Quality Management & Control: Tools, Charts, TQM & Case Studies

TAKEAWAYS:

• Quality control uses statistical tools (X-bar/R-charts) to monitor process stability, while quality assurance prevents defects via design and processes.
• Total Quality Management (TQM) integrates customer focus, employee involvement, and continuous improvement (e.g., Nabil Bank’s zero-defect loan processing).
• Seven quality tools (flowcharts, Pareto charts) help solve problems—Daraz uses Pareto to prioritize delivery delays.
• Control charts (e.g., X-bar for means, R for ranges) detect outliers; a sample mean outside limits signals process drift (worked example: BIROI’s smart appliance defects).
• Cost of quality includes prevention (training), appraisal (inspection), internal failure (rework), and external failure (warranty claims).
• Exam focus: Case studies (30%), calculations (25%), and tool applications (20%)—practice X-bar/R-chart math and TQM stages.

1. Definitions and Scope

Quality Management vs. Quality Control

Key Terms:

• Quality: Degree to which a product/service meets customer expectations (e.g., Ncell’s network reliability).
• Quality Control (QC): Inspection and testing to detect defects (e.g., NTC’s voltage checks).
• Quality Assurance (QA): Proactive steps to prevent defects (e.g., Daraz’s supplier audits).
• Quality Management (QM): Strategic framework integrating QC, QA, and TQM.

2. Historical Evolution of Total Quality Management (TQM)

timeline
  title Evolution of TQM
  1920s : Shewhart (Statistical Process Control)
  1940s : Deming (Plan-Do-Check-Act cycle)
  1950s : Juran (Quality Trilogy: Planning, Control, Improvement)
  1960s : Feigenbaum (Total Quality Control)
  1980s : Ishikawa (Seven Tools, Employee Involvement)
  1990s : Six Sigma (Motorola, DMAIC)
  2000s : Lean + TQM (Toyota Production System)

Stages of TQM:

1. Inspection Era: Defect detection (1920s–1940s).
2. Statistical Quality Control: Shewhart’s control charts.
3. Quality Assurance: Juran’s focus on planning.
4. Total Quality Management: Deming’s 14 Points (e.g., Nabil Bank’s customer-centric loans).
5. Six Sigma: Data-driven defect reduction (e.g., Daraz’s 3.4 defects per million orders).

REAL WORLD:

• Nabil Bank: Uses TQM to reduce loan processing errors via Six Sigma (DMAIC: Define-Measure-Analyze-Improve-Control).
• Daraz: Applies Pareto analysis to identify top 20% of delivery delays causing 80% of complaints.
• NTC: Employs control charts to monitor electricity supply stability across Nepal.

3. Seven Tools for Quality Control

Example: Pareto Chart for Daraz

Action: Focus on delayed courier (30%) and incorrect orders (20%) for 50% improvement.

4. Statistical Process Control (SPC)

Control Charts

Two key charts:

1. X-bar Chart: Monitors sample means (central line = process mean).
2. R-chart: Monitors sample ranges (measures process variability).

Worked Example: BIROI’s Smart Appliances Given 10 samples of size 5, calculate control limits for X-bar and R-charts.

Data:

Steps:

1. Calculate grand mean (X̄̄) and average range (R̄).
   • X̄̄ = (43 + 49 + ... + 45) / 10 = 46.2
   • R̄ = (5 + 6 + ... + 4) / 10 = 5.1
2. Control Limits for X-bar:
   • Center Line (CL): X̄̄ = 46.2
   • Upper Control Limit (UCL): X̄̄ + A₂R̄ = 46.2 + 0.585.1 = 49.2
   • Lower Control Limit (LCL): X̄̄ - A₂R̄ = 46.2 - 0.585.1 = 43.2 (A₂ = 0.58 for n=5 from control chart tables)
3. Control Limits for R-chart:
   • CL: R̄ = 5.1
   • UCL: D₄R̄ = 2.115.1 = 10.8
   • LCL: D₃R̄ = 05.1 = 0 (D₃ = 0 for n=5)

Interpretation:

• If any X̄ > 49.2 or < 43.2 → process out of control (e.g., machine misalignment).
• If any R > 10.8 → excessive variability (e.g., inconsistent raw materials).

5. Cost of Quality (COQ)

pie
  title Cost of Quality Breakdown
  "Prevention Costs" : 20
  "Appraisal Costs" : 30
  "Internal Failure" : 30
  "External Failure" : 20

Components:

Goal: Shift costs from failure to prevention (e.g., Toyota’s Jidoka system).

6. Case Study: Hetauda Kapada Udhyog Ltd.

Problem: High defect rates in textile production. Solution: Applied TQM + SPC.

1. Root Cause Analysis: Used fishbone diagram to identify:
   • Materials: Low-quality yarn (60% of defects).
   • Machinery: Worn-out looms (30%).
   • Labor: Inconsistent training (10%).
2. Action:
   • Switched to ISO-certified yarn (prevention).
   • Installed R-charts to monitor loom variability.
3. Result: Defects reduced from 15% to 2% in 6 months.

7. Exam Tip: How to Score Full Marks

1. Case Studies (30%):
   • Structure: Problem → Tools Used → Solution → Impact.
   • Example: For BIROI, mention X-bar chart to detect defects and Pareto to prioritize issues.
2. Calculations (25%):
   • Memorize A₂, D₃, D₄ values for sample sizes (n=4,5,6).
   • Show all steps for control limits (e.g., X̄̄, R̄, UCL/LCL).
3. Definitions (20%):
   • Differentiate QC vs. QA vs. TQM clearly.
   • Link tools to real examples (e.g., flowcharts for Daraz’s delivery process).
4. Diagrams (15%):
   • Draw control charts with labeled axes and limits.
   • Sketch fishbone diagrams for root causes.
5. Short Answers:
   • Seven tools: List + one example each (e.g., Pareto for Daraz).
   • TQM stages: 5 key eras (Shewhart → Deming → Six Sigma).

Past Exam Pattern:

Final Checklist for Exams:

• Can you calculate UCL/LCL for X-bar and R-charts?
• Can you map a fishbone diagram for a real problem (e.g., Pathao’s driver delays)?
• Do you know 3 Nepali companies using TQM/SPC (Nabil Bank, Daraz, NTC)?
• Can you explain prevention vs. failure costs with examples?