NSSCO Design and Technology (6187) cheat sheet

Design cycle stages in order: identify need, research, write design brief, write specification, generate ideas, develop, model/prototype, test and evaluate, manufacture.

A design brief states the problem and intended user in open terms; a specification converts it into measurable criteria (dimensions, cost, materials, safety, function).

Specification criteria are classified as must (constraints) or should (desirable); evaluation scores are judged only against the stated criteria.

Primary research is data collected first-hand (interviews, questionnaires, user trials); secondary research uses existing sources (standards, catalogues, statistics).

Iteration is legitimate: test results feed back to earlier stages; a linear one-pass model misrepresents real practice.

Anthropometric data (percentiles such as 5th, 50th, 95th) set reach, clearance and handle sizes for products used by people.

Ergonomics matches product geometry and force requirements to human capability; it is a specification input, not a finishing touch.

A design justification must link each decision to evidence from research or testing, not to personal preference.

Third-angle orthographic projection places the plan above the front view and the end view to the side it is viewed from; first-angle places the plan below.

Orthographic views use a single scale, aligned features, hidden detail as dashed lines, centre lines as chain-dotted lines.

Isometric projection uses 30-degree axes with true lengths along each axis; no foreshortening is applied to the axis lengths.

Oblique projection shows the front face true shape with receding lines at 45 degrees; cabinet projection halves the receding depth.

Scale is expressed as a ratio (1:1, 1:5, 1:20); enlargement scales have the larger number second, e.g. 2:1.

Line conventions: continuous thick for visible outlines, continuous thin for dimension and projection lines, arrowheads at both ends of a dimension.

Dimensions state true size regardless of drawing scale and are placed outside the outline where possible; radius is prefixed R, diameter with the diameter symbol.

Exploded and sectional views communicate assembly order and internal detail that hidden lines cannot show clearly.

Hardwoods come from broad-leaved deciduous trees (oak, mahogany, teak); softwoods from conifers (pine, spruce); manufactured boards include plywood, MDF and chipboard.

Ferrous metals contain iron (mild steel, cast iron); non-ferrous metals do not (aluminium, copper, brass, zinc).

Thermoplastics soften repeatedly on heating (acrylic, HDPE, PVC, ABS); thermosetting plastics char rather than soften (epoxy, melamine, polyester resin).

Density = mass / volume; a material's density determines weight for a given component size.

Stress = force / cross-sectional area; strain = change in length / original length; the ratio gives Young's modulus in the elastic region.

Hardness resists surface indentation; toughness resists impact without fracture; brittleness is failure with little plastic deformation.

Thermal conductivity governs heat transfer and insulation choice; electrical conductivity is measured relative to copper for conductor selection.

Material selection weighs properties against cost, availability, machinability, recyclability and finish requirements.

Personal protective equipment: goggles for machining and chiselling, dust mask for sanding and MDF, ear defenders above roughly 85 dB(A), apron or overalls.

Tenon saw for accurate joint cutting, rip saw for cutting along the grain, crosscut saw for cutting across the grain.

A try square checks and marks right angles; a marking gauge scribes a line parallel to a face edge; a mortise gauge has two adjustable pins.

Files cut on the forward stroke only; the grade (bastard, second cut, smooth) sets removal rate, and a file card cleans the teeth.

Drill speeds: small bits and hard metals run fast with light feed; large hole saws run slow; workpiece is clamped, never hand-held.

A pillar drill requires the chuck key removed before starting, the guard lowered and the work clamped to the table.

Sharp edges are removed with a file or abrasive; a blunt tool needs more force and causes more accidents than a sharp one.

Electrical safety: check leads and plugs, use RCD protection, keep water away from sockets, isolate before changing blades or bits.

Wood joints: butt (weak, needs fixing), halving, mortise and tenon, dovetail (resists pull-out), dowel and biscuit joints.

Adhesives: PVA for wood, contact adhesive for laminates, epoxy for mixed materials and metals, cyanoacrylate for fast small-area bonds.

Permanent metal joints: welding, brazing and soldering (solder melts below 450 degrees C, brazing above); temporary: nuts, bolts, screws, rivets.

Rivets form a permanent joint but allow no disassembly; a pop rivet needs access to one side only.

Casting pours molten material into a mould; injection moulding forces molten thermoplastic into a closed steel mould for high volume.

Vacuum forming heats a thermoplastic sheet and draws it over a former; it suits shallow, open shapes without undercuts.

CAD/CAM workflow: draw in CAD, export to CAM, generate toolpaths, machine on CNC router, laser cutter or 3D printer.

