NSSCAS Design and Technology (8256) key terms

A short statement from a client or user describing the problem to solve and the intended outcome, without prescribing a particular solution. It sets the starting point for the design process.

A detailed list of measurable requirements and constraints a product must satisfy, covering function, size, materials, cost, safety and aesthetics. It is used to evaluate design ideas objectively.

The stage of finding and defining a genuine need or shortcoming through observation, interviews, questionnaires or market research, before any design work begins.

A limit placed on a design, such as maximum cost, available machinery, legal standards, time or the client's fixed dimensions. Constraints must be met for a design to be acceptable.

Collecting information about the people who will use a product, including their needs, abilities, tasks and environment, often through interviews, observation or questionnaires.

The study and measurement of human body sizes and reach, used to size products and workspaces so they fit the intended range of users comfortably and safely.

Designing products and workplaces to match human physical and mental capabilities, reducing strain and error. It considers posture, force, reach, visibility and repeated use.

Repeating the design cycle of testing, evaluating and improving a solution so that weaknesses found in a prototype are corrected in the next version.

A working or non-working model built to test a design idea, such as a card model, a 3D-printed part or a full functioning sample, before committing to production.

The specific, measurable points taken from the design specification that are used to judge how well a finished product or idea meets the requirements.

A physical or drawn representation of a product made larger or smaller than full size in a fixed ratio, used to communicate shape and proportion when the real object is impractical to show.

A drawing method showing separate front, plan and side views of an object, arranged in first-angle or third-angle layout, so every dimension can be read without perspective distortion.

A pictorial drawing on three axes at 30 degrees to the horizontal, giving a three-dimensional impression with true lengths along each axis and no foreshortening.

A fully dimensioned, annotated drawing giving a manufacturer everything needed to make a part, including material, tolerances, finishes and assembly details.

The permitted amount of variation in a dimension or fit, so parts still assemble and function when made slightly above or below the nominal size.

Identical components made to the same tolerances so any one can replace another without hand fitting, enabling fast assembly and easy repair.

A material's resistance to being scratched or indented. It is measured by tests such as Brinell or Rockwell and predicts wear resistance and tool life.

A material's ability to absorb impact energy without fracturing, combining strength with some ductility. It matters for tools, helmets and structures subject to sudden loads.

The ability of a material to be stretched into wire or drawn out without breaking. Ductile metals such as copper and mild steel can be formed by bending and drawing.

The ability of a material to be hammered or rolled into thin sheets without cracking. It allows metals to be shaped by pressing, rolling and forging.

The tendency of a material to fracture suddenly with little deformation or warning. Cast iron and glass are brittle and fail under shock or tensile stress.

The measurable characteristics of a material, such as density, strength, hardness, conductivity and thermal expansion, that determine its suitability for a given product.

A material made from two or more distinct constituents that stay separate, such as glass-reinforced plastic, so the combination is stronger or lighter than either alone.

A plastic that cures by a chemical reaction into a rigid, infusible network. It cannot be remelted or reshaped, so it suits heat-resistant and structural parts such as epoxy adhesives.

A plastic that softens when heated and hardens on cooling, so it can be remelted and recycled. Examples include acrylic, polyethylene and polylactic acid.

A high-volume process in which melted thermoplastic is forced into a closed metal mould, then cooled and ejected. It gives accurate, repeatable parts with little finishing.

A process in which a heated thermoplastic sheet is drawn over a mould by suction and cooled. It suits shallow, open shapes such as trays and packaging at low tooling cost.

Making a limited quantity of identical products in groups, using jigs and some machinery but not full automation. It balances tooling cost against the number of units made.

A device that holds work and guides a tool so repeated operations are accurate and fast, such as a drilling jig that positions holes in identical parts.

Using computer-generated instructions, often from a CAD model, to control machines such as CNC routers or laser cutters, giving precise and repeatable production.

Using software to create, edit and analyse 2D drawings or 3D models, allowing rapid modification, simulation and export of data for manufacture or rendering.

Designing products to reduce environmental impact across their life, through efficient material use, low energy in use, recyclability, repairability and long service life.

A structured method of estimating a product's environmental impact at each stage, from raw material extraction through manufacture, use and disposal, to compare design options.

Designing a product so it can be taken apart easily for repair, upgrade or recycling, using detachable fixings rather than adhesives and identifying separable materials.

Judging a design against the social, cultural, economic, ethical and environmental setting in which it will be made and used, including who benefits and who is affected.

A recorded process of identifying hazards in a workshop or product, judging how likely and how severe harm is, and stating controls to reduce the risk.

An assembly of moving parts that changes the size, direction or type of motion, such as a lever, gear train, pulley or four-bar linkage.

The ratio of output force to input force in a mechanism. It can be increased by gearing down or using a longer lever, usually at the cost of speed or distance moved.

A mechanism of rigid bars joined by pivots that transmits or converts motion, such as a four-bar linkage producing an arc or parallel movement.

In a control system, information about the actual output that is compared with the desired value so the system can correct error automatically, as in a thermostat.

A control system that carries out a set sequence without checking the result, so it cannot correct for disturbance. A timer-controlled motor is a simple example.

A component that converts a physical quantity such as temperature, light, pressure or position into an electrical signal a control system can use.

The ratio of a structure's failure load to its expected working load. A value above one allows for uncertainty in loads, materials and workmanship.

A pulling force that stretches a member along its length. Cables in a suspension bridge and the lower chord of a truss work in tension.

A pushing force that shortens a member along its length. Columns and the upper chord of a truss carry compression and may buckle if too slender.

Bracing a frame with diagonal members to form triangles, which prevents racking and makes the structure rigid without adding much weight.

Sudden sideways failure of a slender member under compression, occurring below the material's crushing strength. Longer, thinner members buckle more easily.

The candidate's organised record of a design-and-make project, showing research, specification, ideas, development, making, testing and evaluation with evidence at each stage.