UNIT 2: PRODUCT DESIGN - SHORT NOTES

1.0 PRODUCT DEVELOPMENT FRAMEWORK & STRATEGY

1.1 Product Life Cycle (PLC)

• Definition: A model describing the stages a product goes through from market introduction to eventual decline.

• Four Key Stages:

  1. Introduction: Low sales, high costs (R&D, marketing), few competitors. Strategy: Build awareness, refine product.

  2. Growth: Rapid sales increase, profits rise, competitors enter. Strategy: Expand market, improve product features.

  3. Maturity: Sales peak, market saturated, intense price competition. Strategy: Maximize profit, product differentiation, cost reduction.

  4. Decline: Sales and profits fall. Strategy: Harvest, divest, or rejuvenate product.

[!TIP] Exam Focus: Be prepared to cite examples for each stage (e.g., Smartphones: Introduction=1st iPhone, Growth=Android expansion, Maturity=current market, Decline=older models).

1.2 Product Design Process & Methodology

• Systematic Design Process (Pahl & Beitz Model):

  1. Clarification of Task: Define problem, constraints, objectives.

  2. Conceptual Design: Generate and select solution principles (functional structures).

  3. Embodiment Design: Develop layout, form, materials, interfaces.

  4. Detail Design: Finalize drawings, specifications, tolerances, production documents.

• Objectives of Product Design: Functionality, quality, cost, manufacturability, usability, aesthetics, sustainability.

1.3 Product Strategy & Policy

• Elements:

  • Platform Strategy: Common core architecture for multiple products (e.g., car platforms).

  • Product Line: Group of related products.

  • Portfolio: Collection of all product lines.

• Innovation's Role: Drives new product development, creates competitive advantage, extends PLC.

• Organizational Policies: Define processes for idea generation, portfolio management, resource allocation, and stage-gate reviews.

1.4 Market & Competitive Analysis

• Understanding User Needs: Methods include customer interviews, surveys, observation (ethnography), and focus groups. Goal: Translate latent needs into design specifications.

• Competitive Benchmarking: Systematically assess rival products' features, performance, cost, and weaknesses.

• Customer Involvement: Co-creation (customers collaborate in design) and user testing (prototype evaluation) reduce risk and improve adoption.

2.0 VALUE ANALYSIS & FUNCTIONAL DECOMPOSITION

2.1 Value Engineering (VE) / Value Analysis (VA)

• Definition: A systematic, interdisciplinary function-oriented method to improve Value.

$$\boxed{\text{Value} = \frac{\text{Function}}{\text{Cost}}}$$

• Objective: Maximize value by achieving necessary functions at lowest total cost without sacrificing quality, reliability, or performance.

• VE Job Plan (7-Step Method):

  1. Information: Gather data on function, cost, quantity.

  2. Function Analysis: Identify and classify functions (basic, secondary, unnecessary).

  3. Creative: Brainstorm ways to perform functions.

  4. Evaluation: Screen and rate ideas.

  5. Development: Refine and estimate costs of best ideas.

  6. Presentation: Recommend to management.

  7. Implementation & Follow-up.

• VA vs. VE: VA applies to existing products (cost reduction). VE applies to new products (value optimization during design).

2.2 Function Analysis System Technique (FAST)

• Purpose: To visually model the logical relationship between functions in a system, answering "How?" and "Why?".

• Basic Rules:

  • Scope: Define the overall objective (top-level function).

  • Function: Use active verb + measurable noun (e.g., "support load", "prevent corrosion").

  • Cause-Effect: "How?" (lower-order) and "Why?" (higher-order) logic.

• FAST Diagram Development:

  1. Identify Basic Function (primary purpose).

  2. Identify Secondary Functions (supporting).

  3. Link with "How?" (to the left) and "Why?" (to the right).

  4. Identify Critical Path (chain of basic and essential secondary functions).

  5. Identify Tertiary/Superfluous Functions (can be eliminated without losing primary function).

• Application: Used in automotive systems to deconstruct systems (e.g., braking system: "Slow vehicle" → "Generate friction" → "Apply pad to disc").

[!TIP] Common Pitfall: Confusing functions (what it does) with solutions (how it's done). FAST focuses on functions only, not physical parts.

2.3 Creative Problem-Solving Techniques

• Brainstorming: Free idea generation, no criticism, quantity over quality.