Jigs and fixtures hold work in position and guide tools; they improve repeatability and reduce skill demand in batch production.

Velocity ratio of a gear pair = teeth on driven gear / teeth on driver gear; a larger driven gear reduces speed and increases torque.

Mechanical advantage = load / effort; velocity ratio = distance moved by effort / distance moved by load; efficiency = MA / VR x 100 percent.

Levers are class 1 (fulcrum between), class 2 (load between) and class 3 (effort between); class 3 always has MA below 1.

A pulley system with n supporting rope sections has a velocity ratio of n; a simple gear train's VR is the product of driven teeth over driver teeth.

Four-bar linkage converts rotary motion to oscillation; a crank and slider converts rotary motion to reciprocating motion.

Structural forces: tension pulls, compression pushes, shear slides, torsion twists, bending combines tension and compression.

Triangulation gives rigidity to a frame; a redundant member or gusset prevents racking under load.

Open-loop control has no feedback; closed-loop control compares sensor output with a set value and corrects the error.

Ohm's law: V = I x R; power P = V x I = I squared x R = V squared / R.

Series circuit: current is the same everywhere, voltages add, total resistance R = R1 + R2 + R3.

Parallel circuit: voltage is the same across each branch, currents add, total resistance is less than the smallest branch resistance.

Resistor colour code order: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9; gold and silver are tolerances.

A potential divider output Vout = Vin x R2 / (R1 + R2) with R2 the resistor across the output.

A diode conducts in one direction only; an LED needs a series resistor to limit current; a capacitor blocks DC and passes AC.

A transistor or relay lets a low-power signal switch a higher-power load; a flyback diode protects against inductive spikes.

Energy and power: energy (kWh) = power (kW) x time (h); renewable sources include solar, wind, hydro, tidal and biomass.

Sustainable design strategies: reduce material, choose recycled or recyclable stock, design for disassembly, extend product life, minimise energy in use.

The 6 Rs are rethink, refuse, reduce, reuse, repair, recycle; recycling is the last resort because it still consumes energy.

Life cycle assessment covers raw material extraction, manufacture, distribution, use and end-of-life disposal or recovery.

Planned obsolescence shortens product life by design; it conflicts with sustainability and with consumer protection expectations.

Inclusive design considers age, ability, size and culture; legislation such as accessibility standards makes some provisions mandatory.

Intellectual property: a patent protects function, a registered design protects appearance, copyright protects drawings and text, a trademark protects branding.

Product liability places responsibility on the manufacturer for defects; safety standards and testing (e.g. toy safety, electrical safety) enforce it.

Technology transfer and appropriate technology match the solution to local skills, materials, power supply and maintenance capacity.

A portfolio evidences the full cycle: brief, research, specification, ideas with annotation, development, planning, making records, testing and evaluation.

Annotation explains why a sketch or decision was made; unannotated drawings do not show design thinking and lose marks.

A production plan lists operations in sequence with tools, materials, time and quality checks for each stage.

A cutting list states material, dimensions and quantity per part; it is derived from the working drawings, not from the first idea.

Quality control checks each stage against the specification (dimensions within tolerance, finish, function); quality assurance covers the process itself.

Testing must use measurable criteria from the specification, with results recorded and compared to the target values.

Evaluation judges the finished outcome against each specification point and identifies modifications with reasons.

Risk assessment identifies hazard, who is at risk, likelihood and severity, and the control measure applied before work starts.

A tensile test records extension against load; the yield point marks the end of elastic behaviour and the start of permanent deformation.

A hardness test measures resistance to indentation; results compare materials for wear resistance, not for strength in tension.

A moisture meter checks timber content; wood above roughly 20 percent moisture is unsuitable for fine furniture because it shrinks on drying.

Tolerance is the permitted variation from a nominal dimension; fits are clearance, interference or transition depending on the allowance.

Go/no-go gauges check a feature against limits quickly in batch production rather than measuring an exact value.

Destructive tests (impact, tensile, fatigue) destroy the sample; non-destructive tests (visual, ultrasonic, dye penetrant) do not.

Surface finish is specified by roughness value; a smoother finish usually needs finer abrasives and more operations, raising cost.

Test records must state method, sample, equipment and result so another person could repeat the check.

A working drawing set contains orthographic views, at least one pictorial view, a parts list, dimensions, tolerances, materials and a title block.

The title block records drawing number, scale, projection symbol, material, date, drawn by and revision.

