QUALITY ASSURANCE AND RELIABILITY (QAR)

Dr Jaiprakash Bhamu

NAMES OF BOOKS; Introduction to Statistical Quality Control,

Douglas C. Montgomery, 2nd Edition, Wiley. Charles E. Ebeling, An introduction to reliability

and maintainability engineering, Tata McGraw-Hill Education.

Quality Planning and Analysis, J.M.Juran and F.M. Gryna, McGraw Hill

Quality Control, Dale H. Besterfield, 8th Edition, Pearson/Prentice Hall

Statistical Quality Control, E. L. Grant and Richard S. Leavenworth, Tata McGraw-Hill

Fundamentals of Quality Control and mprovement, Amitava Mitra, 2nd Edition,Prentice Hall 1998

Design and Analysis of Experiments, 5th Edition, Douglas C. Montgomery, Wiley-India 2007

QUALITY “Quality product”- usually think in terms of an excellent product or service that fulfills our expectations.

Expectations are based on “fitness for use” and the selling price of the product.*

DEFINITIONS

Quality is all of the features and characteristics of product or service that contribute to the satisfaction of a customer’s needs.

These needs involve price, safety, availability, maintainability, reliability, and usability.

Conformance of the product or service to these specifications is measurable and provides a quantifiable definition of quality.

Therefore, simply stated, quality is conformance to specifications and the degree of conformance is the measure of quality.

Quality control is the use of techniques and activities to achieve.

Sustain and improve the quality of a product or service.

IT INVOLVES INTEGRATING THE FOLLOWING RELATED TECHNIQUES AND ACTIVITIES:

Specifications of what is neededDesign of the product or service to meet the specifications

Production or installation to meet the full intent of the specifications

Inspection to determine conformance to specifications

Review of usage to provide information for the revision of specifications is needed

STATISTICAL QUALITY CONTROL

It is a branch of quality control. It is the collection, analysis and interpretation of data for use in quality control activities.

A number of different techniques/tools are needed to achieve

THESE TOOLS ARE;

Shewhart control charts for measurable quality characteristics. Average and Range charts, Sample Average and Standard Deviation

Shewhart control charts for fraction rejected, or p chart

Shewhart control charts for number of nonconformities, or c chart

The portion of sampling theory that deals with the quality protection given by any specified sampling acceptance procedure.

QUALITY ASSURANCEAll the actions necessary to provide adequate confidence that a product or service will satisfy consumer needs is called quality assurance.

It involves making sure that effectiveness with a view to having timely corrective measures and feedback initiated where necessary.

QUALITY CONTROL AND QUALITY ASSURANCE.

Quality control is involved with the activities of specification, design, production or installation, inspection, and review of usage. These activities are the responsibility of the functional areas shown in slide no 16.

Quality assurance is involved with these activities as well as the entire quality system.

HISTORICAL REVIEW

Industrial Revolution- The concept of specialization of labor

In 1924. W.A. Shewhart of Bell Telephone Laboratories developed a statistical chart for the control of product variables. H.F. Dodge and H.G. Romig both of Bell Telephone Laboratories, developed the area of acceptance sampling as a substitute for 100% inspection.

Recognition of the value of statistical quality control became apparent by 1942. Unfortunately American managers failed to recognize its value.

In 1946 the American Society for Quality Control was formed (through its publications, conferences, and training sessions has promoted the use of quality control for all types of production and service).

In 1950 W. Edwards Deming gave a series of lectures on statistical methods to Japanese Engineers and on quality responsibility to top management.

Joseph M. Juran made his first trip to Japan in 1954, Japanese set the quality standards for the rest of the world to follow.

In 1960 the first quality control circles were formed for the purpose of quality improvement. Simple statistical techniques were learned and applied by Japanese workers.

By the late 1970s and early 1980s American managers were making frequent trips to Japan to learn about the Japanese miracle. Nevertheless a quality renaissance began to occur in America’s products and services.

RESPONSIBILITY FOR QUALITY

Departments ResponsibleQuality is not the responsibility of any one

person or department: it is every one’s job.

Marketing Marketing helps to evaluate the level of

product quality and the customer wants, needs, and is willing to pay for. In addition, marketing provides the customer with product quality data and helps to determine quality requirements.

