Continuous improvement processes, such as Kaizen™.

Quantity Production – Cambridge IGCSE/A‑Level Design & Technology (9705) – Topic 15

1. From Idea to Product

• Model – Small‑scale, often non‑functional representation used to explore form, aesthetics or ergonomics.
• Prototype – Functional, usually hand‑crafted version that tests key performance criteria (strength, fit, usability) before full‑scale production.
• Marketable product – Final, mass‑produced item that meets the specification, is cost‑effective and ready for sale.

Design‑to‑production pipeline:

Concept → Model → Prototype → Manufacturing Specification → Quantity Production

2. Manufacturing Specification (MS)

The MS translates the design into clear, repeatable instructions for the factory. It is a compulsory part of the specification for any product that will be made in quantity.

Real‑world example – Smartphone MS excerpt

Section	Content (excerpt)
Drawing reference	DWG‑S10‑A (front‑panel assembly)
BOM	1 × Aluminium frame, 1 × glass screen, 1 × battery, 4 × screw M2×4 mm, 1 × flex‑cable
Tolerances	Screen‑to‑frame gap = 0.15 mm ± 0.02 mm
Surface finish	Aluminium anodised, Ra ≤ 0.8 µm, colour “Midnight Black”
Materials	Aluminium 6061‑T6, Gorilla Glass 5, Li‑ion 3000 mAh
Process steps	1. CNC‑mill frame, 2. Laser‑cut glass, 3. Insert battery, 4. Torque screws to 0.4 Nm
QA	Functional test – 100 % visual inspection, 0.5 % random electrical test
Packaging	Anti‑static bag, cardboard box with 10 units, “pull‑card” for JIT supply

3. Production Systems – Comparison

System	Typical volume	Tooling & equipment	Lead‑time	Cost per unit	Flexibility
Individual (one‑off)	1	Custom jigs, manual labour	Weeks–months	High	Very high – design changes easy
Batch (small series)	10 – 10 000	Limited jigs, semi‑automatic machines	Days–weeks	Medium	Moderate – change‑over required
Mass (high‑volume)	> 10 000	Dedicated lines, robots, specialised tooling	Hours–days	Low	Low – design fixed for efficiency

Case‑study note – Choosing batch vs. mass production

Limited‑edition sneaker: a fashion brand expects 5 000 pairs in the first season and wants the ability to change colourways after launch. Batch production is chosen because:

• Volume is too low for the high capital cost of a dedicated line.
• Colour‑way changes require new tooling; batch systems allow relatively quick change‑over.
• Lead‑time of a few weeks matches the marketing calendar.

For a standard commuter bicycle with annual demand of 200 000 units, mass production on an automated line minimises unit cost and meets tight delivery schedules.

4. Commercial Manufacturing Systems (CIM, CIE, Cell Production, In‑line Assembly, JIT, Logistics)

System	Key features (AO3‑d: planning for making in quantity)	Typical example (AO4‑c: evaluate manufacturing systems)
Computer‑Integrated Manufacturing (CIM)	Full digital control from CAD/CAM design through CNC machining to inspection.	Automotive engine block production with CNC centres linked to CAD/CAM.
Computer‑Integrated Engineering (CIE)	Integration of engineering analysis (FEA, CFD) with manufacturing data.	Aerospace wing‑panel optimisation feeding directly to CNC milling.
Cell Production	Self‑contained workstations (U‑shaped) each produce a complete sub‑assembly.	Electronics PCB assembly cell with pick‑and‑place, soldering and testing.
In‑line (continuous) Assembly	Products move sequentially; each station adds a specific feature.	Smartphone assembly line – chassis → screen → battery → final test.
Just‑In‑Time (JIT)	Materials arrive only when needed, minimising inventory and waste.	Toyota “pull” system delivering components to the line at the exact moment of use.
Logistics & Material Handling	Optimised flow of components using conveyors, AGVs, Kanban cards.	Warehouse using automated guided vehicles to replenish work‑stations.

5. Design of Manufacturing System – Jigs, Formers & Templates

Example – Wooden‑panel drilling jig

A steel plate with four hardened bushings locates a 600 mm × 400 mm wooden panel and guides a 6 mm drill to the required positions with ±0.1 mm accuracy.

6. Continuous Improvement – Kaizen™

Kaizen™ (改善) means “change for the better”. It is a culture of small, ongoing improvements involving everyone.

Core Principles (AO3‑c)

1. Gemba – Go to the actual workplace to observe the process.
2. Standardisation – Define clear, repeatable procedures.
3. Eliminate waste (Muda) – Remove non‑value‑adding steps.
4. People involvement – Capture ideas from all staff levels.
5. PDCA (Plan‑Do‑Check‑Act) cycle – Structured method for testing and embedding changes.