A first-angle projection symbol shows a truncated cone with the small end to the left of the circles; third-angle shows the small end to the right.

Section views use hatching at 45 degrees in one direction; adjacent parts are hatched in opposite directions.

A detail view enlarges a small feature and is labelled with its scale, which may differ from the main drawing scale.

A parts list numbers each component and cross-references the balloon numbers on an assembly drawing.

Geometric tolerances control flatness, parallelism, squareness and concentricity where a simple linear dimension is insufficient.

Dimensions are not repeated across views; each feature is dimensioned once on the view that shows it most clearly.

Mechanical power P = torque x angular velocity, with angular velocity in radians per second (2 pi n / 60 for n in rev/min).

Belt drives slip under overload and absorb shock; chain drives do not slip and suit higher torque at low speed.

A worm drive gives a high speed reduction in one stage and is self-locking, but has low efficiency.

A rack and pinion converts rotation to linear motion; a lead screw does the same with higher force and slower travel.

Bearings: plain bushes suit low speed and cheap assemblies; ball and roller bearings reduce friction at higher loads and speeds.

Lubrication reduces friction and wear and carries heat away; over-lubrication of a sealed bearing is unnecessary.

Gear ratio selection trades speed against torque: output torque rises by the same factor that output speed falls, ignoring losses.

Energy storage options include batteries, flywheels, pumped hydro and compressed air, each with different response times and losses.

A system has input (sensor or switch), process (resistor, capacitor, transistor, IC) and output (lamp, motor, buzzer, solenoid).

A light-dependent resistor falls in resistance as light rises; a thermistor falls in resistance as temperature rises (NTC).

A potential divider with an LDR or thermistor converts a resistance change into a voltage change for comparison.

A 555 timer in astable mode produces a continuous square wave; in monostable mode it produces one pulse per trigger.

A logic gate truth table defines output for every input combination; AND needs all inputs high, OR needs any, NOT inverts.

Soldering: clean the iron tip, heat the joint and apply solder to the joint, not the iron; a good joint is shiny and concave.

Stripboard and PCB layout rules: keep tracks short, separate power and signal, allow clearance, and orient polarised parts consistently.

Fault finding proceeds by checking supply, then continuity, then component values, then signal at each stage.

Batch size drives process choice: one-off uses hand methods, batch uses jigs and CNC, mass production uses dedicated tooling and moulds.

Standard components (screws, bearings, resistors) cut cost and lead time compared with bespoke parts.

Design for assembly minimises part count, uses self-locating features, avoids inaccessible fasteners and limits fastener types.

Tolerances widen as process capability falls; specifying tighter tolerance than the process can hold raises cost without benefit.

Draft angle is required on moulded and cast parts so they release from the tool; undercuts need side actions and raise cost.

Material utilisation: nesting parts on sheet reduces waste in laser cutting and CNC routing.

A prototype verifies function; a pre-production sample verifies tooling, assembly sequence and quality checks before full production.

Cost per unit falls with volume because fixed costs (tooling, setup) are spread over more units, but only until capacity is reached.

A risk assessment records hazard, persons at risk, existing controls, risk rating and further action required.

Hierarchy of control: eliminate, substitute, engineering controls, administrative controls, then personal protective equipment last.

COSHH-type principles require assessing substances (adhesives, solvents, dusts) and using the least hazardous option that works.

Machine guarding, emergency stops and isolation procedures are engineering controls that do not rely on user behaviour.

Safety signs use consistent shapes and colours: prohibition, warning, mandatory and safe-condition categories.

Electrical equipment in a workshop needs periodic inspection and portable appliance testing according to use and environment.

The manufacturer's instructions and safety data sheets define the permitted use of a material or tool.

Reporting near misses and accidents supports prevention; an unreported near miss is a free warning ignored.

Freehand sketching communicates ideas quickly; crating and construction lines keep proportions believable.

Thick and thin line technique emphasises outline over internal detail and gives depth without shading.

Rendering with marker or pencil shows form, light source and material; a single consistent light direction avoids confusion.

A mood board gathers visual references; it must be annotated to show what each reference contributes to the design.

Models at scale (card, foam, blue foam) test form and ergonomics faster than full manufacture.

Digital presentation uses consistent type, grid alignment and captions; a screenshot without a caption loses its evidence value.

A client presentation states the problem, the chosen solution, the evidence supporting it and the remaining limitations.

Feedback from users or a client is recorded and answered point by point in the evaluation.

A steel rule reads to about 0.5 mm; a vernier caliper to 0.02 mm; a micrometer to 0.01 mm.