Product Service

Packing and Shipping

Inspection and Test

Marketing

Product Engineering

Purchasing

Manufacturing Manufacturing Engineering

Quality Product

Departments Responsible for Quality

Product EngineeringProduct engineering translates the customer’s quality requirements into operating characteristics, expect specifications. (1)

Manufacturing EngineeringManufacturing engineering has the responsibility to develop process and procedures that will produce a quality product. (2)

Manufacturing Manufacturing has the responsibility to

produce quality products. Quality cannot be inspected into a product. It must be build into the product.

Inspection and TestInspection and test has the responsibility

to appraise the quality of purchased and manufactured items and to report the results. The reports are used to other departments to take corrective action when needed.

Packaging and ShippingResponsibility to preserve and protect the quality of the product. Control of the product quality must extend beyond manufacturing to the distribution installation and product.

Product ServiceTo provide the customer with the means for fully realizing the intended function of the product during its expected life. This responsibility includes reaction, maintenance, repair and replacement parts service.

QUALITY ASSURANCE

The quality assurance or quality control department does not have direct responsibility for quality. It assists or supports the other departments as they carry out their quality control responsibilities.

Quality assurance does have the direct responsibility to continually evaluate the effectiveness of the total quality system.

GENERIC ELEMENTS OF A TOTAL QUALITY SYSTEM ARE:

Policy, planning and administration

Design assurance and design change control.

Control of purchased material.User contact and field performance.

Corrective action.

QUALITY POLICY AND OBJECTIVE

Quality Policy - overall intentions and direction of an organisation related to quality as formally expressed by top management.

Quality Objective - something sought, or aimed for related to quality.

 

To differentiate in simple terms, the Policy would say "The organisation would strive to improve customer satisfaction" - a direction laid down by the management.

The Objective is a measurable derived from the Policy. It could say something like - "Improve on time delivery performance".

THE MAIN PRINCIPLES OF CONTROL CHARTS

1. Measured quality of manufactured product have always subject to a certain amount of variation as the result of chance

2. Some constant system of chance causes is inherent in any particular scheme of production and inspection

3. Variation within this stable pattern is inevitable

4. The reasons for variation outside this stable pattern may be discovered and corrected

Computing Cost of Quality

Internal Failure Scrap Rework Scrap/Rework -

Supplier

Appraisal Inspection Test Quality audits Test equipment - initial

cost & maintenance

External Failure Cost to customer Warranty costs Complaint

adjustments Returned material

Prevention Quality planning Process planning Process control Training

Note: The listed categories provides an understanding of the COQ structure. In general, COQ is comprised of costs due to failure, appraisal, and prevention.

HIDDEN COST OF QUALITY Internal

Troubleshooting and failure analysis Evaluation to determine usability of off specification

material Engineering changes, redesign, buy-offs Costs of reviewing quality problems (i.e, replanning,

meetings, expediting, firefighting, reports, etc.) Inventory costs on held material Overtime because of quality problems Late shipment premiums (delayed collections) Material handling Tool & fixture redesign Machine wear Fringe benefits on labor Loss of productivity due to rework, scrap

HOW TO REDUCE QUALITY LOSSES

Rule of “Tens”Eradicate Killer Re’s…WastePlay Offense (Prevention) vs. Defense (Detection)

RULE OF “TENS”

Not doing it right the first time costs ten times as much to find and fix each time errors escape to a subsequent stage of handling.

$1 Design Effort=$10 Production Cost=$100 Assy/Test Cost=$1000 Field Cost

THE KILLER RE’SReadjust ReprocessReapply ReprogramRecalibrate RerunRecertify RescheduleRecheck ResealRecondition ReshipRecycle RestampRefinish ResockReidentify RetapReinspect RetestRelevel ReturnRemearsure ReweldRenormalize RewindReorder RewireRepack Rework

Reject (The worst kind)

STATISTICS AND SAMPLING DISTRIBUTIONS

Statistical methods are used to make decisions about a processIs the process out of control? Is the process average you were given the true value?

What is the true process variability?

STATISTICS AND SAMPLING DISTRIBUTIONS

Statistics are quantities calculated from a random sample taken from a population of interest.

The probability distribution of a statistic is called a sampling distribution.

