The 7 Basic Quality
Tools
Michele Cano
Agenda
•
•
•
•
Introductions
Basic Tools – Ishikawa
Exercises
Discussion & Video
………………….Lunch……………………….
• Problem solving (Global 8D and TRIZ)
• Case study
• Discussion
Why use tools?
• Measure
• Improve
What are they?
The seven basic tools according to Ishikawa are:
• Check sheets
• Flow charts
• Graphs & Histograms
• Pareto diagram
• Cause and effect diagram
• Scatter diagram
• Control chart
1.Check sheets
• What is a check sheet?
• A form or sheet used to record data.
Function of Check Sheets
According to Ishikawa 1982, check sheets
have the following functions:
1. Production Process distribution checks
2. Defective item checks
3. Defective location checks
4. Defective cause checks
5. Check-up confirmation checks
6. Others
Example of a simple check
sheet. (for car valet operation)
Car type
Car registration
Ford Focus
W357 PHR
Interior vacuumed
√
Upholstery cleaned
√
Dash board cleaned
√
De odorised
√
Body washed
√
Washed waxed & Polished
√
Under car washed
√
Wheels washed
√
Tyres blacked
√
Comments:
can not be covered
Front bumper badly scratched on delivery, this
Performed / Checked by J
Date
2 May 2008
Example of a simple process
check sheet. (attributes)
Model XYZC217
failures
Batch
1
2
3
1
2
1
6
4
2
4
5
6
7
8
9
1
0
Power up
Boot up
1
2
Sink test
2
1
1
1
Case damage
1
1
2
Keyboard damage
Monitor damaged
1
2
Bundled s/w included
3
Checked by
pj
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m
1
jj
[j
l
m
3
l
m
r
m
pj
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Flowcharts
PROCESS MAPPING
• Process mapping is an essential first step.
• It identifies all of the process activities,
sequence and responsibilities.
• This can either be in a written format, or as
a flowchart.
Flowcharts
PROCESS MAPPING (Written format)
Enquiry handling
Activity
1. Customer enquiry
received and
logged onto system
2. Enquiry briefly
overviewed and
allocated to sales
estimator for
through.
3. If it cant be done,
return to customer
Responsibility
Sales Director
Associated documents
Customers enquiry
Customers drawing
Work instruction S10
Sales Director
Sales Director
Customers enquiry
Customers drawing
4. If it has been made
before, prepare a
new quote based on
previous job and
current pricing,
otherwise go to
step 10.
5. Send to customer
for acceptance
6. Review quote
7. Quote is acceptable
8. Log as order and
create order
package
9. Pass to Production
control
Sales Director
Customers enquiry
Customers drawing
Previous job file
Current price list
Sales Director
Quotation
Customer
Customer
Quotation
Quotation
Quotation
Customer drawing
Work instruction S30
10. Allocated to sales
estimator
11. .
12.
Sales director
13.
14.
15.
16.
Sales Director
Order package
Etc.
Customers enquiry
Customers drawing
Flowcharting
• Flowcharting is a graphical tool for
analysing processes.
• Constructing flowcharts leads to a better
understanding of processes.
• Better understanding of processes is a
essential for improvement
Flowcharts
Some standard symbols
Start or end
An activity
a decision point in the process.
a point at which the flowchart connects
with another process.
An off page connection
All records are identified
FLOWCHART
SM01 Enquiry Handling / Quotation Process
Customer
Sales director
Customer sends
enquiry
Estimator
Sales department
receives enquiry
Enquiry entered
into the electronic
Quote log &
Unique serial
number entered
Customer
informed that we
are unable to
quote
No
Can this
enquiry be
Quoted ?
Yes
Have the
item (s) been
made before?
No
Enquiry allocated
to Estimator
Raise estimate
sheet & plan
process
Quote prepared
from Price guide
Organize contract
review to cover
Quality
Contractual &
Manufacturing
aspects
Quote customer
Prepare Quote
Exercise
Draw a flowchart for one of the following
processes:
– Making a cup of coffee
– Enrolling students
– Wiring a plug.
3. Graphs & Histograms
Graphs, either presentational or mathematical
are used to allow understanding and
analysis of collected data sets.
Graphs
BAR CHARTS
• This is the data set totalled up and shown
graphically.
• It immediately identifies the major defects for all
to see.