Before measuring, check the instrument zero and clean the measuring faces.

Vernier reading: main scale value plus the vernier division that aligns, multiplied by the vernier least count.

Micrometer reading: barrel scale value plus thimble division multiplied by the thimble least count (commonly 0.01 mm).

Accuracy is closeness to the true value; precision is repeatability of the measurement.

Parallax error is avoided by reading a scale at eye level directly in front of the mark.

Allowance is the intentional difference between mating parts; tolerance is the permitted variation on one dimension.

A datum is a reference face or line from which dimensions are taken; consistent datums prevent tolerance stack-up errors.

A beam under bending has compression on the upper face and tension on the lower face for a downward load; the neutral axis is unstressed.

A tie is in tension, a strut in compression; a strut can buckle, so its length and cross-section matter more than a tie's.

Second moment of area increases with depth cubed for a rectangular section, so deepening a beam is more effective than widening it.

A triangular frame is rigid; a rectangular frame racks unless braced with a diagonal.

A cantilever is fixed at one end only and carries the greatest bending moment at the support.

A uniformly distributed load is treated as a point load at its centre for simple beam reactions.

Fatigue failure occurs under repeated fluctuating loads below the static failure stress.

Factor of safety = failure stress / working stress; it covers uncertainty in load, material and analysis.

Energy cannot be created or destroyed, only converted; efficiency = useful output energy / input energy x 100 percent.

A machine's overall efficiency is the product of the efficiencies of its stages.

Electrical heating and lighting losses appear as heat; standby power is a continuous loss in mains-powered products.

Mechanical energy forms: kinetic = half m v squared; gravitational potential = m g h.

Friction converts mechanical energy to heat and sound; lubrication and bearings reduce the loss but do not remove it.

Battery capacity in Ah multiplied by nominal voltage gives watt-hours, the usable energy figure for comparison.

Solar panel output depends on irradiance, angle and temperature; rated output is at standard test conditions only.

Embodied energy is the energy used to extract, process and manufacture a product; it is counted in a life cycle assessment.

Market pull starts from an identified user need; technology push starts from a new capability seeking an application.

Product life cycle stages are introduction, growth, maturity and decline; design refresh timing depends on the stage.

A niche product serves a small market with high specification; a mass product competes on price and volume.

Cultural and religious factors affect colour, imagery, form and function; they are research inputs, not afterthoughts.

Universal design aims for one solution usable by the widest range of people without adaptation.

Costing includes material, labour, tooling, overhead, packaging, distribution and margin; material cost alone is not the product cost.

Fair trade and ethical sourcing consider labour conditions and environmental impact in the supply chain.

Obsolescence can be technical (better alternative) or stylistic (fashion change); both shorten the profitable life.

A Gantt chart shows tasks against time and reveals dependencies and slack; it is revised as the project progresses.

Critical path is the longest dependent sequence; delay on it delays the whole project.

Milestones are checkpoints with a deliverable, not activities; each milestone should be evidenced in the portfolio.

A specification point must be testable: state the criterion, the method and the acceptable value.

Evaluation against the brief asks whether the right problem was solved; evaluation against the specification asks whether it was solved well.

Modifications are recorded with the reason and the effect on cost, time or performance.

Photographic records during making evidence process and technique; final photographs alone show only the outcome.

A project review identifies what would be done differently and why, supported by the recorded evidence.

Timber conversion: through-and-through sawing gives wide boards with defects; quarter sawing gives stable, figured boards at higher cost.

Seasoning reduces moisture content; air seasoning is slow, kiln seasoning is fast but needs careful control to avoid case hardening.

Metal forming: annealing softens, work hardening stiffens, tempering reduces brittleness after hardening.

Thermoplastics can be line-bent, vacuum formed, injection moulded or 3D printed; thermosets are cast or laminated.

Sheet metal processes include shearing, folding on a press brake, punching and rolling.

Casting defects include shrinkage voids, porosity and cold shuts; risers and correct pouring temperature reduce them.

Composite lay-up (resin plus glass or carbon fibre) gives high strength-to-weight ratio but is hard to recycle.

Heat treatment of steel: heat and quench to harden, then temper to relieve internal stress and restore toughness.

Select a joint by load type: tension favours bolts or adhesives, shear favours rivets or dowels, peel favours neither adhesive nor staples.

Adhesive joints need clean surfaces, correct gap, clamp pressure and full cure time; a thick glue line weakens most adhesives.

Knock-down fittings (cam and dowel, bolts) allow disassembly and flat packing; glue and weld do not.

