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1、1 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialProcess Capability (Cp / Cpk / Pp / Ppk) Global Training MaterialCreator : Global Mechanics Process Manager Function : Mechanics Approver : Gary Bradley / Global Process Team Document ID : DMT00018-EN Version / Status : V.1.0 /
2、Approved Location : Notes : NMP DOCMANR4 PCP PC Process Library DocManChange History : IssueDateHandled ByComments 1.021st Dec01Jim Christy & Sren Lundsfryd Approved for Global UseNOTE All comments and improvements should be addressed to the creator of this document.2 NOKIA 2001 T0001801.PPT/ 21-Dec
3、-2001 / Jim ChristyCompany ConfidentialContentsSectionHeading / DescriptionPage1Variation, Tolerances and Dimensional Control4 2Population, Sample and Normal Distribution15 3Cp and Cpk Concept28 4Use of the NMP Data Collection Spreadsheet44 5Confidence of Cpk523 NOKIA 2001 T0001801.PPT/ 21-Dec-2001
4、/ Jim ChristyCompany ConfidentialProcess CapabilityProcess Capability - Evaluating Manufacturing Variation- Evaluating Manufacturing VariationAcknowledgementsBenny Matthiassen(NMP CMT, Copenhagen, Denmark) Frank Adler(NMP Alliance, Dallas, USA) Joni Laakso(NMP R&D, Salo, Finland) Jim Christy(NMP SRC
5、, Southwood, UK)4 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialSection 1Section 1Variation, Tolerances and Dimensional Control5 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialTwo Types of Product CharacteristicsVariable: A characteristic measured in ph
6、ysical units, e.g. millimetres, volts, amps, decibel and seconds.ONOFFAttribute: A characteristic that by comparison to some standard is judged “good” or “bad”, e.g. free from scratches (visual quality).In this training we deal with variables only6 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyC
7、ompany ConfidentialThe Sources of Process/System VariationThe Sources of Process/System VariationMethodsOperatorsCustomer SatisfactionMaterialEnvironmentEquipmentProcess7 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialTwo Types of Processes All processes have: Natural (random)
8、 variability = due to common causes Stable Process: A process in which variation in outcomes arises only from common causes Unstable Process:A process in which variation is a result of both common and special causesUSLLSLnominal valueDefectUSLLSLnominal valueUnnatural variability = due to special ca
9、uses8 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialShewhartShewhart (1931) (1931)The Two Causes of Variation Common Causes: Causes that are implemented in the process due to the design of the process, and affect all outcomes of the process Identifying these types of causes r
10、equires methods such as Design of Experiment (DOE), etc. Special Causes: Causes that are not present in the process all the time and do not affect all outcomes, but arise because of specific circumstances Special causes can be identified using Statistical Process Control (SPC)USLLSLNominal valueDefe
11、ctUSLLSLnominal value9 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialTolerancesLSL (lower specification limit) 10,7USL (upper specification limit) 10,9Acceptable partRejected PartRejected ProductNominal 10,80,1Rejected PartA tolerance is a allowed maximum variation of a dimen
12、sion.10 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialMeasurement ReportIn most cases we measure only one part per cavity for measurement report11 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialExample of Capability Analysis Data For some critical dimen
13、sions we need to measure more than 1 part For capability data we usually measure 5 pcs 2 times/hour=100 pcs (but sampling plan needs to be made on the basis of production quantity, run duration and cycle time)12 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialProcess Capability
14、 - What is it? Process Capability is a measure of the inherent capability of a manufacturing process to be able to consistently produce components that meet the required design specifications Process Capability is designated by Cp and Cpk Process Performance is a measure of the performance of a proc
15、ess to be able to consistently produce components that meet the required design specifications. Process Performance includes special causes of variation not present in Process Capability Process Performance is designated Pp and Ppk13 NOKIA 2001 T0001801.PPT/ 21-Dec-2001 / Jim ChristyCompany ConfidentialWhy Make Process Capability StudiesLSL (lower specification limit) 10,7USL (upper specification limit) 10,9Nominal 10,80,1This part is within spec. The tool would be approved if only this part was measuredThese parts are out of spec and could be approved if only one
