Product Design:

Product Design:

1. Properties of Materials

   • Strength: Ability of a material to stand up to forces being applied without bending, breaking, or deforming
     • Elasticity: The ability of a material to absorb force and flex
       • Plasticity: The ability of a material to change shape permanently
       • Ductility: The ability of a material to change shape by stretching along its length
         • Tensile Strength: The ability of a material to stretch without breaking
           • Malleability: The ability of a material to be reshaped in all directions without cracking
             • Toughness: A characteristic of material that doesn't break or shatter under sudden shock
               • Hardness: The ability of a material to resist scratching, wear and tear and indentation
                 • Conductivity: The ability of a material to conduct electricity

2. Plastics

   • Thermoplastic: Can be remolded. Thermosetting plastic: once set, is permanently in that shape. Elastomers: Flexible materials like latex
     • Thermosetting plastic: Urea Formaldehyde, Phenol Formaldahyde
     • Thermoplastics: ABS, Acrylic, Polystyrene
       • Elastomers: Silicon rubber, latex, elastic
   • Plastic processes: Vacuum forming, dome blowing, rotational molding, injection molding, calendering, extrusion, compression molding
     • Wasting Plastic: laser cutter, file, belt sander
   • Finishing Plastic: Plastic can be finished in a number of ways, buffing and wet and dry. Laser cutting is self finishing as is injection molding (they come out that neat that it isn't necessary)
     • Adhesives:
       • Tensol Cement: joins plastics such as perspex and acrylic together permanently
         • Contact Adhesive: Can be used to join plastics. The adhesive is applied to both surfaces. Take a while to dry but becomes almost impossible to take apart. Most adhesives are plastics (araldite is epoxy resin that hardens when a catalyst is added)
           • Super glue: adhesive that joins plastics together quickly
           • Glue Gun: Plastic that soldifies, it is semi-permanent
   • PIC (Plastic Identification Code)
     • 01: PET, 02: PE-HD, 03: PVC, 04: PE-LD, 05: PP, 06: PS, 07: O
   • Vacuum Forming: Process is done to manufacture a variety of products in thermoplastic materials such as food trays. Often used for Polystyrene (HIPS). It's cheap and easy (often done from materials up to 6mm thickness). Some thermoplastics (ABS) need pre-drying as blisters may appear if wet.
     • A mould is attached to a plat, the plastic is then heated from above, once soft enough air is blown to raise the sheet, the mould is then pushed onto plastic and trapped air is then sucked out by a vacuum, once cooled down the plastic is remove and cut
     • Injection Moulding: Highly automated production process for producing loads of identical items. Granulated thermoplastic is heated, melted and then forced under pressure into a mould. the material then cools forming a component in the shape of the mould. HIPS or ABS is used
       • Plastic powder is fed into the hopper, the barrel is surrounded by a jacket of heaters that melt the plastic and a rotating screw pushes the plastic to the end, the screw is forced back as the plastic collects at teh end of the barrel, a hydraulic system pushes the plastic through into the mould, it is then kept in place until the plastic has cooled
         • Blow Moulding: Blow moulding is an automated process that is used extensively to make bottles and other materials with hollow parts. High density polyethylene (HDPE) and low density polyethylene (LDPE) are both commonly used for blow moulding as are other types of thermoplastics
           • The cycle starts with the mould open, a hollow piece of plastic is pushed between the two halves. the mould closes and air is blown inside and the parison inflates pushing the plastic against the cold mould. The plastic is cooled by the mould. Excess material is then cut off
           • Extrusion: This process is like squeezing toothpaste from a tube, its a continuous process used to produce both solid and hollow products that have a constant cross section (e.g hose pipe)
             • Thermoplastic granules are fed from a hopper by a rotating screw through a heated cylinder, the tapered shape compacts the plastic as it becomes plasticised, it is pumped out continuously. The die at the end determines the cross section of the extrusion, as the extrusion leaves it is cooled by passing through cold water
             • Compression Moulding: Oldest commercial moulding process and is mainly used to make products from thermosetting materials. Uses heat and pressure to alter material shape. Done to urea formaldehyde and phenol formaldehyde as they cannot be reheated and reshaped due to a chemical change called polymerisation. Thermosets tend to be stiffer and more resistant to heat and chemical attack than thermoplastic
               • Moulds are made in two parts from steel. Each part of the mould has an attached heater plate and a combination of mould plus a heater. A mould is charged with powder and granules ready to be compressed, the moulds are heated up, when the two halves of the mould are brought together, the plastic material is forced under compression to flow rapidly around the cavity. The mould remains closed for 2-3 minutes
                 • Rotational moulding: A process used for manufacturing hollow shaped products such as footballs, road cones and storage tanks. The moulds can be made from various materials (cast aluminium, steel sheets, beryllium copper or electro form copper nickel). Most mouldings are made from polyethylene. Its extremely cheap to do and can make textured surfaces on the item
                   • An open mould is filled with plastic powder, the mould is closed and begins to rotate, mould is heated and the plastic melts coating the inside, mould is cooled to set the plastic, mould is opened and product is removed
                     • Calendering: Plastic film, sheet and materials such as wall paper and fabrics are produced like this. It involves rolling out premixed plastic material between large rollers to form an accurately sized film. Main materials used include PVC, ABS, Cellulose acetate. PVC ranges from flexible to rigid and the final product is composed of a number of basic materials. Rollers are made of cast iron and heated to 160 degrees
                       • Process begins with the ingredient being blended and fluxed in a mixing mill. The plastic is extruded down the first roller, the rollers then push the plastic along as they are fed through nip rollers which determine the thickness of the plastic. The tension rollers keep the tension, stopping inconsistencies. The plastic is cooled on the cooling rollers
                         • Types of Woods
                           • Man-Made woods
                             • Veneered boards: Ply woods and laminates (done by thin sheets of wood stuck together)
                               • Particle Boards: MDF/ Chipboard hardboard. Chips and wood dust stuck together using special adhesives
