chap02-basic quality tools - uoh.edu.sa 51… · (statistical process control), the 7 new tools for...

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Quality Improvement, 9eDale H. Besterfield

© 2013, 2008 by Pearson Higher Education, IncUpper Saddle River, New Jersey 07458 • All Rights Reserved

QEM 511 - Total Quality Management

Mohamed Aichouni

Professor of Quality Engineering, Hail Universityhttp://faculty.uoh.edu.sa/m.aichouni/

Master Program on Quality Engineering and Management

LECTURE 02

METHODS OF TOTAL QUALITY MANAGEMENT –

THE 7 BASIC QUALITY TOOLS



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Process Variability and Quality

Causes of Variations in Processes

Continuous Process Improvement

SPC Tools (The 7 basic tools) Pareto Diagram

Cause-Effect Diagram

Check Sheets

Process Flow Diagram

Scatter Diagram

Histogram

Control Charts

Outline

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Quality Definition

Quality is defined by the totality of features and characteristics that satisfy customers needs” (ASQ).

Think about a product (watch e.g) that you would bye; What do you look for?

• .........

• ........

• .........

• ........



Quality Characteristics

Variables

Can be measured or expressed with some unit, such as height, length (m), mass (kg), cycle time (s), concrete strength (MPA) etc..

Attributes

Can be counted such as number of defects, errors, accidents etc ..

Process Variations

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Process Variations and Quality

Quality is inversely proportional to variability (Variability & Quality are enemies).

The more variation in product characteristics, in delivery times, in work practices: the more waste, higher costs and poor quality, is delivered to ourcustomers.

(Out of the Crisis, 1982)



Causes of Product Variations

Product characteristics variations are mainly caused by the variations in the components of the process (5 M and E): Man Power Machines Methods Materials Measurements Environment

Raw Material

Process

Product

Man Machine

Measurements Methods

Customer

Environment

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Process Variations Causes

1. Common causes are ever-present in the process;========= Natural Variations

2. Special causes are intermittent effects that must be investigated immediately.

========= Assignable Causes Variations

Management and quality professionals (YOU) should help manufacturing people to identify and remove special causes and reduce the occurrence of common causes in the process..



Process Variation

Process Variability Variations due to:

Natural Causes:• Temperature variation• Material variation• Customer differences• Operator performance

Special Causes:• Machine is breaking• Untrained operative• Machine movement• Process has changed

Must be monitored Early and visible warning required

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Process Improvement

• Process Improvement is basically about the reduction of variability in processes, products and services.

• Based on the Deming PDCA Cycle

• PI results in waste reduction, quality improvement, Customer Satisfaction and more importantly to Business Excellence.



Continuous Process

Improvement:

Reduction of Process

Variability

Standard Deviation () , Cv(%) higher values

Big Variability of Process.

Less variabilityReduce variation by removing special causes from Process

Continually improve the process by reducing variability

() , Cv(%) lower.

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How to Improve Processes and Quality ?

Study and Understand Process Variation.

Use Appropriate Quality Tools (The 7 Basic tools (Statistical Process Control), the 7 New Tools for Management and Planning etc..

Set Process improvement teams Use Employee suggestions

© Copyright : Dr Mohamed AICHOUNI, PhD, SQC, KAQA



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A methodology (or set of tools) for:

monitoring a process to identify special causes of variation and,

signal the need to take corrective action on the process when appropriate.

Statistical Process Control

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Seven Basic Quality ToolsKaoru Ishikawa (1972)

Called the Magnificent Seven

They are simple visual tools based on the use of data to study and understand the things we do (Process) ;

So that we can improve the quality of products in manufacturing plants.

1 2 3 4Dirt

Old

Temp

Fault

xx x

xx

x xx

x

x xxx

xx

x

UCL

LCL

12345

Process



SPC Tools : The 7 Basic Quality Tools

The SPC tools (the 7 basic Quality Tools) are Problem Solving Tools which can: Help to identify and prioritize problems quickly and

more effectively. Assist the decision making process. Provide simple but powerful tools for use in continuous

improvement activity. Provide a vehicle for communicating problems and

resolutions throughout the business. Provide a way of extracting information from the data

collected.

