Evaluation of ideas, testing, feedback, refinement

Design Process – Evaluation of Ideas, Testing, Feedback and Refinement (Cambridge IGCSE Design & Technology 0445)

1. The Full Design Cycle

The design process is iterative and consists of four main phases. Each phase feeds back into the next until the solution fully satisfies the design brief.

1. Pre‑evaluation – need analysis, brief, research, specification, sustainability, health‑&‑safety planning.
2. Idea generation & selection – sketching, CAD modelling, decision‑matrix weighting, resource planning.
3. Evaluation, testing & feedback – systematic comparison, objective data collection, peer/user critique.
4. Refinement & documentation – modify, re‑test, record changes and prepare the final design dossier.

2. Pre‑evaluation – Setting the Foundations

2.1 Need Analysis & Design Brief

• Identify a genuine problem or opportunity (e.g., “students need a portable water bottle that stays cold for 8 h”).
• State the purpose, target users, and context.
• List legal, ethical and market constraints.

Design‑Brief & Specification Checklist (Cambridge wording)

Item	What to Include
Need / Problem	Clear description of the need, why it matters and who it affects.
Target Users	Age, abilities, preferences, cultural considerations.
Purpose & Function	Primary and any secondary functions.
Constraints	Legal, ethical, environmental, budget, size, weight, material limits.
Success Criteria (Specification)	Measurable, quantitative statements (e.g., capacity ≥ 500 ml, weight ≤ 250 g, insulation ≥ 8 h, cost ≤ £15, durability – survive a 2 m drop).

2.2 Research & Specification Development

• Gather information on existing products, materials, technologies and user preferences.
• Translate research into a Specification – a list of measurable success criteria (see checklist above).

2.3 Sustainability, Ethics & Society

• Life‑cycle thinking: renewable, recyclable or biodegradable materials; energy use in manufacture; end‑of‑life disposal.
• Ethical considerations: conflict‑free sourcing, fair‑trade, safe working conditions.
• Design & Technology in Society: how the product will affect the environment, economy and users (e.g., reducing single‑use plastic waste, creating local jobs, meeting market trends).

2.4 Health & Safety – Expanded Tool‑by‑Tool Risk Matrix

Tool / Process	Typical Risks	Control Measures (PPE, Safe Practices, Symbols)
Hand saw / hacksaw	Sharp blade, kick‑back	Safety glasses 🛡, gloves, clamp workpiece; use “Cutting” safety symbol.
Power drill	Flying debris, entanglement	Safety glasses, hearing protection, secure workpiece; “Power tools” symbol.
CNC router / milling	Sharp tools, high speed, noise	Safety glasses, ear defenders, emergency stop, enclose machine; “Machine safety” symbol.
Laser cutter	Eye damage, burns, fumes	Laser safety goggles, fire‑retardant clothing, ventilation, interlock; “Laser” symbol.
Soldering iron	Burns, toxic fumes	Heat‑resistant gloves, fume extractor, keep away from flammables; “Hot surface” symbol.
Heat‑forming plastic	Burns, toxic vapour	Heat‑resistant gloves, well‑ventilated area, fume extractor; “Heat” symbol.
Electrical testing	Shock, short‑circuit	Insulated tools, dry hands, circuit breaker, “Electrical hazard” symbol.

3. Communication of Ideas (AO2)

Effective communication is essential for the design cycle. Use the following toolkit to produce clear, standardised drawings and descriptions.

3.1 Drawing Conventions

Element	Standard Symbol / Line Type	Annotation Guidance
Visible edges	Thick solid line	Label with part name and material.
Hidden edges	Dashed line	Use only when necessary to avoid clutter.
Center lines	Chain‑dotted line	Mark symmetry or rotation axes.
Section cuts	Thick solid line with arrows	Indicate direction of view; include hatching pattern.
Dimensions	Dimension line with arrows, leader lines	Show to 0.1 mm (or as required); use metric units.
Notes & Call‑outs	Leader line + text box	Use technical vocabulary (e.g., “mounting hole Ø 5 mm”).

3.2 Technical Vocabulary (selected)

• Ergonomics – design for comfort and efficiency of use.
• Modular – made of interchangeable units.
• Fastening – joining by screws, rivets, adhesives, etc.
• Finish – surface treatment (painting, anodising, varnish).
• Tolerance – allowable variation in dimensions.

4. Idea Generation & Selection

4.1 Creative Techniques

• Mind‑mapping, SCAMPER, forced‑association, sketching.
• 2‑D CAD (orthographic drawings) and 3‑D CAD (solid models, exploded views).
• Use ICT tools to produce colour‑coded diagrams and virtual prototypes.

