3 Processes, techniques and specialist tools Flashcards
How is copper annealed
Heat copper to ‘dull red’ colour
Remove fro heat source and allow to cool in air
Place in acid bath to remove oxides
Remove acids by placing under running cold water
How is aluminium annealed
Apply soap to aluminium
Gently heat until soap turns black
Remove heat source
Cool under running cold water
How is ferrous metals normalized
Heat up to 900ºC (Cherry Red)
Remove heat source
Allow to cool slowly in air
Why should some metal be hardened
When a metal is hardened the atoms are re arranged, which increases the metals hardness yet also increases its brittleness
How is ferrous metals hardened
Heat up to 900ºC (Cherry Red)
Quench in water
Why are metals annealed
Work hardened metal can be hard to work with, so releases pressure built up in the metal
What is work hardening
When a metal being worked with builds up stress and becomes harder to work with due to the forces that have already been applied. Annealing removes this stress
What is normalising
When a hardened metal needs to be made softer and less brittle so it is easier to work with
What is stainless steel an alloy of
Steel & Chromium optionally with Nickel + Molybdenum
What is duralumin an alloy of
aluminium, copper & magnesium (AKA Al-Cu 2000 alloys)
What is brass an alloy of
Copper & Zinc
What is bronze an alloy of
Copper & Tin
What is solder an alloy of
Lead & Tin
What is nitinol an alloy of
Nickel & Titanium
What is an alloy
An alloy is a metal that’s combined with other substances to create a new metal with superior properties.
Alloys often have properties that are different to the metals they contain. This makes them more useful than the pure metals alone. Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.
What is steel used for
Steel is created from iron and carbon. Iron is a brittle metal, so it’s not suitable for use as a building material for constructing bridges and buildings. Structures created from iron would eventually collapse. Because it’s tough and has a high tensile strength, steel is an ideal construction material.
What is stainless steel used for
Stainless steel, an alloy made from iron and chromium, is more resistant to corrosion and staining when it comes in contact with water as opposed to iron and carbon steel.
What is aluminium used for
Aluminum is soft and relatively weak. Its strength can be increased by adding other elements, including zinc, copper, magnesium, and manganese. When aluminum contains added elements, it’s known as an aluminum alloy.
What is nitinol used for
Nitinol is an alloy of nickel and titanium, and is known as a shape memory alloy. If nitinol is bent out of shape, it returns to its original shape when it is either heated or an electric current is passed through it. This property makes it useful for making spectacle frames - they return to their original shape if they are put in hot water after bending them.
What is offset lithography printing
A printing plate with a relief image is dampened with water and then coated with ink. The ink only sticks to the parts of the plate that are not wet with water. The printing plate is fixed to a roller and the image is transferred onto paper fed under the roller.
What is offset lithography printing used for
Lithography is used for medium and long print runs of products such as magazines, posters, packaging and books
What is flexography printing used for
Flexography can be used to print on materials such as cellophane, polythene and metallic films, so it is often used to print plastic shopping bags. It is also used to print newspapers and paperback books
What is flexography printing
Flexography uses a relief image on thin, flexible printing plates made of rubber
What is screen-printing
The screen is made from a fine mesh material fixed to a wooden frame. A stencil is placed under the screen and ink forced through the stencil onto the material below. Screen printing with stencils is best for blocks of colour
what is screen-printing used for
Screen printing is used to print small runs of posters, display boards, fabrics, wallpaper and control panels of electronic products
What is gravure printing
In gravure printing, the image is made up of small holes sunk in the surface of the printing plate. The holes are filled with ink and any excess is removed. Paper comes into contact with the ink in the holes when it is pressed against the plate
What is gravure printing used for
Gravure printing is used for long, high-quality print runs such as magazines, mail-order catalogues, packaging, and printing onto fabric and wallpaper. It is also used for printing postage stamps and decorative plastic laminates, such as kitchen worktops
What are the 4 printing colours
Cyan
Magenta
Yellow
Black
How is sand casting done
The design is made in two half’s out of a different material like plastic
Both parts are covered by a flask and packed with sand before the plastic can be removed and the pieces attached together
The metal can then be poured into the pattern by a riser hole made to the center
It should be topped up periodically and sanded down when it is released from the sand
How is gravity die casting done
Two permanent mold halves are put together and clamped.
A gap is left from the products mold to the surface called the runner and combined riser, which is a reservoir of molten metal so that when the metal starts to cool and shrink, there is more metal to fill the new space
Once cool, the clamps can be removed and the metal taken out
How is pressure die casting done
The casting process implements a steel mold often capable of producing tens of thousands of castings in rapid succession. The die must be made in at least two sections to permit removal of castings. The casting cycle begins with the two die halves are clamped tightly together by the die casting press. Molten aluminum is injected into the die cavity where it solidifies quickly. These sections are mounted securely in a machine and are arranged so that one is stationary while the other is moveable. The die halves are drawn apart and the casting is ejected. Die casting dies can be simple or complex, having moveable slides, cores, or other sections depending on the complexity of the casting. Most machines use mechanisms actuated by hydraulic cylinders to achieve locking. Others use direct acting hydraulic pressure. Die casting machines, large or small, very fundamentally only in the method used to inject molten metal into the die.
