Quality Control

Unit - 4

QUALITY

• A subjective term for which each person has his or her own definition.

– Characteristics of a product that bears on it’s ability to satisfy the stated or implied needs

– A product or service free of deficiencies.

• Quality can be defined as the degree to which a product can meet the requirements of customer

Steps to Improve Quality• Improved Raw material• Better Technology• Scientific selection of worker• Good working condition• Harmonious relation with management• Industrial Research

Importance of Quality• Motivated employees• Market Share• Reputation• International competitiveness• Revenues generation increased (ultimate goal)

Quality Control

• It is a universal managerial process for conducting operations so as to provide stability--to prevent adverse change and to “maintain the status of company”.

• Quality control can also be described as “a process for meeting the established goals by evaluating and comparing actual performance and planned performance, and taking action on the difference”

Factors influencing Quality (Determinants of Quality)

• Technological Advancement• Quality of Human Resources• Availability of funds• Management commitments• Natural Factors – Geographical, Physical Climatic Condition

The Circle of Quality

PlanBe specificIdentify measurable goals

DoImplement the planRecord and document your actions

CheckReview records and documentsGet feedback from process participants

Act Make adjustments and changesCreate new plan element

Quality Control Process1. Choose control subject

2. Establish Measurement

3. Establish standards of Performance

4. Measure Actual Performance

5. Compare to Standards (interpret the difference)

6. Take action on the difference

Objective of Quality Control• To achieve the quality standards which are economical to achieve

and acceptable to the customer.

• To establish standard of raw material which are to be purchased.

• To evaluate the methods of production and suggest improvements

• To determine the extent of degree of quality deviations in a product during the various stages of production.

• To identify the causes of deviations

• To suggest remedial measure to improve the quality

Statistical Quality Control (SQC)

• It is the scientific technique of controlling quality by means of statistical methods.

• It can be defined as the technique of applying statistical methods based upon the mathematical theories of probability to quality control problems with the purpose of establishing quality standards and maintaining devotion to those standards in cost economical manner

Single Double & Sequential Sampling

• Single sampling: A large no. of enough sample is inspected and the lot is accepted or rejected on the basis of percentage or no. of defectives found in one sample.

• Double Sampling: In case, it is not possible to decide the fate of the lot on the basis of single sample, then a second sample is drawn from the lot. The final decision is based on the combined result from both the samples.

• Sequential Sampling: It is also called as item by item analysis. This sampling involves increasing the sample size by one part at a time till the sample becomes large enough and contains sufficient number of defectives on the basis of results obtained, it is decided whether to accept the lot or not.