Tanalising

Tanalising is simply the process of where a highly toxic blend of copper and arsenic is vacuum pressure impregnated into softwood and is used as a preservative. This treatment process ensures deep penetration into the timber cells, for a longer lasting protective result against fungal decay and insects than the application of a surface coating.

The stages of tanalising

1) The tanalising process involves placing the timber in to a treatment cylinder and creating a vacuum withing the timber vessels.

2) The cylinder is then flooded under vacuum with the preservative treatment

3) Hydraulic pressure is applied forcing the preservative deep into the timber and its cells

4) After a pre-determined period of pressure depending on the species of the timber being treated and its use, the treatment solution is pumped back into storage and a final vacuum extracts any excess treatment solution

5) Finally, low pressure inside the timber draws the surface solution when vented to the atmosphere and the treated timber is left for a specified period for fixation of preservative to occur.

Tanalised timber does not need any further maintenance treatment but will naturally weather over the months finally changing to a grey colour. This is caused by the effect of sun, moisture, wind and other exterior conditions. The timber will produce cracks  that will open and close as an effect of condition changes. They are not detrimental to the long term durability of the product.


Here are pictures illustrating the process of tanalising.

Woodworking joints

Corner Mortise and tenon joint:

Corner mortise and tenon joints are used on tables and front legs or chairs where two rails are joined to a single legs at each corner. The end of the tenons are mitered where they meet inside the leg. The tenon is cut to fit the mortise hole exactly and usually has shoulders that seat when the joint fully enters the mortise hole. The joint may be glued, pinned, or wedged to lock it in place.

Forked mortise and tenon joint:

Forked mortise and tenon joints are found as the end of lock rails on large frame and panel doors. The gaps between the tenons should be no more than one third the width of the rail, this is so that it minimizes the amount of movement in them. The joint can be given extra strength by inserting a wedge at the end of the tenons.

Dowel joint:

Dowel joints can most commonly be found in factory made furniture E.G. When joining rails or 

feet to round legs, it is easier to use dowel joints over mortise and tenon joints. Using dowels in furniture ensures an accurate fit as it is easy to locate the hole and with 2 dowels inserted into the joint it makes it really accurate. Dowel joints are also good because they come in all varieties of size from 4-25mm and have a grooved surface so that the glue can flow easily along the dowel after being inserted into the hole.

Dovetail joint:

A dovetail joint is mostly used in the corners on the backs of drawers, the tapered shape of the tails resists the forces applied to the joints when the drawer is being used. Apart from being a strong joint it can also be used for decorative purposes and to make something look nice. Dovetails consist of one piece having the tails and the other piece having the pins that fit into the tails.

Finger joint: 

Finger joints are fairly easy to make as there are no dovetail styled angles involved in them. The large gluing gives the joint it's strength from each 'finger'. The finger joint can also be valuable when fixing tables and chairs and also can be used in such things as floor boards, timber roof and door construction. To visualize a finger joint simply interlock the fingers of your hands at a ninety degree angle

 

Steam bending processes

Steam bending

Steam bending is a woodworking technique where strips of wood are steam heated using a steam box. The applied heat and moisture makes it easy enough to bend the wood around a mould to create a shape. The moulding process is usually done putting the strips of wood in to a former, with the strips of wood often reinforced on the outside with a metal band to prevent the machine blowing out. Some examples of where you would use steam bending would be in the production of lacrosse sticks, violins and in manufactured wood furniture such as the Windsor chair. Steam bending can also be used to make big things such as the wood frame of a boat hull and lap boards.

Steam bending is also a low energy and economical method of manipulating wood. It doesn't need the expense or drying time of glues to join together several wood pieces to make the desired shape. Steam bending also leaves lower levels of scrap since a smaller piece can bent into shape instead of cutting the desired shape away from larger stock.Steam bending is limited in how much you can actually bend the wood without it breaking, especially for thick wood. Not all species of wood steam-bend well and problems can be that it weakens the wood slightly and can leave residual stresses which may cause breakage or spring-back over time.

After the wood has been steamed, it is to be taken out of the steam box and then placed straight into a former/jig. This is because the wood will contain a lot of moisture after steaming and will be easy to bend. If you put clamps on the jig with the steamed wood in it, it normally expels the moisture quicker and lets it dry faster. After you put it into the jig you clamp it together and wait until it dries. When you take it out it should have taken the shape of the jig. To help it dry faster you can also put it in a kiln to get rid of the moisture in the wood, you can use a variety of controls from temperature to air flow to get rid of some of the moisture and keep the desired amount of moisture in it.