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Flow Chart Check Sheet Pareto Analysis Histogram – Process Capability Cause-and-Effect Diagram Scatter Diagram Control Charts – Process Stability

Seven Basic Quality Control ToolsMagnificent Seven

1 2 3 4Dirt

Old

Temp

Fault

xx x

xx

x xx

x

x xxx

xx

x

UCL

LCL

12345

Process



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It is a schematic diagram that shows the flow of the product or service as it moves through the various processing stations or operations

Makes it easy to visualize the entire system, identify potential trouble spots, and locate activities

Compares and contrasts actual versus ideal flow of a process

Tool 1 - Process Flow Chart

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Uses standardized symbols.

Shows unexpected complexity, problem areas, redundancy, unnecessary loops, and where simplification may be possible.


Process Decision The process flow



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Allows a team to reach agreement on process steps and identify activities that may impact performance

Improvements to the process can be accomplished by eliminating steps, combining steps, or making frequently occurring steps more efficient


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Process Flow Chart

Manufacturing Example



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The main purpose is to ensure that the data are collected carefully and accurately by operating personnel for process control and problem solving.

Creates easy-to-understand data.

Because it clearly organizes data, a check sheet is the easiest way to track information in manufacturing processes (e.g: problems, defects, etc.)

Tool 2 - Check Sheets

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Check Sheets



Check Sheets

Example 2-1 Check Sheet for paint non-conformities

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Example 2-2 Check Sheet for product defects during one week

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Some Sample 80/20 Rule Applications:

80% of process defects arise from 20% of the process issues.

80% of delays in schedule arise from 20% of the possible causes of the delays.

80% of customer complaints arise from 20% of your products or services.

(The above examples are rough estimates.)

Tool 3 - The Pareto Diagram (80/20)

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A Pareto Chart is a special form of vertical bar graph which helps us to determine which problems to solve in what order.

Doing a Pareto Chart based upon either Check Sheets or other forms of data collection helps us direct our attention and efforts to the truly important problems.

We will generally gain more by working on the tallest bar than tackling the smaller bars..)

The Pareto Diagram



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Graph that ranks data classifications in descending order from left to right

Pareto diagrams are used to identify the most important problems

Advantage: Provide a visual impact of those vital few characteristics that need attention

Resources are then directed to take the necessary corrective action

The Pareto Diagram

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Helps a team focus on causes that have the greatest impact

Displays the relative importance of problems in a simple visual format

Helps prevent “shifting the problem” where the solution removes some causes but worsens others

The Pareto Diagram



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Steps:

1. Determine the method of classifying the data: by problem, cause, type of nonconformity, etc

2. Decide if dollars (best), weighted frequency, or frequency is to be used to rank the characteristics

3. Collect data for an appropriate time interval

4. Summarize the data and rank order categories from largest to smallest

5. Compute the cumulative percentage if it is to be used

6. Construct the diagram and find the vital few

Constructing a Pareto Diagram

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Pareto Diagram for Defects Found At In-Process Inspection



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Take the examples 2-1 and 2-2 from check sheet and workout the Pareto diagrams.

Use both hand solution and Minitab solutions

Practice: Pareto Diagram

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A Histogram takes process data, e.g., temperature, dimensions, and displays its distribution.

A Histogram reveals the amount of variation that any process has within it.

It shows the process capability and, if desired, the relationship to the specifications and the nominal characteristic.

Tool 4 - Histogram

Figure 3-11 Histogram for Hole Location



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Displays large amounts of data that are difficult to interpret in tabular form

Shows centering, variation, and shape

Illustrates the underlying distribution of the data

Provides useful information for predicting future performance

Helps to answer the question “Is the process capable of meeting requirements?

Histogram

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The shape of the histogram help us to determine :

a.) Whether the “spread” of the distribution falls within product specifications. If not, how much falls outside of specifications. (VARIABILITY)

b.) Whether the distribution is centered at the right place.Are most items on the “high or low side?”(SKEWNESS)

Histogram



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A sample of process data were obtained and drawn on the table.

Use this data to construct a histogram for analyzing the process .

Practical Example of Histogram (Ex2-3)

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Practical Example of Histogram



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The thickness in mm of a key material in process is given in the table.

Use Minitab to construct the histogram for the process.

Determine the process statistics and compare them with product specifications:

Practical Example of Histogram (Ex 2-4)

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The data have a central tendency around 9.8 to 9.99.

The process has a normal distribution with a mean (.......mm) and a standard deviation (......... mm).

