Quality Progress - February 2018 - 28

F E AT U R E

SIX SIGMA
effect on the mean.
FIGURE 7
A special valve is the key component in the simplified uncoupling
design concept described earlier, so
the design team applies the two-step
optimization strategy to optimize the
design of the inner part of the valve.
The prototype model, a hollow ball
with holes on it, is shown in Figure 7.
In this design, the control system
output is the flow rate. The controllable factors are the ball wall thickness and the hole diameter of the
prototype. The design team set two levels for hole diameter at 100
millimeters and 110 millimeters, respectively, and 2 millimeters and 3
millimeters for ball wall thickness.
Environmental temperature is the uncontrollable factor. The design
team sets the temperature at 10°C and 35°C in the DoE. Next, the team
runs a DoE based on Taguchi L8 orthogonal array design, and records
the flow rate of chemicals A and B during each experiment in columns
three and four of the DoE table (Table 1).
The design analyzer function in Minitab generates two main effects
plots-one for S/N ratios (Figure 8) and one for means (Figure 9).
The thickness of the ball wall is the important DP because it has a
significant effect on the S/N ration, as demonstrated by the steep main
effect line in Figure 8.
At the first optimization step, the design team sets the thickness at 3
millimeters to maximize the S/N ratio. Diameter is the mean adjustment
DP because it doesn't have a significant effect on the S/N ratio, but it
affects the mean significantly. At the second step, the design team sets

Prototype model of
the inner part of the
special valve

Main effects plot for S/N ratios
Data means
Thickness

Mean of S/N ratios

23.0
22.5
22.0
21.5
21.0
20.5
20.0
100

S/N = signal to noise

28 QP

February 2018 ❘ qualityprogress.com

110

2

Crown jewels

Axiomatic design and Taguchi
robust parameter design are the
crown jewels in the DFSS process.
In the design case described
earlier, axiomatic design helps
the design team develop a simple
uncoupling design concept that
maintains the independence of
the FRs while minimizing the
information content of the design
system. Taguchi robust parameter
design enables the design team
to optimize the design for a key
component of the control system.
The team uses these powerful tools to overcome a design's
conceptual and operational
vulnerabilities.

FIGURE 8

Diameter

the diameter at 103 millimeters to
bring the mean flow rate to the
target of 150 liters/minute.
By following the two-step
optimization strategy, the design
team successfully optimizes the
operational functions of one of
the major key components of the
control system.

3


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Table of Contents for the Digital Edition of Quality Progress - February 2018

Seen and Heard
Expert Answers
Progress Report
Mr. Pareto Head
Career Coach
Office Efficiency
The Crown Jewels of Design
Open Lines
Less Is More
ASQ 2018 Six Sigma Resource Guide
Standard Issues
Six Sigma Solutions
Statistics Spotlight
Marketplace
Footnotes
Try This Today
Quality Progress - February 2018 - intro
Quality Progress - February 2018 - cover1
Quality Progress - February 2018 - cover2
Quality Progress - February 2018 - 1
Quality Progress - February 2018 - 2
Quality Progress - February 2018 - 3
Quality Progress - February 2018 - 4
Quality Progress - February 2018 - 5
Quality Progress - February 2018 - Seen and Heard
Quality Progress - February 2018 - 7
Quality Progress - February 2018 - Expert Answers
Quality Progress - February 2018 - 9
Quality Progress - February 2018 - Progress Report
Quality Progress - February 2018 - 11
Quality Progress - February 2018 - Mr. Pareto Head
Quality Progress - February 2018 - 13
Quality Progress - February 2018 - Career Coach
Quality Progress - February 2018 - 15
Quality Progress - February 2018 - Office Efficiency
Quality Progress - February 2018 - 17
Quality Progress - February 2018 - 18
Quality Progress - February 2018 - 19
Quality Progress - February 2018 - 20
Quality Progress - February 2018 - 21
Quality Progress - February 2018 - The Crown Jewels of Design
Quality Progress - February 2018 - 23
Quality Progress - February 2018 - 24
Quality Progress - February 2018 - 25
Quality Progress - February 2018 - 26
Quality Progress - February 2018 - 27
Quality Progress - February 2018 - 28
Quality Progress - February 2018 - 29
Quality Progress - February 2018 - Open Lines
Quality Progress - February 2018 - 31
Quality Progress - February 2018 - 32
Quality Progress - February 2018 - 33
Quality Progress - February 2018 - 34
Quality Progress - February 2018 - 35
Quality Progress - February 2018 - 36
Quality Progress - February 2018 - 37
Quality Progress - February 2018 - Less Is More
Quality Progress - February 2018 - 39
Quality Progress - February 2018 - 40
Quality Progress - February 2018 - 41
Quality Progress - February 2018 - 42
Quality Progress - February 2018 - 43
Quality Progress - February 2018 - ASQ 2018 Six Sigma Resource Guide
Quality Progress - February 2018 - 45
Quality Progress - February 2018 - Standard Issues
Quality Progress - February 2018 - 47
Quality Progress - February 2018 - 48
Quality Progress - February 2018 - 49
Quality Progress - February 2018 - Six Sigma Solutions
Quality Progress - February 2018 - 51
Quality Progress - February 2018 - 52
Quality Progress - February 2018 - Statistics Spotlight
Quality Progress - February 2018 - 54
Quality Progress - February 2018 - 55
Quality Progress - February 2018 - 56
Quality Progress - February 2018 - 57
Quality Progress - February 2018 - Marketplace
Quality Progress - February 2018 - 59
Quality Progress - February 2018 - Footnotes
Quality Progress - February 2018 - 61
Quality Progress - February 2018 - 62
Quality Progress - February 2018 - 63
Quality Progress - February 2018 - Try This Today
Quality Progress - February 2018 - cover3
Quality Progress - February 2018 - cover4
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