Manufactured boards

Plywood

Plywood is an engineered wood product made from thin sheets of wood veneer. It is commonly used instead of timber because of it strength and superior resistance to cracking, shrinkage, twisting and warping. Plywood, depending on how thick it is can be malleable, plywood comes in a range of thicknesses, from 6.5mm – 35mm. Plywood has multiple end uses including:

Skateboard ramps
Indoor furniture
Garage doors
House boats
Skateboards
Plywood can even be as a cement casting, this is normally made from shuttering plywood, a very cheap wood.

Hardboard

Hardboard also called high-density fibreboard is a type of fibreboard, which is an engineered wood product. It is similar to particle board and medium-density fibreboard but is a lot denser and stronger than it because it is made out of exploded wood fibres that have been heavily compressed. Hardboard can come in a range of thicknesses ranging from 3mm thick – 6.4mm thick.

Hardboard can be used for plenty of things such as:

Flooring
Furniture
Automobiles
Skateboard ramps
Clipboards

Chipboard

Chipboard, also known as particle board, is an engineered wood product manufactured from wood chips, sawmill shavings, or even saw dust, and a synthetic resin such as glue or other suitable binder, which is pressed and then extruded. Chipboard comes in 12mm –18mm thickness. There are plenty of things that chip board can be used in, these include:

Indoor furniture
Flooring
Counter tops
Doors
Packaging

Block board
Block board is a wood that is made up of loads of wooden block strips. The places are placed edge-to-edge and are compressed between wooden veneers while being glued. Block board usually comes in a 28mm- 30mm thick board. These are multiple uses for block board, these are:

Tables
Doors
Shelves
Panelling
Partitioning walls

The processes used to dry timber.

Seasoning of woods (reducing the moisture content)


Air drying:
Air drying is the process of drying the timber through exposing it to the air. The technique of air drying consists of making a stack of sawn timber separated by stickers, on raised foundations, in a cool, dry place. The rate that the wood is dries depends on the climate conditions and on air movement. For the wood to be dried successfully it has to be exposed to a continuous flow of air. The loss of moisture can be controlled by coating the planks of timber with a substance that is impermeable to moisture such as mineral oil.

 
Advantages – It can be less expensive to use this drying method and air drying often produces a higher quality of wood and the finished wood is more workable than the finished wood that comes out of kiln drying.

Disadvantages- Depending on the climate of the place you are drying the timber in, it takes several months up to a number of years to air dry the wood, and kiln drying can dry wood a lot quicker than this. Another disadvantage of air drying could be that the wood has to be put somewhere, which takes up space which could also cost some money for the company and that there is little to no control over the drying elements so drying degrade cannot be controlled. If air drying is done improperly and is exposed to sun, the rate of drying may be too quick and will cause the wood to crack and split, if it is done in winter, the opposite may happen and it may take too long to dry.

Kiln drying:
Kiln drying is done by introducing head to the wood. This can be done using natural gas or electricity, through steam heated machines. In this process you can control the temperature, the humidity and air circulation at various stages, the quality of the finished and dried wood that comes out of the kiln often depends on how you controlled each variable. In this machine the wood is stacked in chambers called wood drying kilns which each have equipment that helps it dry faster by increased air circulation and control of temperature. This process over comes the limitations introduced by the climate and weather conditions. In this process the timber can be dried to any moisture content, but in air drying, achieving a moisture content that is under 18% is difficult in most locations.

Here are some pictures of kilns and stacks of timber being put into them.
Advantages- Some advantages of kiln drying is that the temperatures that are introduced during kiln drying are above 60 C which kills of all the fungi and insects that are in the wood, this isn’t really guaranteed in air drying. Another advantage of kiln drying is that the time it takes to dry a load of timber is considerably less than that of air drying as the heat introduced during the process speeds it up rapidly. Also, in kiln drying you can control all of the variables such as moisture content, temperature and air circulation, so overall better control, you would not have much control over that in air drying.

Disadvantages – Depending on the species of wood you are trying to dry, overall is a lot more expensive than air drying, you also need to build the kiln or have it put in costing extra money. Also, as you can control the variables, some people may tune them at different levels and may dry the wood too quickly; this can also result in internal stresses such as splitting and warping.

What plastics are used for and why
ABS - Acrylonitrile butadiene styrene
Bb/airsoft rifles are made out of ABS plastics because it is impact resistant and is very strong, bb guns take a lot of beating and is thrown around when on the field, so this material is useful for this. Most pieces of the air rifle like he internals are made from injection moulding but the outside is normally metal, or if it's all plastic it would have been vacuum formed.

