The Basics 7 QC Tools - ADDVALUE - Nilesh Arora
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Transcript of The Basics 7 QC Tools - ADDVALUE - Nilesh Arora
Best Performing Consulting Organization
by
“TQM / 7 QC Tools”
Adding Value In Totality !!
Introduction• The 7 QC Tools are simple statistical tools used for problem
solving• Inspired after seven famous weapons of Benkei. Viz 1. Masakari-Broad Axe2. Kumade- Rake3. Nagihama - Sickle weapon4. hizuchi- Wooden mallet5. Nokogiri- Saw6. Tetsubo- iron staff7. sasumata- Half moon spear• It was possibly introduced by Kaoru Ishikawa who in turn was
influenced by a series of lectures W. Edwards Deming had given to Japanese engineers and scientists in 1950
Conti…
• “The term “7 tools for QC” is named after the 7 tools of the famous warrior,Benkei. Benkei owned 7 weapons, which he used to win all his battles. Similarly, from my own experience, you will find that you will be able to solve 95% of the problems around you if you wisely use the 7 tools of QC.”
- ISHIKAWA KAORU, Professor Emeritus, University of Tokyo• These tools have been the foundation of Japan's astonishing
industrial resurgence after the second world war.
Basic QC Tools
• The following are the 7 QC Tools :1.Pareto Diagram2.Cause & Effect Diagram3.Histogram4.Control Charts5.Scatter Diagrams6.Flowchart7.Check Sheets
Pareto Diagram 1/2• Origin of the tool lies in the observation by an Italian economist
Vilfredo Pareto that a large portion of wealth was in the hands of a few people.
• Dr.Juran suggested the use of this principle to quality control for separating the "vital few" problems from the "useful many".
• Also referred as 80/20 rule viz your 80% of problems are due to 20% of cause.
• It is used in the field of materials management for ABC analysis. 20% of the items purchased by a company account for 80% of the value. These constitute the A items on which maximum attention is paid
• It works on cumulative frequency and shows how few items exert maximum influence
Pareto Diagram 2/2For E.g• 80 % of sales revenue is earned by 20% of firm’s products• 20 % of the items in a factory Store may account for 80 % of
the volume of items issued• 80 % of defects are caused by 20% of the possible defects
type
• Also used in conjunction with Brainstorming, Cause and Effect Analysis and Cumulative Line Chart. The Diagram displays, in decreasing order, the relative contribution of each cause or problem to the total
• The relative contribution can be based on the number of occurrences, the quality damage or the cost associated with each cause or problem
How to create a Pareto Diagram 1/2
Types of Defects Number of Defects A-Lever Tight 10B-W/High 42C-Less Torque 6D-Pause Fail 104E-Abnormal noise 4F-Auto Stop Fail 20G-Others 14
1 2 3
4
Types of Defects Number of Defects D-Pause Fail 104B-W/High 42F-Auto Stop Fail 20G-Others 14A-Lever Tight 10C-Less Torque 6E-Abnormal noise 4
200
Types of Defects No.of Defects Cumulative Total
D-Pause Fail 104 104B-W/High 42 146F-Auto Stop Fail 20 166G-Others 14 180A-Lever Tight 10 190C-Less Torque 6 196E-Abnormal noise 4 200
200
Types of Defects Number of Defects Cumulative Total % Cumulative D-Pause Fail 104 104 52B-W/High 42 146 73F-Auto Stop Fail 20 166 83G-Others 14 180 90A-Lever Tight 10 190 95C-Less Torque 6 196 98E-Abnormal noise 4 200 100
200
D-Pause
Fail
B-W/H
igh
F-Auto St
op Fail
G-Others
A-Leve
r Tigh
t
C-Less
Torq
ue
E-Abnorm
al noise
020406080
100104
4220 14 10 6 4
5
Number of Defects
0102030405060708090
100104
42
2014 10 6 4
Number of Defects % Cumulative
6
0102030405060708090
100
0102030405060708090100
104
42
2014 10 6 4
52
7383
9095 98 100
Number of Defects % Cumulative
7
How to create a Pareto Diagram 2/2
Pareto Diagram
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9095
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Number of Defects % Cumulative
No. of Defects
Types of Defects
Cause & Effect Diagram 1/2• It is called Fish-Bone Diagram due to the shape of the completed
structure.• This was proposed by Kaoru Ishikawa in the 1960s,hence also
referred as Ishikawa Diagram • The Ishikawa diagram shows the causes of a certain event. A
common use of the Ishikawa diagram is in product design, to identify potential factors causing an overall effect
• It shows the relation between a quality characteristics and factors• Causes in the diagram are often based on a certain set of causes,
such as the 5M+1E,8 P's or 4 S's• Cause-and-effect diagrams can reveal key relationships among
various variables, and the possible causes provide additional insight into process behaviour.
