Unit 3: Product Quality Improvement

Quality Function Deployment (QFD)

QFD is a structured method to translate customer requirements into technical specifications for product or service development. It helps ensure the voice of the customer (VOC) is considered throughout the design process.

📌 Tool Used

House of Quality (HOQ) – a matrix that connects customer needs to design parameters.

📌 Steps in QFD

Example: For a smartphone:

• Customer Requirement (WHAT): Long battery life
• Engineering Requirement (HOW): Higher mAh battery, power optimization
• Other WHATs: Fast charging, lightweight, good camera
• HOQ links these to technical specs, enabling smart design decisions.

✅ Benefit: Aligns product features with real customer needs.

Robust Design

Robust Design is about creating products or processes that consistently perform well despite variations—like changes in environment, user habits, or material properties.

📌 Goal

• Minimize sensitivity to external noise (e.g., temperature, humidity).
• Improve reliability and performance stability.

🧠 Example: Designing a car engine that performs well in both cold (−10°C) and hot (45°C) weather. Rather than changing the environment, the design is optimized to withstand changes in temperature.

✅ Benefit: Reduces product failures and improves customer satisfaction.

Taguchi Method

The Taguchi Method, developed by Genichi Taguchi, is a statistical approach to design robust products. It uses design of experiments (DOE) to identify the best combination of input variables with minimal variation.

📌 Key Concepts:

Example: Suppose you’re making plastic bottles, and you're testing:

• Temperature (Low, Medium, High)
• Pressure (Low, High)
• Time (Short, Long)

Instead of testing all combinations (which is time-consuming), Taguchi’s orthogonal array lets you test a few strategic combinations to identify:

• Best settings
• Least variation

✅ Benefit: Saves time, reduces cost, and improves quality by finding optimal parameters.

✅ Summary Table

Design Failure Mode and Effect Analysis (DFMEA)

DFMEA is a proactive tool used in the product design phase to identify and eliminate potential design failures before the product is launched.

It helps teams:

• Anticipate possible failure modes.
• Understand their effects on customers.
• Prioritize issues based on risk.
• Implement design improvements early.

🛠️ DFMEA Process (Step-by-Step)

Example: Car Door Latch Design

✅ Focus first on the higher RPN (216) to reduce major risks.

🎯 Benefits of DFMEA

• Early problem detection
• Reduced warranty claims
• Safer and more reliable designs

Product Reliability Analysis

Reliability is the probability that a product will perform its intended function without failure for a specific period under stated conditions.

🔍 Key Goal: To ensure that products last longer, work consistently, and meet customer expectations.

⚙️ Key Metrics & Methods in Reliability Analysis

Example: LED Light Reliability

• Expected life: 50,000 hours
• Failure rate: 0.00002 failures/hour
• MTBF = 1 / Failure Rate = 50,000 hours
• Reliability after 10,000 hours:

R(t) = e^(−λt) = e^(−0.00002 × 10,000) = e^(−0.2) ≈ 0.82

So, 82% chance it works after 10,000 hours.

📈 Tools Used

• Reliability Block Diagrams (RBD)
• Weibull Analysis (for life data distribution)
• Stress Testing / Accelerated Life Testing

✅ Summary Table