提高出品率与降低废品率

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1、YIELDIMPROVEMENTSVERSUSSCRAPRATEREDUCTIONConventionalattemptsatreducingcostsareoftenfocusedonscrapreduction.Yieldisoftenindicatedastheratioofthecastingweighttothetotalpourweight.Inahypotheticalcase,letusconsideracastingthathasyieldof48%.Ifthecurrentscraplevelas

2、sociatedwiththecastingisaround5%,theeffectiveyieldisaround45.6%(48%*(100-5/100)=45.6%).Letusassumethattheyieldofthatspecificcastingisincreased(bytheprinciplesoutlinedinthispaper)to73%andthereisanassociatedscrapequalto10%.Theresultanteffectiveyield(consideringlo

3、ssduetoscrap)isaround65.7%(73%*(100-10/100)=65.7%).Thus,theoveralleffectofyieldimprovementcanbeamoresignificantcostreductiontoolinspiteofanincreaseinscraplevels.Theauthorsdonotminimizetheimportanceofqualityimprovementsandscrapreductions.Scrapreductionthroughpro

4、cesscontrolandcontinuousimprovementisessentialforthesurvivalformostfoundries.Itismerelysuggestedthatyieldimprovementshouldalsobegivendueconsideration.Metalweighttomoldratioisoftenconsideredimportantsinceitindicatesthevolumeutilizationofthemoldforagivencasting.T

5、heincreasedvolumesofcoresusedinamoldalsoleadtoincreasedcosts.Allyieldimprovementeffortsshouldincludewaystogetadditionalcastingspermoldandminimizethevolumeofcoresusedineachmold.TENPRINCIPLESTOACHIEVEHIGHYIELDThefollowingtenrulesorideasassistinreducingthegatingsy

6、stemdimensionsandvolumeandresultinhigheryieldswithoutcompromisingcastingquality.Twocasestudiesattheendofthepaperillustrateapplicationsoftheseprinciples.1)UseofCeramicFoamFiltersConventionalapplicationoffiltersisbasedonreducingtheincidenceofscraprelatedtoinclusi

7、ons.However,theproperuseofceramicfoamfiltersintherunnersystemcanhelpreducethelengthoftherunnerandgates[1].Flowmodificationcanhelpreduceturbulenceinthegatingsystemandconsequentlytheformationofreoxidationslag.Longrunnersandingatesarenotneededtoactasslagtraps.Sign

8、ificantyieldincreasescan,thus,beachievedbyshorterrunnersandingates.2)UseofStableRawMaterialsOptimumperformanceisobtainedfromuseofrawmaterialsthatminimizevariationsintheproce