Transcript Slide 1

Chapter7: Quality Tools
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Tools for
Problem
Solving &
ANALYSIS
The QC Tools are
simple statistical tools
used
for
problem
solving. These tools
were either developed
in Japan or introduced
to Japan by the Quality
Gurus such as Deming
and Juran.
In terms of importance,
these are the most
useful. Kaoru Ishikawa
has stated that these 7
tools can be used to
solve 95 percent of all
problems.
QC TOOLS
The problems you face can be large or small, simple or complex,
and easy or difficult to solve. Regardless of the nature of the
problems, a fundamental part of every employee’s role is finding
ways to solve them. Having tools to solve problems and being a
confident problem solver is important to your success. Problem
solving tools are determined by the requirements of the problem
and the amount of time to solve the problem. There are four basic
steps in problem solving regardless of size or complexity:
1.
2.
3.
4.
Defining the problem
Generating alternatives
Evaluating and selecting alternatives
Implementing solutions
Objectives of this training
 To explain various tools that support deep analysis of problem solving.
 Explain how the QC tools Support in decision making after analysis,
 Update on the best proven tools in quality.
Proven
Tools for
industrial
problem
solving and
Analysis
The 7 QC Tools are simple statistical tools used for problem solving. These tools were either
developed in Japan or introduced to Japan by the Quality Gurus such as Deming and Juran.
In terms of importance, these are the most useful. Kaoru Ishikawa has stated that these 7
tools can be used to solve 95 per cent of all problems. These tools have been the foundation
of Japan's astonishing industrial resurgence after the second world war.
The following are the 7 QC Tools :
1.
2.
3.
4.
5.
6.
7.
Pareto Diagram
Cause & Effect Diagram
Histogram
Control Charts
Scatter Diagrams
Graphs
Check Sheets
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QC Tools
The Fishbone Diagram also referred to as the "Ishikawa
diagram," because Kaoru Ishikawa developed it, and the
"fishbone diagram," because the complete diagram
resembles a fish skeleton.
Fishbone Diagram
The symptom or result or
effect for which one wants to
find causes is put in the box
on the right.
Why
The lighter boxes at the end of
the large bones are main
groups in which the ideas
are classified.
The diagram illustrates the main causes and sub causes
leading to an effect (symptom). It is a team brainstorming
tool used to identify potential root causes to problems.
Because of its function it may be referred to as a causeand-effect diagram. In a typical Fishbone diagram, the
effect is usually a problem needs to be resolved, and is
placed at the "fish head".
The causes of the effect are then laid out along the
"bones", and classified into different types along the
branches. Further causes can be laid out alongside further
side branches. So the general structure of a fishbone
diagram is presented below.
Why
MAN
GAUGE
Component
Locking
The causes and its factors
are identified and entered as
branches to these main
groups.
Insufficient
power
Why
Method of
Alignment
Method of
Inspection
The Sub reasons or Sub
factors are linked to the
factors.
External
METHOD
Man
Materials
MATERIAL
Training
Availability
Expertise
Quality
Delivery
Purchase
Unable to complete
Project on time
Multi Use
Utilization
Approval
Availability
Performance
Maintenance
Availability
Funds
Methods
Machines
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QC Tools
Pareto Analysis
Pareto Analysis is a statistical technique in
decision making that is used for the selection of
a limited number of tasks that produce
significant overall effect.
It uses the Pareto Principle (also know as the
80/20 rule) the idea that by doing 20% of the
work you can generate 80% of the benefit of
doing the whole job.
In quality improvement, a large majority of
problems (80%) are produced by a few key
causes (20%). This is also known as the vital
few and the trivial many.
The value of the Pareto Principle for a
Black belt manager is that it reminds
you to focus on the 20% of things that
matter. Of the things you do during
your project, only 20% are really
important.
Pareto Diagram is a tool that arranges items in
the order of the magnitude of their
contribution, thereby identifying a few items
exerting maximum influence. This tool is used
in SPC and quality improvement for prioritising
projects for improvement, prioritising setting
up of corrective action teams to solve
problems, identifying products on which most
complaints are received, identifying the nature
of complaints occurring most often, identifying
most frequent causes for rejections or for other
similar purposes.
