CAPAs and Trending of Quality Data
Measurement Systems Analysis
Spec Setting, Tolerance Analysis and Robust Design
Statistical Process Control
Design of Experiments
- Dr. Wayne A. Taylor
- Ann Taylor
- 1 (847) 367-1032
- 1 (847) 367-1037
- Postal address
- 5510 Fairmont Rd.
Libertyville, IL 60048
- Electronic mail
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A SOLUTION TO THE DILEMMA OF
WORST-CASE VERSUS STATISTICAL TOLERANCING
Dr. Wayne A.
When solving tolerancing problems, one must choose between worst-case tolerancing and
statistical tolerancing. Both of these methods have their pros and cons. If worst-case
tolerancing is used, all tolerances must be specified as worst-case tolerances. If
statistical tolerancing is used, all tolerances must be specified as statistical
tolerances. In reality, the behavior of certain inputs is best described using worst-case
tolerances while the behavior of other inputs is best described by statistical tolerances.
Still other inputs are not adequately represented by either type of tolerance. This
article reviews the two current methods of tolerancing along with their pros and cons. It
then introduces a new method of tolerancing, called process tolerancing, which solves many
of the problems associated with the current approaches. Process tolerancing represents a
unified approach to tolerancing that encompasses both of the previous approaches. Using
process tolerancing, worst-case tolerances and statistical tolerances can be combined into
the same analysis. The flexibility provided by process tolerancing results in solutions to
such common problems as multiple components from the same lot and off-center processes.
KEY WORDS: Statistical Tolerance, Worst-Case Tolerance, Process Tolerance, Variation
Transmission Analysis, Propagation of Error, and Six Sigma Quality.
To see entire
article, click here.
Presented at Fall Technical Conference, 1995