PDCA Cycle

Stage	Purpose	Typical activities
Plan	Identify a problem and devise a solution.	Collect data, set targets, develop a detailed action plan.
Do	Implement the plan on a small scale.	Run a pilot, train operators, record observations.
Check	Evaluate results against expectations.	Analyse data, compare with baseline, identify gaps.
Act	Standardise successful changes and plan the next cycle.	Update work instructions, roll‑out across the line, document lessons learned.

Measuring Improvement (AO4‑c)

• Productivity: \(\displaystyle \text{Productivity} = \frac{\text{Output (units)}}{\text{Input (hours)}}\)
• Cycle‑time reduction: \(\displaystyle \Delta T = T_{\text{old}} - T_{\text{new}}\)
• Defect rate: \(\displaystyle \text{Defect Rate} = \frac{\text{Defective units}}{\text{Total units}} \times 100\%\)
• Cost per unit: \(\displaystyle C_{\text{unit}} = \frac{\text{Total production cost}}{\text{Number of units}}\)
• Throughput vs. Capacity:
  • \(\displaystyle \text{Throughput} = \frac{\text{Units produced in a period}}{\text{Period}}\)
  • \(\displaystyle \text{Capacity} = \frac{\text{Maximum possible output}}{\text{Period}}\)
  • Utilisation \(\displaystyle = \frac{\text{Throughput}}{\text{Capacity}} \times 100\%\)

Example – Reducing Cycle Time on a Machining Operation

Original cycle time: 45 s per part.

• Kaizen suggestion 1: Reduce set‑up time by 5 s.
• Kaizen suggestion 2: Optimise tool path, saving 8 s.

New cycle time:

\[ T_{\text{new}} = 45\text{s} - 5\text{s} - 8\text{s} = 32\text{s} \]

Productivity per hour:

\[ \text{Units/hr (old)} = \frac{3600\text{s}}{45\text{s}} = 80 \] \[ \text{Units/hr (new)} = \frac{3600\text{s}}{32\text{s}} \approx 112.5 \]

Increase: \(\Delta \text{Units} = 112.5 - 80 = 32.5\) units hour⁻¹ (≈ 40 % gain).

Exam‑style question (AO4‑c)

Question: A CNC milling operation currently takes 50 s per part. A Kaizen team proposes two changes: (a) a new fixturing system saves 7 s, and (b) a revised tool‑path saves 10 s. Calculate the new cycle time, the percentage reduction in cycle time, and the increase in productivity (units per hour). Show all working.

7. Strategies to Evaluate Manufacturing System Performance

• Throughput & Capacity analysis – Compare actual output with theoretical maximum to locate bottlenecks.
• Overall Equipment Effectiveness (OEE) – OEE = Availability × Performance × Quality.
• Value‑Stream Mapping (VSM) – Visualise material and information flow; highlight waste (Mura, Muri, Muda).
• Cost‑benefit analysis – Relate improvement costs (e.g., new jig) to savings in labour, material or defect reduction.
• Benchmarking – Compare key metrics with industry standards or previous internal data.

8. Embedding Kaizen™ in Quantity Production

1. Leadership commitment – Senior managers champion the philosophy and allocate resources.
2. Training & tools – Teach staff 5S, VSM, basic statistics and how to complete a Kaizen suggestion form.
3. Suggestion system – Visible board or digital platform for idea capture, with clear evaluation criteria.
4. Rapid testing – Small‑scale pilots, time‑studies and quick feedback loops.
5. Recognition & reward – Publicly acknowledge successful ideas (e.g., “Kaizen of the month”).
6. Standardisation – Incorporate successful changes into work instructions and training.

9. Brief Overview of Materials Processing (Topic 16 – relevance to Quantity Production)

When moving from prototype to quantity production, the chosen processing route must balance cost, volume, material properties and required tolerances.

• Forming – Bending, stamping, deep‑drawing for sheet metal; advantageous for high‑volume metal parts.
• Casting – Sand, investment, die‑casting; suitable for complex shapes with moderate volumes.
• Machining – Turning, milling, drilling; offers high precision, used for low‑to‑medium volumes or where tight tolerances are essential.
• Joining – Welding, brazing, adhesive bonding, mechanical fastening; selected based on material compatibility and strength requirements.
• Finishing – Heat‑treatment, surface coating, polishing; essential for durability and appearance in the marketable product.

Choosing the appropriate process is part of the manufacturing specification and directly influences the design of jigs, tooling and the overall production system.

Summary

Quantity production relies on a clear design‑to‑production pipeline, a detailed manufacturing specification, and an appropriate production system (individual, batch or mass). Commercial systems such as CIM, cell production, JIT and logistics optimise flow and cost, while jigs, formers and templates guarantee dimensional consistency. Continuous improvement through Kaizen™ and the PDCA cycle provides a structured, people‑focused method for incremental gains. By measuring productivity, cycle‑time, defect rate, OEE and utilisation, and by applying evaluation tools like VSM and benchmarking, manufacturers can sustain high performance and meet the expectations of the Cambridge IGCSE/A‑Level Design & Technology syllabus.