Manufacturing Practices (BT-106) - Important Questions

Define Statistical Quality Control (SQC). Explain its objectives and describe the main components of SQC used in manufacturing practice.

Explain the principles of control charts for variables. Describe the construction, interpretation and application of the $\bar{X}$ and $R$ charts. Include the steps for collecting samples, calculating control limits and detecting common and special causes of variation.

Describe control charts for attributes. Explain the construction, control limits and usage of the $p$-chart and the $c$-chart. Discuss situations where each chart is preferred and how to interpret out-of-control signals.

Derive the control limits for the $\bar{X}$ chart for sample size $n$. Show that the theoretical control limits are given by $$UCL\;=\;\mu\;\pm\;3\,\frac{\sigma}{\sqrt{n}}\,$$ and explain the practical use of $A_2$ and $\bar{R}$ when $\sigma$ is unknown.

Define the process capability indices $C_p$ and $C_{pk}$. Give their formulas and explain the interpretation of the indices for assessing a manufacturing process. Include the formulas: $$C_p\;=\;\frac{USL- LSL}{6\,\sigma}\quad\text{and}\quad C_{pk}\;=\;\min\left(\frac{USL-\mu}{3\,\sigma},\;\frac{\mu- LSL}{3\,\sigma}\right)\,$$ where $USL$, $LSL$, $\mu$ and $\sigma$ are process parameters.

Explain a single sampling plan by attributes. Define the operating characteristic (OC) curve and show how to compute the probability of acceptance for a lot with defect proportion $p$ under a single sampling plan with sample size $n$ and acceptance number $c$.

Define AQL (Acceptable Quality Level) and LTPD (Lot Tolerance Percent Defective). Explain their roles in designing a single sampling plan and how producer’s risk ($\alpha$) and consumer’s risk ($\beta$) relate to these concepts.

Explain the concept of Six Sigma and the DMAIC methodology. Describe how Six Sigma relates to process capability and give examples of tools used in each DMAIC phase.

Describe the principles of Total Quality Management (TQM). Discuss commonly used quality tools such as Pareto analysis, Ishikawa (fishbone) diagram, 5S and Kaizen, and explain how they are applied in manufacturing process improvement.

Define the reliability metrics MTTF and MTBF. For a constant failure rate $\lambda$, show the relationship between MTBF and $\lambda$, and explain the significance of the exponential distribution in reliability analysis.

Explain the differences between breakdown maintenance, preventive maintenance and predictive maintenance. Describe the objectives of Total Productive Maintenance (TPM) and key activities used to improve equipment availability.

Explain the purpose of the ISO 9001 quality management system standard. List and briefly describe its main requirements relevant to a manufacturing organization (document control, process approach, corrective action, management review, etc.).