Notes · Design and TechnologyUK · A-Levels

Modern industrial and commercial practice

This chapter explains how products are manufactured commercially: the scales of production and how volume drives unit cost, the techniques that make efficient use of materials, and the computer systems, automation and lean methods that run a modern factory. It develops the quantitative side - economies of scale and material waste - alongside the judgement of which scale and system suit a product.

4 sections~15 min reading time3 competenciesLevel Standard 3 · Advanced 1

T·0555 / 18

Exam profile

AO4 · Explain scales of production, efficient use of materials and computer-based manufacturing systemsAO2 · Calculate material waste and unit cost and interpret economies of scaleAO3 · Analyse and evaluate the appropriate scale of production and manufacturing system for a product

Operators:explaincalculatecompareanalyseevaluatejustify

basic level

AS-Level expects the scales of production described and matched to products, and awareness of material efficiency and automation.

higher level

The full A-Level expects unit cost and material waste calculated and used to justify a scale of production, and the role of CIM, JIT and lean manufacture explained.

Depth

Text

Contents · 4 sections

Modern industrial and commercial practice

Scales of production#

StandardAQA 7552 3.1.5AQA 7552 3.3.7DfE GCE D&T - scales of production

The scales of production

Fig. 1The scales of production ranged by volume: one-off and batch are flexible with higher unit cost; mass and continuous need heavy investment but give the lowest unit cost.

Manufacturing is organised at different scales according to how many identical items are wanted, and the scale drives the processes, machinery, labour and cost. The four scales are one-off (job) production, batch production, mass (line) production and continuous production. Matching the scale to the quantity and to the product is a fundamental commercial decision - the same product made at the wrong scale is either ruinously expensive or impossible to supply.

One-off (job) production makes a single, often bespoke item - a piece of studio furniture, a prototype, a wedding cake. It uses skilled labour and flexible general tools, so it is highly adaptable but slow and expensive per item, with no tooling to amortise. Batch production makes a set quantity (a batch) of identical items, then changes over to make a different batch - a run of a particular garment or a limited edition. It balances flexibility and efficiency, but the changeover (set-up) time between batches is a cost, so batch sizes are chosen to keep it economic.

Mass (line) production makes large quantities of a standardised product on a flow line, often with automation and a division of labour, so each worker or machine performs one task repeatedly - cars, appliances, packaged goods. It gives a very low unit cost and high output but needs heavy investment and is inflexible, so it suits stable, high-demand products. Continuous production runs the plant non-stop, 24 hours a day, for products in constant huge demand - chemicals, steel, paper, glass - where stopping and starting is costly, giving the lowest unit cost of all but the least flexibility.

The scale of production is chosen by weighing the quantity required, the acceptable unit cost, the need for flexibility and the capital available. Low volumes favour one-off or batch (flexible, low tooling cost, higher unit cost); high, stable volumes favour mass or continuous (huge investment, inflexible, very low unit cost). A product's scale can also change over its life, moving from a one-off prototype to batch trials to mass production as demand grows - so the designer must anticipate the scale the product will eventually need.

Worked example

Matching scale to a product

For (a) a bespoke reception desk for one hotel, (b) 500 branded conference bags and (c) a soft drink sold nationally, recommend a scale of production and justify each.

The reception desk
One-off (job) production: a single bespoke item made by skilled labour with flexible tools - no tooling to amortise, high adaptability, accepted higher unit cost for a unique product.
The conference bags
Batch production: 500 identical items made in one run then the line changes to another product - efficient for a moderate, defined quantity while keeping flexibility.
The soft drink
Continuous production: constant, huge demand and a product cheap to keep flowing but costly to stop and start, giving the lowest possible unit cost - the plant runs non-stop.

Result: One-off for the bespoke desk, batch for the 500 bags and continuous for the mass-market drink - each scale matched to the quantity, unit cost and flexibility the product demands.