A screw into end grain holds poorly; into side grain or with a pilot hole it holds well and resists splitting.

Welded joints suit permanent structural work; brazing suits dissimilar metals and thinner sections at lower temperature.

A gusset plate or corner block reinforces a joint and spreads load over a larger area.

Wood movement must be allowed for in wide panels; fixed joints across the grain cause splitting.

Threadlocking compound or a locking washer prevents vibration loosening of a threaded fastener.

A control system is described by input devices, process, output devices and the sequence or logic linking them.

A flowchart uses standard symbols: terminator, process, decision, input/output, and flow lines with arrowheads.

A truth table for two inputs has four rows; for three inputs, eight rows; the number of rows is two to the power of the inputs.

A microcontroller repeats a loop; a delay or sensor check sets the timing of the output.

Feedback sensors (limit switch, thermistor, encoder) close the loop and allow the system to correct itself.

Analogue sensing needs an analogue-to-digital conversion before a digital controller can use the value.

A relay or transistor driver isolates a low-power control circuit from a high-current load.

Fail-safe design makes the output revert to a safe state on power loss or sensor failure.

Material choice for sustainability considers recycled content, recyclability, toxicity, embodied energy and end-of-life route.

Single-material products are easier to recycle than composites or bonded assemblies.

Design for disassembly uses reversible fasteners and marks parts for separation at end of life.

Biodegradable does not mean harmless; degradation may release methane or require industrial conditions.

Energy in use often exceeds embodied energy over a product's life for powered products.

Waste hierarchy: prevent, reuse, recycle, recover energy, dispose; design decisions sit mostly at the top.

Local sourcing reduces transport impact but may conflict with performance or cost requirements.

Extended producer responsibility places end-of-life take-back obligations on the manufacturer.

Workspace dimensions are set from anthropometric percentiles: reach from the 5th percentile, clearance from the 95th.

Seat height for a general population is set near the 50th percentile with adjustability to cover the range.

Grip design: handle diameter and length depend on hand size and required force; a larger grip reduces pressure on the palm.

Repetitive strain is reduced by neutral wrist posture, support and limiting force and repetition.

Colour and contrast affect legibility; controls should be distinguishable by shape and touch as well as colour.

Force required at a control should suit the weakest expected user, not the strongest.

Feedback (click, light, sound) confirms an action and reduces error.

Anthropometric data varies by population; data from one country cannot be applied directly to another.

A mock-up tests size and ergonomics in the real context before detailed design is fixed.

A scale model tests form and proportion; it does not reliably test strength or function at full scale.

A functional prototype tests performance and reveals manufacturing problems before tooling is committed.

Rapid prototyping (3D printing) suits complex geometry and small quantities; it is slower per part at high volume.

Test criteria come from the specification; a test without a stated criterion cannot pass or fail.

Repeat tests and record variation; a single test result is weak evidence.

User trials with representative users reveal problems the designer cannot see.

Each prototype should state what it is testing and what was learned from it.

A standard specifies requirements for dimensions, performance, safety or testing; compliance may be voluntary or legally required.

A quality management approach records procedures, checks and corrective actions so results are repeatable.

Inspection checks conformance; testing measures performance; both produce records used for traceability.

Traceability links a finished item to its batch, material and inspection records.

A bill of materials lists every component, quantity and specification needed to build one unit.

Work instructions state the sequence, tools, settings and checkpoints for an operation.

A revision-controlled drawing shows the current issue; superseded drawings must be withdrawn from use.

Calibration confirms that a measuring instrument reads correctly against a known reference.

Colour wheels: complementary colours sit opposite and give maximum contrast; analogous colours sit adjacent and give harmony.

Warm colours advance and cool colours recede; this affects perceived depth in a rendering.

Value contrast (light against dark) carries more legibility than hue contrast alone.

A grid aligns text and images; consistent margins and type sizes make a layout readable.

Type hierarchy uses size, weight and spacing to show importance; too many typefaces reduce clarity.

Rendering shows a single light source with consistent shadow direction and a highlight on the nearest surface.

Material indication uses texture, reflection and edge treatment rather than flat colour alone.

Annotation lines should not cross; labels are placed outside the drawing with leader lines to the feature.

A multimeter measures voltage in parallel with the component and current in series with the circuit.

Continuity testing is done with the circuit unpowered; a reading confirms a low-resistance path.

Resistor tolerance bands: gold plus or minus 5 percent, silver plus or minus 10 percent, brown plus or minus 1 percent.

