DT (Resistant Materials) 2015

DT (Resistant Materials) 2015

1. Metals

   • Types
     • Ferrous
       • Are Magent
         • Because there have iron in them that makes them magent.
         • Stainless steel does not rust and some of te grades of Stainless steel is not magnet.
       • Are prone to rusting
       • Example
         • Iron
         • Mild steel
         • Tool Steel
         • stainless steel
         • Cast Iron
     • Non-Ferrous
       • Don't have any iorn in them
         • so thay are not magent and do not rust when exposed to moisture
           • But that do tarnish and oxidise.
       • Example
         • Copper
         • Alumonoum
         • Tin
         • Zinc
     • Alloys
       • are a combined materials. Alloys are metals that contain two or more elements.
         • The elements that make up the alloy may be metal and non-metal.
       • Example
         • Pewter
         • Brass
       • Alloys are chosen for a particular purpose.
         • Because of there properties they have.
           • Example
             • Low melting [oints
             • corrosion resistance
             • overall wight
   • Propteys of metals
     • Workability
     • Appearance
     • Structural strenght
   • Joining
     • Welding
     • Soldering
     • Nuts and bolts
     • Rivets
   • Hardening
   • Finishing

2. Plastics

   • Types
     • Thermosetting
       • Example
         • Epoxy Resin
           • Used in castings, printed circuit boards (PCBs), surface coating, araldite glue.
         • Polyester Resin
           • Used in laminated to form glass reinforced plastic (GRP) castings, encapsulations, car bodies, boats.
           • Polymerises at room temperature
           • Often reinforced with glass fibre.
         • Melamine formaldehyde
           • Used in Tableware,, elecctrial installations, synthetic resin paints, decorative laminates, worktops.
         • Phenol Formaldehyde
           • Used in dark coloured eletrical fittings and parts for domestic appliances. Kettle iron saucepan handles
           • Also know as phenol Methanal (PF) or bakelite
           • Hard, and brittle
           • heat resistant
           • Dark colour with a glossy finish
         • Urea Formaldehyde
           • Used indoor and cupboard handles, electrical switches, electrical fittings.
           • colourless
           • Coloured with pigments.
     • Thermoplastics
       • Example
         • Rigid PVC (polyvinyl chloride)
           • Used in Air and water pipes, chemical tanks, shoe soles,shrink and blister packaging, floor and wall coverings.
           • Stiff and hard wearing
           • Plasticiser can be added to create a softer, more rubbery material.
         • Acrylic (polymethyl-methacrylate)
           • Used in Display signs, Baths, roof light, machine guards.
           • known as perspex
           • Glass-like transparency or opaque. an be coloured with pigments.
           • Hard wearing but will shatter if treated roughly.
         • Nylon (Polyamide)
           • Used for Curtain rail fittings, Combs, hinges, bearings, clothes, gear wheels
           • Hard material
           • Good resistance to wear and tear.
           • Sold nylon has low friction qualities and hight melting point.
         • High Impact Polystyrene (HIPS)
           • Used in Vacuum forming, very common for school projects
           • light but strong
           • softens at 95C
         • Polypropylene (PP)
           • Used in bottle crates and boxes, medical equipment and syringes, food containers, nets, storage.
           • high impact strength
           • softens at 150C
           • flexed many times without breaking
         • Polythene (low density) LDPE
           • used in packaging, film, carrier bags,toys, 'squeezy' detergent bottles
           • stiff, strong plastic
           • Softens at 85C
         • Polythene (high density) HDPE
           • Stiff and strong plastic
           • Softens at120-130 C
           • Used in pipes and bowls,milk crates, buckets
   • Jioning
     • Nutes and Bolts
     • Adhesives and solvents cement
       • most common solvent cement is dichloromethane which dissolves the surface of hard plastics.
         • E.G. Acrylic and jight impact polystrene.
   • Finishing
   • Moulding
     • Line Bending
       • Heats a line of the plastic so it can be bent along that line.
     • vacuum forming
       • Is where a sheat of thermoplastic is headed.
         • Then a mould is lifted up in to the thermoplastic then vacuum holds it on to the mould.
           • Then the mould is lowered.
     • yoke moulding
       • Plastic heated then when malleable them mould foce it in to the yoke.
     • injection moulding
       • Plastic powder or granules that are fed in to a hopper that are heated then foces it to a mould at the end of the hopper. when the plastic is cool down the mould splits to remove it on the mould.
     • Extrusion moulding
       • Plastic powder or granules that are fed in to a hopper that are heated then foces it to a die in a continuous stream that create a long tube or setional extrusions. Then past through a cooling chamber then cut to length.
     • blow moulding
       • Plastic powder or granules that are fed in to a hopper that are heated then foces it to a mould that has air being blown in to foce the plastic to the out side. then the mould spilt to reov the moulding.
     • rotational moulding
       • It a alternative to.
         • Blow moulding
         • Injection moulding
       • It's done by puting plastic in to a mould that splits apart. then the mould is closed and heat is appllied while the mould is being rotated. This lines the inner surface with plastic. when cooling the mould is opened and the product is ejected.
     • compression moulding
       • A slug of thermosetting plastic is place in a mould that is heated then a hydraulic press spuash the slug what a large force.