                                 • Block Boards: Made of strips of wood glued together
                                   • Natural Woods
                                     • Hardwoods: oak / teak, mahogany, beech / willow. Often comes from trees that lose their leaves in winter
                                       • Softwoods: Pine / spruce, cedar, larch. Softwoods usually come from trees that have needles and evergreens
                                       • Stage one: Tree is cut down
                                         • Stage 2: Logs are stacked in the forest for a year
                                           • Stage 3: Partially seasoned logs are taken to the saw-mill to be cut down
                                             • Stage 4: Logs are cut to planks
                                               • Stage 5: Cut up planks are stacked so that they have spacers between them so air gets to them and seasons them
                                                 • Stage 6: Stacked in a kiln and left for 3 months to dry, can be done outside for a year
                                                   • Stage 7: Once seasoned, wood is cut into useful shapes
                                                     • Stage 8: Timber is now ready to be sold
                                                       • Laminating
                                                         • Laminated wood is manmade and put in layers. They are done in perpendicular directions to each other.
                                                           • To laminate, adhesive is put on the board, then laminate material is put ontop, it is then pushed together with a roller
                                                             • Laminating strengthens the material.
                                                               • Wood Joints
                                                                 • Lap joint: easiest to construct, uses nails or screws with the glue to provide strength. The end grain of one piece will show
                                                                   • Miter joint shows no grain and is difficult to make as it must be cut at 45 degree angles. Finishing nails are often needed with glue for strength
                                                                     • Tongue & groove joint is stronger than the LAP joint but needs more work to create, this joint works well on horizontal pieces like drawer supports
                                                                       • DADO joint is stronger and looks better than the LAP joint. Finishing nails can be hidden. Works well on drawer fronts
                                                                         • Dovetail: Strongest of the joints shown as the two pieces interlock. Requires more work to construct but is considered high quality
                                                                           • Mortise and Tenon: Strong and takes work to construct, works well for chair legs
                                                                             • Dowel: Strong , dowel is made from 25" birch. Often used to join boards along long edges
                                                                               • Wood Preservatives
                                                                                 • Protects wood that are susceptible to fungus and insects and the elements. Soaking timber in a preservactive
                                                                                   • Paint: suitable for internal and external use. Most paint is oil based. Wood needs to be sanded down, primed, undercoated and painted on with multiple layers of gloss, egg-shell or matt paint. The wood needs to be rubbed down between each layer
                                                                                     • Plastic finishes: Polyerethane vanish, the finish may be matt or gloss. Varnish shows the grain and natural colour of the wood and produces a waterproof, transparent finish which can be used internally or externally
                                                                                       • Wax: Produces a dull finish and as varnish shows the natural wood grain. Can be made by shredding bees-wax into turpentine. Inbetween each layer, the wood needs to be rubbed down with fine wire wool. The end finish needs to be polished with a rag
                                                                                         • Oil: Uses teak oil, produces a natural finish. Can use linseed oil but olive oil is used for wood that will come into contact with food. The surface needs regular recoating
                                                                                           • Stain: Can be mixed with varnish to protect the wood. On its own it darkens the wood (wood cant be stained lighter)
                                                                                             • Laminates: This covers the wood in a thin piece of wood that is already finished. Normally used on man-made woods
                                                                                               • Steam Bending:
                                                                                                 • Woodworking technique where strips of wood are steamed and bent around a mold. Uses heat and moisture to make the wood pliable. Can be shaped with various jigs that allow pressure to be applied until the wood dries. Its achieved by placing the wood in a steam chamber subjecting it to saturated 100 degree steam.

3. Hardwoods

   • Beech: Hard wood for furniture, tough and strong and withstands wear and shocks. Don't work outside (not good w/ moisture changes), white/pink colour
     • Oak: Good for boat building, garden furniture. Strong, durable and easier to use than beech. Its heavy and expensive and can be split (erodes iron and steel)
       • Elm: Turnery, Garden furniture (once treated). Its elastic, tough, durable, good for underwater. It will warp unless well-seasoned. The colour is light reddish brown
         • Teak: Ships decks, garden furniture. It is naturally durable due to its oil content. it doesn't corrode iron and steel and its hard
           • Mahogany: Shopping fittings, furniture. Available in wide and long boards, easy to work with and strong. It warps and hardness varies
   • Softwoods
     • Pine: Suitable for all types of inside work, used for wood turning, can be used outside with suitable preservatives. Fairly cheap and readily available, easy to work and finishes well, has lots of knots
       • Parana Pine: Staircases and furniture, best quality softwood. Attractive grain, available in long and wide boards and works easily. Lacks toughness and tends to warp, can be expensive
         • Fir: Outside construction, ladders. Knot free and water resistant (durable and easy). Splits easily.
           • Spruce: outside work, resistant to splitting and easy to work. Small knots