Design for manufacture and project management · Designing and making principles
Revision notes
Making recommendations for accuracy
Recommendations for accuracy should suit the scale of production, required tolerance, product risk and manufacturing process.
One-off and prototype manufacture
For one-off products and prototypes, accuracy can be improved by:
working from clear drawings and dimensions
using a common datum
accurate marking out
using templates where shapes repeat
checking dimensions with appropriate measuring equipment during manufacture.
Batch production
For repeated batches, designers can recommend:
jigs and fixtures to locate components consistently
templates to remove repeated marking-out errors
standardised components
planned quality-control checks
vernier calipers, micrometers or go/no-go gauges where appropriate.
Large-scale and mass production
For high-volume manufacture, recommendations may include:
CNC or automated equipment for repeatability
dedicated tooling and fixtures
automated or rapid inspection systems
statistical sampling where appropriate
clearly specified tolerances and quality-control points.
The most accurate method is not automatically the best choice. The required accuracy must be balanced against production speed, cost and the consequences of a component being outside tolerance.
Planning, quality assurance and quality control help production remain accurate, efficient and consistent.Vacuum forming: a heated thermoplastic sheet is drawn over a former and held while it cools.Injection moulding: granules are melted and driven by a screw through a nozzle into a closed mould.Extrusion forces softened material through a shaped die to produce a continuous cross-section.Blow moulding: air expands a hot polymer parison against the inside of a mould.Rotational moulding coats the inside of a heated rotating mould before the hollow product cools.Compression moulding uses heat and pressure to form a measured charge inside a mould.A pattern forms a cavity in sand before molten metal is poured, cooled and removed.Die casting injects molten metal into a reusable metal die under pressure.Investment casting forms a ceramic mould around a sacrificial pattern for detailed components.MIG welding feeds a consumable wire electrode into a gas-shielded weld pool.TIG welding uses a non-consumable tungsten electrode and separate filler where required.Spot welding clamps sheet between electrodes and creates localised heat through electrical resistance.Steam softens lignin so timber can be bent around a former and held until dry.Thin veneers are glued and clamped around a former to create strong curved components.Flexography uses a relief plate and rollers to transfer ink to the substrate.Offset lithography transfers the image from plate to blanket cylinder and then to the substrate.Screen printing pushes ink through open areas of a mesh stencil onto the substrate.A focused laser follows a programmed path while assist gas helps clear the cut.Milling removes material with a rotating multi-point cutter while the work is accurately positioned.In turning, the workpiece rotates while a cutting tool removes material to create cylindrical forms.FEA divides a model into elements so stresses and deformation can be calculated.CFD predicts how fluids move around or through a product.A go/no-go gauge quickly checks whether a feature lies within its permitted tolerance.Vernier callipers measure external, internal and depth dimensions accurately.A micrometer uses a precision screw to measure small dimensions accurately.A tensile test records how a standard specimen responds as an increasing axial load is applied.Hardness tests compare resistance to permanent indentation under controlled conditions.Anthropometric data provides measured human dimensions for designing appropriate product sizes and clearances.Ergonomics applies knowledge of people to improve comfort, safety, usability and performance.Bauhaus design favoured functional forms, modern materials and design suited to industrial production.Art Deco is recognisable through geometric decoration, symmetry, luxury materials and machine-age influence.Memphis challenged restrained modernism with bold colour, pattern, geometry and playful forms.Arts and Crafts valued skilled making, natural inspiration, material honesty and resistance to poor-quality mass production.The life-cycle model helps explain how sales, competition and redesign priorities change over time.Sustainable design decisions should reduce resource use and keep products and materials useful for longer.
ACTIVE RECALL
Think you have got this topic?
Test yourself before moving on, or use flashcards for a quick recall session.