4.2 Decision‑Matrix with Weighting (AO2)

Assign a weight (1–5) to each specification criterion, score each concept (1–5), multiply and total for a quantitative ranking.

Criterion	Weight	Concept A	Concept B	Concept C
Insulation	5	4 × 5 = 20	3 × 5 = 15	5 × 5 = 25
Weight	4	3 × 4 = 12	5 × 4 = 20	2 × 4 = 8
Cost	3	5 × 3 = 15	4 × 3 = 12	2 × 3 = 6
Durability	4	4 × 4 = 16	5 × 4 = 20	3 × 4 = 12
Ergonomics	2	3 × 2 = 6	4 × 2 = 8	5 × 2 = 10
Total		69	75	61

Concept B scores highest and is selected for prototyping.

4.3 Resource & Time Planning

• List materials, tools, skills, estimated costs.
• Produce a Gantt chart showing key milestones (research, CAD, prototype, test, refinement).

5. Evaluation of Ideas (Before Prototyping)

• Checklists – verify every success criterion is addressed.
• Weighted Decision‑Matrix – provides an objective ranking.
• Risk Assessment – ensure safety of chosen materials and processes (see Section 2.4).
• Environmental Impact Matrix – score material choices on carbon footprint, recyclability, renewability.

6. Testing – Gathering Objective Data

6.1 Test Planning (AO2)

• Define variables – independent, dependent, controlled.
• State clear success criteria (e.g., temperature drop ≤ 5 °C after 8 h).
• Complete a risk‑assessment checklist (refer to Section 2.4).
• Select appropriate measuring instruments (thermocouples, digital scales, stop‑watches, calipers).

6.2 Conducting the Test

1. Record initial conditions (ambient temperature, water temperature, humidity).
2. Run the test under repeatable conditions (same volume, same container shape, same environment).
3. Take measurements at regular intervals (e.g., every hour).
4. Repeat at least three times to allow statistical analysis.

6.3 Data Analysis – Quantitative Tools (AO3)

• Enter results in a table and plot a temperature‑time graph.
• Calculate mean and standard deviation for each time point.
• Perform an error analysis (instrument precision, human reaction time, ambient fluctuations).
• Compare measured ΔT with the specification using the thermal‑loss formula:
  Q = (k · A · ΔT) / d where k = thermal conductivity, A = surface area, d = wall thickness. Use the calculation to predict performance and explain any discrepancy.

6.4 Reporting Results

Use a standard test‑report template that includes:

• Purpose & hypothesis
• Method (including safety measures)
• Raw data (tables)
• Processed data (graphs, statistics)
• Conclusion – does the prototype meet the success criteria?
• Recommendations for improvement.

7. Feedback – External Perspectives

• Peer/teacher critique – structured rubric covering function, aesthetics, ergonomics, sustainability.
• User surveys / interviews – Likert‑scale questions on comfort, ease of use, visual appeal.
• Technical feedback – from test data, CAD simulations (stress, thermal, motion).

Record feedback in a Feedback‑Log table and link each comment to a specific evaluation criterion.

8. Refinement & Iteration

1. Identify required modifications from evaluation, test analysis and feedback.
2. Update CAD models to reflect changes (e.g., add silicone sleeve, reduce wall thickness).
3. Document each change on a Design Revision Sheet (date, description, reason, expected impact).
4. Produce a revised prototype and repeat the testing cycle.
5. Continue iterating until all success criteria are satisfied and the design is optimised for cost, sustainability and user satisfaction.

9. Use of ICT, CAD/CAM & Digital Modelling (AO2)

• 2‑D CAD – orthographic drawings, dimensioned schematics for manufacture.
• 3‑D CAD – solid models, exploded views, virtual assembly checks.
• CAM – generate CNC toolpaths, 3‑D‑printer slicer settings.
• Simulation – thermal, stress or motion analysis to predict performance before physical testing.
• All digital artefacts must be saved, version‑controlled and referenced in the final design dossier.

10. Sustainability & Ethics Integration (AO2)

• Choose materials with low embodied energy (recycled aluminium, biodegradable polymers).
• Design for disassembly – use fasteners rather than permanent bonds.
• Calculate a simple carbon‑footprint estimate: mass (kg) × CO₂ kg per kg material.
• Consider social responsibility – fair‑trade sourcing, safe working conditions, impact on local economies.

11. Specialist Option – Resistant Materials Snapshot (AO2)

This brief overview supports the specialist option on resistant materials. It can be used to inform the decision‑matrix and material‑selection stages.

