalletfixtureisaworkholdingdevicethatisdesignedto
(1)fixturethepartinapreciselocationrelativetoitsbaseand
(2)bemoved,located,andaccuratelyclampedinpositionatsuccessiveworkstationsbythetransfersystem.
16.4Whatisadial-indexingmachine?
Answer:
Adial-indexingmachineisanautomatedsystemconsistingofmultipleworkstationsthatprocessworkpartsattachedtofixturesaroundtheperipheryofacircularworktable,andthetableisindexed(rotatedinfixedangularamounts)topositionthepartsatthestations.
16.5Whyarecontinuousworktransportsystemsuncommononautomatedproductionlines?
Answer:
Continuousworktransportsystemsareuncommononautomatedlinesduetothedifficultyinprovidingaccurateregistrationbetweenthestationworkheadsandthecontinuouslymovingparts.
16.6IsaGenevamechanismusedtoprovidelinearmotionorrotarymotion?
Answer:
AGenevamechanismprovidesrotarymotion.
16.7Whatisastoragebufferasthetermisusedforanautomatedproductionline?
Answer:
Asdefinedinthetext,astoragebufferisalocationinaproductionlinewherepartscanbecollectedandtemporarilystoredbeforeproceedingtosubsequent(downstream)workstations.
16.8Namethreereasonsforincludingastoragebufferinanautomatedproductionline?
Answer:
Thetextliststhefollowingfivereasons:
(1)toreducetheeffectofstationbreakdowns,
(2)toprovideabankofpartstosupplytheline,(3)toprovideaplacetoputtheoutputoftheline,(4)toallowforcuringtimeorotherrequireddelayassociatedwithprocessing,and(5)tosmoothcycletimevariations.
16.9Whatarethethreebasiccontrolfunctionsthatmustbeaccomplishedtooperateanautomatedproductionline?
Answer:
Thethreebasiccontrolfunctionsare
(1)sequencecontroltocoordinatethesequenceofactionsofthetransfersystemandassociatedworkstations,
(2)safetymonitoringtoensurethattheproductionlinedoesnotoperateinanunsafecondition,and(3)qualitycontroltomonitorcertainqualityattributesoftheworkpartsproducedontheline.
16.10Namesomeoftheindustrialapplicationsofautomatedproductionlines.
Answer:
Applicationslistedinthetextincludemachining,sheetmetalformingandcutting,spotweldingofcarbodiesinfinalassemblyplants,paintingandplatingoperations,andassembly.
16.11Whatisthedifferencebetweenaunitizedproductionlineandalinkline?
Answer:
Aunitizedproductionlineisanautomatedproductionlinethatconsistsofstandardmodulesandisassembledinanappropriateconfigurationtosatisfytheproductionrequirementsofthecustomer.Alinklineisaproductionlinethatconsistsofstandardmachinetoolsthatareconnectedtogetherbystandardorspecialmaterialhandlingdevices.
16.12Whatarethethreeproblemareasthatmustbeconsideredintheanalysisanddesignofanautomatedproductionline?
Answer:
Thethreeproblemareasidentifiedinthetextare
(1)linebalancing–thesamebasicproblemasinmanualassemblylines;
(2)processingtechnology–cuttingtooltechnology,speedsandfeeds,andsoon;and(3)systemreliability–duetothecomplexityofanautomatedproductionline.
16.13Asthenumberofworkstationonanautomatedproductionlineincreases,doeslineefficiency(a)decrease,(b)increase,or(c)remainunaffected?
Answer:
(a).Lineefficiencydecreasesbecauseeachadditionalstationincreasestheprobabilityofalinestop.
16.14Whatisstarvingonanautomatedproductionline?
Answer:
Starvingonanautomatedproductionlinemeansthataworkstationispreventedfromperformingitscyclebecauseithasnoparttoworkon.Whenabreakdownoccursatanyworkstationontheline,thedownstreamstationswilleitherimmediatelyoreventuallybecomestarvedforparts.
16.15Intheoperationofanautomatedproductionlinewithstoragebuffers,whatdoesitmeanifabufferisnearlyalwaysemptyornearlyalwaysfull?
Answer:
Intheoperationofanautomatedproductionlinewithstoragebuffers,ifanyofthebuffersarenearlyalwaysemptyornearlyalwaysfull,thisindicatesthattheproductionratesofthestagesoneithersideofthebufferareoutofbalanceandthatthestoragebufferisservinglittleusefulpurpose.
PROBLEMS
TransferMechanisms
16.1ArotaryworktableisdrivenbyaGenevamechanismwithfiveslots.Thedriverrotatesat48rev/min.Determine(a)thecycletime,(b)availableprocesstime,and(c)indexingtimeeachcycle.
Solution:
(a)Tc=
=
=0.020833min=1.25sec
(b)=
=72Ts=
=0.01458333min=0.875sec
(c)Tr=
=0.00625min=0.375sec
16.2AGenevawithsixslotsisusedtooperatetheworktableofadial-indexingmachine.Theslowestworkstationonthedial-indexingmachinehasanoperationtimeof2.5sec,sothetablemustbeinadwellpositionforthislengthoftime.(a)AtwhatrotationalspeedmustthedrivenmemberoftheGenevamechanismbeturnedtoprovidethisdwelltime?
