Quality control and improvement concepts

Outline

1. History2. Development 3. Dimensions of Quality 4. Quality Control5. Total Quality management

History1. 13th century – craftsmen into union(guilds).2. 1700 – Industrial Revolution3. 1776 – Adam Smith – division of labour4. 1790 – Eli Whitney – Interchangeable parts5. Henry Ford – car industry in USA6. World War II- Inspection of every unit of

product (bullets, rifles).7. Walter Shewhart (1924) introduced statistical

control chart concepts.

The Development• 1950 – Productivity• 1960 – Productivity + service• 1970 – Productivity + service + Financial Control• 1980 – Productivity + service + Financial Control + Quality

+ Technology• 1987 – ISO publishes the first quality systems standard • 1990 – Productivity + service + Financial Control +

Quality + Technology + Direction• 2002 – Productivity + service + Financial Control + Quality

+ Technology + Direction + Information.

The Meaning of Quality & Quality Improvement We may define quality in many ways. Most people

have a conceptual understanding of quality as relating to one or more desirable characteristics that a product or service should possess.

Quality has become one of the most important consumer decision factors in the selection among competing products and services.

The phenomenon is widespread, regardless of whether the consumer is an individual, an industrial organization, a retail store, a bank or financial institution, or

a military defense program.

Cont.. Consequently, understanding and Improving

quality are key factors leading to business success, growth and enhanced competitiveness.

There is a substantial return on investment from improved quality and from successfully employing quality as an integral part of overall business strategy.

Quality means: fitness for use - quality of design - quality of conformance

Quality is inversely proportional to variability.

Dimensions of Quality

1) Performance 5) Aesthetics2) Reliability 6) Features3) Durability 7) Perceived Quality4) Serviceability 8) Conformance to Standards

The quality of a product can be described and evaluated in several ways.

Garvin (1987) provides an excellent discussion of eight components or dimensions of quality.

Quality is fitness for useWhether the product, even when produced to standards,

was actually “fit-for-use” by the customer.

All goods and services are produced in variousgrades or levels of quality. These variations in grades orlevels of quality are intentional, and, consequently, theappropriate technical term is quality of design.

The quality of conformance is how well the productconforms to the specifications required by the design

For example, all automobiles have as their basicobjective providing safe transportation for the consumer.However, automobiles differ with respect to size,appointments, appearance, and performance. These differences are the result of intentional designdifferences among the types of automobiles. Thesedesign differences include the types of materialsused in construction, specifications on the components,reliability obtained through engineering development ofengines and drive trains, and other accessories orequipment.

Cont..

Cont..

Quality is inversely proportional to variability This definition of Montgomery implies that if the

variability in a product's important characteristics decreases, the quality of the product increases.

Quality improvement is the reduction of variability in processes and products

Excessive variability in process performance often results in waste.

Cont..

Therefore, an alternate and frequently very useful definition isthat quality improvement is the reduction of waste. This definition is particularly effective in service industries,where there may not be as many things that can be directlymeasured. In service industries, a quality problem may be an error or amistake, the correction of which requires effort and expense. Byimproving the service process, this wasted effort and expensecan be avoided.

For example, consider the wasted money, time, and effort that is associated with the repairs represented.

Every product possesses a number of elements that jointly describe what the user or consumer thinks of as quality. These parameters are often called qualitycharacteristics. Sometimes these are called critical-to-quality (CTQ) characteristics. Quality characteristics may be of several types:

1. Physical: length, weight, voltage, viscosity2. Sensory: taste, appearance, color3. Time Orientation: reliability, durability, serviceability

Quality characteristics:

Statistical Methods for Quality Control and Improvement

Specifically, we focus on three major areas

1)Statistical process control.2)Design of experiments.3)Acceptance sampling.

Statistical Process Control (SPC)

• Control charts are used for process monitoring and variability reduction.

• SPC is an on-line(in-process) quality control tool.• The chart has a center line (CL) and upper and

lower control limits (UCL and LCL).The center line represents where this process characteristic should fall if there are no unusual sources of variability present.

Advantages These charts are extremely useful in phase I implementation of SPC, where the process is likely to be out of control and experiencing assignable causes that result in large shifts in the monitored parameters.