• SCAMPER: Checklist for idea generation:

  • Substitute, Combine, Adapt, Modify, Put to another use, Eliminate, Reverse.

• Morphological Analysis: Create a matrix of independent design parameters and their possible values to generate combinations.

• Synectics: Use analogies and metaphors to force new perspectives ("Make the strange familiar, make the familiar strange").

3.0 DESIGN FOR X (DFX) PRINCIPLES

3.1 Design for Manufacture (DFM) & Assembly (DFA)

• DFM Objective: Design for low-cost, high-quality manufacturing.

• DFM Guidelines (Material & Process):

  • Material Selection: Choose material compatible with process (e.g., polymers for injection molding, aluminum for die casting).

  • Process-Specific Design:

    • Injection Molding: Uniform wall thickness, adequate draft angles (1°-2°), avoid sharp corners, incorporate ribs for strength, proper gate location.

    • Die Casting: Thin walls (2-3mm), draft angles, avoid undercuts, define parting line.

    • Sand Casting: Provide draft, radii, machining allowances, avoid deep cavities.

  • General: Minimize part count, use standard components, specify achievable tolerances.

• DFA Objective: Minimize assembly time and cost.

• DFA Guidelines (Manual Assembly):

  • Symmetry: Design parts to be symmetric for easy orientation.

  • Minimize Handling: Reduce part movements and rotations.

  • Self-Locating: Features that automatically align parts.

  • Minimize Fasteners: Use snap-fits, integral fasteners.

  • Accessibility: Ensure easy access for assembly tools.

• DFM vs. DFA: DFM focuses on making parts cheaply; DFA focuses on putting parts together cheaply. DFMA integrates both.

3.2 Design for Environment (DFE) / Sustainable Design

• Core Principles (4R): Reduce (material, energy), Reuse (components), Recycle (materials), Recover (energy from waste).

• Material Selection: Use recycled/biodegradable materials, avoid hazardous substances.

• Design for Disassembly: Use modular design, standard fasteners, minimize adhesive/ bonding, mark materials.

• Design for Remanufacturing: Design for easy cleaning, inspection, and refurbishment.

• Eco-Packaging: Minimize material, use recyclable/biodegradable packaging.

• Life Cycle Assessment (LCA): Quantify environmental impact from raw material to disposal.

3.3 Design for Robustness (Taguchi Methods)

• Concept: Design products that perform consistently despite noise factors (uncontrollable variations: temperature, humidity, wear).

• Quality Loss Function:

$$\boxed{L = k(y - T)^2}$$

Where $L$ = loss, $y$ = actual value, $T$ = target value. Loss increases quadratically as performance deviates from target.

• Parameter Design: Use Orthogonal Arrays to systematically test the effect of control factors (design parameters) on performance while noise factors vary. Goal: Find settings insensitive to noise.

• Tolerance Design: Set optimal tolerances balancing cost and quality loss.

• Implementation Challenges: Requires statistical expertise, multi-disciplinary team, cultural shift from "inspection" to "robust design".

3.4 Ergonomics (Human Factors) in Product Design

• Anthropometry: Application of human body measurements. Use percentiles (e.g., design for 5th-95th percentile users). Critical for workspace dimensions, control reach.

• Cognitive Ergonomics: Mental workload, decision-making, information presentation (displays, controls).

• Physical Ergonomics: Posture, force requirements, repetitive motion (RSI prevention).

• Visual Design Elements:

  • Color: Coding, attention, cultural meaning.

  • Shape: Intuitive affordances (e.g., round button for push).

  • Texture: Tactile feedback, slip resistance.

4.0 MANUFACTURING PROCESS CONSIDERATIONS

4.1 Material & Process Selection Guidelines

• Sand Casting:

  • Design: Provide draft (2-3°), add fillets (radii) at corners, define machining allowances, avoid deep pits.

  • Pattern: Must be slightly larger to account for shrinkage.

• Die Casting:

  • Design: Thin, uniform walls (<3mm), draft (1-3°), define parting line, avoid undercuts (require slides), maintain minimum section thickness.

  • Material: Non-ferrous (Al, Zn, Mg alloys).

• Injection Molding:

  • Design: Uniform wall thickness (to avoid sink marks/warpage), adequate draft for ejection, proper gate location (flow balance), incorporate ribs for strength (avoid thick bases), bosses for fasteners.

  • Key Defects: Sink marks (thick sections), warpage (uneven shrinkage), weld lines (flow fronts meeting).

