Friday 20 November 2009
Thursday 8 October 2009
Different types of wood
Manufactured board
- We use manufactured board rather than wood because the wood may still be moist and could change shape or rot (a lumber is usually around 70% water).
- Another reason is because it is widely available compared to wood.
- Manufactured board comes in sizes every 3mm. This is because it is much easier and more efficient for manufacturers as well as consumers.
- The average size of a piece of manufactured board is 1.24m X 2.44m (8'X4').
- Woods can be made stronger by laminating with the layers' grains facing the other way each layer.
Different woods
- Plywood: laminated from thin veneers. The main reason for using plywood instead of plain wood is its resistance to cracking, shrinkage, twisting/warping, and its general high degree of strength. Also, plywood can be manufactured in sheets far wider than the trees from which it was made.
- MDF (medium density fibreboard): made by wood chippings and adhesive being compressed together. A problem for manufacturers is that is is sometimes too hard to cut.
- HDF (high density fibreboard): made by the same process but compressed more.
- Chipboard: used in kitchens a lot. It's very cheap to make and relatively strong, so usually a coating is applied over it to make it look good cheaply.
- Blockboard: wood sandwitched between two veneers.
- Aeroply: used in the manufacture of aircraft. Most aircraft have wooden internal frames made from aeroply.
- Maplex: new type of wood recently discovered. It's used in furniture and easy to machine.
Methods of veneering
- There are various ways to make veneers of woods, such as:
- Slice veneering: simply sawing off the thin layers of wood.
- Rotary veneer: this is a more commom method. It involves slicing the wood as the log rotates; the diameter gets smaller. I.e. like a toilet roll.
Types of finish
- Products made from wood, especially for outdoor use, need some sort of protection. The different types of finish for woods are:
- Polyurethane finish: the most common type. It protects the surface and gives a smooth, shiny finish.
- Wood stain: changes the colour of the wood. Doesn't actually protect the wood that well, so there is a need to apply a different finish as well.
- Oils: can be rubbed in to the wood to maintain its matural appearence.
- Preservative: usually used on timbers being used outdoors.
- Paint: gives the wood a strong colour as well as protecting it.
- Another way of protecting timbers is to inject a wood with tanaliser into the wood. This is why some woods look green.
It's only injected 5mm into the surface of each edge.
The process is called tanalising, and lengthens the life of the wood by around 4 times.
Metals
- Before woods, metals used to be the most commonly used material.
- Metals can be split into four different sections:
- Ferrous: contain iron & carbon
- Non-ferrous: do not contain iron
- Ferrous alloy: a mixture of 2 or more metals where at least one contains iron & carbon
- Non-ferrous alloy: mixtures of 2 or more metals that do not contain iron
- We use manufactured board rather than wood because the wood may still be moist and could change shape or rot (a lumber is usually around 70% water).
- Another reason is because it is widely available compared to wood.
- Manufactured board comes in sizes every 3mm. This is because it is much easier and more efficient for manufacturers as well as consumers.
- The average size of a piece of manufactured board is 1.24m X 2.44m (8'X4').
- Woods can be made stronger by laminating with the layers' grains facing the other way each layer.
Different woods
- Plywood: laminated from thin veneers. The main reason for using plywood instead of plain wood is its resistance to cracking, shrinkage, twisting/warping, and its general high degree of strength. Also, plywood can be manufactured in sheets far wider than the trees from which it was made.
- MDF (medium density fibreboard): made by wood chippings and adhesive being compressed together. A problem for manufacturers is that is is sometimes too hard to cut.
- HDF (high density fibreboard): made by the same process but compressed more.
- Chipboard: used in kitchens a lot. It's very cheap to make and relatively strong, so usually a coating is applied over it to make it look good cheaply.
- Blockboard: wood sandwitched between two veneers.
- Aeroply: used in the manufacture of aircraft. Most aircraft have wooden internal frames made from aeroply.
- Maplex: new type of wood recently discovered. It's used in furniture and easy to machine.
Methods of veneering
- There are various ways to make veneers of woods, such as:
- Slice veneering: simply sawing off the thin layers of wood.
- Rotary veneer: this is a more commom method. It involves slicing the wood as the log rotates; the diameter gets smaller. I.e. like a toilet roll.
Types of finish
- Products made from wood, especially for outdoor use, need some sort of protection. The different types of finish for woods are:
- Polyurethane finish: the most common type. It protects the surface and gives a smooth, shiny finish.
- Wood stain: changes the colour of the wood. Doesn't actually protect the wood that well, so there is a need to apply a different finish as well.
