Thursday, 26 November 2009
Friday, 9 October 2009
Metal Processes
Plasma Arc Cutting
- Components are drawn using CAD software.
- Exported as DXF file.
- Sent to a nesting program which arranges components in a way that creates least waste.
- Sheet metal is placed on the bed of the cutter.
- Design is cut out using a high heat plasma arc.
- Components are finished and ready for machining.
Sand Casting
- A metal box is partly filled with sand and resin.
- A shape made of wood or plastic is placed on to the first layer.
- The box is filled up with the rest of the resin and sand.
- The mixture is left to dry and the shape mould is taken out.
- Molten metal is poured into the mould and left to cool.
- The sand is taken away, leaving the shape formed in metal.
- The piece is now ready for polishing.
Thursday, 8 October 2009
Metals
Types of metals
The range of metals are classified as ferrous and non ferrous.
Metals can then be separated under alloys and non alloys.
Ferrous metals- Metals that contain iron and carbon.
Non ferrous- metals that do not contain iron.
Ferrous alloys- A mixture of two or more metals. At least one of which contain iron and carbon.
Non ferrous alloys- A mixture of two or more metals. Non of them containing iron and carbon.
Mild steel- Quite strong and cheap, rusts easily. Cant be hardened or tempered.
- Car bodies
- Nuts and bolts
High carbon steel- Harder than mild steel and can be hardened and tempered. Difficult to work with and rusts.
- Drills
- Tiles
- Chisels
- Saws
Cast iron- Hard, however brittleorder impact.
- Machine parts
- Brake disks
- Engines
Non- ferrous metals
Aluminium- Light weight and corrosion resistant. Expensive and not nearly as strong as steel.
- Aeroplanes
- Cars
- Ladders
Brass- Quite strong, corrosion resistant, malleable, ductile and looks good.
- Door furniture
- Electrical parts
Copper- Relative soft, malleable and ductile and a very good conducter of electricity.
- Wires
- Pipes
Ferrous alloys
- Stailess steel
- High speed steel
- Die (tool) steel
Non ferrous
- Brass
- Bronze
- Duraliumin
The range of metals are classified as ferrous and non ferrous.
Metals can then be separated under alloys and non alloys.
Ferrous metals- Metals that contain iron and carbon.
Non ferrous- metals that do not contain iron.
Ferrous alloys- A mixture of two or more metals. At least one of which contain iron and carbon.
Non ferrous alloys- A mixture of two or more metals. Non of them containing iron and carbon.
Mild steel- Quite strong and cheap, rusts easily. Cant be hardened or tempered.
- Car bodies
- Nuts and bolts
High carbon steel- Harder than mild steel and can be hardened and tempered. Difficult to work with and rusts.
- Drills
- Tiles
- Chisels
- Saws
Cast iron- Hard, however brittleorder impact.
- Machine parts
- Brake disks
- Engines
Non- ferrous metals
Aluminium- Light weight and corrosion resistant. Expensive and not nearly as strong as steel.
- Aeroplanes
- Cars
- Ladders
Brass- Quite strong, corrosion resistant, malleable, ductile and looks good.
- Door furniture
- Electrical parts
Copper- Relative soft, malleable and ductile and a very good conducter of electricity.
- Wires
- Pipes
Ferrous alloys
- Stailess steel
- High speed steel
- Die (tool) steel
Non ferrous
- Brass
- Bronze
- Duraliumin
Non ferrous
- Brass
- Bronze
- Duraliumin
Where does metals come from ?
Gold is the only metal that is extracted and usable without processing. All other metals and found as ores.
Common metals ores
- Iron- Magnnetite, heamatite
- Copper- Chalcopyrite
- Tin- Cassiterite
- Aluminium- Bauxite
- Lead- Galena
- Zinc- Zinc blende
25% of the earth crust is made of ores. the more rare, the more expensive it is. Aluminium is the most common.
Iron is converted from its ore by heating. The resulting impurities (slag) are removed from the furnace leaving a soft greyish metal once it has cooled. Iron is rarely used without combining it with carbon, gibung it a greater strength. The result in this combination is steel.
Steel- Iron and carbon. The amount of carbon determines on the strength. Alloymy increases properties- toughness and corrosion.
Carbon- found in the earth and is made up of coal and diamond. Amount of carbon in steel determines strength and hardens BUT increases how brittle.
More carbon= more hardness/ less dutcile/ more brittle.
Non ferrous metals doesnt contain iron.
Metals Melting point (degrees) Uses
Aluminium 660 Saucepans and kitchen tools
Copper 1083 Water and gas pipes- wire
Gold 1063 Jewellery
Lead 330 Construction, roofing
Monday, 5 October 2009
Man Made Boards And Finishes
Polyurethane varnish-(Spray) used to seal and protect the surface of wood to give it a smoother finish. There is clear or coloured, in gloss, silk or matt finish.
Wood stain- applied to enhance apperance of wood grains. Natural colours or in some brighter colours such as red or blue etc. It doesnt usually protect the wood but varnish may be applied afterwards to protect.
Oils can be used to maintain the natural apperance. Some oil- based finishes also offer protection used outdoors.
Preservatives are generally applied to timber that is used outdoors. Enhances the apperance of the timber but will extend the useful life of timber, as much as 3 or 4 times.