• Non-Metallic Products (Polymers/Composites):

  • Consider mechanical loads (stress concentrations), thermal loads (CTE, operating temp), environmental (UV degradation, chemical resistance).

4.2 Quality in Injection Molding

• Factors Affecting Quality:

  1. Material: Drying, viscosity, filler content.

  2. Process Parameters: Melt temp, mold temp, injection pressure/speed, cooling time.

  3. Mold Design: Gate location, cooling channel layout, venting.

• Critical Defects:

  • Shrinkage: Volume decrease upon cooling. Must be compensated in mold.

  • Warpage: Uneven cooling/shrinkage causes distortion.

  • Sink Marks: Surface depressions over thick sections.

  • Weld Lines: Weak lines where flow fronts meet (poor bonding).

5.0 RAPID PROTOTYPING & CAD/CAM

5.1 Rapid Prototyping (RP) Technologies

• General Process: CAD Model → Data Conversion (STL) → RP Machine (layer-by-layer) → Post-processing.

• Classification & Comparison:

• STL Format: Stereolithography Tessellation Language. Represents 3D model as mesh of triangular facets. Significance: Universal RP input format, but only approximate geometry (facet size controls accuracy).

• Applications: Concept models, functional testing, custom tooling (molds/jigs), medical models, end-use parts (SLS).

5.2 CAD/CAM & Simulation

• 2D vs. 3D CAD:

  • 2D: Orthographic views (front, top, side). No inherent volume/relationship data.

  • 3D: Solid or surface models. Contains complete geometry, enables interference checking, mass properties, and direct manufacturing output.

• Role of CAD in DFM: Built-in DFM analysis tools check for draft angles, minimum radii, wall thickness uniformity, and manufacturability rules for specific processes (injection molding, sheet metal).

• Simulation & Analysis Tools:

  • FEA (Finite Element Analysis): Structural stress, deflection, vibration.

  • CFD (Computational Fluid Dynamics): Fluid flow, heat transfer.

  • Purpose: Virtual prototyping to validate performance, optimize design, and reduce physical prototyping cycles.

6.0 SPECIALIZED TOPICS & APPLICATIONS (Product Context)

6.1 Power Transmitting & Fluid Devices

• Fluid Coupling:

  • Working: Hydraulic device connecting motor to load. Impeller (driven by motor) imparts kinetic energy to fluid, which drives runner (connected to load). Slip (difference in impeller/runner speed) is inherent.

  • Application: Soft-start for conveyors, crushers, protect against overload.

• Torque Converter:

  • Components: Impeller (pump), Turbine, Stator (redirects flow, multiplies torque).

  • Working: Similar to coupling but stator provides torque multiplication at low speed (vehicle start). At high speed, stator freewheels (lock-up clutch in modern autos).

  • Application: Automatic transmissions.

• Hydraulic Intensifier:

  • Working: Uses low-pressure, large-area piston to drive high-pressure, small-area piston.

$$\boxed{P_1 A_1 = P_2 A_2}$$

*   **Application:** Generate high pressure from low-pressure source for testing, clamping.

6.2 Draft Tubes (Hydraulic Turbines)

• Purpose: Pressure recovery device. Converts kinetic energy of exit flow to pressure, allowing turbine to be placed above tailrace, improving net head.

• Types:

  • Conical: Simple, efficient for high-head.

  • Elbow: For horizontal shaft turbines, saves space.

  • Moody: Inclined, reduces excavation.

  • Simple Circular: For low-specific-speed turbines.

• Effect on Efficiency: Properly designed draft tube increases overall turbine efficiency by reducing exit kinetic energy loss.

6.3 Centrifugal Blowers

• Working Principle: Similar to centrifugal pump. Impeller rotates, imparts kinetic energy to air, which is converted to pressure in volute casing.

• Construction Differences from Pumps:

  • Clearances: Much larger (air vs. water, lower density).

  • Blades: Often backward-curved for stability.

  • Sealing: Less critical.

  • Materials: Often lighter (sheet metal).

• Applications: HVAC systems, industrial ventilation, combustion air supply, dust collection.

[!NOTE] Context: In Product Design, these are studied as components/subsystems to be integrated into larger products (e.g., torque converter in a car, draft tube in a hydro plant). Focus is on function, integration, and design constraints, not detailed turbomachinery performance calculations (like Euler equation).