- Oils: can be rubbed in to the wood to maintain its matural appearence.
- Preservative: usually used on timbers being used outdoors.
- Paint: gives the wood a strong colour as well as protecting it.
- Another way of protecting timbers is to inject a wood with tanaliser into the wood. This is why some woods look green.
It's only injected 5mm into the surface of each edge.
The process is called tanalising, and lengthens the life of the wood by around 4 times.
Metals
- Before woods, metals used to be the most commonly used material.
- Metals can be split into four different sections:
- Ferrous: contain iron & carbon
- Non-ferrous: do not contain iron
- Ferrous alloy: a mixture of 2 or more metals where at least one contains iron & carbon
- Non-ferrous alloy: mixtures of 2 or more metals that do not contain iron
Thursday 1 October 2009
Woods, Soft & hardwoods, Things to consider, Steam bending & Laminating
Woods
A lumber is a tree that has just been felled, i.e. just after it has been cut down in the forest. The definition of a timber is a wood that's been cut down and processed. This is the next stage from the tree being cut down. You can tell how old a tree is by looking at its anual rings, which are the circular shapes seen when looking directly down at a cross section of the tree. One of these rings is equivelant to one year of growth. Fibres in the trunk run parallel to the annual rings, so the wood can be called 'fiberous'. Another point to note is that 58% of a tree is cellulose and 28% us resin, which protects the tree.
Softwoods & Hardwoods
There are two types of wood, soft and hard woods. Hardwoods generally take longer to grow, and are more dense and robust. Softwoods are more readily available, and some of its species are fast growing. Some examples of hardwood are ash, oak, beech, teak and walnut, and some examples of softwoods are larch, spruce, scot's pine and douglas fir. Hardwoods come from deciduous trees, in the autumn these trees change colour and lose their leaves. Softwoods come from coniferous trees, i.e. trees with needles or cones.
When these woods are cut down as lumbers, they are 70% moisture. In order to dry the wood, there are two main processes used. You can either air dry the material or kill dry it. Air drying is literally stacking the wood and then leaving it for several years. The moisture will evaporate out of the wood and, eventually, leave the material completely dry. Kill drying is leaving a load of wood in an oven - this takes only a few hours as opposed to air drying. However, this is obviously a lot more expensive than air drying.
Things to consider when chosing a wood
There are many factors you need to consider when chosing a wood for a particular job, such as:
- Physical strength: how strong and rigid the wood needs to be
- Aesthetic properties: how the wood looks, e.g. the grains, etc
- Moisture properties: is the wood completely dry for use?
- Protection: for example, varnishing a wooden bench for outdoor use
- Operating conditions: Any particular features of the environment or product the wood's being used in or for
- Costs: How expensive and affordable the wood is, and which is the cheapest wood of that range?
- Sustainability/environmental issues: Consider how many trees are being cut down, as well as the FSC: Forestry Stewardship Council
- Size of boards available: Is there a board of wood big enough for the job or product needed?
Steam Bending
This process is used to bend woods using the pressure and heat from steam. It takes sometimes several hours but gives an end product of a high quality and a good shape.
However, only bentwood can be used in this process. This it because the primary attribute of bentwood is that its grain runs continuously along its entire length and not in any other direction. If the bend is made across more than one axis then the timber will be twisted to align to the grain, so the process will not work. The main advantage bentwood has over other types of wood is its strength, as it won't snap after being bent or under the pressure during the process.
It takes around one hour to steam bend 25mm of ash, and ash is the most common wood used in steam bending.
Laminating
The definition of a laminate is something that is built up in layers. A lamination is the process of joining the layers together. This is a widely used process in industry as it strengthens and thickens a material, and also allows different materials to me mixed into one. For example, plastic laminate is made of composite layers of paper and plastic.
An alternative way of bending wood to steam bending is lamination. There are two main methods of how to laminate woods:
- Laminating using a male & female mould.
- Laminating using a vacuum bag or vacuum frame.
A lumber is a tree that has just been felled, i.e. just after it has been cut down in the forest. The definition of a timber is a wood that's been cut down and processed. This is the next stage from the tree being cut down. You can tell how old a tree is by looking at its anual rings, which are the circular shapes seen when looking directly down at a cross section of the tree. One of these rings is equivelant to one year of growth. Fibres in the trunk run parallel to the annual rings, so the wood can be called 'fiberous'. Another point to note is that 58% of a tree is cellulose and 28% us resin, which protects the tree.
