Pancyprian Design & Tech cheat sheet

Iterative design cycle: identify need → research → specify → generate → model/prototype → test/evaluate → refine; evaluation can return to any earlier stage.

A design brief states the problem and constraints in the client's terms; the specification converts it into measurable criteria (dimensions, loads, cost, safety standards).

Functional analysis decomposes a product into sub-functions (e.g. store energy, transmit motion, protect contents) before seeking solutions for each.

Weighted decision matrix: score each concept against criteria on a common scale (e.g. 1–5), multiply by criterion weight, sum; highest total is preferred, but sensitivity to weights must be checked.

Morphological chart: list sub-functions as rows and alternative solutions as columns, then combine one solution per row into candidate concepts.

Constraints are fixed limits (must not exceed); criteria are desirable targets ranked by importance - confusing the two invalidates concept selection.

Prototypes are classified as proof-of-concept (tests feasibility), proof-of-product (tests fit/form), or production prototype (tests tooling and assembly).

Design fixation is reduced by deliberately generating concepts from different analogies or by reversing the problem statement (e.g. 'how to make it fail').

Stress σ = F/A (N/m² or Pa); strain ε = ΔL/L₀ (dimensionless); Young's modulus E = σ/ε in the linear elastic region.

Ductile materials (mild steel, copper) show large plastic strain before fracture; brittle materials (cast iron, glass, ceramics) fracture with little or no plastic deformation.

Hardness (e.g. Brinell, Vickers) resists indentation; toughness is energy absorbed before fracture (area under stress–strain curve); stiffness is resistance to elastic deflection (E).

Thermoplastics soften on heating and can be remoulded (PE, PP, PVC, ABS); thermosets cure permanently (epoxy, polyester resin, melamine); elastomers recover large strain (natural rubber).

Ferrous metals: low-carbon steel is ductile and weldable; high-carbon steel is harder and less weldable; stainless steel contains ≥10.5% Cr, forming a passive oxide layer that resists corrosion.

Non-ferrous: aluminium is ~1/3 the density of steel with good corrosion resistance but lower stiffness; copper has high electrical/thermal conductivity; zinc is used for sacrificial galvanising.

Material selection uses property charts (e.g. E vs density) with performance indices; a light stiff beam favours high E/ρ, a light strong tie favours high σy/ρ.

Composites (e.g. glass-fibre-reinforced polyester) combine high strength-to-weight with anisotropy: properties differ along and across the fibre direction.

Casting: molten material fills a mould cavity; sand casting suits one-offs and large parts, die casting suits high-volume non-ferrous parts with good surface finish.

Injection moulding requires draft angles (typically 1–2°), uniform wall thickness, and radii at internal corners to avoid stress concentration and warping.

Vacuum forming draws a heated thermoplastic sheet over a male or female mould; deep draws need large radii and are limited by sheet thinning.

Subtractive processes remove material (turning, milling, drilling); CNC machines follow programmed toolpaths and suit low-to-medium batches with high accuracy.

Additive manufacturing (FDM, SLA, SLS) builds parts layer by layer; it enables internal channels and lattices but has anisotropic strength and slower cycle times.

Joining: adhesives spread load over an area and avoid heat distortion; welding gives continuous metallic joints; mechanical fasteners allow disassembly.

Tolerance is the permitted dimensional variation; clearance fit allows relative motion, interference fit creates a permanent grip by elastic/plastic deformation.

Scale of production: one-off (jigs and moulds amortised over one unit), batch, and mass/continuous production each change the balance of tooling cost versus unit cost.

First-angle projection: the view from the front is placed above the plan and the view from the left is placed on the right; third-angle reverses this arrangement.

Scale is drawing length : real length; a 1:5 scale means 20 mm on paper represents 100 mm in reality.

Line conventions: continuous thick for visible outlines, dashed for hidden edges, chain-dotted for centre lines, thin continuous for dimension and projection lines.

Dimensions state true size regardless of drawing scale; they include a dimension line, arrowheads, and extension lines that do not touch the object outline.

Section views use hatching at 45° to show cut material; adjacent parts are hatched in opposite directions or at different spacings.

Isometric drawings use axes at 30° to the horizontal with true lengths along the axes; oblique drawings keep the front face true and project depth at an angle.

Geometric tolerancing expresses form (flatness, straightness), orientation (parallelism, perpendicularity), and position (true position) where size tolerance alone is insufficient.

Physical and CAD models allow virtual testing (FEA, motion simulation) before manufacture; exploded views and assembly drawings communicate part order and fit.

Static equilibrium: ΣF = 0 and ΣM = 0; a simply supported beam has a pinned and a roller support, giving two vertical reactions determined by moment balance.

Bending moment M along a beam equals the algebraic sum of moments of forces to one side; maximum bending moment often occurs where shear force is zero.

Second moment of area for a rectangle about its centroidal axis: I = b·h³/12; deflection of a simply supported beam under central load: δ = F·L³/(48·E·I).

Triangulation gives rigidity: a pin-jointed triangle is statically determinate and cannot deform without member length change; a rectangle needs a diagonal brace.

Gear ratio = driven teeth / driver teeth = input speed / output speed; torque is multiplied by the same ratio (ignoring losses).

Four-bar linkage: Grashof condition s + l ≤ p + q guarantees at least one link can rotate fully; a crank-rocker converts continuous rotation to oscillation.

Open-loop control has no feedback and cannot correct error; closed-loop control compares sensor output with a setpoint and acts on the error (negative feedback).

Sensors: thermistor (temperature), LDR (light), potentiometer (position), limit switch (end of travel); actuators: DC motor, stepper motor, solenoid, servo.

Energy cannot be created or destroyed, only converted; efficiency η = useful output energy / input energy × 100%.

Power P = energy transferred / time = work done / time; for electrical devices P = V·I and energy = P·t (joules or kWh).

Life-cycle assessment stages: raw material extraction, manufacture, distribution, use, and end-of-life (reuse, remanufacture, recycle, energy recovery, landfill).

Embodied energy is the energy consumed across a product's life up to the point of use; it is often dominated by material production, not assembly.

The 6Rs hierarchy: refuse, reduce, reuse, repair, recycle, rot (recover); prevention and reuse generally outrank recycling in environmental benefit.

Design for disassembly uses reversible fasteners, material labelling, and snap fits to enable repair and material separation at end of life.

Renewable sources (solar, wind, hydro, biomass) are replenished at the rate of use; fossil fuels are finite and release CO₂ when combusted.

Carbon footprint is expressed as CO₂-equivalent mass; it aggregates greenhouse gases by global warming potential over a defined horizon (commonly 100 years).

Inclusive design considers the extremes of user capability (e.g. reach, grip strength, vision) so the product works for the widest population.

Ergonomics matches product dimensions to anthropometric data: 5th-percentile values for reach, 95th-percentile for clearance, and adjustability for mixed populations.

Product evaluation criteria include function, aesthetics, ergonomics, cost, safety, durability, environmental impact, and fitness for the brief.

Planned obsolescence shortens product life by design (functional, technological, or aesthetic); it conflicts with circular-economy goals and consumer protection norms.

Intellectual property: patents protect novel technical function, registered designs protect appearance, trademarks protect brand identity, copyright protects original works.

Standards and legislation (e.g. CE marking, toy safety, WEEE for electronic waste) impose mandatory requirements that override aesthetic or cost preferences.

Ethical sourcing considers labour conditions, conflict minerals, and fair trade; a product can be technically sound yet ethically unacceptable.

User testing (observation, interviews, task analysis) reveals use errors that specification-only evaluation misses; findings feed back into the design iteration.