自动化课后答案ch16 transfer lines3esi.docx

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