DESCRIBING VARIATION

One of the proverb or truism of manufacturing is that no two objects are never made exactly alike.

Variations –very large and noticeable

Variations – very small and can be noticed by precision instruments

Three categories of variations in piece part production

1. Within – piece variation: like surface finish of two portion of the same piece

2. Piece to piece variation: within pieces, produced in same time

3. Time-to-time variation: products produced in different times of the day

FIVE CONTRIBUTING FACTORS OF VARIATION

They are; 1. Processes 2. Material3. Environment4. Operators5. Inspection

CHANCE CAUSES OF VARIATION AND ASSIGNABLE CAUSES

As long as these five sources of variation fluctuate in a normal or expected manner, a stable pattern of many chance causes of variation develops.

Chance causes of variation are inevitable and because they are very small in magnitude. They are difficult to identify.

Those causes of variation which are large in magnitude, and therefore readily identified, are classified as assignable causes.

When only chance causes are present in a process, the process is considered to be in control.

However, when an assignable cause of variation is also present, the variation will be excessive and the process is classified as out of control or beyond the expected normal variation.

PATTERN OF VARIATIONAs we discussed variations seems

inevitable in nature. Now it is necessary to have some simple

methods of describing patterns of variation. Statistician have developed such methods.

One useful method involves a frequency distribution. Another involves the finding of a measure of the central tendency of a distribution (that is, an average) combined with some measure of dispersion, or spread, of the distribution.

FUNDAMENTALS OF STATISTICSIt has two generally accepted meanings:A collection of quantitative data pertaining

to any subject or group, especially when the data are systematically gathered and collated examples of this meaning are blood pressure statistics, statistics of a football game, employment statistics etc.

The science that deals with the collection, tabulation, analysis, interpretation, and presentation of quantitative data.

The use of statistics in quality control deals with the second and broader meaning and involves the divisions of collection, tabulating, analyzing, interpreting and presenting the quantitative data.

Each division is depended on the accuracy and completeness of the preceding one.

There are two phases of statistics:Descriptive or deductive statistics, which endeavors to describe and analyze a subject or group.

Inductive statistics which endeavors to determine from a limited amount of data (sample) an important conclusion about a much larger amount of data (population).*

COLLECTION OF DATA

Data may be collected by direct observation or indirectly through written or verbal questions*.

Data that are collected for quality control purposes are obtained by direct observation and are classified as either variables or attributes.

Variables are those quality characteristics which are measurable, such as a weight measured in grams.

Attributes, on the other hand are those quality characteristics which are classified as either conforming or not conforming to specifications such as a “go / no go gage”.

A variable that is capable of any degree of subdivision is referred to as continuous. The weight of a gray iron casting which can be measured as 11 kg, 11.33 kg or 11.3398 kg (25 ib), depending on the accuracy of the measuring instrument, is an example of a continuous variable.

Measurements such as meter (feet), liters (gallons) and Pascal’s (pounds per square inch) are examples of continuous data.

Variables that exhibit gaps are called discrete. The number of defective rivets in a travel trailer can be any whole number, such as 0,3,5,10,96…..however, there cannot be say 4.65 defective rivets in a particular trailer.

In general, continuous data are measurable, while discrete data are countable.

Describing the DataIn industry, business and government the mass of data that have been collected is voluminous.

There are a number of different ways to present the frequency distribution.

Two techniques are available to accomplish the summarization of data- graphical and analytical.

Graphical techniques is a plot or picture of a frequency distribution, which is summarization of how the data points (observations) occurs within each subdivision of observed values or groups of observed values.

Analytical techniques summarize data by computing a measure of central tendency and a measure of the dispersion.

FREQUENCY DISTRIBUTION

UNGROUPED DATA- Comprise a listing of the observed values

GROUPED DATA- Lumping together of the observed values

HISTOGRAM

BAR GRAPHS AND POLYGON GRAPHS

GROUPED DATA

The construction of a frequency distribution for grouped data is more complicated because there are a large number of data values. Process is as follows;

1. Collect data and construct a tally sheet 2. Determine the range3. Determine the cell interval4. Determine the cell midpoints5. Determine the cell boundaries6. Post the cell frequency

Any ? Thanks