WEEK7: PLASTIC FORMATION
-First plastic: celluloid – casein – phenolic
-Case: Well Coates – AD65 radio, round shape, easy to mold, economical, cheap.
-Plastics Industry: chemical(raw material for resin) – processor(molder, extruder, coater) – fabricator(convert forms to finished product)
-Plastic: synthetic(man-made) organic(carbon) compounds: hydrogen, oxygen, chlorine, sulfur, coal, petroleum, cellulose
–Thermosetting: soften with heat, but stay soft for a short time, set when heat continues, no heat makes it soft again, manufacturer choose: can be heated to 500 degrees.
–Thermoplastic: remains soft if heat continues, set when cooling, can be softened again by reheating, heated before being ported into mold.
-Polystyrene PS: easy to hold, coloured, high clarity like glass, weak tensile strength, food container, packaging.(Thermoplastic)
-Polypropylene PP: exceptional strength and resilience, resistant to water, ropes, garden furniture, underwear.
–ABS: tough, resilient, easily molded, opaque form, good temperature resistance, good transparent qualities, TV, computer.
–Resin: raw material, casting & molding, can be rigid or flexible,
-Most often cast thermoset: epoxy, phenolic, polyester
-Most thermoplastic: nylon, acrylic.
–Foam molding: flexible, furniture industry. Rigid foam: insulating, interior and exterior building.
–Foam density: depends on pressure created by the volume of the mixture of the mold & around of gas injected.
–Contact molding: hand lay-up or contact, labour intensive process.
–Reaction injection molding(RIM): resin&catalysi mixture combined& chemically react in mold cavity, upholstery.
–Compression molding: thermosetting resin& rubber, container caps, electronic component, no sprues or runner.
–Pultrusion: opposite of extrusion, shapes similar to extruded shapes, ladder, walkway, thermosetting.
–Injection molding: originally designed for thermoplastic, but can be used with both resin, high-rate production process, LEGO.
-Thermoplastic types: PVC,PA Nylon, PMMA Acrylic, PC, PU, silicones, PET, PE.
–Plasticizers: add to resin to make them flow better, flexible, rubber-like object.
–Design process: design – prototype – evaluate – analyze- design / design thinking – conceptual design- design production / empathize(observe, engage, immerse), define, ideate, prototype, test.
-Design paradigms: engineering(reliability, user performance, avoiding error), human inform processing(mind & computer as symmetrically coupled inform processor) design thinking(emotional& phenomenological concern)
–Personas: a design tool to help visualize who you are designing for and imagine how that person will use the product.
WEEK9 STRESSES ON MATERIAL
-Case: Comet Airliner Disaster, first jet-powered airliner(Dehavilland Comet), one plane exploded over Malta, a crack due to metal fatigue. Solution: design fuselage windows with larger radii.
–Four properties of metal:
Ductility: withstand plastic deformation without rupture, e.g.balloon
Compression: extent, deform prior to rupture.
Hardness: withstand penetration and scratching.
Brittleness: opposite of ductility, e.g. glass
–Six forces of stress:
Compression: direct expression of gravity (case: marshmallow blaster) first man-made (piles of loose stone), Roman invented the arch, stone& cement brick strong.
Tension: opposite from compression (case: Licorice string) wood, wrought iron, steel, fabrics, structures are light, thin, linear.
Shearing, Torsion(twist), Bending
–Join plastic materials:
Chemical bonds: adhesive, solvent(welding).
Thermo bonding: ultrasonic welding, a tool or horn vibrating at an ultrasonic frequency, gain uniform results.
Mechanical: snap-fit assembly, hinge&lock(cover/lid), self-tapping screw, threaded metal fastener.
–Join metal:
Adhesive: synthetic organic adhesive(strength, toughness, resistance to fluid,chemical, environmental degradation)
Thermo: soldering(seal food tins, 850degree), gas welding, arc welding(automobile industry, rapid, economical), laser beam welding
WEEK 10 FINISHING MATERAIL
–Shearing force: unaligned forces, two parts in opposite direction.(case: goodyear tires)
–Finishing plastic:
Heat transfer: printing, fast, profitable, clean, environmentally safe.
Hydro Printing: immersion / water transfer printing, 3d, on metal, plastic, glass, wood.
Decals: on pre-cut transparent plastic with adhesive backing, endless colour, style.
Pattern: companies provide texture.
-Other processes: flocking, metallization, electroplating, sputtering(bright, durable, resistance, cheap) case: polymer money
–Metal finishing:
Deburring: burr may interfere with assembly, jamming, short-circuited; use grinding fluid.
Polishing: belts are made of fabric, leather; add aluminum powder.
Shot or sandblasting: mat finish; add primer, paint.
Electroplating: coating of an electrically conductive object with a layer of metal using electrical current.
Electropolishing: mirror-like, smooth surfaces, ideal for irregular shapes.
Anodic coating or anodizing: oxidation process, convert aluminum surface to oxide layer.
Vacuum metallizing: metal is evaporated at high temperatures in a vacuum, provide complex part.
Porcelain-Enamel: old technology, high temperatures, steel, casting iron, aluminum, acid-resistant.
–Environmental forces: wear, caused by friction(wind, water, human), parallel, compromise, both substances lose at the point of contact, depends on speed , pressure, hardness, direction.
–Design intent: (case tires material), softer than road surface, traction.
–Antidote to reduce wear:
Lubricant: high viscous(thick, gooey), low viscous(flow easier, low tolerance), smooth by levelling the ins and outs, compromises the movement from both side.
Others: Machine bearing, water& liquid(rot, rust)
WEEK11 SUSTAINABILITY
-Ethical issues (plastic): Raw materials are not unlimited, cost, waste.
-Solutions: second life, fountain of youth, Ford Soybean Car using bioplastic.
1. Incinerate plastic: 6% of refuse is processed for the reclamation of energy.
pros: calorific value of material, cons: irretrievable material(hydrochloric acid).
-Everything burnt in a waste disposal incinerator can provide heat energy but is irretrievably lost as a raw material.
-The recycling process must not provide more pollution than waste disposal.
2. Break plastic down for re-use
hydrolyse, pyrolysis.
pros: end-product only slight differ from virgin material.
cons: can only be used for articles which are not subject to high stresses.
3. Degradable pastic
Biodegradation: not work, recycled
Photo-degradation: no organic additive, recycled, way of future
Polymer degradation: physical(environmental stress, plasticizer migration), chemical(oxidation, hydrolysis)
4. Smart manufactring
5. Make longer-lasting product: (doubling life)
Planned obsolescence: designed to fail after a certain period of time.
–Strategies: to do more with less, recycling, longevity.
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