Cause & Effect Diagram 2/2• Causes in a typical diagram are normally grouped into categories,
the main ones of which are:• The 5M+1E- recommended for the manufacturing industryMachine, Method, Materials, Measurement, Men and Environment• The 8 P's - recommended for the administration and service
industriesPrice, Promotion, People, Processes, Place / Plant, Policies, Procedures, and Product (or Service)• The 4 S's - recommended for the service industrySurroundings, Suppliers, Systems, Skills • Causes should be specific, measurable, and controllable derived
from brainstorming sessions. Then causes should be sorted through affinity-grouping to collect similar ideas together. These groups should then be labeled as categories of the fishbone.
Procedure for making C&E diagram
STEP 1:• Determine the Pain point/ characteristicSTEP 2:• Draw in the backbone from left to right, and enclose the characteristic in a square• Next, write the primary causes which affect the characteristics as big bones also enclosed by squaresSTEP 3:• Write the causes (Secondary Causes) which affect the big bones (Primary Causes) as medium sized bones• Write the causes (Territory Causes) which affect the medium sized bones as small bones.
STEP 4:
• Assign an importance to each factor, and mark the particularly important factors that seem to have a significant effect on the quality characteristics.
STEP 5:
• Record any necessary information
Conti…
Histogram 1/2
• Histogram is a graphical technique to represent dispersion of data
• Ideally it will have symmetrical shape tapering away on both sides from target value
• For E.g 1. Production from same production line usually differs slightly
in dimensions, hardness, or others qualities2. when we commute to work every day, the time required
varies from one day to otherThus , Histogram can be used to • To find out if the lot has acceptance dispersion• To compare with target value and specification limits to
identify special causes of variation
• Histogram is a graph that represents the class frequencies by vertical adjacent rectangles in a frequency distribution.
• In a histogram, the magnitude of the class interval is plotted along the horizontal axis and the frequency on the vertical axis
• Since each class has lower and upper values, hence two equal vertical lines represent the frequency.
• Upper ends of the two lines representing the class interval are joined together. The height of rectangle thus obtained are proportional to their frequencies.
Histogram 2/2
Methodology for drawing Histogram
1 2How to calculate frequency in Excel1. Select the cell2. Go to Formulas/More
Functions/ Statistical/Frequency
3. Select the Data & Bin limits
4. You will have the frequency
5. Select the cell range of FREQ equal to BIN LIMITS 6. Go to Formula Bar in Excel
and press ctrl+shift+enter7. You will have FREQ for defined range
STUDENT %A 47B 45C 78D 82E 89F 45G 55H 65I 58J 68K 52L 57M 89N 35O 65P 58Q 50R 52S 73T 62U 59V 65W 68X 84Y 82Z 80
STUDENT % BIN LIMITS FREQUENCYA 47 0 0B 45 5 0C 78 10 0D 82 15 0E 89 20 0F 45 25 0G 55 30 0H 65 35 1I 58 40 0J 68 45 2K 52 50 2L 57 55 3M 89 60 4N 35 65 4O 65 70 2P 58 75 1Q 50 80 2R 52 85 3S 73 90 2T 62 95 0U 59 100 0V 65W 68X 84Y 82Z 80
HISTOGRAM
Almost a TWIN PEAK
Case
3. Draw the Bar graph and set the limits. You will have a histogram
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1000
0.5
1
1.5
2
2.5
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3.5
4
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Histogram- Student's Performance
FREQUENCY
Bin limits
Freq
uenc
y
Types of histograms
A. General Type
G. Comb Type
C. Positively skew Type D. Left hand precipice type
E. Plateau Type F. Twin-peak Type
B. Isolated-peak Type
Control Charts 1/2• Variability is inherent in all manufacturing processes. These
variations may be due to two causes :i. Random / Chance causes (un-preventable)ii. Assignable causes (preventable)• Control charts was developed by Dr. Walter A. Shewhart during
1920's while he was with Bell Telephone Laboratories.• These charts separate out assignable causes.• Control chart makes possible the diagnosis and correction of
many production troubles and brings substantial improvements in the quality of the products and reduction of spoilage and rework.
• It tells us when to leave a process alone as well as when to take action to correct trouble
• Control chart is a chart to examine whether a process is in a stable condition.
• The control limits are drawn for the process characteristics to be controlled.
• Data is of two types :1. Variable - measured and expressed quantitatively2. Attribute - qualitative• The elements of a control chart- Mean is the average of a sub-groupR - Range is the difference between the minimum and maximum in a sub-group1. CL - Center line: This is the expected mean of the process2. UCL - Upper Control Limit and3. LCL - Lower Control Limit These are limit to maximum expected variation of the process.