The specification for the thickness characteristicis 7.5 to 10.5, with a target of 9. Thus, we can see that our Histogram indicates the process is running highand that defective material is being made.

Practical Example of Histogram (Ex 2-4)



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Developed by Dr. Kaoru Ishikawa in 1943

Picture composed of lines and symbols designed to represent a meaningful relationship between an effect and its causes

Effect (characteristics that need improvement) on the right and causes on the left.

Called also Fishbone diagram or Ishikawa diagram.

Tool 5 - Cause-and-Effect Diagram

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Enables a team to focus on the content of a problem, not on the history of the problem or differing personal interests of team members.

Creates a snapshot of collective knowledge and consensus of a team; builds support for solutions.

Focuses the team on causes, not symptoms.

Used to investigate either a “bad” effect and to take action to correct the causes or a “good” effect and to learn those causes responsible.

Cause-and-Effect Diagram



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Steps in the construction of a

Cause-and-Effect Diagram:1. Identify the effect or quality problem2. Determine the major causes 3. Determine all the minor causes. Request a

brainstorming session 4. Once the diagram is complete, evaluate it to

determine the most likely causes5. Develop solutions


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Advantages:

1. Analyzing actual conditions for the purpose of product or service quality improvement

2. Elimination of conditions causing nonconforming product or service and customer complaints

3. Standardization of existing and proposed operations

4. Education and training in decision-making




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The 4 M’s: Methods, Machines, Materials, Manpower

The 4 P’s: Place, Procedure, People, Policies

The 4 S’s: Surroundings, Suppliers, Systems, Skills

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Cause and Effect Analysis

QualityProblem

MachinesMeasurement Man

Methods(Process)Environment Materials

Faulty testing equipment

Incorrect specifications

Improper methods

Poor supervision

Lack of concentration

Inadequate training

Out of adjustment

Tooling problems

Old/worn

Defective from vendor

Not to specifications

Material-handling problems

Deficienciesin product design

Ineffective qualitymanagement

Poor process design

Inaccuratetemperature control

Dust and Dirt



Cause and Effect Analysis for Improvement of the Engineering College (UoH)

WhatCan be

ImprovedAt the EngCollege ?

People (Faculty)Policies People (Students)

ProceduresEnvironment Teaching Facilities

…….

…….

……..

……

…..

……..

……….

…………….

…………..

…..

…..

…… ………

……

….…..

…….

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Tool 6 - Scatter Diagram

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A Scatter Diagram is used to study the possible relationship between two variables.

Used to test for possible cause and effect relationships.

When we need to display what happens to one variable when another variable changes in order to test a theory that the two variables are related.



Scatter Diagram – Possible cases

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The following are the various patterns and meaningsthat Scatter Diagrams can have.

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Scatter Diagram – Example

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Scatter Diagram of Average of manufacturing errors versus Average hours overtime / week in a manufacturing plant.

Average of Manufacturing Errors / Week



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Focuses attention on detecting and monitoring process variation over time.

Distinguishes special from common causes of variation

Provides a common language for discussion process performance.

Tool 7 - Control Chart

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Focuses attention on detecting and monitoring process variation over time.

Distinguishes special from common causes of variation.

Provides a common language for discussion process performance.

Control Charts



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Control charts can be used to monitor processes and make continuous process improvement by reducing process variability (removing special causes variation).

Will be dealt in depth in next chapters.

Tracking Improvement using Control Charts

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The SPC tools (the 7 basic Quality Tools) are Problem Solving Tools which can:Help to identify and prioritize problems quickly and more

effectively. Assist the decision making process. Provide simple but powerful tools for use in continuous

improvement activity. Provide a vehicle for communicating problems and

resolutions throughout the business. Provide a way of extracting information from the data

collected.




1. Flow-charts - for describing a process, the current situation

2. Check Sheets - for data collection

3. Pareto Charts - for ordering causes

4. Histograms - for monitoring one variable.

5. Cause and Effect diagrams - for digging to the root causes

6. Scatter Diagrams - for examining the relationship between two variables

7. Control Charts - for monitoring processes

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Conclusions

"Quality control truly begins and endswith education",

K. Ishikawa (1990).

Lecture Finished

Any Question?

Ask questions

Teachers answers

Train your self (Google, YouTube, course webpage

End (See you next lecture)

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