Typical mistakes

Confusing batch (a set quantity then a changeover) with mass production (a continuously running line of one product).
Proposing mass or continuous production for a low-volume or bespoke product, ignoring the huge investment and inflexibility.

Active revision

A designer's chair sells first as a handmade one-off, then in small runs, then, if it becomes popular, in tens of thousands. Explain how the scale of production would change and the effect on unit cost and flexibility.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for design and technology (Department for Education) · AQA A-level Design and Technology: Product Design (7552) specification (AQA)

Choosing a scale and economies of scale#

AdvancedAQA 7552 3.1.5DfE GCE D&T - economies of scale

Unit cost falls with volume (economies of scale)

Fig. 2Unit cost = variable cost + fixed cost / quantity. The fixed cost is spread over more units as volume rises, so unit cost falls steeply at first and then levels towards the variable cost - the mechanism of economies of scale.

The reason higher volumes lower the unit cost is economies of scale. Every product carries fixed costs (tooling, machinery, factory, design) that do not change with the number made, and variable costs (materials, direct labour, energy per unit) that do. Spreading the fixed cost over more units makes each unit's share of it smaller, so the unit cost falls as volume rises. This is the mathematical heart of why mass production is cheap per item and one-off production is dear.

The unit cost can be written as the variable cost per unit plus the fixed cost divided by the quantity: unit cost = variable cost + (fixed cost / quantity). As quantity increases, the fixed-cost term shrinks towards zero and the unit cost approaches the variable cost - a curve that falls steeply at first and then levels off. This is why doubling output from 100 to 200 cuts unit cost sharply, while doubling from 10,000 to 20,000 barely moves it: the fixed cost is already thinly spread.

Economies of scale extend beyond spreading fixed costs. Buying materials in bulk earns discounts (purchasing economies), larger specialised machines are more efficient (technical economies), and workers become faster at repeated tasks (the division of labour). But there are limits: beyond a point, diseconomies of scale can appear as a very large operation becomes harder to manage and coordinate, so bigger is not always cheaper without end.

For a designer or entrepreneur the practical use of this is the break-even and volume decision: expensive tooling (a mould) is only worth buying if the volume is high enough for the low unit cost to repay it. Calculating unit cost at different volumes shows whether a high-tooling process such as injection moulding beats a low-tooling one such as 3D printing for the expected quantity - a calculation that turns 'mass production is cheaper' into an evidenced decision.

\text{Unit cost} = \text{variable cost per unit} + \dfrac{\text{fixed cost}}{\text{quantity}}

Unit cost

The unit cost is the per-unit variable cost plus each unit's share of the fixed cost. As quantity rises the fixed-cost term shrinks, so unit cost falls towards the variable cost - economies of scale.

Worked example

Calculating economies of scale

A moulded product has fixed costs (mould and set-up) of £10,000 and a variable cost of £4 per unit. Calculate the unit cost at 500 units and at 5,000 units and comment on the effect of volume.

State the formula
Unit cost = variable cost + fixed cost / quantity.
At 500 units
Unit cost = 4 + 10,000/500 = 4 + 20 = £24 per unit.
At 5,000 units
Unit cost = 4 + 10,000/5,000 = 4 + 2 = £6 per unit.
Comment
Producing ten times as many cuts the unit cost from £24 to £6 - a quarter - because the £10,000 fixed cost is spread over far more units (economies of scale). At still higher volumes the unit cost would keep approaching the £4 variable cost but fall ever more slowly.

Result: Unit cost is £24 at 500 units and £6 at 5,000 units; the fall comes from spreading the £10,000 fixed cost over more units, and it levels off towards the £4 variable cost as volume rises.

Typical mistakes

Thinking unit cost keeps falling in proportion to volume - it approaches the variable cost and levels off; the early savings are the largest.
Forgetting that very large scale can bring diseconomies of scale, so bigger is not endlessly cheaper.

Active revision

A product has fixed costs of £20,000 and a variable cost of £5 per unit. Calculate the unit cost at 1,000 and at 10,000 units and explain the difference in terms of economies of scale.

