©

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