Two resistors in parallel: product over sum for two only; three or more need the reciprocal formula.

A capacitor stores charge; its reactance falls as frequency rises, so it passes high frequencies more readily.

A relay coil is an inductor and needs a diode across it to suppress the switch-off spike.

A fuse protects against overcurrent by melting; it is chosen above normal operating current but below the cable rating.

Insulation resistance and earth continuity are the key safety checks on mains-powered equipment.

A cam and follower converts rotation into a specific follower motion; the cam profile determines the motion law.

An eccentric cam gives simple harmonic motion; a snail cam gives a gradual rise and sudden return.

A ratchet and pawl allows motion in one direction only and prevents reversal.

A Geneva mechanism converts continuous rotation into intermittent rotation.

A toggle clamp gives a large holding force near the over-centre position and locks without continuous effort.

A linkage's output path is determined by pivot positions and link lengths; changing one length changes the whole motion.

A bearing surface and pivot should be sized for the load; an undersized pivot wears oval and the mechanism jams.

A spring stores energy and returns a mechanism; spring rate is force per unit deflection.

A design proposal states the need, the concept, the evidence, the cost and the risks in the client's terms.

A questionnaire needs unambiguous questions, a defined sample and a stated purpose to give usable data.

Interviews give depth on reasons; questionnaires give breadth on frequency; the two are complementary.

Observation of users in context reveals behaviour that users cannot report accurately.

Feedback must be recorded verbatim where possible and analysed for themes, not selectively quoted.

A client sign-off at each stage reduces the risk of redesign late in the project.

Confidentiality and consent apply when photographing or recording users.

Presenting limitations honestly supports credibility; an overstated claim damages trust when the product is used.

Evidence must be dated and attributable; an undated photograph or note has weak evidential value.

A design diary records decisions, problems and reasoning as they happen, not reconstructed at the end.

Working drawings, cutting lists, production plans and test records are the core technical evidence.

Screenshots of CAD should show dimensions, views and the model, not only a shaded image.

Test data is presented in a table with units and compared against the specification value.

Evaluation references specific evidence: drawing number, test result, photograph or user comment.

A bibliography records sources used for research so the work can be verified.

The portfolio should be readable by a stranger: each section has a heading and a short purpose statement.

One-off production uses general-purpose tools and high skill; unit cost is high and setup cost is low.

Batch production uses jigs, fixtures and CNC programmes; setup cost is spread over the batch.

Mass and continuous production use dedicated machinery and line balancing to keep stations matched in time.

Just-in-time supply reduces stock holding but increases vulnerability to supply disruption.

Lean production targets waste: overproduction, waiting, transport, over-processing, inventory, motion, defects.

Line balancing assigns tasks to stations so each station's cycle time is close to the takt time.

Automation suits repetitive, high-volume, consistent tasks; it needs high capital and stable demand.

A production plan sequences operations so that a part is not machined after it has been finished or painted.

Product analysis examines function, materials, manufacturing process, ergonomics, aesthetics, cost and environmental impact.

Reverse engineering disassembles a product to understand how each part is made and why it was chosen.

A function analysis lists what each component must do, independent of how it is made.

Value analysis asks whether each component's cost is justified by the function it performs.

A failure modes review lists how a part could fail and the effect of each failure on the user.

Comparing competing products on the same criteria gives a benchmark for the specification.

A disassembly record notes fixings, sequences and tools needed, which informs design for assembly.

Obsolescence and repair history reveal weaknesses that the original design did not anticipate.

On a lathe, the workpiece is held in a chuck or between centres; the tool is fed along or into the rotating work.

Lathe safety: remove the chuck key, secure the tool post, keep hands clear of rotating parts, do not leave the key in the chuck.

Milling uses a rotating multi-tooth cutter with the work clamped to a table; climb and conventional milling differ in cutter rotation against feed.

Band saw blade selection depends on material thickness and tooth pitch; too few teeth per thickness causes snagging.

Abrasive wheels are dressed to keep them true and free-cutting; a glazed wheel overheats the work.

Brazing and soldering need clean, fluxed surfaces and a heat source matched to the filler melting range.

Hand tools are stored and carried so that edges are protected; a chisel is never carried in a pocket.

Machine guards are never removed for convenience; interlocks prevent operation with the guard open.

A circular economy keeps materials in use through reuse, repair, remanufacture and recycling rather than disposal.

Product-service systems (leasing, servicing) can extend product life and shift responsibility to the producer.

Design for repair needs accessible fasteners, available spare parts and published service information.

