文档介绍：Process Capability (Cp / Cpk / Pp / Ppk) Global Training Material
Creator : Global Mechanics Process Manager
Function : Mechanics
Approver : Gary Bradley / Global Process Team
Document ID : DMT00018-EN
Version / Status : / Approved
Location : Notes : \\…\ NMP \ DOCMANR4 \ PCP \ PC Process Library DocMan
Change History :
Issue Date Handled ments
21st Dec’01 Jim Christy & Søren Lundsfryd Approved for Global Use
NOTE – ments and improvements should be addressed to the creator of this document.
Contents
Section Heading / Description Page
1 Variation, Tolerances and Dimensional Control 4
2 Population, Sample and Normal Distribution 15
3 Cp and Cpk Concept 28
4 Use of the NMP Data Collection Spreadsheet 44
5 Confidence of Cpk 52
Process Capability
- Evaluating Manufacturing Variation
Acknowledgements
Benny Matthiassen (NMP CMT, Copenhagen, Denmark)
Frank Adler (NMP Alliance, Dallas, USA)
Joni Laakso (NMP R&D, Salo, Finland)
Jim Christy (NMP SRC, Southwood, UK)
Section 1
Variation, Tolerances and Dimensional Control
Two Types of Product Characteristics
Variable: A characteristic measured in physical units, . millimetres, volts, amps, decibel and seconds.
ON
OFF
Attribute: A characteristic that parison to some standard is judged “good” or “bad”, . free from scratches (visual quality).
In this training we deal with variables only
The Sources of Process/System Variation
Methods
Operators
Customer Satisfaction
Material
Environment
Equipment
Process
Two Types of Processes
All processes have:
Natural (random) variability => due mon causes
Stable Process: A process in which variation in es arises only mon causes
Unstable Process: A process in which variation is a result of mon and special causes
USL
LSL
nominal value
Defect
USL
LSL
nominal value
Unnatural variability
=> due to special causes
Shewhart (1931)
The Two Causes of Variation
Common Causes:
Causes that are implemented in the process due to the design of the proc