Type
Monitor
damaged
Bundled
s/w
included
Keyboard
damage
Case
damage
Sink test
Boot up
16
14
12
10
8
6
4
2
0
Power up
Quantity
Defects
100
90
80
70
60
50
40
30
20
10
0
01/02/03
02/02/03
03/02/03
04/02/03
05/02/03
06/02/03
07/02/03
08/02/03
09/02/03
10/02/03
11/02/03
12/02/03
13/02/03
14/02/03
15/02/03
16/02/03
17/02/03
18/02/03
19/02/03
20/02/03
21/02/03
22/02/03
23/02/03
24/02/03
25/02/03
26/02/03
27/02/03
28/02/03
Graphs
• The below graph shows a factory output for
February. This time it shows specific dates
which could be analysed.
Feb production output
Output %
Average
Graphs
• The graph below shows the major cause for
customer complaint, the use of the pie chart and
the colours enforce the message.
Customer complaints 2007
by qty
15
20
Product quality
5
Shipped Late
Shipped early
Shipped wrong goods
60
Rules for Graphing
• Use Clear titles an indicate when the data
was collected
• Ensure the scales are clear,
understandable and represent the data
accurately.
• When possible use symbols for extra data.
• Always keep in mind the reason why the
graph is being used.
Exercise
Graphs
• You are the marketing director of XZY automotive, a new
Scottish company. You have organised a local survey to
rate your car against other small cars.
• 30 people were polled and the results are shown below.
• Xzy, ka, Clio, Clio, ka, fiesta, xzy, ka, 206, xzy, fiesta,
fiesta, xzy, polo, fiesta, 206, 206, polo, 206, fiesta, fiesta,
fiesta, polo, xzy, polo, fiesta, xzy, xzy, ka, xzy.
• You recognise the power that graphs produce. And you
have decided to Graph the results as part of you
marketing drive. Explain your choice of graph.
What is a Histogram?
• The Histogram is a graphical
representation of data that is a
dimensional measurement of one feature.
What is a Histogram?
• This is the computer defect data set totalled up
and shown graphically, but is it a histogram?
Defects
Sink test
5
Case damage
4
Keyboard damage
0
Monitor damaged
3
Bundled s/w included
7
Type
Bundled
s/w
included
15
Keyboard
damage
Boot up
Sink test
4
16
14
12
10
8
6
4
2
0
Power up
Power up
Total
Quantity
Checks/only record failures
What is a Histogram?
• The answer to the previous question is
NO
• The Histogram is a graphical
representation of data that, is a
dimensional measurement of one
feature.
When is a Histogram Used?
• To look at one particular set of results
• To check for patterns in a process
• To examine large amounts of data
Histograms
• The following data was collected when measuring
the bow (warp) of a plastic component. The
specification is 0 to 8 x10-3 mm.
• At a glance this tells you very little, but it can be
plotted as a histogram because we have quantities
data with target limits.
Bow measurements
2
5
8
8
2
4
6
6
6
4
4
7
6
6
4
8
7
7
5
9
Histograms
More
Frequency
6
0
0
1
0
2
2
3
0
4
4
5
2
6
5
7
3
8
3
9
1
0
5
Frequency
Bin
4
3
2
1
0
Thou
What is a Histogram?
Exercise
• Sort the following data into appropriate
sets, then plot them.
• The limits are 3 volts ± 0.1
• What can you deduce from this?
What is a Histogram?
Exercise
3.00
3.00
2.80
2.85
2.85
2.85
2.90
2.90
2.85
2.80
2.80
2.80
2.85
2.90
3.05
2.95
2.70
2.90
3.00
2.90
2.85
2.75
2.90
2.85
2.95
3.00
2.85
2.80
2.85
3.05
2.80
2.65
2.95
3.00
3.05
2.80
2.85
2.85
2.85
2.85
2.85
2.90
2.85
2.90
2.95
2.85
2.90
2.85
2.75
2.85
4. Pareto Analysis
Pareto
What is Pareto Analysis?
• Pareto analysis is a method for prioritising
data.
• It consists of a Bar Chart displayed either
in order of frequency or relative cost.
Pareto
Example:
The information to be represented on a Pareto diagram should already
have been collected in some sort of record.
