SACE Stage 2 Design, Technology and Engineering cheat sheet
SACE Stage 2 Design, Technology and Engineering · Keep the key ideas within reach.
Design and Technology Skills and Knowledge
Design process cycle: investigate and define the problem, generate concepts, develop and test, produce, evaluate - each stage produces documented evidence that feeds the next.
Functional requirement vs. constraint: a requirement states what the product must do; a constraint is a fixed limit (budget, deadline, available machinery, standard, safety rule) that narrows acceptable solutions.
Design brief essentials: client, target user, purpose, key requirements, constraints, and success criteria; a brief without measurable success criteria cannot be objectively evaluated.
Ergonomics: anthropometric data are usually given as 5th, 50th and 95th percentile values; design for the 5th percentile where reach is limiting (clearances) and the 95th where space is limiting (openings).
Factor of safety = failure stress (or load) ÷ working stress (or load); a value above 1 means the design has reserve capacity beyond expected service conditions.
Mechanical advantage of a lever = effort arm ÷ load arm; velocity ratio of a pulley system = number of rope segments supporting the moving load; efficiency = (work output ÷ work input) × 100%.
Orthographic projection conventions: third-angle places the top view above the front view and the right-side view to the right; first-angle reverses this arrangement.
Material selection criteria: strength-to-weight ratio, stiffness, durability, corrosion resistance, machinability, cost per unit, availability, and recyclability are compared against the functional requirements.
Sustainability hierarchy applied to design: avoid or reduce material use, choose renewable or recycled stock, design for disassembly and repair, then plan end-of-life recovery.
Design and Technology Application
Manufacturing plan sequence: raw stock → marking out → primary shaping (cutting, machining, moulding) → joining → finishing → inspection against tolerances.
Tolerance stack-up: total variation equals the sum of individual component tolerances in a chain, so critical fits should be toleranced tightly while non-critical dimensions are left loose to control cost.
Risk control hierarchy in the workshop: eliminate the hazard, substitute a safer process, use engineering controls (guards, extraction), then administrative controls (procedures, signage), then PPE as the last line.
Testing protocol design: state the variable changed, the variables held constant, the measurement method and instrument resolution, the number of repeats, and the acceptance threshold taken from the brief.
CAD-to-production workflow: parametric model → assembly check for interference → drawing with dimensions and tolerances → toolpath or CAM output → first-article inspection before full batch.
Quality control sampling: a first-off check confirms setup, in-process checks catch drift, and a final inspection confirms the batch; record measurements against the drawing rather than a pass/fail judgement alone.
Costing a product: material cost + labour (time × rate) + machine or process overhead + finishing + packaging + contingency; break-even quantity = fixed costs ÷ (unit price − variable cost per unit).
Design evaluation evidence: user trials, load or function tests, comparison of measured performance against the brief's success criteria, and a documented list of modifications for the next iteration.