BITS PilaniPilani Campus

Statistical Quality Control (SQC)

Suhas A Chougule

BITS PilaniPilani Campus

Lecture-1

Quality improvement in the modern business

environment

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Introduction to Statistical Quality Control By DOUGLAS C. MONTGOMERY, Sixth Edition 2009 by John Wiley & Sons, Inc

Prescribed Textbook and Study Material

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A Mechanical Engineer with post-graduation in Operations management with 14 years of corporate experience in versatile fields of Quality

Professional credentials: • Certified Six Sigma Black Belt from ASQ, • Certified Automotive-SPICE assessor from Intacs™  ,

Certified Lead auditor for ISO 9001:2008, Environment (ISO 14001:2004), Health & Safety Management System (OHSAS 18001:1999 ),

• Certified assessor for Business Excellence Model based on Malcom Baldrige model.

Corporate Experience• TATA Auto comp Ltd, • 3M India Ltd, • HERE Solutions India Pvt. Ltd

About the Faculty

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What we will cover today?

• Quality and Quality dimensions• Quality history• What is SQC? Need for Quality control• Judgmental inspection and SQC inspection• Management aspects of Quality improvement• Quality philosophy and management principles• Designed experiment• Other Quality philosophies- TQM,QMS, Six Sigma• Quality cost

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What is Quality and its dimension?

Quality means fitness for use

Two Aspects of fitness for use: Quality of design and quality of conformance

Quality of design is decided by type of materials used, its grade, tolerance on the processed parts etc.

Quality of conformance is how well the product conform to specifications required by the design.

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What is Quality and its dimension?

Quality Engineering:• Variability is existing in every process because of which no two

products/services are exactly identical• E.g. Time taken to address the service request in Bank , call center will

never match• Sources of variability include difference in skill, competency, line

bandwidth, environment etc.• The best way to describe variability is through statistical methods• While applying statistical methods, data need to classfy either as

attribute data or variable data• Variable data: Are usually continuous measurements e.g. Length,

voltage, weight– Attribute data: Are usually discrete data often expressed in terms of

counts e.g. Color of eyes: blue, green, brown, etc. » Socio-economic status: high, middle, low » Categories: good / bad, machine 1 / machine 2

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What is Quality and its dimension?

• Quality characteristics are often evaluated relative to specifications

• Nominal or Target value: A value of a measurement that corresponds to desired value

• USL- The largest allowable value for a quality characteristics

• LSL- The smallest allowable value for a quality characteristics

• Non-conforming products/defects- are those that fail to meet one or more of its spefications

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What is Quality and its dimension?

Modern definition:

Quality in inversely proportional to variability

LSL USL

Defects

Distribution of critical dimensions for transmission

Japan

Unites states

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Quality dimension?

1. Performance

2. Reliability

3. Durability

4. Serviceability

5. Aesthetics

6. Features

7. Perceived Quality

8. Conformance to standards

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Quality History

• 1900- Frederick W. Taylor introduces “Scientific management” principles

• 1924- W. A Scewhart introduces the control chart concept• 1946- The American Society for Quality control was formed• 1951- A. V. Feigenbaum publishes the first edition of his

book, Total Quality Control• 1975-1978- Interest in quality circle begins in North

America-this grows into the total quality management movement

• 1987- ISO publishes the first quality system standard, Motorola’s six-sigma initiative begins

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What is SQC?

Statistical quality control (SQC) is the term used to describe the set of statistical tools used by quality professionals for Quality Control

Statistical quality control can be divided into three broad categories:

1. Descriptive statistics2. Statistical process control (SPC)3. Acceptance sampling

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NEED OF QUALITY CONTROL

• In each process, excessive variations and errors can cause nonconformities, which leads to three undesirable consequences:

• (a) scrapped or wasted resources;• (b) degraded process throughput;• (c) “contamination” from undetected non

conformities, reducing the value of the product to the customer.

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JUDGMENT INSPECTIONS

• Historically, the first quality-control methods were based on judgment inspections.

• Judgment inspections are made after a process has transformed inputs into a product.

• Based on inspection, the product is accepted, rejected, or reworked.

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SQC INSPECTIONS

• The next major breakthrough in quality control was made by a team led by Shewhart at Bell Laboratories.

• His team demonstrated that variation on the production floor could be described statistically and that statistical data could identify when a process was drifting out of control.