Shewhart charts are also very useful in the diagnostic aspects of bringing an unruly process into statistical control, because the patterns on these charts often provide guidance regarding the nature of the assignable cause.

DisadvantagesA major disadvantage of a Shewhart control chart is that it uses only the information about the process contained in the last sample observation and it ignores any information given by the entire sequence of points. This feature makes the Shewhart control chart relatively insensitive to small process shifts. This potentially makes Shewhart control charts less useful in phase II monitoring problems(Cusum and EWMA control charts).

Design of Experiments

• A designed experiment is extremely helpful in discovering the key variables influencing the quality characteristics of interest in the process.

• Experimental design is an approach to systematically varying the controllable input factors in the process and determine the effect these factors have on the output responses.

• Experimental designs are off-line(used during development activities) quality tools.

• Crucial for variability reduction.

ApplicationsExperimental design is a critically important engineering tool for

improving a manufacturing process. It also has extensive application in the development of new processes.

Application of these techniques early in process development can result in

1. Improved yield2. Reduced variability and closer conformance to the nominal3. Reduced development time4. Reduced overall costsExperimental design methods can also play a major role in engineering

design activities, where new products are developed and existing ones improved.

Acceptance Sampling• Acceptance sampling is the inspection and classification

of a sample of the product selected at random from a larger batch or lot and the ultimate decision about disposition of the lot.

• Two types:1. Outgoing inspection – after production2. Incoming inspection – before use in production

Advantages of Sampling

When acceptance sampling is contrasted with 100% inspection, it has the following advantages:

1. It is usually less expensive because there is less inspection.2. There is less handling of the product, hence reduced

damage.3. It is applicable to destructive testing.4. Fewer personnel are involved in inspection activities.5. It often greatly reduces the amount of inspection error.

Disadvantages of Sampling1. There are risks of accepting “bad” lots and rejecting “good” lots.

2. Less information is usually generated about the product or about the process that manufactured the product.

3. Acceptance sampling requires planning and documentation of the acceptance sampling procedure whereas 100% inspection does not.

Quality must be consider at all stages in the life cycle, as shown below, of a product.

Marketing &Market Research

Requirements&Specification

Design&Development

Procurement(buying goods and services)

Process Planning&Development

Production

Inspection, testing&Examination

Packaging&Storage

Sales&Distribution

Installation&operation

Technical Assistance&Maintenance

Disposal

Quality Planning

Quality planning is a strategic activity, and it is just as vital to an organization’s long term business success as the product development plan, the financial plan, the marketing plan, and plans for the utilization of human resources. Without a strategic quality plan, an enormous amount of time, money, and effort will be wasted by the organization dealing with faulty designs, manufacturing defects, field failures, and customer complaints.

Quality Assurance

Quality assurance is the set of activities thatensures the quality levels of products and servicesare properly maintained and that supplier andcustomer quality issues are properly resolved.

ACTIVITY QUALITYASSESSOR

Input Output

Bad

Good

Quality control and improvement Involve the set of activities used to ensure that the products and services meet requirements and are improved on a continuous basis. Since variability is often a major source of poor quality, statistical techniques, including SPC and designed

experiments, are the major tools of quality control and improvement.

Total Quality Management

“A strategy for improving overall performanceand quality competitiveness”

1. Involves every aspect of the business2. Involves every person3. Requires total commitment

Total quality management (TQM) is a strategy for implementing and managingquality improvement activities on an organization wide basis.

TQM began in the early 1980s, with thephilosophies of Deming and Juran as the focalpoint.

TQM include

1) Lack of top down, high-level management commitment and involvement

2) General as opposed to specific business-results-oriented objectives

3) Too much emphasis on widespread training as opposed to focused technical education.

Implementation of Total Quality1. The need for an overall business strategy2. Top management commitment3. Adoption of new values and putting the customer

first4. Improving the quality of work life5. Involvement, teamwork and people empowerment6. Effective data driven problem solving7. Eliminating waste and non-value added activities

Elements of Total Quality1. Meeting customer requirements2. Striving to do error free work3. Managing by prevention4. Measuring the cost of non-quality5. Never ending improvement (continuous

improvement)6. Education and training.

Presented:BANDARU KRISHNA KUMARQualification: M.SC(APPLIED STATISTICS)