Houshold repairs over the last 10 years
Problem
frequency
Light bulb fails
Broken central heating
pump
Broken window
Leaking taps
Faulty central heating
boiler
Leaking radiators
Cost £ per Total cost
occurance £
100
0.6
60
1
2
16
190
50
2.5
190
100
40
1
3
3000
15
3000
45
Pareto
Pareto Chart
The data are then displayed graphically. Firstly in terms of
frequency.....
120
100
80
60
40
20
0
frequency
Fault
Broken
central
heating
Faulty
central
heating
Broken
window
Leakiung
radiators
Leaking
taps
Cum %
Light
bulb fails
Occurance
House repairs 1998-2008
Pareto
... and then by cost.
House repairs 1998-2008 Total cost £
3500
3000
2500
2000
1500
1000
500
0
Total cost £
Faulty
central
heating
boiler
Broken
central
heating
pump
Broken
Light Leakiung Leaking
window bulb fails radiators
taps
Exercise
Pareto
Plot the following data as a Pareto chart
Model XYZC217
Checks/only record failures
Batch number
1
2
3
1
2
1
6
4
2
4
5
6
7
8
9
10
Power up
Boot up
1
2
Sink test
2
1
1
1
Case damage
1
1
2
Keyboard damage
Monitor damaged
1
2
Bundled s/w included
3
1
3
Checked by
pj
am
jj
[j
lm
lm
rm
pj
am
pj
6. Cause and Effect
Diagrams (Ishikawa)
A method for the identification of
the root cause of a problem.
cause and effect
What is Brainstorming?
• A way to get creative ideas.
• A way to get everyone’s views.
• A way to generate alternatives.
cause and effect
Potential Uses (Brainstorming)
• For identifying areas for improvement.
• For finding potential causes of problems.
• For developing possible preventive
actions.
cause and effect
Some Guidelines (Brainstorming)
Do’s
• Give wild and
unusual ideas.
• Aim for quantity.
• Build on ideas of
others.
• Encourage
participation.
Don'ts
• Evaluate or criticise.
• Stop to soon.
• Allow domination or
idea ownership.
cause and effect
Ranking
Ranking can be used after brainstorming to assess the teams
Priority position on a list of ideas. The basic procedure is:
•Each person privately selects 3 to 5 items from the list
•Each person ranks their selection in order of priority
•The marks are then totalled for each item
•The item having the highest total is then judged to have the
highest priority
cause and effect
What is a Cause and Effect Diagram?
• The process of a cause and effect diagram consists of
defining an effect in terms of possible causes and is
normally carried out in the form of a Brainstorming
session.
• The principal causes are typically Man, Materials,
Methods or Machines.
• These are then reduced to sub-causes.
• Finally, the most likely causes are then circled and are
subject to future examination.
cause and
effect
Layout:
Method
Man
Sub-Cause
Sub-Cause
Sub-Cause
Effect
Sub-Cause
Materials
Sub-Cause
Sub-Cause
Machines
6. Scatter Diagrams
A method for the identification the
relationship (effect) between two
factors (Causes).
Scatter diagrams
What is it used for?
• Validating "hunches" about a cause-andeffect relationship between two variables.
• Displaying the direction of the relationship
(positive, negative, etc.)
• Displaying the strength of the relationship
Scatter diagrams
Constructing scatter diagram
Variable b
• In order to construct a scatter diagram you need two
variables to be plotted against each other. One on
the x axis the other on the y axis.
• The relationship is then plotted.
relationship
Variable a
Scatter diagrams
Constructing scatter diagram
Variable b
• This process is continued, showing the effect of
changes in one of the variables against the other
variable.
Variable a
Scatter diagrams
Interpreting a scatter diagram
Variable b
• The diagram below shows a Strong Positive
relationship between the variables (an in crease in a
results in a positive increase in b, which is almost
uniform.)
Variable a
Scatter diagrams
Interpreting a scatter diagram
Variable b
• The diagram below shows a Strong Negative
relationship between the variables (an in crease in a
results in a decrease in b, which is almost uniform.)
Variable a
Scatter diagrams
Interpreting a scatter diagram
Variable b
• The diagram below shows a Weak Positive
relationship between the variables.
Variable a
Scatter diagrams
Interpreting a scatter diagram
Variable b
• The diagram below shows a Weak Negative
relationship between the variables.