Active recall

Recall the key points — then reveal.

Sources: AQA A-level Design and Technology: Product Design (7552) specification (AQA)

Efficient use of materials#

StandardAQA 7552 3.1.5DfE GCE D&T - efficient use of materials

Nesting parts on a stock sheet

Fig. 3Nesting packs the parts as tightly as possible on the stock sheet so the offcut waste between them is minimised - raising material utilisation and cutting cost and environmental impact.

Material is a major cost and a major source of environmental impact, so using it efficiently is both commercial and responsible. The key idea is to minimise waste - the material that is bought but ends up as offcuts, swarf or rejects rather than in the product. Efficient use of materials is measured by material utilisation, the proportion of the bought material that ends up in finished products, and its complement, the percentage waste.

The main techniques reduce the gap between what is bought and what is used. Nesting arranges the parts to be cut from a sheet as tightly as possible so the offcuts between them are minimised; tessellation designs the part shapes so they interlock and pack without gaps; and standard stock sizes are chosen so that whole numbers of parts fit a sheet with little left over. Cutting patterns are now optimised by CAD nesting software that packs parts automatically to maximise utilisation.

Standardisation of components and materials also cuts waste and cost. Using standard fixings, standard board thicknesses and standard sections means fewer part types to stock, bulk purchasing, and designs that fit available stock without trimming. Designing to standard sizes - a shelf that uses a whole board width, a frame that uses standard tube lengths - avoids the offcuts created by awkward, non-standard dimensions.

Reducing waste connects manufacturing efficiency to sustainability. Less waste means lower material cost, less energy embodied in discarded material, and less to dispose of - so efficient nesting and standardisation serve both the bottom line and the environment. Offcuts that cannot be avoided can be recycled or used for smaller parts, and this thinking links directly to the 6 Rs and design-for-manufacture covered later.

\text{Material waste} = \dfrac{\text{waste area}}{\text{total sheet area}} \times 100\%

Percentage material waste

The proportion of the stock material that is not used. Material utilisation is its complement: utilisation = used area / total area x 100%.

Worked example

Calculating material waste

Rectangular parts each 250 mm by 180 mm are cut from a stock sheet 2,400 mm by 1,200 mm. Find how many whole parts fit, the material utilisation and the percentage waste.

Parts per sheet
Along the 2,400 mm side: 2400/250 = 9.6, so 9 whole parts. Along the 1,200 mm side: 1200/180 = 6.67, so 6 whole parts. Total = 9 x 6 = 54 parts.
Used and total area
Part area = 250 x 180 = 45,000 mm^2; used area = 54 x 45,000 = 2,430,000 mm^2. Sheet area = 2,400 x 1,200 = 2,880,000 mm^2.
Utilisation and waste
Utilisation = 2,430,000 / 2,880,000 x 100 = 84.4%. Waste = (2,880,000 - 2,430,000) / 2,880,000 x 100 = 15.6%.
Improve it
Rotating some parts, choosing a stock size that divides evenly by the part dimensions, or nesting differently could raise utilisation and cut the 15.6% waste.

Result: 54 whole parts fit, giving 84.4% material utilisation and 15.6% waste; choosing a better-fitting stock size or nesting the parts differently would reduce the waste.

Typical mistakes

Dividing by the wrong area - waste is the unused area divided by the whole sheet area, not by the used area.
Ignoring that offcuts have both a cost and an environmental impact, so treating waste as unimportant.

Active revision

A 1,000 mm by 1,000 mm sheet is cut into parts each 240 mm by 240 mm. Calculate how many whole parts fit, the percentage material waste, and suggest one way to improve utilisation.

Active recall

Recall the key points — then reveal.

Sources: AQA A-level Design and Technology: Product Design (7552) specification (AQA)

Computer systems, automation and lean manufacture#

StandardAQA 7552 3.1.5DfE GCE D&T - computer systems in manufacture

Just-in-time and sub-assembly flow

Fig. 4In a just-in-time, lean flow, suppliers deliver components exactly when needed; sub-assemblies are built in parallel and brought to final assembly, minimising stock but demanding a reliable supply chain.

