(SEM VI) THEORY EXAMINATION 2024-25 QUALITY CONTROL & RELIABILITY

BOE061 – QUALITY CONTROL & RELIABILITY

Section-Wise Solved Answers (2024–25)

SECTION A

Attempt all questions in brief (2 × 7 = 14 marks)

(a) Define quality. What are the major factors influencing quality?

Quality is the degree to which a product or service satisfies customer needs and expectations. It is not only related to performance but also to reliability, durability, and appearance.
Major factors influencing quality include design quality, quality of raw materials, manufacturing process, skill of workforce, inspection and testing methods, and after-sales service.

(b) What is the cost of quality? Name its major components.

Cost of quality refers to the total cost incurred to ensure that products meet quality standards and the costs resulting from failures.
The major components are prevention cost, appraisal cost, internal failure cost, and external failure cost. Investing in prevention and appraisal reduces failure costs.

(c) Explain the use of X-bar and R-chart in quality control.

X-bar chart is used to monitor variations in the process mean, while the R-chart monitors variation within samples. Together, they help detect assignable causes of variation and ensure that the process remains under statistical control.

(d) What are the fundamental principles of TQM?

Total Quality Management is based on customer focus, continuous improvement, employee involvement, leadership commitment, process-oriented approach, and data-based decision making. These principles aim at long-term success through customer satisfaction.

(e) Define reliability. What is MTTF?

Reliability is the probability that a system or component performs its intended function without failure for a specified period under stated conditions.
MTTF (Mean Time to Failure) is the average time a non-repairable system operates before failure occurs.

(f) Distinguish between MTBF and MTTR.

MTBF (Mean Time Between Failures) represents the average time between consecutive failures of a repairable system.
MTTR (Mean Time To Repair) is the average time required to repair a system and restore it to operational condition.

(g) List any two reliability test methods.

Two commonly used reliability test methods are life testing and accelerated life testing.

SECTION B

Attempt any three (7 × 3 = 21 marks)

(a) Explain the concept and benefits of quality circles.

Quality circles are small groups of employees who voluntarily meet to identify, analyze, and solve work-related quality problems. They promote teamwork, improve morale, reduce defects, enhance productivity, and encourage employee participation in quality improvement.

(b) Discuss the construction and application of control charts for attributes.

Attribute control charts are used when quality characteristics are measured in terms of defectives or defects. Common charts include p-chart, np-chart, c-chart, and u-chart. These charts help monitor process performance and detect variations in defect levels.

(c) Elaborate on ISO 9000 standards and their role in quality improvement.

ISO 9000 is a set of international standards for quality management systems. It ensures consistency in processes, improves customer satisfaction, enhances credibility, and promotes continuous improvement through documented procedures and audits.

(d) Define hazard rate and failure density function. Explain their role in reliability estimation.

Failure density function represents the probability of failure at a given time.
Hazard rate is the rate at which failures occur at a given time, assuming survival up to that time. Both are essential for predicting system life and reliability performance.

(e) Explain the temperature-humidity bias model in reliability management.

The temperature-humidity bias model explains how high temperature and humidity accelerate failure mechanisms such as corrosion and insulation breakdown. It is widely used in electronics reliability testing to predict product life under normal conditions.

SECTION C

Attempt any one (7 × 1 = 7 marks)

(a) Discuss the types of quality and quality characteristics with examples.

Quality can be classified as design quality and conformance quality.
Quality characteristics are categorized as variables (measurable, such as length or weight) and attributes (countable, such as number of defects). Both are essential for effective quality control.

(b) Quality improvement plan for reducing customer complaints

As a quality assurance manager, the plan would start with systematic inspection and data collection. Statistical tools such as Pareto charts, cause-and-effect diagrams, and control charts would be used to identify root causes. Corrective actions would then be implemented, followed by continuous monitoring. This integrated approach ensures sustainable quality improvement and customer satisfaction.