Quality control techniques


Various techniques of quality control have been developed. More prominent of them are: Just-In-Time, quality at the source, quality circles, inspection, statistical quality control and total quality management. A brief explanation of each, is as follows.

1. Just-In-Time (JIT): JIT has different interpretations. For some, it is buying material on time, for some others, it means planning and controlling production on the shop floor, and for others it is a philosophy of production that permeates every facet of organizations. For our purpose, JIT is viewed as a technique of quality control. Just as JIT has different interpretations, it has varied names too. For some companies, IBM for examples, continuous flow manufacture; for some others, Hewlett – Packard, for example, it is called stockless production and repetitive manufacturing system; GE calls it management by sight; and many Japanese firms use the term Toyota system instead of JIT.

JIT helps achieve quality, because it is a philosophy that seeks to constantly improve production processes and methods. Specifically, JIT contributes to high product quality in the following ways:

1. Production is highly standardized. Workers perform standard tasks everyday. They are familiar with their tasks. Familiarity ensures high quality.

2. In-process inventories are drastically reduced by cutting lot-sizes. Any interruption, therefore, causes production to stop until the problem has been solved. In this way, JIT has been called a system of enforced problem solving. Now, this stoppage in production forces everybody to solve the quality problem, so that the defect will not repeat. Hence, high product quality is ensured.

3. Suppliers of materials, under the JIT system supply materials of perfect quality. Many companies do not even inspect suppliers’ deliveries of materials; rather, the emphasis is on working with suppliers to produce perfect parts and materials.

4. JIT system envisages the use of automated equipment and robots in production processes. Use of such sophisticated machines will ensure high product quality.

5. JIT system also envisages the use of intensive preventive maintenance programs in order to prevent any machine break–down. This results in machines producing parts of perfect quality.

6. Workers are responsible for producing parts of perfect quality or with zero defects, before they are passed on to the next production operation.

Quality at the source

Where workers are made responsible to produce parts of perfect quality, before they are passed on to the next operation, the concept of quality at the source emerges. The worker is put in the driver’s seat in controlling product quality. The principles underlying quality at the source are:

1. Every worker’s job becomes a quality control station. The worker is responsible for inspecting his own work, identifying any defects and reworking them into non-defectives, and correcting any cause of defect.

2. Statistical quality control techniques are used to monitor the quality of parts produced at each work station, and easy-to-understand charts and graphs are used to communicate progress to workers and managers.
3. Each worker is given the right to stop the production line to avoid producing defective parts.

4. Workers and managers are organized into quality circles – groups of people who analyze quality problems, work to solve the problems and implement programs to improve product quality.


The act of determining conformance or non-conformance of the expected performance is the function of inspection. In other words, by inspection, a manager seeks to determine the acceptability or non-acceptability of the parts, products or services. The basis for inspection is usually a specification, which is called inspection standard. Inspection is made by comparing the quality of the product to the standard.

When to inspect is the next relevant question. In general, inspection is desired at —

1. Finished products and parts to know that, correct parts are to be assembled or products are right when shipped;

2. Before an expensive processing.

3. The output of automatic machine periodically, so that, possible errors are confined to small quantities, and

4. Before an operation that cannot be undone, for example , in mixing paint.