Modern factories are run by integrated computer systems. Computer-integrated manufacture (CIM) links design, planning, manufacture and stock control into one data system, so a change in the CAD model flows automatically through to the CAM machines and the ordering of materials. Automation replaces or assists human labour with machinery, and robotics performs repetitive, precise or hazardous tasks (welding, painting, assembly) consistently and around the clock. These systems raise consistency, speed and quality and lower labour cost, at the price of high investment and reduced flexibility and employment.

Just-in-time (JIT) manufacturing schedules materials and components to arrive exactly when they are needed rather than being held in stock. This slashes the cost and space of holding inventory and exposes quality problems quickly, but it depends on utterly reliable suppliers and logistics - a single late delivery can stop the line, as global supply shocks have shown. JIT is therefore a powerful efficiency but a risk that must be managed with dependable supply chains.

Lean manufacturing is the wider philosophy of eliminating all waste - not just material, but wasted time, motion, overproduction, defects and stock - to deliver maximum value with minimum resources. Techniques include continuous improvement (kaizen), standardised work, and pulling production from actual demand rather than pushing it. Lean thinking underlies JIT and modern quality systems, and it aligns commercial efficiency with the sustainability goal of using less.

Sub-assembly and the division of labour organise complex manufacture. A product is broken into sub-assemblies (a car door, a pump unit) built separately, often by specialised teams or suppliers, and then brought together on the final assembly line. This lets sub-assemblies be tested before final assembly, made in parallel to speed production, and sourced from specialists - the standardised, modular approach that makes mass production of complex products possible. A designer therefore designs products as sets of sub-assemblies suited to this flow.

Worked example

Evaluating just-in-time manufacture

A manufacturer is considering moving to just-in-time (JIT) supply for its assembly line. Evaluate the advantages and risks and reach a supported conclusion.

State the advantages
JIT cuts the cost and warehouse space of holding stock, frees up cash tied in inventory, and exposes quality problems quickly because there is no buffer of parts to hide behind - all lowering cost and raising responsiveness.
State the risks
JIT depends entirely on reliable, prompt suppliers and logistics; a single late or defective delivery can stop the whole line, so a disruption (strike, weather, global shock) is far more damaging than with buffer stock.
Reach a conclusion
JIT is worthwhile where the supply chain is dependable and demand is stable, because the stock savings are large; but the firm should mitigate the risk with trusted suppliers, local sourcing or a small safety buffer for critical parts - the benefit is real but the risk must be managed.

Result: JIT lowers stock cost and exposes defects but risks halting production if supply fails; it is justified with a reliable supply chain and risk mitigation, showing the decision is a managed trade-off, not a free saving.

Typical mistakes

Describing JIT only as a benefit and ignoring its dependence on reliable suppliers - a single delay can halt production.
Confusing automation (machinery doing tasks) with CIM (the integrated data system linking design to manufacture).

Active revision

A car plant uses just-in-time delivery and robotic assembly. Evaluate the benefits and risks of this approach and explain how sub-assembly helps manage the complexity.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for design and technology (Department for Education) · AQA A-level Design and Technology: Product Design (7552) specification (AQA)

References & sources

Sources

Department for Education

GCE AS and A level subject content for design and technology

AQA

AQA A-level Design and Technology: Product Design (7552) specification

Modern industrial and commercial practice

4 sections~15 min reading time3 competenciesLevel Standard 3 · Advanced 1

Modern industrial and commercial practice

Key points

Matching scale to a product

Key points

Calculating economies of scale

Key points

Calculating material waste

Key points

Evaluating just-in-time manufacture

Sources

Modern industrial and commercial practice

Key points

Matching scale to a product

Key points

Calculating economies of scale

Key points

Calculating material waste

Key points

Evaluating just-in-time manufacture

Sources