Variable a
Scatter diagrams
Interpreting a scatter diagram
Variable b
• The diagram below shows a that there is no
relationship between the variables.
Variable a
7. Control Charts
A method for monitoring a process
for preventing defects.
Control charts
What are control charts
• Control charting is the most technically sophisticated tool
of the 7 quality tools.
• It was developed in the 1920s by Dr. Walter A. Shewhart
of the Bell Telephone Labs. Dr. Shewhart developed the
control charts as a statistical approach to the study of
manufacturing process variation.
• The purpose was to improve the process effectiveness
and therefore reduce costs.
• These methods are based on continuous monitoring of
the process variation.
Control charts
Why use control charts
• A Control chart is a device for describing in a precise
manner what is meant by statistical control.
• it helps the process perform consistently and
predictably.
• it can minimise the variation in output.
• it can help to achieve lower product costs.
• it can help to increase effective capacity.
• it can help to meet customer expectations
Control charts
Types of control charts
• You will come across two types of Control
Charts used in SPC (Statistical Process
Control).
1.Attribute SPC
2.Variable SPC
Control charts
Attribute control charts
• Attribute data is based upon two conditions (pass/fail, go/nogo, present/absent) which are counted, recorded and
analysed.
• Control chart techniques are important for the following
reasons:



Attribute-type situations exist in any process.
Attribute-type data is already available in many situations –
(existing inspections, repair reasons, reject segregation &
sorting) In these cases, no additional data collection is
required, you just have to convert the data into chart form.
Where new data must be collected, attribute information is
usually quick and inexpensive to obtain.
Control charts
Variable control charts
• Control charts for variables are used to
control the variation of processes in cases
where the characteristic under
investigation is a measurable quantity.
Control charts
Variable control charts
• Xbar&R CHARTS.
• Xbar&R charts are used as a pair;
Control charts
Example of an Attribute control chart
Control charts
Example of a variable control chart
Moving Range Variable Control Chart
Process
ESPC coating
Characteristic
Oven temperature
Upper Spec:
185.0 Lower Spec
X Bar
181
R Bar
(Sub-group Sampling)
UCL R
175.0 Upper Control Limit
Frequency
Lower Control Limit
60 Piece Capability Study
190
188
186
UCL
USL
2
184
X bar
182
3
180
xbar
178
LCL
176
LSL
174
172
1
R bar
170
15.0
10.0
5.0
0.0
X1
X2
X3
X4
X5
X bar
R
Op
Time
Date
UCL
182 182.5 176.0 183.5 183.0 183.0 184.0 183.0 184.0 183.5 176.0 176.0 176.0 182.0 176.0 178.0 176.0 186.0 187.0 182.0
176 182.0 183.5 184.5 184.0 183.5 184.0 183.0 186.0 184.5 183.0 183.0 176.0 176.0 176.0 175.0 176.0 185.0 186.0 176.0
176.0 183.0 184.0 183.5 184.0 182.5 182.0 176.5 184.5 172.0 183.5 176 176.0 184.0 182.5 182.5 180.0 180.0 182.0 184.0 184.0 184.0 183.0 183.0 176.0 175.0 174.0 183.0 183.0 186.0 183.5
182.0 182.0 183.0 176.0
183.5
184.0 183.5 183.0 183.0 170.0 176.0
183.0 176.0 183.0 176.0
176.0
183.5 182.5 182.0 183.0 173.5 176.0
180.3 180.3 183.3 178.5
181.2
183.3 182.7 180.5 183.5 171.8 178.5 178.0 180.2 181.2 183.5 183.2 182.2 182.7 182.7 184.7 184.0 181.0 180.7 178.3 178.0 175.7 175.7 178.3 184.7 186.3 180.5
7.0
7.0
1.0
7.5
8.0
1.5
1.5
6.5
1.5
3.5
7.5
6.0
6.5
8.0
2.0
1.5
3.5
4.0
1.0
2.0
1.0
8.0
7.0
7.0
6.0
1.0
4.0
7.0
3.0
1.0
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
R.Mc
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
5/4
Cp
0.61
NEW CALCULATED LIMITS
X bar
180.823
R Bar
4.6094
UCL X
185.524
LCL X
176.121
UCL R
30.089
Cpk 0.51
Sigma
2.7274
7.5
5/4
Problem Solving
• 5 Why
• Global 8D
• TRIZ