• Statistical data were useful in guiding adjustment of the process to reduce the probability that nonconforming product would be produced

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SQC INSPECTIONS

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Importance of Data

• decisions are made all the time that affect quality and yield

• data based decisions are more accurate than intuitive [assumption] based decisions

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Statistical Thinking

Underlying Principles

• All work is a process• All processes vary• All variation is caused• Knowledge & management

of variation are keys to success

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Statistical Thinking

A Control Chart- •One of primary techniques of SPC•A very useful process monitoring technique when unusual sources of variability are present•The chart has a center line (CL) and upper & lower control limits . The center line represents where the process characteristics should lie if there are no unusual sources of variation•The control limits i.e. UCL & LCL are determines from some simple statistical considerations•Control charts are applied or used for output variable (s)

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Statistical Thinking

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Designed experiment

• Is extremely helpful in discovering the key variable influencing the quality characteristics of interest in the process

• Are a major off-line quality control tool, because they are often used during development activities and the early stage of manufacturing

• Example- Factorial design – factors are varied together in such a way that all possible combinations of factor levels are tested

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Acceptance sampling

• Inspection and classification of a sample of units selected at random from a large batch or lot and ultimate decision about the lot usually occurs by quality of samples

• Different acceptance sampling are : Outgoing inspection, incoming inspection

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Short break

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Management aspects of Quality improvement

Three activities for effective management of Quality:• Quality planning- It involves identifying customers

(internal & external) and identifying their needs, Planning for quality improvement on a specific, systematic basis

• Quality Assurance- Is a set of activities that ensures quality levels of products and services are properly maintained and that supplier and customer quality issues are properly resolved

• Quality control and improvement- It involves set of activities used to ensure that the products and services meet requirements and are improved on a continuous basis

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Quality Philosophy and mgmt. principles

Major contributors for Quality improvement and management philosophy:•W.E. Deming-

14 points for Quality & productivity improvement Seven deadly diseases of management Shewhart cycle-PDCA Cycle

•J M Juran- Juran Triology ( planning, control, improvement)•A V Feigenbaum- 19 step improvement process

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Other Quality philosophy

• TQM• Quality system and standards e.g ISO 9001• Quality awards e.g. Malcom Baldrige National Quality award• Six Sigma- Focus is on reducing the variability in key

product quality characteristics to the level at which failure or defects are extremely unlikely

• Just in time , Poka-Yoke etc.- Initiatives developed for improving the production systems

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Other Quality philosophy-TQM

• TQM is a strategy for implementing and managing quality improvement activities on an organization wide basis.

• TQM involves broader spectrum of concepts and ideas e.g. participative management & work culture, customer focus, supplier quality improvement, integration of Quality system with business goals

• TQM approach involves quality councils or high level teams that deal with strategic quality initiative, workforce level teams and cross functional teams

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Other Quality philosophy-TQM

Reasons for lack of conspicuous success of TQM:•Lack of top down, high level management commitment & involvement•Inadequate use of statistical methods and insufficient recognition of variability reduction as a prime objective•General concept against a specific business –results oriented objectives•Too much emphasis on widespread training

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Other Quality philosophy- QMS

International organization for standardizationPublishes international agreements: international standards.

ISO 9001 requirementsA tool that looks into processes in order to help you to find weaknesses / improvement opportunities. Serves as a foundation.

The ISO standard describes what is needed for an effective quality management system… not how to develop the system.

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Other Quality philosophy- QMS

This International Standard is used by internal and external parties, including certification bodies, to assess the organization's ability to meet customer, regulatory and the organization's own requirements.

The standard has 8 requirements and a set of sub-requirements for each

1. Scope

2. Normative Reference

3. Terms and definitions

4. Quality Management System requirements

5. Management Responsibility

6. Resource Management

7. Product Realization

8. Measurement, Analysis and Improvement

Six Sigma

• Problem-solving method

• Data-driven approach to continuous improvement– Understand critical inputs = control output– “How good can we be?”

• Common language

• Set of tools to tackle change

• In other words...

• An approach to sustainable continuous improvement that: - Moves us toward the goal of being a world-class company by improving the quality and consistency of our processes - Uses statistical tools for significant process capability improvement.

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Other Quality philosophy- Six SigmaSix Sigma Is……Data driven approach to

process improvement

Changing the way companies solves it problems

Making a difference with our results

Making a difference with our customers

Applied to our top Priorities

Six Sigma is Not….• A

• A Separate Initiative

• A replacement for common sense

• A passing Fad

• Separate or additional Work

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When is Six Sigma Used?

When?– Have a problem (process isn’t working effectively or efficiently)– Aren’t sure of actions needed to improve– Can measure the improvement we want

Examples of project goals?– Reduce errors (mistakes, claims, material waste)– Improve quality (to a specification)– Reduce time (lead-time)– Improve productivity (speed, lost time, wasted effort)– Improve conformance to a target– Increase capacity, market share (growth)– Reduce inventory (cash flow)

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When is Six Sigma Used?

