B4.1 — Production systems (HL)

Key concepts

Producing one prototype is different from producing 10 million units. Production systems organise people, machines, materials, and workflow to make products at specified quantities, costs, and quality. Understanding production systems lets designers make decisions compatible with how their product will actually be made.

Production types

Production systems are classified by volume and variety:

One-off (jobbing) production — a single unique unit. Bespoke furniture, custom engineering, fine art. Highest cost per unit, maximum customisation.

Batch production — identical groups of units produced in runs. Bakery trays, limited-edition products, small machine parts. Economies of scale within each batch; flexibility between batches.

Mass production — continuous production of identical units at high volumes. Cars, packaged goods, consumer electronics. Lowest cost per unit, least flexibility.

Continuous production — non-stop flow of material through the plant. Chemical processes, refineries, paper mills. Optimised for one product 24/7.

Just-in-time (JIT) — components arrive exactly when needed, minimising inventory. Toyota pioneered this at automotive scale.

Mass customisation — mass production techniques producing individualised products. Nike ID shoes, Adobe Express, configurable car builds. Enabled by modular design and digital manufacturing.

Production planning and flow

Production planning answers: what do we make, when, in what sequence, using which resources?

Tools: - Gantt charts — schedule tasks against time - Process flow diagrams — show material/information flow - Capacity planning — ensures machines and people aren't overloaded - Lean / kaizen — continuous improvement of flow, reducing waste

Good production flow minimises waiting, movement, and inventory. Each of these represents cost without adding value.

Quality control and quality assurance

Quality control (QC) — inspecting products (or samples) to reject defects. Quality assurance (QA) — designing the process so defects don't occur in the first place.

QA is proactive and cheaper long-term. QC catches failures but doesn't fix their cause.

Statistical Process Control (SPC) — measuring a sample of production output and detecting drift before defects become common. Charts show measurements over time with upper and lower control limits. If the data drifts, the process is adjusted before parts fail.

Six Sigma — a quality methodology targeting 3.4 defects per million opportunities. Used by Motorola, GE, Toyota.

Cost implications of scale

Unit cost typically drops with scale because fixed costs (tooling, setup, engineering) are amortised over more units. But scale has limits:

• High tooling investment is only justified by large runs.
• Customisation becomes harder at higher volumes.
• Inventory risk rises (unsold stock from overproduction).

A designer must know target volume before choosing manufacturing processes. Designing for 1,000 units and discovering demand is 1 million causes redesign; designing for 1 million and selling 10,000 wastes tooling investment.

Industry case studies

Different industries show different production logics:

• Automotive — mass production with high automation, JIT supply chains, multiple vehicle variants on shared assembly lines.
• Fashion — fast-batch production turning designs into retail-ready product in weeks. High SKU variety, high waste.
• Consumer electronics — global supply chains, contract manufacturing (Foxconn), rapid product cycles.
• Pharmaceuticals — continuous and batch production with extreme QC demands. Regulatory scrutiny at every stage.
• Craft / maker — one-off and batch, direct-to-customer, distinct product story. Etsy economy.

Case studies

Toyota Production System (TPS) — introduced JIT, kaizen, and poka-yoke (error-proofing). Transformed automotive manufacturing globally in the late 20th century. Key insight: reducing waste (muda) and variability (mura) lowers cost and raises quality simultaneously.

IKEA flat-pack logistics — IKEA designs products for flat packaging, reducing shipping volumes by 75–80% compared with assembled furniture. Production system (design for flat-pack, volume manufacture, customer self-assembly) locks together. Individual design decisions serve the whole system.

Tesla Gigafactory — vertically integrated battery cell and car production at unprecedented scale. Designed from the ground up for automation and JIT supply of cells to vehicle assembly lines.

Fairphone — modular smartphones designed for repair and longevity. Production system chooses suppliers for conflict-free materials and worker wages. Cost per unit is higher than mainstream phones; the company competes on ethics, not price.

Glossary

• One-off production — the manufacture of a single unique unit.
• Batch production — manufacture of identical units in groups.
• Mass production — continuous manufacture of identical units at high volume.
• Continuous production — uninterrupted production of a single product.
• JIT — Just-in-Time; components arrive exactly when needed.
• Mass customisation — mass-production methods producing individualised products.
• Quality Control (QC) — inspection to detect defects.
• Quality Assurance (QA) — process design that prevents defects.
• Statistical Process Control (SPC) — measuring production drift before it becomes defect.
• Lean manufacturing — systematic reduction of waste in production processes.
• Fixed cost — investment independent of units produced (tooling, setup).
• Variable cost — cost that scales with units produced (materials, labour).

Check your understanding

1. Distinguish between one-off, batch, and mass production, with an example of each.

One-off: single unique units, e.g. a bespoke wedding ring by a jeweller. Batch: identical groups produced in runs, e.g. 500 limited-edition sneakers. Mass: continuous production of identical units at volume, e.g. plastic water bottles at millions per day. The three differ in unit cost, flexibility, and tooling investment.

2. Explain the difference between quality control and quality assurance.

Quality control (QC) inspects products or samples after manufacture to detect defects — reactive. Quality assurance (QA) designs the process so defects do not occur — proactive. QC catches problems; QA prevents them. A mature production system relies primarily on QA with QC as verification; a weak system depends on QC and throws away many defective units.

3. Why does unit cost typically decrease as production volume increases?

Fixed costs (tooling, setup, initial engineering, quality systems) are spread across more units. If a £50,000 injection-moulding tool produces 1,000 parts, it adds £50 to each; producing 1,000,000 parts adds 5p. Variable costs (material, labour, energy) don't change per unit with volume, but their share shrinks. Beyond a point, diminishing returns set in — additional capacity requires new plants, and inventory risk grows.

4. Describe how Just-in-Time (JIT) manufacturing changes inventory and supplier relationships.

JIT arranges for materials and components to arrive only when needed for production, rather than being held in warehouses. This drastically reduces inventory costs and capital tied up in unused stock. It also exposes production to supplier reliability — a late delivery halts the line. JIT requires tightly coordinated, trusted supplier relationships, precise forecasting, and robust logistics. Toyota's JIT supply system collapsed temporarily when the 2011 earthquake disrupted component shipments, demonstrating its sensitivity to disruption.