Material passports record what a product contains so it can be separated and recovered at end of life.

Recycling quality falls with mixed materials; separation at design stage protects material value.

Energy recovery from waste is below recycling in the hierarchy because the material is lost.

Take-back schemes and deposit return systems create a route for recovery.

Life cycle costing includes purchase, use, maintenance and disposal, not just the purchase price.

A table needs column headings with units, consistent decimal places and a clear caption.

A bar chart compares categories; a line graph shows change over a continuous variable; a pie chart shows parts of a whole.

Axes are labelled with quantity and unit, and the scale is linear and evenly divided.

Trend lines are drawn to show the pattern; individual data points remain visible.

A scatter graph shows correlation; correlation does not establish cause.

Results are reported to the precision the instrument supports, not to a spurious number of decimal places.

Anomalous results are identified and either explained or excluded with a stated reason.

A conclusion states what the data shows and how it compares with the specification criterion.

A patent protects a new, inventive and industrially applicable product or process for a limited term.

A registered design protects the appearance of a product; copyright protects original drawings, text and images automatically.

A trademark protects signs that distinguish goods; it can be renewed indefinitely.

Confidentiality agreements protect ideas before a formal application is filed.

Professional practice includes honest reporting, respecting client confidentiality and avoiding conflicts of interest.

Designers have a duty to design out foreseeable hazards rather than rely on warnings alone.

Attribution of others' work avoids plagiarism and is a requirement in assessed portfolios.

Records of authorship and dates support a claim to ownership if a dispute arises.

A system boundary defines what is inside the product and what is in its environment.

Inputs, processes, outputs and feedback describe any system, whether mechanical, electrical or organisational.

Modular architecture allows parts to be swapped and upgraded; integral architecture optimises for one configuration.

Interfaces between subsystems (mechanical fixing, power, signal) are where most integration faults occur.

A block diagram shows function and signal flow without showing the physical layout.

Redundancy improves reliability at the cost of weight, complexity and price.

Subsystem testing before full assembly isolates faults faster than testing the finished product.

A system's overall reliability falls as the number of series components rises.

Ductile failure shows deformation before fracture; brittle failure occurs with little or no warning.

Fatigue cracks start at stress concentrations such as sharp corners, holes and surface scratches.

Corrosion of steel needs moisture and oxygen; coatings, galvanising and alloying slow it.

Galvanic corrosion occurs where dissimilar metals are joined in the presence of an electrolyte.

Stress concentration is reduced by generous fillets and gradual section change.

Creep is slow deformation under sustained load at elevated temperature.

A failure investigation records the fracture surface, service history and loading to establish cause.

Design changes from failure analysis should be verified by test before release.

Total cost = fixed costs + (variable cost per unit x quantity); break-even quantity = fixed costs / (price - variable cost per unit).

Gross margin is the difference between selling price and direct cost; it must cover overhead and profit.

Tooling is a fixed cost; high tooling is justified only by sufficient volume.

Material yield affects cost: offcuts and scrap are paid for but not sold.

Labour cost per unit falls with jigs and automation but the capital cost must be recovered.

Pricing considers competitor price, perceived value and target margin, not cost alone.

A cost model is revised as the design changes; early estimates are ranges, not single figures.

Packaging, distribution and warranty provision are part of the unit cost and are often underestimated.

A warning label is the last line of defence; the design should prevent the hazard first.

A control should move in a direction consistent with its effect; a mismatch causes error.

Emergency stops must be reachable, clearly marked and reset only deliberately.

Guard against entrapment, sharp edges, pinch points and hot surfaces in the user's normal path.

Products for children require specific tests for small parts, toxicity and stability.

Instructions must match the product and the user's reading level; poor instructions cause misuse.

Fail-safe behaviour means loss of power leaves the product in a safe state.

User testing with representative users reveals hazards the designer has become blind to.

A motor converts electrical energy to rotational mechanical energy; a generator does the reverse.

A transformer changes AC voltage by the turns ratio; it does not work on steady DC.

A rectifier converts AC to DC; a bridge rectifier uses four diodes to give full-wave output.

A battery converts chemical energy to electrical energy; charging reverses the reaction with losses.

A solar cell converts light to electrical energy; output current is roughly proportional to irradiance.

A thermocouple converts a temperature difference to a small voltage; a thermistor changes resistance with temperature.

A piezoelectric element converts mechanical strain to voltage and is used in sensors and buzzers.

Efficiency figures compare output energy with input energy over the same period.

