EMSE 182, 282 - Professor Jim Harris -Process Capability- 1PROCESS CAPABILITYOVERVIEW OF PROCESS CAPABILITYA measure of the ability (capability) of a process to produce acceptable partsSpecifically the ability of the process to produce parts within specified tolerancesNatural Tolerance Limits are often taken to be at 3„.5• For normal distribution this represents 99.73% of the process outputAprocess Capability Analysis is an engineering study to estimate process capability. Thismay include estiation of distribution, mean and variance• May be performed with regards to specifications about the quality characteristic• May be expressed as a percentage outside quality specifications• Specifications are not necessary but often usedUses• Predicting how well the process will hold the tolerances• Assisting product developers/designers in selecting or modifying a process• Assisting in establishing an interval between sampling for process monitoring• Specifying performance requirements for new equipment• Selecting between competing vendors• Planning the sequence of production processes when there is an interactive effect ofprocesses on tolerances• Reducing the variability in a manufacturing process
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EMSE 182, 282 - Professor Jim Harris -Process Capability- 2MEASUREMENT OF PROCESS CAPABILITYHistogram• Based on 100 or more points- obtain sample mean and variance and histogram• Shape aids in determining distribution