Dr.Juran suggested the use of this principle to quality control for separating the "vital few"
problems from the "trivial many" now called the "useful many".
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QC Tools
What is the shape of your data?
Knowing the shape of your data is as
significant as the measures like Mean,
Median etc. The shape of the data set
helps in identifying any obvious errors
and outliers that may be removed and
the measures recomputed. The shape
also helps in determining the spread in
the data. An important aspect of the
description of a variable is the shape of
its distribution, which tells you the
frequency of values from different
ranges of the variable. A data analyst
is interested in knowing how well the
distribution can be approximated by
the normal distribution. A simple study
of the shape gives a fair idea about the
datas approximation to normality.
Target
3.75 mm
Histogram
0.03 mm
USL:3.78
LSL:3.72
Histograms or Frequency Distribution Diagrams are bar charts
showing the distribution pattern of observations grouped in
convenient class intervals and arranged in order of magnitude.
Histograms are useful in studying patterns of distribution and in
drawing conclusions about the process based on the pattern.
Target
The Histogram is normal if the highest frequency is in the central
group and there is symmetrical tapering on either side of the central
group. The natural or normal distribution would indicate that the
process being studied is under control. A Histogram with an
unnatural pattern may indicate that there is possibly something
unusual with the process, but is not an evidence of a process being
out of control. For instance a Histogram depicting the distribution of
age of all citizens will not peak at the centre. It will start with a cliff
tapering gradually till around the life expectancy then dropping a
little faster and once again tapering into along tail.
Upon studying a histogram the following can be immediately
inferred.




Where is the process output concentrated?
What is the spread in the process?
Is the process performing within specification limits?
What are the outliers in the process and how to set
controllable limits?
 If action needs to be taken on the process, what action is
appropriate?
 Is the assumption on the distribution of the variable correct?
0.03 mm
USL:3.78
LSL:3.72
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QC Tools
Stage 5 Defects
Correlation
When solving a problem or analyzing a situation
one needs to know the relationship between two
variables. A relationship may or may not exist
between two variables. If a relationship exists, it
may be positive or negative, it may be strong or
weak and may be simple or complex. A tool to
study the relationship between two variables is
known as Scatter Diagram. A relation expressed in
correlation coefficient is between -1 and +1. The
extremes mean high correlation or relation ship
TOTAL
MADE
FIRST
TIME
PASSE
D
TOTAL
REJEC
TED
REJEC
TION
IN PPT
100
SHAFT
DAMA
GE
75
R2=0.84
50
10
BINDI
NG
20
FOULI
NG
30
OBSTR
UCTIO
N
Stage
3 Defects
40
Non
Unifor
m air
gap
FAN
BEND/
WOBB
LING
BRUS
H
NOISE
TOTAL MADE
FIRST TIME
PASSED
0.96
TOTAL REJECTED
0.51
0.23
REJECTION IN PPT
-0.05
-0.33
0.83
SHAFT DAMAGE
0.49
0.53
0.13
-0.19
BINDING
0.35
0.28
0.35
0.14
-0.10
FOULING
0.36
0.30
0.39
0.20
0.04
0.68
OBSTRUCTION
0.56
0.57
0.20
-0.15
0.13
0.73
0.58
Non Uniform air gap
0.62
0.55
0.43
0.11
0.54
0.14
-0.01
0.51
FAN
BEND/WOBBLING
0.19
-0.02
0.68
0.68
0.04
-0.18
0.08
-0.44
-0.03
BRUSH NOISE
-0.29
-0.52
0.57
0.87
-0.18
-0.09
-0.06
-0.53
-0.16
0.64
BEARING NOISE
0.21
0.21
0.07
-0.04
-0.17
-0.32
-0.01
-0.05
-0.06
0.24
-0.15
When solving a problem or analysing a situation one
needs to know the relationship between two
variables.
A relationship may or may not exist between two
variables. If a relationship exists, it may be positive
or negative, it may be strong or weak and may be
simple or complex.
A tool to study the relationship between two variables
is known as Scatter Diagram.
