LGCSE Design & Technology (0189) flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Iterative design cycle

A repeating process of research, specification, ideation, prototyping, testing and evaluation in which evaluation evidence feeds back to any earlier stage to improve the design.

Product design specification

A set of measurable criteria a product must meet, covering function, performance, cost, size, safety, environment and user needs, each stated with a value and a test method.

Design fixation

Being locked onto one early concept so alternatives are not explored. It is reduced by generating a fixed quota of ideas before judging any of them.

Anthropometric percentile design

Using body measurement data: design to the 5th percentile for reach and the 95th percentile for clearance so most users are accommodated.

Young's modulus

The ratio of stress to strain in the linear-elastic region of a material's stress-strain graph, measured in MPa; a measure of stiffness.

Thermoplastic versus thermoset

Thermoplastics soften reversibly when heated and can be remoulded; thermosets cure permanently and char rather than melt, so they cannot be recycled by remelting.

Ferrous and non-ferrous metals

Ferrous metals contain iron, such as mild steel and cast iron; non-ferrous metals do not, such as aluminium, copper and brass, and are generally non-magnetic.

Composite material

A reinforcement such as glass or carbon fibre embedded in a matrix resin; the fibre carries tensile load while the matrix transfers load and protects it.

Tap drill size rule

The hole diameter before tapping equals the thread major diameter minus the pitch, for example 5.0 mm for an M6 thread with 1.0 mm pitch.

Vacuum forming limitation

Vacuum forming pulls heated thermoplastic sheet over a mould but cannot form undercuts or sharp internal corners, and needs draft angle for release.

Go/no-go gauge

A fixed gauge with a go end that must pass and a no-go end that must not, giving a fast pass/fail check of one dimension against tolerance.

Injection moulding draft angle

A slight taper on all vertical mould faces that allows the part to eject without scuffing; undercuts need side-action tooling and increase cost.

Velocity ratio of gears

The product of driven gear tooth numbers divided by the product of driving tooth numbers; a ratio above one reduces speed and increases torque.

Mechanical advantage and efficiency

Mechanical advantage is load divided by effort; efficiency is mechanical advantage divided by velocity ratio, expressed as a percentage.

Lever classes

Class 1 has the fulcrum between effort and load; class 2 has the load in the middle; class 3 has the effort in the middle and always gives mechanical advantage below one.

Triangulation for rigidity

Adding a diagonal to a square frame divides it into triangles, which cannot change shape without changing side length, so the frame resists racking.

Potential divider formula

The output voltage equals the supply voltage multiplied by the resistance across which the output is taken, divided by the total resistance of the chain.

LED series resistor

The resistor value equals supply voltage minus LED forward voltage, divided by the desired LED current; typical LED current is 10 to 20 milliamps.

Open and closed loop control

Open-loop control gives no feedback, such as a timed motor run; closed-loop control compares sensor feedback with a set point and corrects the output.

Relay driver purpose

A microcontroller output supplies only a few milliamps, so a transistor or relay is used to switch the larger current a motor or heater needs.

Pulse-width modulation

Rapidly switching a supply on and off to control average power; the average voltage equals the duty cycle multiplied by the supply voltage.

Parametric CAD modelling

Modelling with constrained sketches and driving dimensions so that changing one dimension updates all dependent features automatically through the feature history.

STL file requirements

An STL file describes a surface as triangles and must be watertight, or manifold, for slicing software to generate valid toolpaths for 3D printing.

Laser cutter kerf

The width of material removed by the laser beam, typically 0.1 to 0.3 mm, which must be compensated in the drawing so parts fit accurately.

Digital twin

A virtual model of a physical product fed with live sensor data, used to predict maintenance needs and test changes without altering the real asset.

The 6 Rs hierarchy

Rethink, Refuse, Reduce, Reuse, Repair and Recycle, in that order of preference; recycling is last because it still uses energy and loses material quality.

Design for disassembly

Designing joints with reversible fasteners such as screws and snap fits instead of adhesives or welding, so parts can be repaired, replaced and separated for recycling.

Embodied energy

The total energy consumed in extracting, processing and manufacturing a material, considered alongside recyclability when comparing material choices.

Life cycle assessment

A structured evaluation of environmental impact across raw material extraction, manufacture, distribution, use and end-of-life, rather than a single stage alone.

Third-angle projection layout

In third-angle projection the plan is placed above the front elevation and the right-hand side view to its right, each view on the side it is seen from.

Hidden detail line convention

Short evenly spaced dashes show edges not visible in that view; hidden detail is normally omitted from sectioned views to keep the drawing clear.

Isometric drawing convention

A pictorial view drawn on axes at 30 degrees to the horizontal with all lines at true length, used to communicate shape rather than to dimension manufacture.

Risk assessment hierarchy

Control measures in order: eliminate the hazard, substitute a safer process, apply engineering controls such as guards, then administrative controls, with PPE last.

Lock-out tag-out isolation

Before changing a blade or bit, switch off, isolate the supply, fit a lock and tag, then verify the machine cannot start.