(b)Whatistheindexingtimeeachcycle?
Solution:
(a)=360/6=60Ts=
=
=2.5sec(given)
N=
=0.2667rev/sec=16rev/min
(b)Tr=
=1.25sec
16.3SolvethepreviousproblemexceptthattheGenevahastenslots.
Solution:
(a)=360/10=36Ts=
=0.60/N=2.5sec(given)
N=0.60/2.5=0.241rev/sec=14.4rev/min
(b)Tr=
=1.66sec
AutomatedProductionLineswithNoInternalStorage
16.4Aten-stationtransfermachinehasanidealcycletimeof30sec.Thefrequencyoflinestopsis0.075stopspercycle.Whenalinestopoccurs,theaveragedowntimeis4.0min.Determine(a)averageproductionrateinpc/hr,(b)lineefficiency,and(c)proportiondowntime.
Solution:
(a)Tp=0.5+0.075(4)=0.5+0.3=0.8min
Rp=1/0.8=1.25pc/min=75pc/hr
(b)E=0.5/0.8=0.625=62.5%
(c)D=0.3/0.8=0.375=37.5%
16.5Costelementsassociatedwiththeoperationoftheten-stationtransferlineinProblem16.4areasfollows:
rawworkpartcost=$0.55/pc,lineoperatingcost=$42.00/hr,andcostofdisposabletooling=$0.27/pc.Computetheaveragecostofaworkpieceproduced.
Solution:
ReferstoProblem16.4:
Cpc=0.55+42(0.8)/60+0.27=0.55+0.56+0.27=$1.38/pc
16.6InProblem16.4,thelinestopoccurrencesareduetorandommechanicalandelectricalfailuresontheline.Supposethatinadditiontothesereasonsfordowntime,thatthetoolsateachworkstationonthelinemustbechangedand/orresetevery125cycles.Thisproceduretakesatotalof15.0minforalltenstations.Includethisadditionaldatatodetermine(a)averageproductionrateinpc/hr,(b)lineefficiency,and(c)proportiondowntime.
Solution:
ReferstoProblem16.4:
(a)F1Td1=0.075(4.0)=0.3min
F2Td2=15.00/125=0.12min
Tp=0.5+0.3+0.12=0.92min
Rp=1/0.92=1.087pc/min=65.22pc/hr
(b)E=0.5/0.92=0.5435=54.35%,
(c)D=0.42/0.92=0.4565=45.65%
16.7ThedialindexingmachineofProblem16.2experiencesabreakdownfrequencyof0.06stops/cycle.Theaveragedowntimeperbreakdownis3.5min.Determine(a)averageproductionrateinpc/hrand(b)lineefficiency.
Solution:
ReferstoProblem16.2:
(a)FromProblem16.2,Tc=To+Tr=2.5+1.25=3.75sec
Tp=3.75/60+0.06(3.5)=0.0625+0.021=0.2725min
Rp=1/0.2725=3.67pc/min=220.2pc/hr
(b)E=0.0625/0.2725=0.2294=22.94%
16.8Intheoperationofacertain15-stationtransferline,theidealcycletime=0.58min.Breakdownsoccuratarateofonceevery20cycles,andtheaveragedowntimeperbreakdownis9.2min.Thetransferlineislocatedinaplantthatworksan8-hrday,5daysperweek.Determine(a)lineefficiency,and(b)howmanypartswillthetransferlineproduceinaweek?
Solution:
(a)Tp=0.58+9.2/20=0.58+0.46=1.04min
E=0.58/1.04=0.5577=55.77%
(b)Rp=60/1.04=57.69pc/hrWeeklyproduction=40(57.69)=2307.7pc/wk.
16.9A22-stationin-linetransfermachinehasanidealcycletimeof0.58min.Stationbreakdownsoccurwithaprobabilityof0.01.Assumethatstationbreakdownsaretheonlyreasonforlinestops.Averagedowntime=8.0minperlinestop.Determine(a)idealproductionrate,(b)frequencyoflinestops,(c)averageactualproductionrate,and(d)lineefficiency.
Solution:
(a)Rc=
=1.724pc/min=103.45pc/hr
(b)F=np=22(0.01)=0.22
(c)Tp=0.58+0.22(8)=0.58+1.76=2.34minRp=
=0.4274pc/min=25.64pc/hr
(d)E=
=0.248=24.8%
16.10Aten-stationrotaryindexingmachineperformsninemachiningoperationsatnineworkstations,andthetenthstationisusedforloadingandunloadingparts.Thelongestprocesstimeonthelineis1.30minandtheloading/unloadingoperationcanbeaccomplishedinlesstimethanthis.Ittakes9.0sectoindexthemachinebetweenworkstations.Stationsbreakdownwithafrequencyof0.007,whichisconsideredequalforalltenstations.Whenthesestopsoccur,ittakesanaverageof10.0mintodiagnosetheproblemandmakerepairs.Determine(a)lineefficiencyand(b)averageactualproduction
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