CA - Cellulose acetate
Cellulose acetate magnetic tape was introduced by IBM for use on their tape drive. It was much lighter and easier to handle than the metal tape. It was used for many reasons because the cellulose acetate is really tough and strong, and is transparent so can be printed on. Magnetic tape would normally be poduced using a machine called and extruder, the process itself is called extrusion moulding.

NYLON – Polyamide
One thing that can be made out of nylon is parachutes. This material is used because it is strong, springy, light weight, easy to pack, not too expensive and is elastic. Another important property of Nylon is that it resists wear. The parachutes are made from webbing the material together

PMMA – Acrylic
Rear lights on cars can be made out of acrylic, this is because acrylic can come in a wide variety of transparencies and colours, this make it an ideal material for the rear lights of cars. Acrylic is also good for lights because it is resistant to inorganic acids, extremely rigid with good Ultra Violet Resistance. The PMMA car lights are normally vacuum formed or pressed together.

PP – Polypropylene
Plastic garden chairs can be made out of polypropylene, this is because PP is light, tough, has good resistance to chemicals and resists work fatigue, this makes it an ideal material for this chair and garden chairs tend to be thrown about a lot. The plastic garden chairs are most commonly injection moulded.


HIPS - High impact polystyrene
High Impact Polystyrene is a versatile, economical and impact-resistant plastic that is easy to machine and fabricate. High Impact Polystyrene is often specified for low strength structural applications when impact resistance, machinability, and low cost are required. This is commonly used to wrap up electronics and other delicate products when shipping. High impact polystyrene that is used to protect electronics is nomally pressed over a mould.

PS – Polystyrene
Polystyrene cups are made from polystyrene for many reasons, this includes the material being light, hard, and stiff and has good water resistance, this is an ideal material for this product as its main purpose is to hold liquid such as water! Polystyrene cups are made by getting the material and pressing it into a shape using a machine.

LDPE - Low density polyethylene
LDPE is commonly used in bubble wrap to wrap up products when shipping; this is because it is soft, flexible and has a good resistance to chemicals. This can keep the product safe. Bubble wrap is made by having layers laminated together to stpo the air that has ben injected into the bubble from coming out.

HDPE - High density polyethylene
HDPE is used in bottles because it is stiff, strong, tough, resistant to chemicals and moisture, permeability to gas, easy to processing, and easy to form. The bottles are made by blow moulding where a pipe of heated HDPE is put into a machine and then gets pressurized air blown into it so it fits the mould.

uPVC - Polyvinyl chloride uPVC can be used to make window frames and door frames, this is because it is strong, waterproof and has an agent in it that makes it resistant to ultra violet light, meaning that it will keep the colour it has originally come in. Sections of the window are made from an extruder machine and are then welded together to make the shape of the window frame.
 
PVC - Unplasticated flexible polyvynal chloride
PVC is used in PVC piping, this is because it is very flexible, very strong, waterproof, its low cost and it being chemical resistance. PVC pipe is made using a machine called an extruder, PVC plastic is directed through a double screw stem, moulded the wall to thickness and the distance of the pipe, this is called extrusion moulding.

PET - Polyetheylene terepheluate
PET can be used in many things such as bottles, this is because it is hard, stiff, strong and is a stable material that absorbs very little water. It has good gas barrier properties (for carbonated drinks) and good chemical resistance. These bottles are made from where the bottle gets blown into a mould, this is cheap and has no waste materials.

PC – Polycarbonate
Polycarbonate is a versatile, tough plastic used due to its strength and it’s lightweight properties. It has a variety of uses electronic components, construction material, data storage e.g. DVDs, water bottles, construction of airplanes and cars. In addition to this, due to its strong nature and its high refractive index, it is used to make bulletproof glass and optical lenses. The products made from this are usually made from blow moulding or vacuum forming

Rotation moulding:
Rotation moulding is a process mainly to create hollow shaped products such as balls. The machine works by having 3 separate arms that rotate around a central point, these stop at different stages, otherwise known as processing points. Moulds are attached to these arms and are rotated throughout the moulding process. The only times in which they are not being rotated is the first stage (where the moulds are filled with the plastic granules) and the final stage (where the product is removed).

The stages of Rotational moulding:
1- The first stage of rotational moulding is simply filling the mould with thermoplastic granules/pellets
2- The second stage would consist of transferring the mould into an oven chamber where the plastic is heated to mould to the shape of the cavity
3- The machine then rotates with heat, after this the mould is put in to a cooling chamber where it is cooled by cold air or jets of cold water.
4- The final stage is when the product has been cooled; it is removed from the mould as a complete product.

