How do manufacturers control quality and accuracy, and what do tolerances, jigs and standards contribute?
Quality control and quality assurance, tolerances and how they are stated and checked, jigs and fixtures for accuracy, and quality standards and marks (ISO 9000, BSI Kitemark, CE marking) in manufacture.
A focused answer to OCR A-Level Product Design on quality control and quality assurance, the difference between them, tolerances and how they are stated and calculated, the role of jigs and fixtures, and quality standards and marks such as ISO 9000, the BSI Kitemark and CE marking.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
OCR wants you to distinguish quality control from quality assurance, work with tolerances (limits and band), explain the role of jigs and fixtures, and recognise the main quality standards and marks. Quality is how a manufacturer guarantees that every product made is fit for purpose.
Quality control versus quality assurance
The exam point is the contrast: QC finds and removes defects after they happen; QA designs the process so they do not happen.
Tolerances
A tighter tolerance (a smaller band) needs more precise machines and produces more rejects, so it costs more. Designers therefore set the tolerance as wide as the function allows, tight only where parts must mate accurately (a bearing) and loose where they need not (a cosmetic cover).
Jigs, fixtures and consistency
Quality standards and marks
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20204 marksExplain the difference between quality control and quality assurance in manufacturing.Show worked answer →
A Component 01 short-answer question. Two marks for each clearly explained term, or marks for the contrast.
Award marks for: quality control (QC) is the checking of products during or after manufacture to detect faults and reject or rework defective items (inspection, sampling, testing against a standard); it catches faults that have already happened. Quality assurance (QA) is the planning and managing of the whole production system to prevent faults from occurring in the first place (documented procedures, staff training, supplier checks, process monitoring). The key contrast is that QC is reactive (find and remove defects) while QA is proactive (design the process so defects do not arise).
A common dropped mark is treating QC and QA as the same thing; the mark is for the reactive-versus-proactive distinction.
OCR 20224 marksA shaft is specified as 25 mm with a tolerance of plus or minus 0.1 mm. State the maximum and minimum acceptable sizes, the tolerance band, and explain why a tolerance is given rather than a single exact size.Show worked answer →
A Component 01 calculation and explanation question. Marks for the two limits, the band and the reason.
The maximum acceptable size is mm and the minimum is mm. The tolerance band (the total permitted variation) is mm. A tolerance is given rather than an exact size because no manufacturing process can make a part to a perfect dimension every time; allowing a small range that still works lets the part be made economically while guaranteeing it fits and functions. A tighter tolerance costs more (more precise machines, more rejects), so the tolerance is set as wide as the function allows.
A common dropped mark is giving the limits but not the band, or not linking tighter tolerance to higher cost.
Related dot points
- Shaping and forming processes for metals (casting, forging, machining), polymers (injection moulding, blow moulding, extrusion, vacuum forming, rotational moulding) and timber (sawing, turning, laminating), and the tooling, accuracy and scale each suits.
A focused answer to OCR A-Level Product Design on shaping and forming processes: casting and forging of metals, machining, injection moulding, blow moulding, extrusion, vacuum forming and rotational moulding of polymers, and timber processes, with the tooling cost, accuracy and scale each suits.
- The scales of production (one-off or bespoke, batch, mass and continuous), their use of jigs, fixtures and automation, the relationship between fixed cost, volume and unit cost, and Just in Time (JIT) stock control.
A focused answer to OCR A-Level Product Design on the scales of production: one-off (bespoke), batch, mass and continuous production, the use of jigs, fixtures and automation, the calculation of unit cost from fixed and variable costs, and Just in Time stock control.
- Digital design and manufacture: CAD modelling, CAM and CNC machining, 3D printing (additive manufacture), laser cutting, and their effects on accuracy, repeatability, iteration speed, mass customisation and the role of the designer.
A focused answer to OCR A-Level Product Design on digital design and manufacture: CAD modelling, CAM and CNC machining, additive manufacture (3D printing), laser cutting, and their effects on accuracy, repeatability, iteration speed, mass customisation and employment.
- Scale, ratio and tolerance calculations: scale factors and reading scale drawings, ratio and proportion, tolerance limits and bands, and the use of these in technical drawings and dimensioning, with worked calculations.
A focused answer to OCR A-Level Product Design on scale, ratio and tolerance calculations: scale factors and reading scale drawings, ratio and proportion, tolerance limits and bands, and their use in technical drawings and dimensioning, with worked calculations.
- Product analysis and product disassembly: evaluating an existing product against function, materials, manufacture, ergonomics, aesthetics, sustainability, cost and market, and taking products apart (reverse engineering) to understand construction and inform new designs.
A focused answer to OCR A-Level Product Design on product analysis and disassembly: evaluating an existing product against function, materials, manufacture, ergonomics, aesthetics, sustainability, cost and market, and taking products apart (reverse engineering) to understand construction and inform new designs.