Crating encloses a form in a box to keep proportions and perspective consistent.

One-point perspective has one vanishing point; two-point perspective uses two on the horizon.

Isometric drawing keeps all three axes at true scale, which is why it is used for technical illustration.

Exploded sketches show assembly order with leader lines and part numbers.

A sectional sketch reveals internal detail; hatch lines at 45 degrees identify cut material.

Marker rendering builds tone in layers from light to dark; paper choice affects bleed and blend.

Photographing a model against a plain background with consistent lighting shows form clearly.

Annotation on a sketch states the material, the function and the reason for the choice.

A type test is carried out on a representative sample to verify a design meets a standard.

Routine tests are carried out on every unit produced to confirm consistency.

A conformity mark shows the product meets the applicable standard; it is not a guarantee of quality beyond that standard.

Test houses are independent; self-declaration is permitted only where the standard allows it.

A test report states the standard, the sample, the method, the results and any deviations.

Non-conformance requires corrective action and re-test before release.

Sampling plans define how many units are inspected and the acceptance number.

Documentation must be retained so that a batch can be traced if a fault appears in service.

A design brief is short and open: it states the problem, the user and the context without prescribing the solution.

A specification is a list of measurable requirements derived from research and the brief.

Constraints are fixed limits (budget, size, standard, material); criteria are desirable targets ranked by importance.

Each specification point should name the test method that will verify it.

A specification is revised as research reveals new information, with the revision recorded.

A design brief that already names the solution removes the exploration the project is meant to show.

Client requirements and user requirements may conflict; the conflict is recorded and resolved with reasons.

The evaluation returns to the specification point by point, not to general impressions.

Marking out starts from a true face and a true edge; all dimensions are taken from these references.

A winding strip checks that a board is not twisted; opposite corners are compared.

Cutting lists give finished sizes; allowance for planing and saw kerf is added before cutting.

Angles: the sum of angles in a triangle is 180 degrees; a mitre for a right-angled frame is 45 degrees.

A 3-4-5 triangle sets out a right angle on site without a square.

Area of a circle = pi r squared; circumference = 2 pi r; volume of a cylinder = pi r squared x height.

Percentage waste = (material bought - material used) / material bought x 100.

Convert units consistently before calculating; mixing millimetres and metres is a common source of error.

Embodied energy varies widely: aluminium from ore is energy-intensive, recycled aluminium far less so.

Timber stores carbon while in use; its impact depends on sustainable sourcing and transport distance.

Plastics from fossil feedstock are not renewable, but some are recyclable or biobased.

Machining waste (swarf, offcuts) can often be recycled if kept separated by material.

Finishes and coatings can prevent recycling by contaminating a single-material stream.

Water use and effluent matter in processes such as anodising, dyeing and paper making.

Transport mode and distance contribute to impact; sea freight is lower impact per tonne-kilometre than air.

Impact assessment compares options on the same functional unit to be meaningful.

Set a realistic scope: a well-finished simple product scores better than an unfinished complex one.

Plan making time against available workshop access and machine booking.

Order materials and standard parts early; delays in supply are the most common cause of late completion.

Record each making stage with a photograph and a note of any deviation from the plan.

Check dimensions against the working drawing at each stage rather than at the end.

Keep a risk assessment and update it when the process or material changes.

Test the finished product against every specification point and record the results.

Leave time for finishing and evaluation; these are assessed and are often rushed.

Evaluation criteria come from the specification; each point is judged met, partly met or not met with evidence.

User feedback is collected with a defined method and sample, and reported without selection bias.

Fitness for purpose asks whether the product does the job for the intended user in the intended context.

Whole-life considerations include maintenance, repair, disposal and running cost.

Comparing the outcome with competing products shows whether the design is competitive.

A modification proposal states the change, the reason and the expected effect.

Limitations are stated honestly; an evaluation that claims everything succeeded is not credible.

Evaluation of the process (planning, time, decisions) is separate from evaluation of the product.

A sharp tool is safer than a blunt one because it needs less force and is more predictable.

Clamp work securely; a workpiece that moves during cutting causes kickback and injury.

Keep hands behind the cutting edge and use a push stick on narrow cuts.

Power tool leads are routed away from the cutting path and checked for damage before use.

Change blades and bits with the tool isolated from the power supply.

Dust from MDF and hardwoods is hazardous; extraction and respiratory protection are required.

Do not wear loose clothing, ties or jewellery near rotating machinery; long hair is tied back.

Work areas are kept clear, and tools are returned to storage after use to prevent trips and cuts.