Extrusion moulding:
This product can be compared to toothpaste being squeezed from the tube. It is a continuous process that can be used to create solid and hollow products that have the same cross section throughout. It cannot create a shape with an alternating cross section as the die is one solid shape.

The stages of Extrusion moulding:
1- Thermoplastic granules are put into a hopper which are then fed through the machine by a rotating screw that runs throughout the whole machine, this runs through the heating area, where when the plastic granules run through it, are melted down into liquid.
2- The plastic granules are given a plasticiser after being heated, which adds a flow property making it easier to flow through the die
3- As the plastic flows through the mould; it is cooled by water coolers so that it comes out the other side as a hard, solid shape.

Injection moulding

Injection moulding is a manufacturing process for producing parts by injecting material into a mould. Injection molding can be performed with a number of different materials, including metals, glasses and most commonly thermoplastic and thermosettingplastics. Material for the part is put into a heated barrel, mixed, and forced into a mould  where it cools and hardens to the shape of the mould. 
What is a 'jig' and what is the purpose of one?
A jig is a type of custom-made tool used to control the location and/or motion of another tool. A jig's main purpose is to provide a stable working envrionment for the product making them able to accurately repeat a product. A jig is often confused with a fixture; a fixture holds the work in a fixed location. A device that does both functions (holding the work and guiding a tool) is called a jig.

Thermoplastics:
There are no links inbetween the polymer chains of thermoplastics, this means they can be recycled as they can be heated and re-moulded over and over

Thermosetting plastics: They can not be re-heated and re-moulded because the polymer chains have links in between each one making it a rigid structure


Properties of plastics 
Good thermal and electrical insulators 
Good straight against weight ratio 
Good resistance against chemical and atmospheric erosion (doesn't decompose)
Low melting point
Available in wide range of colours and transparency
Two main categories thermoplastic and thermosetting plastics


Ways to improve properties of plastics
Fillers: fillers are used to bulk up plastics and means that they can get a more plastic without using up loads of crude oil
Flame retardants: This is used to help reduce the risk of combustion
Anti static agents: Reduces the effects of static charges (Can be used in carpets)
Plasticisers: makes material less brittle and improves the flow properties
Stablisers: reduce the effect the ultra violet light has upon the object so that the colour of the plastic isn't lost (Outdoor benches or Window frames)


Types of thermoplastics
ABS -  Acrylonitrile butadiene styrine
CA - Cellulose acetate
NYLON - Polyamide
PMMA - Acrylic
PP - Polypropylene
HIPS - High impact polystyrene
PS - Polystyrene
LDPE - Low density polyethylene 
HDPE - High density polyethylene
uPVC - Polyvynal chloride 
PVC - Unplasticated flexible polyvynal chloride 
PET - Polyetheylene terepheluate
PC - Polycarbonate 

Types of thermosetting plastics

Epoxy resins: surface coating, adhesives
Malamine formaldehyde: table ware, laminate 
Polyester resins: castings
Urea formaldehyde: electrical fittings, adhesives

Closed loop recycling:

Closed loop recycling is where a waste or byproduct of a process or product is used in making another product. E.g., recycling waste newspaper to make paper-board or other types of paper.

I should never have purchased... Assignment 1

A few weeks ago my dad bought two airsoft rifles off of a website, designed by a company called G&G, as a present for my 16th birthday and for him to use when he goes airsofting.

It was reviewed as a 'new revolutionary piece of kit that every airsoft player will want on the field' and 'is considered perfect for indoor and outdoor encounters'. admittedly the weapon has a short body with a long outer barrel for accuracy, but the long barrel hinders movement within close quarter environments and just isn't what was advertised on the website.


This weapon is a replica of the American armed forces M4/M16 and is aesthetically pleasing in the sense that it looks exactly like the real fire arm, but with it being aesthetically pleasing, there comes a lack of function and ergonomics some of which make the gun unsuitable for certain people.
Every time I come to use the gun, it is extremely uncomfortable as the grip you use to operate the gun is really small and doesn't have any finger grips. Also when using the gun in competitions I've either dropped the gun or I have had to hold it in a way which wasn't comfortable for me.
Another disadvantage of this gun is that is it not suitable for left handed shooters, the magazine release is only on the right side and so is the trigger safety. This means that a left handed shooter would not be able to access these parts of the gun without putting it down and using them, which shouldn't happen as it means when on the battlefield the shooter would take a lot longer than someone who was a right handed shooter, using this exact gun.
One thing the designer should have done is make this a little more ergonomically friendly!