Measuring Process Capability: Techniques and Calculations for Quality and Manufacturing Engineers

460 Pages·1997·29.256 MB·English

by  Davis R. Bothe

PROCESS
CAPABILITY
Techniques and Calculations for Quality
and Manufacturing Engineers
-1
DAVIS R. BOTHE
I fi.
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Measuring Process Capability
Techniques and Calculations for Quality and
Manufacturing Engineers
Davis R. Bothe
Umversidad Carlos In de Madrid
1176068
McGraw-Hill
NowYoifc SanFrancisco Washington,D.C. Auckland Bogota
Caracas Lisbon London Madrid MexicoCity Milan
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Sydnoy Tokyo Toronto
LibraryofCongressCataloging-in-PublicationData
Bothe.DavisR.
Measuringprocesscapability:techniquesandcalculationsfor
qualityandmanufacturingengineers/DavisR Bolhe
p. cm.
Includesindex.
ISBN0-07-006652-3(alk.paper)
I. Manufacturingprocesses. 2. Qualitycontrol-Statistical
methods. I. Title
TS176.B67 1997
658.5-dc21 96_30087
C1P
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Contents
Preface xiii
Chapter 1. Introduction
1.1 References 4
Chapter 2. Importance of Process Stability 5
2.1 Definition ofStability 6
2.2 ReviewofVariable-DataControl Charts 8
2.3 WhyControl Charts Are BetterThan Inspection 13
2.4 Control Limit FormulasforVariable-DataCharts 17
2.5 Operational Definition of "In Control" 20
2.6 Specification Limitsvs. Control Limits 21
2.7 Summary 22
2.8 Exercises 23
2.9 References 26
Chapter 3. Estimating Process Parameters
from Variable-Data Charts 29
3.1 Estimatingthe Process Average,ji 29
3.2 Estimatingthe Process Standard Deviation,a 32
3.3 Why Process Parameters CannotBeCorrectlyEstimated
foran Unstable Process 42
3.4 Summary 46
3.5 Exercises 47
3.6 References SO
Chapter 4. Defining Process Capability 53
4.1 Process Capability DefinedforBilateralSpecifications 54
4.2 Process CapabilityDefinedfor Unilateral Specifications 55
4.3 Need forDifferentCapabilityMeasures 55
4.4 Selecting Critical Characteristics 58
vii