Welcome to the Development Stage: Making Ideas Work
Welcome to one of the most critical and rewarding chapters of your A2 coursework! In Unit A2 2: Coursework – Product–System Design and Manufacture (which makes up 30% of your total A Level and 50% of your A2 award), the Development section is where your chosen design concept transforms from an exciting sketch on paper into a fully engineered, rigorously tested, and manufacturable reality.
Don't worry if this sounds intimidating at first. Development is not about getting everything perfect on your first try. Instead, it is an iterative journey—a step-by-step process of testing, tweaking, calculating, and refining every single part of your product-system before you build the final version in the workshop.
Key Takeaway: Development is the bridge between "What could this look like?" and "How exactly is this manufactured, assembled, and guaranteed to work?"
1. Understanding Assessment: AO1 and AO2 in Development
In your A2 portfolio (typically completed on A3 sheets alongside your physical prototype), the Development section demonstrates your mastery of two primary Assessment Objectives:
AO1 (Knowledge & Understanding): Applying design theory, showing iterative development strategies, solving sub-system problems, and communicating your design decisions clearly.
AO2 (Application & Practical Skills): Selecting materials, planning manufacturing processes, testing physical and virtual prototypes, and detailing exact working dimensions to turn your idea into a functioning product.
Memory Aid: Remember the mnemonic T.E.S.T. for your development pages:
T – Tolerances & Dimensions: Exact sizes and fits.
E – Engineering Calculations: Quantified proof that mechanisms and circuits will work.
S – Simulations & Models: Physical and virtual mock-ups.
T – Technical Materials: Justified choices with precise material names.
2. The Iterative Refinement Process & Sub-System Integration
A common mistake in A2 coursework is making a "leap to the final design"—jumping straight from an initial thumbnail sketch to a finished CAD model without showing how you solved intermediate problems. CCEA examiners want to see your trail of thought!
Breaking Down Product-Systems
Modern products are rarely just a simple box; they are integrated product-systems. During development, you must resolve each sub-system individually and then prove they fit together harmoniously:
1. Structural & Aesthetic Enclosure: Developing the casing, chassis, or frame to ensure it is robust, ergonomic, and visually appealing.
2. Mechanical Drive Trains: Calculating and refining mechanisms such as gear trains, linkages, pulleys, or pneumatic actuators to achieve required movements, speeds, and forces.
3. Electronic & Control Systems: Designing and simulating circuit schematics, microcontroller / PIC inputs and outputs, sensor integration, and power management.
Real-World Analogy: Think of designing a cordless power drill. You cannot just design the plastic shell; you must simultaneously engineer the motor torque (mechanical), the battery protection and speed trigger (electronic), and the handgrip contours (ergonomic) so they all nest perfectly inside the casing.
3. Quantitative Systems Development: Backing Design with Math
To score top marks in AO1 and AO2, your development cannot rely on guesswork. You must include quantitative calculations that prove your design decisions are sound.
Depending on your chosen project pathway, you should integrate clear calculations such as:
Mechanical Calculations:
• Gear Ratios and Velocity Ratios: \( \text{Gear Ratio} = \frac{\text{Number of Teeth on Driven Gear}}{\text{Number of Teeth on Driver Gear}} \)
• Output Speed and Torque: Calculating if your motor has sufficient torque to move the intended load without stalling.
• Mechanical Advantage in linkages and levers.
Electronic & Pneumatic Calculations:
• Component rating values (e.g., Ohm's law \( V = I \cdot R \) to calculate exact current-limiting resistor values for LEDs or transistors).
• Potential divider calculations for sensor calibration.
• Pneumatic force calculations: \( \text{Force} = \text{Pressure} \times \text{Area} \) (\( F = P \cdot A \)) to size cylinders correctly.
Key Takeaway: Never just say "I used a 100 rpm motor". Show the calculation proving why that specific speed and torque are required for your system!
4. Modeling, Prototyping, and Testing
How do you prove a mechanism works or that a handle fits comfortably before spending hours on the CNC machine? You model and test!
Virtual Prototyping
3D CAD Modeling: Creating detailed parametric solid models of individual components and full assemblies.
Simulations: Using Finite Element Analysis (FEA) or virtual stress testing to detect weak points under load, and using software such as Circuit Wizard or Yenka to test circuit schematics and pneumatic sequences prior to physical assembly.
Physical Prototyping
Low-Fidelity Models: Quick, inexpensive models made from card, corrugated plastic, or high-density modeling foam to validate scale, visual proportion, and anthropometric grip comfort.
Rapid Prototyping: 3D printing (FDM) functional brackets or test gears to verify real-world fits.
Electronic Breadboarding & Stripboarding: Building temporary hardware test rigs to verify sensor triggers and program code in real ambient lighting or load conditions.
Did you know? Professional aerospace and automotive engineers spend up to 70% of their development time purely on iterative modeling and simulations before any metal is cut for the final product!
