Untitled Document

1. Introduction to Quality and Quality Control

1.1 Introduction to Quality :

Concept of Quality

Simply, quality refers to one or more desirable characteristics that a product should possess.

Quality is inversely proportional to (unwanted) variability.

Quality Characteristics:

Every product possesses a number of properties that jointly describe what the user or consumer thinks of as quality. These properties are known as quality characteristics.

For example, fiber length is known to be one of the important quality characteristics of a fiber.

Quality Cost :

Preventing, detecting and dealing with defects cause costs that are called quality costs or costs of quality.

Quality costs can be broken down into four broad groups.

(1). Prevention Costs:

	product/process design.
	Process control.
	Burn-in.
	Training.
	Quality data acquisition and analysis.

(2)Appraisal Costs:

	Inspection and test of incoming material.
	Product inspection and test.
	Material and services consumed.
	Maintaining accuracy of test equipment.

(3).Internal failure Costs:

	Scrap
	Rework
	Retest
	Failure analysis
	Downtime
	Yield losses
	Downgrading/ off-spacing

(4). External failure costs:

	Complaint adjustment
	Returned product/material
	Liability costs
	External costs

Quality history [1]

Year	Event
1700-1900	Quality was largely determined by the efforts of an individual craftsman.
1915-1919	WWI- British government began a supplier certification program.
1919	Technical Inspection Association was formed in England, this later becomes the Institute of Quality Assurance.
1924	W A Shewhart introduced the concept of control charts in Bell Laboratories technical memorandum.
1928	Accepatance sampling techniques were developed and refined by H. F. Dodge and H. G. Romig at Bell Labs.
1931	W. A. Shewhart published Economic control of quality of manufactured product – outlining statistical methods for use in production and control chart methods.
1932-1933	British textile industry began use of statistical techniques for product/process development.
1944	Industrial Quality Control began publication.
1954	E. S. Page introduced CUSUM control chart.
1960	The concept of quality control circle was introduced in japan by K. Ishikawa.
1960	The zero defects (ZD) programs are introduced in US induatries.