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©
7.Control Charts
1.Check Sheets
2.Pareto Analysis
3.Flow Charts
4.Cause & Effect Diagram
5.Histograms
6.Scatter Diagrams
Basic Quality Tools
© Check Sheet is a data-gathering and interpretation tool.
Check Sheets
©Check Sheets
• Want to find out cause-wise defects Defects 1 2 3 4 5 6 Total
Missing component
III IIII II I III IIII 18
No solder II III I IIII 10
Wrong Insertion
IIII I IIII II IIII IIII 20
Shorts by component
II IIII II III 11
Total 11 9 9 6 7 17 59
©Check Sheets
• More defects on the last day of the
week.
• Missing components and Wrong
Insertion occur more frequently.
©Check Sheets
• Check sheet is a data pattern
detector.
• Check sheet to be used during
problem definition stage and after
implementation stage.
©
3.gathering data about the type of problem occurring.
1.Distinguishing between fact and opinion.
2.Gathering data about how often a problem is occurring.
Check Sheets
©
2.Defect Location Sheet – identify problem areas.
1.Confirmation Check Sheet – List of steps which must be complete before shipping a product.
Check Sheets
© The Pareto Principle states that only a "vital few" factors are responsible for producing most of the problems.
Majority of problems (80%) are due to a few key causes (20%). If we correct these few key causes, we will have a greater probability of success.
Pareto Analysis
©
Causes FrequencyBreakout 37Hanger 4Tundish nozzle choking 4Dummy bar obstraction 5Overflow 8Sheer trouble 7Tundish nozzle erosion 6Withdrawal problem 12Bad stream 1Auto control failure 1
Pareto Analysis
©
Causes % Freq. % Cum. Freq.Breakout 44 44Withdrawal problem 14 58Overflow 9 67Sheer trouble 8 75Tundish nozzle erosion 7 82Dummy bar obstraction 6 88Hanger 5 93Tundish nozzle choking 5 98Bad stream 1 99Auto control failure 1 100
Pareto Analysis
©Pareto Analysis
©
A flow chart is defined as a pictorial representation describing a process.
Flow Chart
©
1.A diagrammatic picture showing all steps or stages in a process.
2.Flow charts help facilitate a greater understanding of the entire process by identifying where problems have occurred or may occur.
3.You cannot improve a process until everyone agrees what the process is.
Flow Chart
©
1.Also called Ishikawa Diagram, Fishbone Diagram.
2.Used to sort out potential causes of problems.
3.Organizes theories by cause-and-effect relationships.
Cause & Effect (C-E) Diagram
©
4.Provides a guide for process analysis.
5.Highlight likely root causes.
Cause & Effect (C-E) Diagram
©
Coke moisture
Method
Coke temp.
Flue temp.
Machine
Water flow rate
Quench time
Nozzle condition
Man
Spot quenching
Quench car speed
Drainage time
Coke distribution in quench car
©
1.Graphical representation of individual measured values according to frequency or relative frequency of occurrence.
1.Used to show distribution shape for one variable (location, dispersion).
Histogram
©
Daily production data (t)
Histogram
©
230225220215210205200195190185
9876543210
Daily Production (t)
Freq
uenc
y
Histogram
©
1.Used to visualize relationship between two variables.
Features of a single product.
Product output & process input.
Two different products.
2.Issues
Strength of correlation, non-linear relationships.
Scatter Diagrams
©Scatter Diagrams
© 1.Purpose
Separate common (inherent) and special causes.
Monitor process over time.
2.Used to Identify Special Cause Variation.
Process shifts / Cyclic patterns
Runs / trends.
Control Charts
©
0 5 10 15
129.45
129.55
129.65
129.75
129.85
Subgroup
Mea
ns (
X-b
ar)
0.0
0.1
0.2
0.3
Ran
ges
MU=129.7
UCL=129.88
LCL=129.52
R=0.09412
UCL=0.3076
LCL=0.000
Xbar and R Chart for : Major OD Minimum
Control Charts