spc x-bar r control chart presentation

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1、STATISTICALPROCESSCONTROLSPCPROCESSINASTATEOFSTATISTICALCONTROLPROCESS“NOT”INASTATEOFSTATISTICALCONTROLPROCEDURETODETERMINEIFPROCESSISINASTATEOFSTATISTICALCONTROL1.Randomlysample“n”unitsthroughouttheday(canbeevery5minutes,every30minutes,etc.-whateverisappropriateforyourcase)2.Foreachsample,c

2、alculate“X-BAR”toestimatethemeanand“R(range)”toestimatevariability.NOTE:THERANGECANBEUSEDTOESTIMATETHESTANDARDDEVIATION.PROCEDURETODETERMINEIFPROCESSISINASTATEOFSTATISTICALCONTROL3.Aftercollectingthe20-25samples,calculateX-BAR-BAR(theaverageofalltheX-BARs)andR-BAR(theaverageofalltheranges)4.

3、UsingX-BAR-BARandR-BAR,calculatethecontrollimitsforyourX-BARandRControlCharts.X-BARCONTROLLIMITS:(X-BAR-BAR)+A2(R-BAR)RCONTROLLIMITS:D3(R-BAR)andD4(R-BAR)CONTROLCHARTCONSTANTSPROCEDURETODETERMINEIFPROCESSISINASTATEOFSTATISTICALCONTROL5.FortheRControlChart,plotallRvaluesontheRControlCharttose

4、eifalltheRangesare“betweenthecontrollimits”.Iftheyare,thenyourprocessisconsideredtobeinastateofstatisticalcontrol(asfarasthevariabilityoftheprocessisconcerned)6.FortheX-BARControlChart,plotalltheX-BARsontheX-BARcontrolcharttoseeifalltheX-BARsare“betweenthecontrollimits”.Iftheyare,thenyourpro

5、cessisconsideredinastateofstatisticalcontrol(asfarastheaverageoftheprocessisconcerned)NOTE1:IftheRchartisnotstable,donottrytoevaluatestabilityoftheX-BARchart.(alwayslookatRchartfirst)NOTE2:Thereareotherrulesavailabletohelpdeterminestatisticalstability,otherthanallobservationsbeingwithintheco

6、ntrollimits.ThesearenormallyreferredtoastheWECOrules.PLOTDATAONCONTROLCHARTSCALCULATEDTODETERMINESTATISTICALSTABILTIY(EXAMPLE:PROCESSINCONTROL)PLOTDATAONCONTROLCHARTSCALCULATEDTODETERMINESTATISTICALSTABILTIY(EXAMPLE:PROCESSNOTINCONTROL)PROCEDURETODETERMINEIFPROCESSISINASTATEOFSTATISTICALCONT

7、ROL7.Ifprocessisdeterminedtobe“NOTSTABLE”,thenstopandfindoutwhatanassignablecausemightbe,fix,andthenrepeatthecompleteprocessofcollectingnewdata.DONOTUSETHESEORIGINALCONTROLCHARTSTHATREFLECTEDANUNSTABLEPROCESSTOMONITORFUTUREPRODUCTION.8.Iftheprocess