3. Wood

   • Types
     • Soft Wood
       • Fast growing
       • Example
         • Pitch pine
         • Western Red Cedar
         • Parana pine
         • Scots pine (Red deal)
         • Yew
       • They come from coniferous trees that have needles rather than leaves.
       • usually softer to work
       • Cost less
     • Hard Wood
       • Grow slow
         • But can be harder than other woods
       • Example
         • Beech
         • Oak
         • Ash
         • Mahogany
         • Teak
       • Cost more
     • Manufactured boards
       • Made by Gluing together wood layers (veneers) or wood fibres.
   • joints pages 43-46
     • simple joints
       • Butt jiont
         • A weak jiont
         • Often used in picture frames.
       • Halving joint
         • Can be strengthened with dowel through the joint.
         • Used to frame
       • Dowel joint
         • Easy too make
         • used in frame and carcase joints for chair legs and cupboard corners.
       • Lap joint
         • stronger than as butt joint. (as it has a bigger surface area for gluing.)
         • Often strengthened with nails.
         • Used in frame and carcase joints.
       • housing joint
         • simple slot cut in to a piece. (to make a support fo a cupboard shelf ans increase the gluing area.)
         • Made using ellectrically-powered router
     • Complicated joints
       • Mortise and Tenon
         • strong joint
         • Used in frame joints for chair and table legs.
       • Dovetail Joint
         • Strongest joint for box constructions in natural wood
         • Used in carcase joints for cupboard corners and drawer constructions.
     • Temporary joints
       • Screw
         • Strong across the grain
         • Use to fix other materials as metals or plastics to timber.
       • Nail
         • Make weak joints on there own.
         • For holding wood while glue dries.
         • Fixing the backs of cupboards.
         • Decorative mouldings.
     • Permanent joints
       • Biscuit Joint
         • At anght angles
         • side by side to make wider boards.
         • Slots are made in the board using an electrically powered cutter. the biscuits are elliptical pieces of timber, which have beed dried and compressed then fixed with glue.
     • Knock-down fittings (KD)
       • Cam Bolt
       • Cabinet Screws
       • Pronged Nut
       • Cross dowel
       • Modesty Blocks
     • Glue
       • Polyvinyl acetate {PVS)
         • Is water based adhezive that soaks into the surface of the wood and sets where all water is absorbed.
       • Hot melt glue (Hot Glue)
         • Used for quick modelling.
         • Difficult to control
         • not used in final products
       • Epoxy resin
         • very versatile
         • Expensive
         • Sticks most clean and day materials together.
         • When equal amount of resin and hardener are mixed together and it sets chemically that is very hard.
       • Latex adhesive
         • rubber solution
         • cheap and very safe
         • Used for gluing felt into a box.
       • Contact adhesive
         • ideal for gluing plastic laminated to chipboard.
         • Both surface are coated and allowed to be become touch-day. adhesion happens when the two surfaces meet.
   • Finishing
     • Sanding sealer/ french polish
       • Quick-drying liquid seals the surface but raises the fibres of the timber.
         • Meaning they have to be cut back (rubbed down) with a fine abrasive paper.
       • suitable as a first coat before applying varnish or wax polish.
     • Polyurethane varnish
       • tough and heatproof
         • As well there being waterproof finish available.
       • Different colours and matt, satin or gloss surface finish.
     • cellulose
       • Quick-drying finish thats hard.
       • Use for wood turning.
     • polish
       • is applied to wood to
         • Protect from moisture.
         • Protect from insect attack.
         • Enhance colour of the grain
         • Make it easier to wipe the surface clean.
     • wax polish

4. Production and Manufacture