Material Family	Typical Properties	Common Shaping Processes	Joining Methods	Finishing & Testing
Metals (e.g., aluminium, steel)	High strength, good thermal conductivity, recyclable.	CNC milling, laser cutting, water‑jet, bending, casting.	Screws, rivets, welding, adhesives.	Surface polishing, anodising, hardness test (Rockwell), tensile test.
Plastics (e.g., PET‑E, ABS, biodegradable PLA)	Lightweight, low cost, variable rigidity, poor heat resistance.	3‑D printing, injection moulding, laser cutting, thermoforming.	Snap‑fits, screws, solvent welding, adhesives.	Impact test, melt flow index, surface coating.
Wood (e.g., plywood, MDF, hardwood)	Good strength‑to‑weight, renewable, anisotropic.	Sawing, CNC routing, sanding, lamination.	Screws, dowels, glue, biscuits.	Sand finish, varnish, moisture content test, bend test.
Composites (e.g., fibre‑reinforced polymers)	High strength, low weight, corrosion‑resistant.	Lay‑up, vacuum bagging, resin transfer moulding.	Adhesives, mechanical fasteners, bonding with epoxy.	Four‑point bend test, delamination inspection, surface finish.

When completing the decision‑matrix, assign weights to material properties that are most relevant to the brief (e.g., “thermal conductivity” for an insulated bottle).

12. Summary Table of Evaluation Tools

Tool	Purpose	When to Use	Key Benefits
Checklists	Ensure every specification is considered	Idea generation & final review	Quick, comprehensive overview
Weighted Decision‑Matrix	Quantitative comparison of concepts	Selecting a concept for prototyping	Transparent, objective ranking
Prototype Testing	Gather real‑world performance data	After low‑ or high‑fidelity prototype	Evidence‑based validation (AO3)
Statistical Analysis (mean, SD, error)	Interpret test data rigorously	During data analysis phase	Supports AO3 evaluation
Peer/Teacher Critique	External viewpoint on function & aesthetics	Design reviews	Highlights blind spots
User Surveys	Collect ergonomic and preference data	After functional prototype	Ensures user‑centred design
CAD Simulation (thermal, stress)	Predict behaviour before building	During design development	Reduces material waste
Sustainability Matrix	Assess environmental impact	Specification & evaluation stage	Integrates ethics into decision‑making
Resistant‑Materials Snapshot	Inform material selection for specialist option	Idea generation & decision‑matrix	Links material properties to success criteria

13. Example Workflow (Water‑Bottle Project)

1. Need & Brief: Portable bottle keeping drinks ≤ 5 °C for 8 h.
2. Research: Study double‑wall steel, insulated plastic, foam‑filled silicone.
3. Specification (see Section 2.1 checklist).
4. Idea Generation: Hand sketches + 3‑D CAD models of three concepts.
5. Decision‑Matrix (weights: Insulation 5, Weight 4, Cost 3, Durability 4, Ergonomics 2) – Concept B (insulated plastic) scores highest.
6. Resource Planning: Materials – PET‑E, silicone, aluminium lid; Cost ≈ £12; Time – 6 h CAD, 4 h CNC, 3 h assembly.
7. Prototype: Low‑fidelity 3‑D printed shell, aluminium lid, silicone sleeve.
8. Test Plan:
   • Independent variable – wall thickness.
   • Dependent variable – temperature drop (°C) over 8 h.
   • Controls – 500 ml water at 20 °C, ambient 22 °C, identical shape.
9. Testing: Record ΔT at 0, 2, 4, 6, 8 h; repeat three times.
10. Data Analysis:

    Time (h)	ΔT (°C) – Run 1	Run 2	Run 3	Mean ± SD
    0	0	0	0	0 ± 0
    2	2.1	2.0	2.2	2.1 ± 0.1
    4	3.8	3.9	3.7	3.8 ± 0.1
    6	5.0	5.2	5.1	5.1 ± 0.1
    8	6.4	6.5	6.3	6.4 ± 0.1

11. Feedback: Peer critique (function 8/10, aesthetics 7/10), user survey (comfort 4/5), thermal simulation (predicted ΔT = 6.2 °C).
12. Refinement: Add 2 mm silicone sleeve, reduce wall thickness from 3 mm to 2.5 mm, update CAD, produce revised prototype, re‑test.
13. Final Documentation: Complete design dossier with brief, specification, drawings (with conventions), risk assessments, test reports, feedback log, sustainability analysis, and a reflective evaluation.