Paint can be used on any wood but it has to be primed first. Paint has something to adhere to. Oil base paints are used.
Man made wood- No moisture content. Will not bow or bend. Will not moved.
MDF- (Medium density fibre board) Cheap. Wood chippings and glue then pressed to make a block of wood. Glue is stronger than normal wood so the tools used to cut it would blunt more quickly.
Plywood- Alternating grain at 90 degrees to eachother to improve strength.
Veneered- Thin slie of wood.
Chipboard- Chipping glued together. Blunts toold quickly. If you buy it in the shop you can get it as thick as you like. Strongerthan MDF. Kitchen work surfaces are made out of this with a thick layer of laminate on the top.
Hard board- Not hard at all. Fibreous- takes on water. Breaks easily. Very cheap.
Block board- Veneered around the top and bottom with a block of wood in the middle.
Man made wood-
3, 6, 9, 12, 15, 18, 21, 24 mm- Width
2440- Length
1120- Height
Flexi MDF- Groves on one side of the wood. Bends and curves into the shape wanted easily without snapping.
Flexi ply- Groves on one side of the wood. Bends and curves into the shape wanted easily without snapping.
Aeroply- Posh plywood. Used for the outer skin of an aircraft- basically a thin section. A very high grade plywood stuck to a timber frame.
maplex- New type of MDF that is used for the furniture industry. This composite is a higher grade and easier to machine. This is expensive.
Wood stain- applied to enhance apperance of wood grains. Natural colours or in some brighter colours such as red or blue etc. It doesnt usually protect the wood but varnish may be applied afterwards to protect.
Oils can be used to maintain the natural apperance. Some oil- based finishes also offer protection used outdoors.
Preservatives are generally applied to timber that is used outdoors. Enhances the apperance of the timber but will extend the useful life of timber, as much as 3 or 4 times.
Paint can be used on any wood but it has to be primed first. Paint has something to adhere to. Oil base paints are used.
Man made wood- No moisture content. Will not bow or bend. Will not moved.
MDF- (Medium density fibre board) Cheap. Wood chippings and glue then pressed to make a block of wood. Glue is stronger than normal wood so the tools used to cut it would blunt more quickly.
Plywood- Alternating grain at 90 degrees to eachother to improve strength.
Veneered- Thin slie of wood.
Chipboard- Chipping glued together. Blunts toold quickly. If you buy it in the shop you can get it as thick as you like. Strongerthan MDF. Kitchen work surfaces are made out of this with a thick layer of laminate on the top.
Hard board- Not hard at all. Fibreous- takes on water. Breaks easily. Very cheap.
Block board- Veneered around the top and bottom with a block of wood in the middle.
Man made wood-
3, 6, 9, 12, 15, 18, 21, 24 mm- Width
2440- Length
1120- Height
Flexi MDF- Groves on one side of the wood. Bends and curves into the shape wanted easily without snapping.
Flexi ply- Groves on one side of the wood. Bends and curves into the shape wanted easily without snapping.
Aeroply- Posh plywood. Used for the outer skin of an aircraft- basically a thin section. A very high grade plywood stuck to a timber frame.
maplex- New type of MDF that is used for the furniture industry. This composite is a higher grade and easier to machine. This is expensive.
Natural Woods
Structure
Wood is fiberous with the finbres running along the length of the trunk.
55% of the tree is cellulose, 28% of the tree is lignin resin- holds the structure of the tree together.
Timber is therefore a natural reinforced polymer.
Harvesting- cutting he tree down.
Conversion- Cutting trunk and large branchees into boards.
- Slab sawn
- Quarter sawn.
Seasoning- reducing the moisture content of thew timber.
- Natural seasoning
- Kiln seasoning
Board preparation- sawn to size and planning. eg, PAR (planed all round)
Slab or plain sawnig uses the whole tree- no waste. BUT- not as stable- more liable to warp and twist.
Quarter sawn timber is commonly used for expensive hardwood timbers. More waste and more stable. Less liable to warp and twist- often exposed more attractive grain structure.
Wood is fiberous with the finbres running along the length of the trunk.
55% of the tree is cellulose, 28% of the tree is lignin resin- holds the structure of the tree together.
Timber is therefore a natural reinforced polymer.
Harvesting- cutting he tree down.
Conversion- Cutting trunk and large branchees into boards.
- Slab sawn
- Quarter sawn.
Seasoning- reducing the moisture content of thew timber.
- Natural seasoning
- Kiln seasoning
Board preparation- sawn to size and planning. eg, PAR (planed all round)
Slab or plain sawnig uses the whole tree- no waste. BUT- not as stable- more liable to warp and twist.
Quarter sawn timber is commonly used for expensive hardwood timbers. More waste and more stable. Less liable to warp and twist- often exposed more attractive grain structure.
Timber shinks most along the annual ring. Salb sawn board- long annual ring- lots of shrinkage- result.
Quarter sawn board- shorter annual ring- very little shrinkage- stable.
Planed timber
- PAR- planed all round.
- PSE- planed square edge.
Sawn in inches, planned in cm.
Timber mouldings- multi cutter.
Edge jointing narrow timber to make wider boards.
- It stays straight because the wood is working against itself.
No two pieces of wood are the same colour. There is a huge variety of colour and grain pattern.
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