Treść książki
Przejdź do opcji czytnikaPrzejdź do nawigacjiPrzejdź do informacjiPrzejdź do stopki
TobeabletoanalyzeproductsandprocessespropernesswithSPC,ameasure-
mentoftheircharacteristicsshouldbemadeandmeasurementuncertaintyshould
beestimated.Analysisresultsshouldbearchived.
Thefirstprobleminstatisticalprocesscontrolisdisturbancediagnostics,which
isdoneusingqualitycharacteristicmonitoring(dataobtainedfrommeasure-
mentsorfromarchive,usuallyprocessedandverified,aredisplayedoncomputer
screenstomonitorthechangesandtendencies-sothisphaseiscalledmonitor-
ing).Thepresentationmethodofcollecteddataandprocessingmethodsusedde-
pendsontherecipientandpurpose.Inthesimplestcase,thismaybethedisplayof
anon-processedflowofmonitoredvalues.Presentationsofstatistics,projections,
basicquantityrelationsorglobalindicesincludingprocesscontrolcharts,device
functionalstates,machinetoolandprocesscapabilityfactorsaremoreimportant.
Informationondisplayshouldbeprocessedtothestatethatallowstoconclude
quicklyandeasily.Measurements,analysesandconclusionsmadecreatetogether
so-called“diagnostics”.Thesubjectofdiagnosticsmaybethetechnicalstateof
machinetools,aswellasdynamicstatesofprocesses.Diagnosticstasksarevery
differentandwide.Diagnosticsmayserveforon-lineoroff-lineprocesscontrol
orforcontrolprocessoptimization.Technicalstates(devices)ordynamicstates
(processes)determinedindiagnosticsareabasisforactionstobetakenondevices
orprocesses.Correctingorimprovingactivitiesunderstoodthiswayiscalled“su-
pervising”[19].
Accordingtotheabove,themainrulesofSPCmaybedeterminedas:
focusonprocesses;theresultofagoodprocessisalwaysagoodproduct,
minimizevariationsofprocesses,
superviseflowofproductionprocessestocheckiftheyarekeptatacertain
levelofprecision,
catch,atapropermoment,systematicalorspecialinfluenceswhichputthe
processoutofcontrol,
takecorrectionalandpreventiveactions,
constantlyimproveprocessquality,
fulfilltherequirementsofqualitymanagementstandards(e.g.ISO9001),
createthecompany’strustworthinessforcustomers.
Thethirdgoalmaybeactuallyachievedonlyifthemeasurementresults
areobtainedimmediately.Itispossibleonlywhenprocessmonitoringisdone
on-linewiththeuseofproperstatisticaltools(e.g.controlcharts)andtheCAQ
systemisincorporatedintothecompanycomputersystem.Apositiveconse-
quenceofSPCuseisthetighteningofrequirementsformanufacturingproc-
esses,moreeconomicaluseofmachinetoolsandcreationofconditionsfor
constantprocessimprovement[17].Insuchcase,theabilitytodifferentiate
14
