支撑掩护式液压支架总体及立柱设计

摘要矿井液压支架的应用对增加采煤工作面产量、提高劳动生产率、降低陈本、减轻工人的体力劳动和保证生产是不可缺少的有效措施，因此液压支架的设计师技术上先进、经济上合理、安全上可靠、是实现采煤综合机械化和自动化的主要体现。采煤综合机械化，是加速我国煤炭工业发展，大幅度提高劳动生产率，实现煤炭工业现代化的一项战略措施。综合机械化不仅产量大，效率高，成本低，而且能减轻笨重的体力劳动，改善作业环境，是煤炭工业技术的发展方向。液压支架是综合机械化采煤方法中最重要的设备之一。液压支架主要由以下几个基本部分组成：顶梁，掩护梁和四连杆机构，侧护板，底座，立柱，千斤顶。设计要遵从从支柱性能好、强度高、移架速度快安全可靠等原则。支架采用四连杆机构，改善支架的受力状况，缩小支架升降过程中的顶梁前段前后移动的距离。立柱采用双伸缩液压缸，以满足支架最低及最高位置时的高度要求关键字：液压支架;立柱;掩护;支撑。AbstractTheapplicationofhydraulicsupportincoalminingfaceofincreasingproductionandraiselaborproductivityreducecosts,reduceworkersandtoensuresafetyinproductionisindispensableforeffectivemeasuresto,Thereforethedesignofhydraulicsupportistechnicallyadvancedandeconomicallyrational,safeandreliableisthemainmanifestationofthecomprehensiveofthecomprehensivemechanizationandautomationofmining.Thecomprehensivemechanizationofcoalminingisaccelerationcoalindustry.Synthesizemechanizationnotonlyoutputbig,efficiencyhaslowcosthighandcanalleviateheavyphysicallaborandimprovementschoolworkenvironment,isthetechnologyofcoalindustrydevelopdirection.Hydraulicsupportistheoneofcomprehensivemostimportantequipmentinthemechanizationmethodofcoalmining.Hydraulicsupportmajorformsomefollowingbasicallypartialcompositions:Topbeam,screensbeamand4linkagemechanisms,sidefender,base,prop.Designtofollowprotectperformancegood,strengthisspeedhigh,moverapidreliableetc.principle.Thesupportusesfourlinkmotiongears,improvethesupportthestresscondition,reducesthesupporttoriseandfullthedistancewhichintheprocessfortendthetop-beamaroundmoves.Thecolumnusesthelistexpansionandcontractionhydrauliccylinder,frontendhaslegthensthepole,satisfiesthesupporttobelowestandtimethehighestpositionshighrequest.KeyWords:coal;mechanization;bracket;column目录TOC\o"1-3"\h\u8790前言 ④建立软件来检查零件，程序和机器的可得性，并且考察三者是否能相容。大体上，计划使用生产力政策需要详细的描述，对制造业程序详细的理解和他们的准确性。以不同政策为基础的制造业决定采取几个标准来解决个人的操作问题，并且适应或调整他们所需要的地方附录BAutomaticAssemblyThemodernassemblylinetechniquewasfirstemployedintheassemblyofaflywheelmangneto.Intheoriginalmethod,oneoperatorassembledamagnetoin20min.Itwasfoundthatwhentheprocesswasdividedinto29indibidualoperations,carriedoutbyseparateoperatorsworkingatassemblystationsspacedalonganassemblyline,thetotalassemblytimewasreducedto13min10s.Whentheheightoftheassemblylinewasraisedby8in,thetimewasreducedto7min.Afterfurtherexperimentswerecarriedouttofindtheoptimumspeedoftheassemblylineconveyor,thetimewasreducedto5min,whichwasonlyone-fourthofthetimetakenbytheoriginalprocessofassembly.ThisresultencouragedHenryFordtoutilizehissystemofassemblyinotherdepartmentofthefactory,whichwereproducingsubassembliesforthecar.Subsequently,thisbroughtacontinousandrapidlyincreasingflowofsubassembliestotheoperatorsworkingonthemaincarassembly.Itwasfoundthattheoperatorscouldnotcopewithincreasedflow,anditsoonbecameclearthatthemainassemblywouldalsohavetobecarriedoutonanassemblyline.Atfirst,themovementofthemainassemblieswasachievedsimplybypullingthembyaropefromstationtostation.Howere,eventhisdevelopmentproducedtheamazingresultofareductioninthetotaltimeofassemblefrom12h28minto5h50min.Eventuallyapower-drivenendlessconveyerwasinstalled.Itwasfulshwiththefloorandwideenoughtoaccommodateachassis.Spacewasprovidedforworkerstoeithersitorstandwhiletheycarriedouttheiroperationsandtheconveyrsmovedataspeedof6ft/minpast45separateworkstations.Withtheintroductionofthisconveyor,thetotalassembletimewasreducedto93min.Furtherimprovementsledtoanevenshorteroverallassemblytimeandeventually,aproductionrateofonecarevery10softheworkingdaywasachieved.Thetypeofassemblyoperationdealtwithaboveisusuallyreferredtoasoperatorassembly,anditisstillthemostwidespreadmethodofassemblingmass-orlarge-batch-producedproducts.However,incertaincases,morerefinedmethodsofassemblyhavenowemerged.Asalogicalextensionofthebasicassemblylineprinciple,methodsofreplacingoperatorsbymechanicalmeansofassemblyhavebeendebised.Here,itisusualtoattempttoreplaceoperatorswithautomaticworkheadswherethetasksbeingperformedwereverysimpleandtoretaintheoperatorsfortasksthatwouldbeuneconomicaltomechanize.Thismethodofassemblyhasrapidgainedpopularityformassproductionandisusuallyreferredtoasautomaticassembly.However,completeautomationwheretheproductisassembledcompletelybymachineisessentialynonexistent.ChoiceofAssemblymethodWhenconsideringtheassemblyofaproduct,amanufacturerhastotakeintoaccountthemanyfactorsthataffectthechoiceofassemblysystem.Foranewproduct,thefollowingconsiderationsaregenerallyimportant:① Costofassembly;② Productionratrequired;③ Availabilityoflabor;④ Marketlifeoftheproduct.Ifanattemptistobemade3tojustifytheautomationofanexistingoperatorassemblyline,considerationhastobegiventotheredeploymentofthoseoperatorswhowouldbecomeredundant.Iflaborisplentiful,thedegreeofautomationdependsonthereductionincostofassemblyandtheincreaseinproductionratebroughtaboutbytheautomationoftheassemblyline.However,itmustberememberedthat,ingeneral,thecapitalinvestmentinautomaticmachineryhastobeamortizedoverthemarketlifeoftheproductunlessthemachinerymaybeadaptedtoassembleanewproduct.Itisclearthatifthisisnotthecaseandthemarketlifeoftheproductisshort,automationisgeneralllynotjustifiable.AdvantagesofAutomaticAssemblyFollowingaresomeoftheadvantagesofautomation:① Reductioninthecostofassembly;② Increasedproductivity;③ Amoreconsistentprodect;④ Removalofoperatorsfromhazardousoperations.Areductionincostsisoftenthemainconsiderationand,exceptforthespecialcircumstanceslistedabove,itcouldbeexpectedthatautomationwouldnotbecarriedoutifitwasnotexpectedtoproduceareductionincost.Productivityinanadvancedindustrialsocietyisanimportantmeasureofoperatingefficiency.Increasedproductivity,althoughnotdirectlybeneficialtomanufacturerunlesslaborisscarce,isnecessarytoanexpandingeconomybecauseitreleasespersonnelforothertasks.Itisclearthatwhenputintoeffect,automationofassemblylinesgenerallyreducesthenumberofoperatorsrequiredandhenceincreasesproductivity.Someoftheassemblytasksthatanoperatorcanperformeasilyareextremelydifficulttoduplicateoneventhemostsophisticatedautomaticworkhead.Anoperatorcanoftencarryoutavisualinspectionoftheparttobeassembled,andpartsthatareobviouslydefectivecanbediscarded.Sometimesaberyelaborateinspectionsystemisrequiredtodetecteventhemostobviouslydefectivepart.Ifanattemptismadetoassembleapartthatappearstobeacceptablebutisinfactdefective,anoperator,afterunsuccessfullytryingtocompletetheassembly,canrejectthepartveryquicklywithoutasignificantlossinproduction.Inautomaticassembly,however,unlesstheparthasbeenrejectedbythefeedingdevice,anautomaticworkheadwillprobablystopantimewillthenbewastedlocatingandeliminatingthefault.Ifaparthasonlyaminordefect,anoperatormaybeabletocompletetheassembly,buttheresultingprodectmaynotbecompletelysatisfactory.Itisoftensuggestedthatoneoftheadvantagesofautomaticassemblyisthatitensuresaproductofconsistentlyhighqualitybecausethemachinefaultsifthepartsdonotconformtotherequiredspecifications.Insomesituations,assemblybyoperatorswouldbehazardousduetohightemperaturesandthepresenceoftoxicsubstancesandothermaterials.Underthesecircumstances,assemblybymechanicalmeansisobviouslyadvantageous.Theincreasingneedforfinishedgoodsinlargequantitieshas,inthepast,ledengineerstosearchforandtodevelopnewmethodsofproduction.Manyindibidualdevelopmentsinthevariousbranchesofmanufacturingtechnologyhavebeenmadeandhaveallowedtheincreasedproductionofimprovedfinishedgoodsatlowercost.Oneofthemostimportantmanufacturingprocessesistheassemblyprocess.Thisprocessisrequiredwhentwoormorecomponentpartsaretobebroughttogethertoproducethefinishedproduct.Theearlyhistoryofassemblyprocessdevelopmentiscloselyrelatedtothehistoryofthedevelopmentofmass-productionmethods.Thus,thepioneersofmassproductionarealsothepioneersofthemoderassemblyprocess.Theirnewideasandconceptshavebroughtsignificantimprovementsintheassemblymethodsemployedinlarge-volumeproduction.However,althoughsombranchesofmanufacturingengineering,suchasmetalcuttingandmetalformingprocesses,haverecentlybeendevelopingveryrapidly,thetechnologyofthebasicassemblyprocesshasfailedtokeeppace.Table28.1showsthatintheUnitedStatesthepercentageofthetotallaborforceinbolvedintheassemblyprocessbariesfromabout20%forthemanufactureoffarmmachinerytoalmost60%forthemanufactureoftelephoneandtelegraphequipment.Becauseofthis,assemblycostsoftenaccountformorethan50%ofthetotalmanufacturingcosts.Statisticalsurveysshowthatthesefiguresareincreasingeveryyear.Inthepastfewyears,certaineffortshavebeenmadetoreduceassemblycostsbytheapplicationofautomationandmoderntechniques,suchasultrasonicweldinganddie-casting.Howerer,successhasbeenverylimitedandmanyassemblyoperatorsarestillusingthesamebasictoolsasthoseemployedatthetimeoftheIndustrialRevolution.Intheearlydaysofmanufacturingtechnology,thecompleteassemblyofaproductwascarriedoutbyasingleoperatorandusually,thisoperatoralsomanufacutredtheindividualcomponentpartoftheassembly.Consequently,itwasnecessaryfortheoperatortobeanexperinallthebariousaspectsofthework,andtraininganewoperatorwasalongandexpensivetask.Thescaleofproductionwasoftenlimitedbytheavailabilityoftrainedoperatorsratherthanbythedemandfortheproduct.In1798,theUnitedStatesneededalargesupplyofmusketsandfederalarsenalscouldnotmeetthedemand.BecausewarwiththeFrenchwasimminent,itwasalsonotpossibletoobtainadditionalsuppliesfromEurope.However,Eliwhitney,nowrecognizedasoneofthepioneersofmassproduction,offeredtocontracttomake10000musketsin28menths.Althoughittook10.5yuarstocompletethecontract,Whitney’snovelideasonmassproductionhadbeensuccessfullyproved.ThefactoryatNewHaven,Connecticut,builtspeciallyforthemanufactureofthemuskets,containedmachinesforproducinginterchangeableparts.Thesemachinesreducedtheskillsrequiredbythebariouoperatorsandallowedsignificantincreasesintherateofproduction.Inanhistoricdemonstrationin1801,Whitneysurprisedhisdistinguishedvisitorswhenheassembledmusketlocksafterrandomlyselectedpartsfromaheap.TheresultsofEliWhitney’sworkbroughtaboutthreeeprimarydevelopmentsinmanufacturingmethods.First,partsweremanufacturedonmachines,resultinginaconsistentlyhigherqualitythanthatofhand-madeparts.Thesepartswerenowinterchangeableandasaconsequenceassemblyworkwassimplified.Second,theaccuracyofthefinalproductcouldbemaintainedatahigherstandard,andthird,productionratescouldbesignificantlyincreased.OliverEbans’sconceptionofconveyingmaterialsfromoneplacetoanotherwithoutmanualeffortledeventuallytofurtherdevelopmentsinautomationforassembly.In1793,heusedthreetypesofconveyorsinanautomaticflourmill,whichrequiredonlytwooperators.Thefirstoperatorpouredrainintoahopperandthesecondfilledsackswithflourprocducedbythemill.Alltheintermediatoperationswerecarriedoutautomaticallywithconveyorscarryingthematerialfromoperationtooperation.ThenextsignificantcontributiontothedevelopmentofassemblymethodswasmadebyElihuRoot.In1849,ElihuRootjoinedthecompanythatwasproducingColt“six–shooters”.Eventhoughatthattimethevariousoperationofassemblingthecomponentpartswerequitesimple,hedividedtheseoperationsintobasicunitsthatcouldbecompletedmorequicklyandwithlesschanceoferror.Toot’sdivisionofoperationsgaverisetotheconcept“dividetheworkandmultiplytheoutput”.Usingthisprinciple,assemblyworkwasreducedtoverybasicoperationsandwithonlyshortperiodsofoperatortraining,highefficienciescouldbeobtained.FrederickWinslowTaylorwasprobablythefirstpersontointroducethemethodsoftimeandmotionstudytomanufacturingtechnology.Theobjectivewastosavetheoperator’stimeandenergybymakingsurethattheworkandallthingsassociatedtotheworkwereplacedinhebestpositionsforcarryingouttherequiredtasks.Tayloralsodiscoveredthatanyworkerhasanoptimumspeedofworkingwhich,ifexceeded,resultsinareductioninoverallperformance.Undoubtedly,theprincipalcontributortothedevelopmentofproductionandassemblymethodswasHenryFord.Hedescribedhisprinciplesofassemblyinthefollowingwords:“First,placethetoolsandthenmeninthesequenceoftheoperationssothateachpartshalltraveltheleastdistancewhilstintheprocessoffinishing”.“Second,useworkslidesorsomeotherformofcarriersothatwhenaworkmancompletehisoperationhedropsthepartalwaysinthesameplacewhichmustalwaysbethemostconvenientplacetohishandandifpossiblehavegravitycarrytheparttothenextwokman.“Third,useslidingassemblylinesbywhichpartstobeassembledaredeliveredatconvenientintervals,spacedtomakeiteasiertoworkonthem”.TheseprinciplesweregraduallyappliedintheproductionoftheModelTFordautomobile.Theincreasingneedforfinishedgoodsinlargequantitieshas,inthepast,ledengineerstosearchforandtodevelopnewmethodsofproduction.Manyindibidualdevelopmentsinthevariousbranchesofmanufacturingtechnologyhavebeenmadeandhaveallowedtheincreasedproductionofimprovedfinishedgoodsatlowercost.Oneofthemostimportantmanufacturingprocessesistheassemblyprocess.Thisprocessisrequiredwhentwoormorecomponentpartsaretobebroughttogethertoproducethefinishedproduct.Theearlyhistoryofassemblyprocessdevelopmentiscloselyrelatedtothehistoryofthedevelopmentofmass-productionmethods.Thus,thepioneersofmassproductionarealsothepioneersofthemoderassemblyprocess.Theirnewideasandconceptshavebroughtsignificantimprovementsintheassemblymethodsemployedinlarge-volumeproduction.However,althoughsombranchesofmanufacturingengineering,suchasmetalcuttingandmetalformingprocesses,haverecentlybeendevelopingveryrapidly,thetechnologyofthebasicassemblyprocesshasfailedtokeeppace.Table28.1showsthatintheUnitedStatesthepercentageofthetotallaborforceinbolvedintheassemblyprocessbariesfromabout20%forthemanufactureoffarmmachinerytoalmost60%forthemanufactureoftelephoneandtelegraphequipment.Becauseofthis,assemblycostsoftenaccountformorethan50%ofthetotalmanufacturingcosts.Statisticalsurveysshowthatthesefiguresareincreasingeveryyear.Inthepastfewyears,certaineffortshavebeenmadetoreduceassemblycostsbytheapplicationofautomationandmoderntechniques,suchasultrasonicweldinganddie-casting.Howerer,successhasbeenverylimitedandmanyassemblyoperatorsarestillusingthesamebasictoolsasthoseemployedatthetimeoftheIndustrialRevolution.HistoricalDevelopmentoftheAssemblyprocessIntheearlydaysofmanufacturingtechnology,thecompleteassemblyofaproductwascarriedoutbyasingleoperatorandusually,thisoperatoralsomanufacutredtheindividualcomponentpartoftheassembly.Consequently,itwasnecessaryfortheoperatortobeanexperinallthebariousaspectsofthework,andtraininganewoperatorwasalongandexpensivetask.Thescaleofproductionwasoftenlimitedbytheavailabilityoftrainedoperatorsratherthanbythedemandfortheproduct.In1798,theUnitedStatesneededalargesupplyofmusketsandfederalarsenalscouldnotmeetthedemand.BecausewarwiththeFrenchwasimminent,itwasalsonotpossibletoobtainadditionalsuppliesfromEurope.However,Eliwhitney,nowrecognizedasoneofthepioneersofmassproduction,offeredtocontracttomake10000musketsin28menths.Althoughittook10.5yuarstocompletethecontract,Whitney’snovelideasonmassproductionhadbeensuccessfullyproved.ThefactoryatNewHaven,Connecticut,builtspeciallyforthemanufactureofthemuskets,containedmachinesforproducinginterchangeableparts.Thesemachinesreducedtheskillsrequiredbythebariouoperatorsandallowedsignificantincreasesintherateofproduction.Inanhistoricdemonstrationin1801,Whitneysurprisedhisdistinguishedvisitorswhenheassembledmusketlocksafterrandomlyselectedpartsfromaheap.TheresultsofEliWhitney’sworkbroughtaboutthreeeprimarydevelopmentsinmanufacturingmethods.First,partsweremanufacturedonmachines,resultinginaconsistentlyhigherqualitythanthatofhand-madeparts.Thesepartswerenowinterchangeableandasaconsequenceassemblyworkwassimplified.Second,theaccuracyofthefinalproductcouldbemaintainedatahigherstandard,andthird,productionratescouldbesignificantlyincreased.OliverEbans’sconceptionofconveyingmaterialsfromoneplacetoanotherwithoutmanualeffortledeventuallytofurtherdevelopmentsinautomationforassembly.In1793,heusedthreetypesofconveyorsinanautomaticflourmill,whichrequiredonlytwooperators.Thefirstoperatorpouredrainintoahopperandthesecondfilledsackswithflourprocducedbythemill.Alltheintermediatoperationswerecarriedoutautomaticallywithconveyorscarryingthematerialfromoperationtooperation.ThenextsignificantcontributiontothedevelopmentofassemblymethodswasmadebyElihuRoot.In1849,ElihuRootjoinedthecompanythatwasproducingColt“six–shooters”.Eventhoughatthattimethevariousoperationofassemblingthecomponentpartswerequitesimple,hedividedtheseoperationsintobasicunitsthatcouldbecompletedmorequicklyandwithlesschanceoferror.Toot’sdivisionofoperationsgaverisetotheconcept“dividetheworkandmultiplytheoutput”.Usingthisprinciple,assemblyworkwasreducedtoverybasicoperationsandwithonlyshortperiodsofoperatortraining,highefficienciescouldbeobtained.FrederickWinslowTaylorwasprobablythefirstpersontointroducethemethodsoftimeandmotionstudytomanufacturingtechnology.Theobjectivewastosavetheoperator’stimeandenergybymakingsurethattheworkandallthingsassociatedtotheworkwereplacedinhebestpositionsforcarryingouttherequiredtasks.Tayloralsodiscoveredthatanyworkerhasanoptimumspeedofworkingwhich,ifexceeded,resultsinareductioninoverallperformance.Undoubtedly,theprincipalcontributortothedevelopmentofproductionandassemblymethodswasHenryFord.Hedescribedhisprinciplesofassemblyinthefollowingwords:“First,placethetoolsandthenmeninthesequenceoftheoperationssothateachpartshalltraveltheleastdistancewhilstintheprocessoffinishing”.“Second,useworkslidesorsomeotherformofcarriersothatwhenaworkmancompletehisoperationhedropsthepartalwaysinthesameplacewhichmustalwaysbethemostconvenientplacetohishandandifpossiblehavegravitycarrytheparttothenextwokman.“Third,useslidingassemblylinesbywhichpartstobeassembledaredeliveredatconvenientintervals,spacedtomakeiteasiertoworkonthem”.TheseprinciplesweregraduallyappliedintheproductionoftheModelTFordautomobile.Processplanninghasbeendefinedas“subsystemresponsiblefortheconversionofdesigndatatoworkinstruction”.Amorespecificdefinitionfoprocessplanningis“thatfunctionwithinamanufacturingfacilitythatestablishestheprocessesandprocessparameterstobeused(aswellasthosemachinescapableofperformingtheseprocesses)inordertoconvertapiece-partfromitsinitialformtoafinalformthatispredetermined(usuallybyadesignengineer)onadetailedengineeringdrawing.”Theinput(raw)materialtoaprocessmaytakeanumberofforms(inmachinning,thesematerialsnormallyresultfromametal-formingprocess;themostcommonofwhicharebarstock,castings,forgings,orperhapsjustaslabofmetal,otherprocesseshaveotherinputmaterials).Anothermachinningmaterialmightbeaburn-out(apartproducedbyaflame-cuttingoperation)cuttosomeroughdimension,orjustarectangularblockofmaterial.Thisinputmaterialmighthavealmostanyshapeandphysicalproperty.Someprocessesmayalterthesizeorsurfacetextureofapart.Otherprocess,likeheat-treating,changethephysicalpropertiesofmaterials.Morespecifically,annealingwouldtendtolessenthematerialhardnesssanddecreasetheworkpiecetensilestrength.Withthesetypesofrawmaterialsasabase,theprocessplannermustpreparealistofthose(machingning)processesneededtoconvertthisnormallypredeterminedmaterialintoitsspecifiedfinalgeometry.Thecommonestmetal-removalprocessthataprocessplannerhasathisdisposalareturning,facing,milling,drilling,boring,broaching,shaping,gundrilling,reaming,planing,sawing,trepanning,burnishaing,punching,andreinding.Somemanufacturingpeoplemayconsidersomeoftheoperationsassubsetsofamajorcategory.Reamingisoftenconsideredasubsetofdrilling.Othersmaydefinefurthermajorcategories.Someless-familiarprocesssuchaselectricdischargemachining(EDM),electrochemicalmachining(ECM),andlasermachiningzrealsousedformaterialremoval.Allapplicableprocessesthatareavailavleforproductionshouldbeconsideredbytheprocessplanner.ElementsofProcessPlanningDoyleseparatestheactivitiesperformedinprocessplanningintsveengeneralcategories.① Interpretthespecificationrequirements.② Positionthepartonthemachine.③ Determinetheintermediateproductrequirementsateachstageofprocessing.④ Selectthemajorpiecesofequipmenttohandletheprocessing.⑤ Selectthetoolingandsequenceofprocessingstepswithineachoperation.⑥ Computetheprocesstimerequirements.⑦ Documenttheprocessplan.Someoftheseactivitiescanbedividedintsmallerunits;however,theactivitiesdscribedprovidedaconbenientcategorizationforanalysis.Aprocessplannernormallyoperatesunderthefollowingconstraints.① Heplansforagivensetofmachines.② Themachinesarecapableofalimitednumberofmanufacturingoperations.③ Themachineshaveaspecificburden/workload.Giventhesemachineconstraints,andasetofengineeringdrawingscontainingspecificpatrtgeometryrequirements,theprocessplannerreliesonhisexperiencetodevelopasetofprocesscapableofproducingapart.Theselectionoftheprocessisneitherentirelyrandomnortotallypredictable.Thereisusuallymorethanoneprocesscapableofproducingaspecificsurface:theprocessplannermustchoosewhathebelievesisthebestprocess.Thisisnormallydonebyrecallingaimilarparts,oratleastsimilarsurfaces,andthemeansutilizedinmanufacturingthatpart.Inthismanner,theplannercomparesspecificprocessusedtoobtainsomesetoffinalspecificationsandchooseswhathebelievestobethebestalternative.Thistypeofplanningisknowasmanvariantprocessplanningandisthecommonesttypeofplanningusedforproductiontoday.Planningtheoperationtobeusedtoproduceapartrequiresknowledgeoftwogroupsofvariables:thepartrequirements(asindicatedbyanengineeringdrawing);andtheavailablemachinesandprocess,andthecapabilitiesofeachprocess.Giventhesevariables,theplannerselectsthecombinationofprocessesrequiredtoproduceafinishedpart.Inselectingthiscombinationofprocessesanumberofcriteriaareemployed.Productioncostortimeareusuallythedominatcriteriainprocessselection;however,machineutilizationandroutingoftenaffecttheplanschosen.Ingeneral,theprocessplannertriestoselectthebestsetofprocessesandmachinestoproduceawholefamilyofpartsratherthanjustasinglepart.Asonemightimagine,alargepartofprocessplanning,asitcurentlyexists,isanartratherthanascience.P