Control Charts 2/2
1 2 3 4 5
Target
Lower control line
Upper warning line
Lower warning line
Sample Number
Upper control line
Lower control line
Sam
ple
Sta
tistic
sControl Chart
24
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8
Sample Number
Sta
tistic
s
UWL
LCL
LWL
One point outsidecontrol limit
25
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8
Sample Number
Sta
tistic
s
UWL
LCL
LWL
Two points out of three consecutive points between warning limit and corresponding control limit
26
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8
Sample Number
Sta
tistic
s
UWL
LCL
LWL
Two consecutive points between warning limit and corresponding control limit
27
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8
UWL
LCL
LWL
Seven consecutive points on one side of the centre line
Sample Number
Sta
tistic
s
28
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8
Sample Number
Sta
tistic
s
UWL
LCL
LWL
Seven consecutive points having upward trend
29
Interpreting Control Chart
UCL
1 2 3 4 5 6 7 8Sample Number
Sta
tistic
s
UWL
LCL
LWL
Seven consecutive points having downward trend
Scatter Diagram 1/2
• 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• Examples:• The relationship between moisture content in threads and
elongation.• The relationship between an Ingredient and Product
Hardness.• The relationship between cutting speed and variations in the
length of parts.
• The method consists of plotting the two series on a graph and fitting a Line of Best Fit free hand
• The direction of line shows the extent of correlation. If the line goes upward from left to right, it means the correlation is positive.
• If the line goes downward from left to right, it means the correlation is negative.
• If the points on the plot are scattered largely, it shows little or no correlation.
• Although Scatter Diagrams are very convenient tools for asserting two-way relationships, they don’t provide formal measures of these relationships.
• Scatter Diagrams also don’t provide any means of establishing whether any apparent associations are actually due to chance or not.
Scatter Diagram 2/2
How to draw scatter diagram
Year Average Sales (Lac) Profits (Lac)
1987 168 661988 182 701989 192 761990 235 921991 304 1171992 304 1321993 333 1471993 343 1511994 423 1591995 484 1701996 553 1881997 548 1861998 589 2041999 639 2232000 661 234
1
1. Select the Sales & Profit column and insert a Scatter chart
2. Add the axis label & Trend line
2
100 200 300 400 500 600 7000
50
100
150
200
250
Sales vs. profit
Profits (Lac)Linear ( Profits (Lac))
Avg. Sales (Lacs)
Profi
ts (L
acs)
3Strong
Positive correlation
Y Y
YY
Y
XXX
XX
Positive correlation Positive correlation may be present
No correlation
Negative correlation may be present
Negative correlation present
Various plot patterns of scatter diagrams
X
Y
Strong CurvilinearAssociation
Flow chart 1/2Purpose:Visual illustration of the sequence of operations required to complete a task• To develop understanding of how a process is done• To study a process for improvement• To communicate to others how a process is done• When better communication is needed between people involved with the
same process• To document a process• When planning a projectBenefits:
• Identify process improvements• Understand the process• Shows duplicated effort and other non-value-added steps • Clarify working relationships between people and organizations • Target specific steps in the process for improvement.
Benefits• Show what actually happens at
each step in the process • Show what happens when non-
standard events occur • Graphically display processes to
identify redundancies and other wasted effort
How is it done?• Write the process step inside
each symbol• Connect the Symbols with
arrows showing the direction of flow
Toolbox
Flow chart 1/2
Check sheet
WHAT IS A CHECK SHEET ?
A Check Sheet is a method for collecting the right data in a simple manner.
Classification of check sheets according to functions:
1. Recording check sheet
(A) Defective Item Check Sheet(B) Defective Cause Check Sheet(C) Production process distribution Check Sheet2. Inspection Check sheet(A) Check up Confirmation Check Sheet(B) Evaluation item inspection Check Sheet
How to make check sheet1. Clearly indicate the purpose of the data collection2. Decide on how to collect data3. Estimate the total quantum of data4. Decide on the Check Sheet form5. Enter the data and draw up the Check Sheet.6. Check if it meet the objectives. Is it easy to record? If there
are any improvement points, freely amend it.Reading and using the check sheet:A) Read the whole pictureB) To see the time series of time, day and monthC) Tie-up the use of other tools
1. Defective Item Check Sheet for a motor
Recording check sheet 1/2
3. Production process distribution Check
Sheet
2. Defective Cause Check Sheet
Recording check sheet 2/2
INSPECTION CHECK SHEET1. Check up Confirmation Check Sheet
2. Evaluation item inspection Check Sheet
To sum up 7 QC tools ,they are used to
Tools ResultPareto Diagram To Identify the major cause/issue
Cause and Effect Diagram
To identify the cause and effect relationship
Histogram To see the distribution of dataControl Charts To find out abnormalities and identify the
current status
Scatter Diagrams To identify the relationship between two things
Flow chart illustration of the sequence of operations required to complete a task
Check Sheets To record data collection
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