Testing and evaluating products in industrial or commercial contexts.
Critical analysis and evaluation · Designing and making principles
Revision notes
Critical Analysis, Testing and Feedback
Critical analysis is an objective study of a design's strengths and weaknesses. It considers its purpose, users, materials, manufacture, usability and safety.
Evaluation judges how well a design meets its specification. It should use evidence from testing. For example, if users struggle to open a box, the designer should identify why and test a different handle or opening mechanism.
Product Testing
Commercial products are tested before sale to check function, safety, durability and performance. Tests should reflect conditions of use. Failure to identify a serious fault can lead to a product recall, where products are withdrawn or returned for correction.
Destructive Testing
Destructive testing pushes a sample until it breaks or is permanently damaged. It reveals limits such as maximum load but makes the sample unusable.
Non-destructive Testing
Non-destructive testing (NDT) checks a component for faults without destroying it. Examples include visual inspection and scanning for internal defects. It is useful when a finished part is valuable or must still be used after inspection.
Choosing a Test
The choice of test depends on the product and the property being checked. A chair might undergo repeated load testing; an electrical appliance might be checked for overheating.
Critical analysis uses evidence from users, testing and product performance to judge strengths and identify improvements.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.
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