Execute a process(Example: NPI)

Improvea process

Designa new process

Business ResultsLoyal Customers

Business Strategy

Six Sigma Tool Box:DMAICDFSSLeanLeadershipProject Mgmt.

Functional Tool Boxes: Sales Mktg. Mfg. R&D Engr.SourcingSupply ChaineProductivity, etc.

Key Business Process Needs

Profitable Growth Operational Excellence

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Other Quality philosophy- Poka Yoke

POKA-YOKE to avoid (yokeru) inadvertent errors (poka)

What is Poke-yoke?A method that uses sensor or other devices for catching errors that may pass by operators or

assemblers.

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Other Quality philosophy- Poka Yoke

1. Control Approach - Shuts down the process when an error occurs. - Keeps the “suspect” part in place when an operation is incomplete.2. Warning Approach - Signals the operator to stop the process and correct the problem.

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Other Quality philosophy- Malcom Baldrige National Quality award

In the early and mid-1980s, many industry and government leaders saw that a renewed emphasis on quality was no longer an option for American companies but a necessity for doing business in an ever expanding, and more demanding, competitive world market. But many American businesses either did not believe quality mattered for them or did not know where to begin. The Baldrige Award was envisioned as a standard of excellence that would help U.S. organizations achieve world-class quality.

Most popular and influential model in the western world is the one launched by the US government called the Malcolm Baldrige Award Model (also commonly known as the Baldrige model, the Baldrige criteria, or The Criteria for Performance Excellence). More than 25 countries base their frameworks upon the Baldrige criteria.

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Other Quality philosophy- Malcom Baldrige National Quality award

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Other Quality philosophy- Malcom Baldrige National Quality awardP Preface: Organizational Profile

P.1 Organizational Description P.2 Organizational Situation

Category and Items Point Values1 Leadership 120 1.1 Senior Leadership 70 1.2 Governance and Societal Responsibilities 502 Strategic Planning 85 2.1 Strategy Development 40 2.2 Strategy Implementation 453 Customer Focus 85 3.1 Voice of the Customer 45 3.2 Customer Engagement 404 Measurement, Analysis, and Knowledge Management 90 4.1 Measurement, Analysis, and Improvement of Organiza

tional Performance 45

4.2 Management of Information, Knowledge, and Information Technology

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5 Workforce Focus 85 5.1 Workforce Environment 40 5.2 Workforce Engagement 456 Operations Focus 85 6.1 Work Systems 45 6.2 Work Processes 407 Results 450 7.1 Product and Process Outcomes 120 7.2 Customer-Focused Outcomes 90 7.3 Workforce-Focused Outcomes 80 7.4 Leadership and Governance Outcomes 80 7.5 Financial and Market Outcomes 80 TOTAL POINTS 1,000

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Other Quality philosophy- Malcom Baldrige National Quality award

Leadership—Examines how senior executives guide the organization and how the organization addresses its responsibilities to the public and practices good citizenship.

Strategic planning — Examines how the organization sets strategic directions and how it determines key action plans.

Customer focus — Examines how the organization determines requirements and expectations of customers and markets; builds relationships with customers; and acquires, satisfies, and retains customers.

Measurement, analysis, and knowledge management —Examines the management, effective use, analysis, and improvement of data and information to support key organization processes and the organization’s performance management system.

Workforce focus — Examines how the organization enables its workforce to develop its full potential and how the workforce is aligned with the organization’s objectives.

Process management — Examines aspects of how key production/delivery and support processes are designed, managed, and improved.

Results — Examines the organization’s performance and improvement in its key business areas: customer satisfaction, financial and marketplace performance, human resources, supplier and partner performance, operational performance, and governance and social responsibility. The category also examines how the organization performs relative to competitors.

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Quality costs

• Quality costs are those categories of costs that are associated with producing, identifying , avoiding or repairing products that do not meet requirements

Four categories of Quality costs:• Prevention cost• Appraisal cost• Internal failure cost• External failure cost

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Quality costs

• Prevention cost• Quality planning & engineering• New products review• Products/process design• Process control• Training• Quality data acquisition and analysis

• Appraisal cost• Inspection and test of incoming material• Products inspection and test• Materials and service consumed• Calibration cost

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Quality costs

• Internal failure cost• Scrap• Rework• Retest• Failure analysis• Downtime• Yield losses

• External failure cost• Complaint analysis• Returned products/material• Warranty charges• Liability costs• Indirect costs

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Summary of Lecture-1

• Quality and Quality dimensions• Quality history• Management aspects of Quality improvement• Quality philosophy and management principles• SQC, Need of Quality control• Judgmental inspection and SQC inspection• Designed experiment• Other Quality philosophies• Quality cost

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Summary of Lecture-1

End of Lecture -1