Skip to main content
SpringerLink
Log in

Measuring process yield based on the capability index Cpm

  • Original Article
  • Published:
The International Journal of Advanced Manufacturing Technology Aims and scope Submit manuscript

Abstract

Process capability indices Cp, Ca, Cpk and Cpm have been proposed to the manufacturing industry as capability measures based on various criteria including variation, departure, yield, and loss. It has been noted in recent quality research and capability analysis literature that both the Cpk and Cpm indices provide the same lower bounds on process yield, that is, Yield≤2Φ(3Cpk)-1=2Φ(3Cpm)-1. In this paper, we investigate the behaviour of the actual process yield in terms of the number of nonconformities (in ppm) for processes with a fixed index value of Cpk=Cpm, but with different degrees of process centring, which can be expressed as a function of the capability index Ca. The results illustrate that it is advantageous to use the index Cpm over the index Cpk when measuring process capability, since Cpm provides better customer protection.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Kane VE (1986) Process capability indices. J Qual Technol 18(1):41–52

    Google Scholar 

  2. Chan LK, Cheng SW, Spiring FA (1988) A new measure of process capability: Cpm. J Qual Technol 20(3)162–175

    Google Scholar 

  3. Pearn WL, Kotz S, Johnson NL (1992) Distributional and inferential properties of process capability indices. J Qual Technol 24(4):216–231

    Google Scholar 

  4. Pearn WL, Lin GH, Chen KS (1998) Distributional and inferential properties of the process accuracy and process precision indices. Commun Stat Theory Method 27(4):985–1000

    Google Scholar 

  5. Ruczinski I (1996) The relation between Cpm and the degree of includence. Dissertation, University of Würzburg, Würzburg, Germany

  6. Boyles RA (1991) The Taguchi capability index. J Qual Technol 23(1):17–26

    Google Scholar 

  7. Vännman K (1997) Distribution and moments in simplified form for a general class of capability indices. Commun Stat Theory Method 26(1):159–179

    Google Scholar 

  8. Lin PC, Pearn WL (2002) Testing process performance based on the capability index Cpm. Working Paper, Center of General Education, National Chin-Yi Institute of Technology, Taiwan

Download references

Author information

Authors and Affiliations

  1. Department of Industrial Engineering & Management, National Chiao Tung University, Taiwan

    W.L. Pearn

  2. Center of General Education, National Chin-Yi Institute of Technology, Taiping, Taichung, 411, Taiwan

    P.C. Lin

Authors
  1. W.L. Pearn
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. P.C. Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to P.C. Lin.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Pearn, W., Lin, P. Measuring process yield based on the capability index Cpm. AMT 24, 503–508 (2004). https://doi.org/10.1007/s00170-003-1586-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00170-003-1586-1

Keywords

Search

Navigation