It consists of plotting a series of points representing
several observations on a graph in which one variable
is on X-axis and the other variable in on Y-axis. If
more than one set of values are identical, requiring
more points at the same spot, a small circle is drawn
around the original dot to indicate second point with
the same values. The way the points lie scattered 6
in
the quadrant gives a good indication of the
relationship between the two variables.
QC Tools
Component replacement method:
Component
replacement
Use this method to find the sub system that contributes to the
problem and also to identify the source of this problem.
Replace subcomponents from good with bad and find the
subsystem that contributes to the problem.
Component search is part of statistical engineering, as developed by Shainin, is a contrast
based approach to problem solving. Statistical engineers ask what's different rather than
what's wrong. They look for the largest source of variation, not all possible causes. They
avoid identifying lists of potential variables until the convergent process has substantially
narrowed the possibilities.
Dorian Shainin … has given us DOE tools that can diagnose and greatly reduce
variation, leading us beyond zero defects, beyond the milestone of Cpk of 2.0, to
near zero
variability. These tools are:
• Simple – understood by engineers and line workers alike. The mathematics
involved are unbelievably – elementary!
• Logical – based on common sense.
• Practical – easy to implement – in production, in design, with suppliers.
• Universal in scope – applicable in a wide range of industries, big and small,
process-intensive as well as assembly-intensive.
• Statistically powerful – in terms of accuracy, with no violations of statistical
principles.
• Excellent in terms of results – with quality gains not in the inconsequential
range of 10-50% improvement but in the 100-500% range!”
Consider component search on an electrical part with several subcomponents, by
swapping the good subcomponents with bad parts and also by replacing bad ones with
good subcomponents the results should vary based on the output. This should also be
repeated on many samples.
The Shainin methods look for the "Big Red X" as the main root cause of product
deficiencies. They help to identify the failed part in a few iterative steps, so that the
failure can be fixed quickly with minimum cost.
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Why?
QC Tools
Why?
Bad quality milk
Bad quality milk
5 Whys
Milk gone off
Milk gone off
Milk gone off
Milk gone off
When something goes wrong,
we tend to see it as a crisis and
seek to blame. A better way is
to see it as a learning
opportunity. Not in the
existential sense of general
self-improvement. Instead, we
can use the technique of asking
why five times to get to the
root cause of the problem.
Why?
Local store closed
Local store closed
Why?
Fridge Cold
Fridge Cold
etc.
etc.
Can't go to store
Can't go to store
Large store too far
Large store too far
No Milk in Fridge
No Milk in Fridge
The 5-Why is a useful exercise
to track a single line of cause
and effect but it seems to lead
to a causal factor rather than a
root cause.
Housemates
Housemates
finished milk
finished milk
No Money to buy
No Money to buy
milk
milk
To eat cereal
To eat cereal
To feed cat
To feed cat
Rent too high
Rent too high
Too many debts
Too many debts
Insufficient Salary
Insufficient Salary
The choice faced by people trying to solve problems is: HOW MUCH EFFORT IS NEEDED TO
FIND A REAL, EFFECTIVE SOLUTION TO A PROBLEM? IS IT WORTH MY TIME?
My point is that 5-Whys are EASY and easy-to-understand but often don’t get us to an
effective solutions. Thus no matter how easy the technique is, most people are wasting their
time but they THINK they are doing effective analysis. What they are really doing is trying
solutions and seeing what works.
But I think that it could be applied to 5-Whys. People have activity (they are asking
questions) but that doesn’t mean that the questions are helping them understand the
problem and develop effective solutions. Instead, they are guiding the questions to get to
answers THEY ALREADY KNOW. They then apply these answers which may work or which may
appear to work (because the incident doesn’t repeat in the near-term
Corrective actions:
bring the site back up remove the bad code
help so-and-so understand why his code
doesn't work as written train so-and-so in
the principles of TDD change the new
engineer orientation to include TDD.
