Quality Progress - February 2018 - 64

A new twist on an established
quality concept

The Physics
Of the Failure

Identify a problem's physical aspects to find its root cause
When developing a cause and effect diagram, it is important to start with the physics of the problem by identifying
exactly how such a situation could have happened while also
digging down as deep as possible into the fundamental physical mechanisms that could have caused the problem.
If two parts that shouldn't have contact are rubbing against
each other during operation, for example, the clearance
between the parts must have gone to zero, meaning part A
moved, part B moved or both moved.
Which of these three movements is physically possible or
likely under the circumstances of the rubbing? More broadly,
what hypotheses are compatible with your evidence? To determine this, you must look at the parts-or as Dorian Shainin said,
"Talk to the parts."1
Typically, a cause and effect diagram is created by:
+ Defining the problem.
+ Identifying major categories of causes of the problem (typically method, material, employee, machine, measurement
and environment).
+ Drawing the diagram.
+ Brainstorming potential causes of the problem under the
major categories.
+ Identifying potential subcauses for each cause.2
However, such a cause and effect analysis is opinion driven
and "A root cause analysis (RCA) should be empirical."3 Understanding the physics of the failure, creating a cause and effect
diagram and investigating the failure based on this understanding helps achieve the necessary empiricism to correctly
identify a root cause.

Broken welds

Suppose a cross-functional team is investigating the cause
of repeated broken welds in a welded frame. A typical cause
and effect diagram would depict method, material, employee,
machine, measurement and environment. Often, all six
aspects must be considered when evidence is scant and the
root cause is wide open.
When brainstorming to create a cause and effect diagram,
the first question should be, "What are the physics of the
failure?" In this example, the RCA team moderator or leader
should ask the subject matter experts what exactly could
explain the evidence.
One possible cause of a bad weld could be the welder's poor welding technique, but how do you test for poor

64 QP

February 2018 ❘ qualityprogress.com

by Matthew Barsalou and Robert Perkin

technique? Training records can be checked and the welder can be
observed while welding additional parts, but what if it was just a
momentary lapse in proper welding technique? Days of watching
the welder's future performance won't reveal what exactly happened when the failure occurred.
To explain the evidence, the RCA team must start by explaining the
physics of the failure. A poor welding technique may result in poor
contact between the material that is being welded, so this should be
listed in the cause and effect diagram, as shown in Online Figure 1.
There's no need to dig deeper into causes of an imperfect
contact at this point in the investigation. Possible causes should
be listed as subbranches of the diagram, as shown in Online Figure
1, if the team already has identified them, but this is just to ensure
the ideas are not forgotten over time. The team should consider
method, material, employee, machine, measurement and environment as potential causes, but branches shouldn't be added for the
sake of adding them.
This approach will eliminate many root cause hypotheses
that seem reasonable on their own, but in context cannot or are
unlikely to explain the problem you have.
REFERENCES
1. Keki R. Bhote, World Class Quality: Using Design of Experiments to Make It
Happen, Amacon, 1991.
2. Michael S. Perry, "A Fish(bone) Tale," Quality Progress, November 2006, p. 88.
3. Matthew Barsalou, "More Than Just Opinion," Quality Progress, March 2016,
pp. 38-43.

Matthew Barsalou is a statistical problem
resolution Master Black Belt at BorgWarner
Turbo Systems Engineering GmbH in
Kirchheimbolanden, Germany. He has a
master's degree in business administration
and engineering from Wilhelm Büchner
Hochschule in Darmstadt, Germany, and a
master's degree in liberal studies from Fort Hays State University
in Hays, KS. Barsalou is an ASQ senior member and holds several
certifications.

Robert Perkin is the chief engineer for
problem resolution and statistical methods
at BorgWarner Turbo Systems. Perkin
has master's degrees in management of
technology and engineering management
from Washington University in St. Louis.
He is a Smarter Solutions-certified lean Six
Sigma Master Black Belt.


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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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