Softwoods & Hardwoods
There are two types of wood, soft and hard woods. Hardwoods generally take longer to grow, and are more dense and robust. Softwoods are more readily available, and some of its species are fast growing. Some examples of hardwood are ash, oak, beech, teak and walnut, and some examples of softwoods are larch, spruce, scot's pine and douglas fir. Hardwoods come from deciduous trees, in the autumn these trees change colour and lose their leaves. Softwoods come from coniferous trees, i.e. trees with needles or cones.
When these woods are cut down as lumbers, they are 70% moisture. In order to dry the wood, there are two main processes used. You can either air dry the material or kill dry it. Air drying is literally stacking the wood and then leaving it for several years. The moisture will evaporate out of the wood and, eventually, leave the material completely dry. Kill drying is leaving a load of wood in an oven - this takes only a few hours as opposed to air drying. However, this is obviously a lot more expensive than air drying.
Things to consider when chosing a wood
There are many factors you need to consider when chosing a wood for a particular job, such as:
- Physical strength: how strong and rigid the wood needs to be
- Aesthetic properties: how the wood looks, e.g. the grains, etc
- Moisture properties: is the wood completely dry for use?
- Protection: for example, varnishing a wooden bench for outdoor use
- Operating conditions: Any particular features of the environment or product the wood's being used in or for
- Costs: How expensive and affordable the wood is, and which is the cheapest wood of that range?
- Sustainability/environmental issues: Consider how many trees are being cut down, as well as the FSC: Forestry Stewardship Council
- Size of boards available: Is there a board of wood big enough for the job or product needed?
Steam Bending
This process is used to bend woods using the pressure and heat from steam. It takes sometimes several hours but gives an end product of a high quality and a good shape.
However, only bentwood can be used in this process. This it because the primary attribute of bentwood is that its grain runs continuously along its entire length and not in any other direction. If the bend is made across more than one axis then the timber will be twisted to align to the grain, so the process will not work. The main advantage bentwood has over other types of wood is its strength, as it won't snap after being bent or under the pressure during the process.
It takes around one hour to steam bend 25mm of ash, and ash is the most common wood used in steam bending.
Laminating
The definition of a laminate is something that is built up in layers. A lamination is the process of joining the layers together. This is a widely used process in industry as it strengthens and thickens a material, and also allows different materials to me mixed into one. For example, plastic laminate is made of composite layers of paper and plastic.
An alternative way of bending wood to steam bending is lamination. There are two main methods of how to laminate woods:
- Laminating using a male & female mould.
- Laminating using a vacuum bag or vacuum frame.
Friday 4 September 2009
I should never have purchased...
A few months ago I bought an Accurist silver watch from Argos. I needed a watch to be more organised and keep track of the time more.
I chose the particular watch in hand because, at first, it looked good and it appeared to be reasonably aesthetic; it was sliver and shiny with big hands and a large clock face. It had extra features such as showing the date, glow in the dark hands and an adjustable strap. So, with a price of £35.00, overall the watch seemed great value for money.
However, a couple of weeks after purchase, the product seemed not to live up to what I had assumed it was going to be like. The wrist strap began to get laced in very noticeable scratches and scuffs, with the silver paint wearing off and revealing a very dull metal surface underneath. I was not using the watch excessively or when it could have got damaged (i.e. when playing sport or in the rain). I was only mainly wearing it to school, so clearly there was a problem with the quality of the watch’s silver paint. Furthermore, although the watch hadn’t stopped ticking, every week or two I noticed how it had become five or ten minutes fast, meaning I had to reset the time regularly.
I began to realise that the quality of the product was not sound and regretted buying the watch. Although it looked good at first, it turned out not to be practical or a good buy.
I chose the particular watch in hand because, at first, it looked good and it appeared to be reasonably aesthetic; it was sliver and shiny with big hands and a large clock face. It had extra features such as showing the date, glow in the dark hands and an adjustable strap. So, with a price of £35.00, overall the watch seemed great value for money.
However, a couple of weeks after purchase, the product seemed not to live up to what I had assumed it was going to be like. The wrist strap began to get laced in very noticeable scratches and scuffs, with the silver paint wearing off and revealing a very dull metal surface underneath. I was not using the watch excessively or when it could have got damaged (i.e. when playing sport or in the rain). I was only mainly wearing it to school, so clearly there was a problem with the quality of the watch’s silver paint. Furthermore, although the watch hadn’t stopped ticking, every week or two I noticed how it had become five or ten minutes fast, meaning I had to reset the time regularly.
I began to realise that the quality of the product was not sound and regretted buying the watch. Although it looked good at first, it turned out not to be practical or a good buy.
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