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Process mapping is a tool that is used to understand, analyse and
document processes and activities in an organisation and assist in
identifying opportunities for improvement. A proper process map is like a
strong foundation for six sigma project and to be successful. A process
map displays the sequential steps involved in converting a specific input
into the required output,
QC Tools
Process Mapping
A Map is a visual representation for the team leader’s or an entire team’s thoughts, ideas
and questions relative to accomplishing the project goal. It should be one of the first tools
employed when starting any Six Sigma or process improvement project. The Map presents
a structure of information and helps a team progress through the DMAIC process. It is a
living document that will change throughout the project and has no set format. The process
map can be used to drive specific actions and select the Six Sigma tools that should be
employed. early in a project is it ensures that nothing is left out or missed. It is an effective
tool for ensuring all potential questions and issues of a project have been both identified
and addressed from the beginning of a project to completion. The following are the steps in
development of a process map.
Start
Marking
out
Cutting
to
Size
Testing
Review
Ship
Ship
Stop
Step 1: Define the Project Goal(s)
First and foremost, a team needs to clearly define the goal. What is the team trying to
accomplish? Is it a problem that needs to be solved? Is it a potential opportunity for
growth that needs to be explored? By defining the goal, the team also will define the
project scope. This is essential to do early on in a project. the scope, includes a problem
statement, objective, benefits, team members, process owner and Champion) is very
helpful in this step, as it should contain the goal or problem statement of the project.
Eg: “The receipt and processing of delivered materials takes too much time.”
Step 2: List the Knowns and Unknowns
For this step, it is most helpful to simply create two columns – one for what the team
knows and one for what the team does not know. It might be surprising how much
information is known, but even more surprising how much the team does not know.
Information can include, but is not limited to metrics, times, costs, issues, potential
barriers, points-of-contact, current problems, customer requirements, outputs, inputs,
process steps, quantities and locations.
Knowing pertinent information and data in the initial stages is important; however, equally
important is realizing what data the team will need to research.
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QC Tools
Process Mapping
Step 3: Ask DMAIC Questions and ‘Grouped’ Questions
This step coincides closely with the previous step. Team members will recognize that their
unknowns (from Step 2) and questions from this step are very similar. The main difference is
the approach. Using two separate approaches allows very different pieces of information and
questions to surface. In the previous step, the team is stating inquiries from the perspective
that they simply do not know a vital piece of information. In this step, they are asking
questions from both the DMAIC approach, as well as a grouped approach.
First, ask questions from the categorical perspectives of DMAIC: Define, Measure, Analyse,
Improve and Control. These will be the five areas into which all questions will be categorized.
It is important to ask as many questions as possible – this is really a brainstorming exercise
and no question is a bad question.
A MAP should include, but is not limited to:
Next, the team needs to ask
questions from the perspective of
groups that are within or affect the
process
 The project goal(s) or problem statement(s)
 Specific areas/parts of a process to be
analysed
 Any issues or questions to address
 What is known about those issues or
questions
 What is not known about those issues or
questions
 Initial assumptions about each issue or
question.
 What data or information is needed
 Potential barriers reaching the project goal
 Interconnections between each
part/issue/question
 Potential Six Sigma tools to be used
 When creating a MAP, the only wrong piece of
information is the one left out.
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QC Tools
Process Mapping
Step 4: Sequence and Link the Questions
Now it all comes together. Sequence questions below the problem
statement (or goal) and flow them down. Additionally, link
questions that are related to each other. The team members will
find in this step that they will generate many additional questions.
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QC Tools
Process Mapping
STEP 5: Identify Possible Tools to Be Used
Finally, the project team should identify the potential Six Sigma tools
to be used to answer the questions posed. The most effective way to
perform this step is to create a four-column matrix, as illustrated in
the table below. It should have a column for the question, the tool or
method, who is responsible, and the due date. And with this table,
the TMAP process is complete, and the Six Sigma project is off to a
strong start.
Matrix for Identify Potential Six Sigma Tools/Methods
Question
Tool/Method
How long and how many people
does the transportation steps
take?
Value Stream Map
How long and how many people
does the process steps take?
Value Stream Map
Where are our failure modes?
FMEA
How is the material inspected?
MSE
Percentage of small packages
versus large packages?
Data Analysis
Person
Responsible
Due Date
Another common format for a MAP is using a Mind Map or a relationship flow as illustrated
in the following process flow. This format often works better for processes that have many
links. The five-step process can still be used to create it. Format is not significant as long
as the MAP helps the team in achieving its objective of a successful Six Sigma project. This
approach gives a high level view of projects and processes in hand, also supports in
decision making for management.
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