5. Material Selection and Rigorous Justification
One of the most frequent examiner criticisms is superficial material justification. Writing "I chose plastic because it is cheap and waterproof" will limit your marks.
At A2 level, you must specify the exact material classification and justify your choice using specific mechanical, physical, thermal, or chemical properties:
Polymers:
• ABS (Acrylonitrile Butadiene Styrene): High impact resistance, rigid, excellent for 3D printing and injection-molded casings.
• HIPS (High-Impact Polystyrene): Tough, lightweight, easily thermoformed via vacuum forming for internal protective linings and covers.
• Acrylic (PMMA): Hard, optically clear, brittle under impact, excellent for laser cutting display panels.
Metals:
• 6061 / 6082 Aluminium Alloy: High strength-to-weight ratio, excellent corrosion resistance, highly machinable for structural brackets and turned shafts.
• Mild Steel: High tensile strength, ductile, easily welded, ideal for heavy-duty structural frames.
Timbers & Composites:
• Hardwoods (e.g., Oak, Beech): High compressive strength, durable, dense grain resistant to wear.
• Manufactured Boards (e.g., MDF, Birch Plywood): Stable, uniform strength in all directions, no grain direction weakness.
Quick Material Evaluation Formula: When justifying a material, state: 1. Specific material name \( \rightarrow \) 2. Key mechanical property \( \rightarrow \) 3. Operating condition/demand of your product that requires this property.
6. Design for Manufacture (DfM) and Design for Assembly (DfA)
A brilliant design is useless if it cannot be built with the tools and processes available in a workshop or industrial setting.
Design for Manufacture (DfM)
You must detail how each raw material will be processed:
• Wasting / Subtractive: Turning on a lathe, CNC milling, laser cutting, drilling.
• Forming / Deforming: Vacuum forming, line bending, sheet metal folding.
• Addition: 3D printing, composite layup.
Design for Assembly (DfA) and Component Standardization
You must specify how parts connect and whether they are meant to be serviced:
• Permanent Joints: Welding, brazing, structural adhesives (epoxy resin, acrylic cement) for permanent rigidity.
• Semi-Permanent / Temporary Fixings: Machine screws into threaded inserts, nuts and bolts, snap-fit joints, or machine fasteners that allow maintenance, battery replacement, and end-of-life recycling.
• Standardized Components: Specifying standard off-the-shelf parts (e.g., standard bearings, microswitches, fasteners, gears) to reduce production costs and guarantee replacement availability.
Tolerances and Allowances
Nothing is manufactured to an exact zero-error dimension. In moving parts (such as a steel shaft rotating in a bronze bush), you must specify clearance tolerances (e.g., \( \pm 0.1\text{ mm} \) or exact push-fit allowances) so that components do not seize or rattle.
7. Formal Technical Drawings & Working Details
The culmination of your Development section is the production of comprehensive Working Drawings. These provide all technical information needed for manufacture.
British Standard (BS 8888) Conventions
Your working drawings must strictly follow standard engineering conventions:
• 3rd Angle Orthographic Projection: Showing Front, Top (Plan), and End elevations with the standard 3rd angle projection symbol.
• Sectioned Views: Showing internal details, rib thicknesses, and hidden component arrangements.
• Exploded Assembly Views: Showing the sequence of assembly and how standard fasteners lock parts together.
• Complete Dimensioning: All dimensions stated in millimeters (\(\text{mm}\)), using standard projection lines and leader lines without duplicate dimensions.
Bill of Materials (BOM) / Parts List
A fully detailed table on your drawing sheet that accounts for every item in your product. A complete BOM must include:
1. Item Number / Part ID
2. Part Description / Name
3. Quantity Required
4. Material Specification (e.g., 3mm Cast Acrylic, 6061-T6 Aluminium)
5. Finishing / Treatment (e.g., Anodized, Polished, Powder Coated)
8. Avoiding Common Coursework Pitfalls: Examiner Checklist
Before submitting your Development section, review this quick sanity check to protect your marks:
1. Did you avoid the "Leap"? Ensure your portfolio shows the step-by-step evolution from initial concept to final form, including failed tests and adjustments.
2. Are your materials specific? Replace words like "metal", "wood", or "plastic" with precise technical names and property justifications.
3. Did you include quantitative data? Check that gear ratios, electronic component values, and load forces are supported by math.
4. Does Development match Manufacture? The working drawings and specifications in your development section must perfectly match the final prototype you manufacture in the workshop!
Quick Review: The 5 Pillars of A2 Development
1. Iteration: Systematically refining form, function, and ergonomics through multiple drafts.
2. Testing & Modeling: Combining 3D CAD/simulation with physical card/foam/3D-printed test rigs.
3. Scientific Justification: Calculating component ratings and choosing materials based on measurable mechanical properties.
4. DfM & DfA: Designing with clear processes, tolerances, and standardized fixings.
5. Technical Communication: Concluding with BS 8888 compliant 3rd angle drawings, exploded assemblies, and a comprehensive Bill of Materials.