NSSCO Design and Technology (6187) flashcards

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

Design brief

A short statement of the problem, the intended user and the context, written openly so that it does not prescribe a particular solution.

Product specification

A list of measurable requirements derived from research and the brief, split into fixed constraints and ranked desirable criteria, each with a test method.

Iteration in design

Returning to an earlier stage after testing or evaluation and revising decisions, so the process loops rather than running once in a straight line.

Third-angle projection

An orthographic layout in which the plan is placed above the front view and each end view appears on the side from which it is viewed.

Isometric drawing

A pictorial drawing on three axes at 30 degrees to the horizontal, with true lengths marked along each axis and no foreshortening applied.

Hardwood versus softwood

Hardwoods come from broad-leaved deciduous trees such as oak and teak; softwoods come from conifers such as pine and spruce. The terms describe botany, not hardness.

Thermoplastic versus thermoset

Thermoplastics soften repeatedly when heated and can be reshaped; thermosetting plastics cure once and char rather than soften on reheating.

Stress and strain

Stress is force divided by cross-sectional area; strain is change in length divided by original length. Their ratio in the elastic region gives Young's modulus.

Tenon saw use

A saw with a stiffened back and fine teeth, used for accurate joint cutting and for cutting tenon cheeks and shoulders in timber.

Marking gauge

A tool with a pin or knife that scribes a line parallel to a face edge, used to mark joint positions and widths consistently along a workpiece.

Pillar drill safety

The chuck key is removed, the guard is lowered and the workpiece is clamped to the table before the drill is started at the correct speed.

Mortise and tenon joint

A joint in which a projecting tenon on one part fits a matching mortise cut in the other, giving good resistance to twisting and to pulling apart.

Vacuum forming

A thermoplastic sheet is heated, clamped over a former and drawn down by vacuum. It suits shallow open shapes and cannot form undercuts.

Velocity ratio of gears

The number of teeth on the driven gear divided by the number on the driver. A larger driven gear reduces output speed and increases output torque.

Triangulation

Bracing a rectangular frame with a diagonal so that it forms triangles. A triangle cannot change shape without a side changing length, so the frame resists racking.

Closed-loop control

A control system that measures the output with a sensor and compares it with the set value, correcting the error. It responds to disturbance; open-loop does not.

Ohm's law

Voltage equals current multiplied by resistance, written V = I x R. It applies to resistive components and allows the third value to be calculated from two.

Parallel circuit rule

Voltage is the same across each branch, branch currents add to give the total, and the total resistance is lower than the smallest branch resistance.

Potential divider

Two resistors in series across a supply. The output across one resistor is the supply voltage multiplied by that resistance over the total resistance.

Life cycle assessment

An assessment of environmental impact across raw material extraction, manufacture, distribution, use and end-of-life disposal or recovery, compared on a functional unit.

Planned obsolescence

Designing a product with a deliberately limited useful life or with parts that cannot be replaced, so that the buyer must repurchase sooner.

Patent versus registered design

A patent protects a new and inventive function or process; a registered design protects the appearance of a product. Copyright protects drawings and text automatically.

Cutting list

A table giving material, finished dimensions and quantity for every part, derived from the working drawings and used to order and prepare stock.

Annotation on a sketch

Notes placed next to a drawing that explain material, function, dimensions and the reason for a design decision, so the thinking is visible to the reader.

Tolerance and allowance

Tolerance is the permitted variation on a single dimension; allowance is the intentional difference between the sizes of two mating parts.

Working drawing title block

A panel on a drawing recording its number, scale, projection symbol, material, date, author and revision, so the correct issue can be identified.

Worm drive

A screw-like worm driving a toothed wheel. It gives a large speed reduction in one stage and is usually self-locking, but efficiency is low.

Light-dependent resistor

A component whose resistance falls as the light falling on it increases, used with a potential divider to produce a voltage that indicates light level.

Design for assembly

Reducing part count, using self-locating features and limiting fastener types so that a product can be put together quickly, reliably and without special skill.

Risk assessment

A record of each hazard, who is at risk, the likelihood and severity, the existing controls and any further action needed before work starts.

Vernier caliper reading

The main scale value plus the vernier division that lines up with a main scale mark, multiplied by the vernier least count, commonly 0.02 millimetres.