Why is suds used
To act as a lubricant and reduce friction and therefore heat created between the tool and the metal that is being worked on
Whats the difference between milling and routing
Generally, routers are designed to cut softer materials. However, softer materials can fall under a wide range – wood, plastic and even softer metal like aluminum.
Meanwhile, milling machines are made to cut metal, plain and simple. Milling machines can cut basically any type of metal, even metal as hard as titanium. Milling machines can also cut thicker material and that with more varied shapes than routers because they can operate on a horizontal or vertical configuration.
Explain blow moulding
- The plastic is fed in granular form into a ‘hopper’ that stores it.
- A large thread is turned by a motor which feeds the granules through a heated section.
- In this heated section the granules melt and become a liquid and the liquid is fed into a mould.
- Air is forced into the mould which forces the plastic to the sides, giving the shape of the bottle.
- The mould is then cooled and is removed.
Explain injection moulding
- Granulated or powdered thermoplastic plastic is fed from a hopper into the Injection Moulding machine.
- The Injection Moulding machine consists of a hollow steel barrel, containing a rotating screw (Archemidial Screw). The screw carries the plastic along the barrel to the mould. Heaters surround the barrel melt the plastic as it travels along the barrel.
- The screw is forced back as the melted plastic collects at the end of the barrel. Once enough plastic has collected a hydraulic ram pushes the screw forward injecting the plastic through a sprue into a mould cavity. The mould is warmed before injecting and the plastic is injected quickly to prevent it from hardening before the mould is full.
- Pressure is maintained for a short time (dwell time) to prevent the material creeping back during setting (hardening). This prevents shrinkage and hollows, therefore giving a better quality product. The moulding is left to cool before removing (ejected) from the mould. The moulding takes on the shape of the mould cavity.
Explain vacuum forming
- First, a wooden mould is made. This is made in the shape to which the plastic will form around. Often where possible, the mould should have angled edges, in order to allow the tooling to pop out of the plastic when made.
- The mould is then placed into the vacuum former oven. A plastic sheet is then clamped above, but not on the mould.
- In the oven, the heater is positioned above the plastic. This will heat up, warming the plastic & allowing it to become flexible & mouldable.
- After a few minutes, the plastic should be at a temperature to allow moulding.
- The shelf on which the wooden mould is sat on, is moved upwards & into the flexible plastic using a handle.
- The vacuum is then switched on, removing all air from the oven. This allows the plastic to form to the shape of the mould.
- Once cooled, the sheet is then removed from the oven, the mould is removed & any excess trimmed.
Explain extrusion
1: Raw plastic materials like granules, pellets, or powder are loaded into a hopper and then fed into a long heated cylindrical chamber called an extruder. It is moved through this chamber by a revolving screw. Some extruders can have either one or two revolving screws.
2: The raw materials flow from the hopper down through the feed throat and onto a large spinning screw operating within a horizontal barrel.
3: Not all materials have the same properties, so the raw material is processed by a heating temperature specific to the type of raw material being passed through. At the end of the heated chamber, the molten plastic is forced through a small opening called a die to form the shape of the finished product.
4: As the plastic is extruded from the die, it is fed onto a conveyor belt for cooling. Cooling can happen by air or water. The process is similar to the injection moulding process except that the melted plastic is forced through a die instead of into a mould.
5: The die for an individual plastic profile is designed so that the plastic flows smoothly and evenly from the cylindrical profile of the extruder into the final profile shape. Consistency in this flow is critical to achieving an end product with integrity.
Explain rotational moulding
- The mould opens and is filled with powdered polyethylene or polypropylene and closed. The moulds are usually manufactured from aluminium, on CNC machines . Accuracy is vital, as any fault will be repeated in the finished product, every time one is manufactured.
- The mould moves to the next stage, where it is heated to 300oC. At the same time the mould rotates so that the powder is forced against the wall of the mould.
- The mould moves onto the cooling stage. Cool air is blown around the mould, aided by large fans. The mould cools slowly and solidifies.
- The finished product is then removed.
What is the three types of laminated boards
Laminated board (lamin board)
Block board
Plywood
What is laminated board (lamin board)
Manufactured boards made up of strips of natural timber that are between 5/7mm thickness
What is block board
Manufactured boards made up of strips of natural timber that are up to 25mm in thickness
The outer surfaces are clad with veneer for decoration and strength purposes
What is plywood
Manufactured board made up of layers of natural timber veneers or laminates that are glued together. Alternative veneers have their grains running at right angles to each other leaving the outside two veneers with the same grain direction. There is always odd numbers
What is polyvinyl acetate (PVA) used for and good for
Wood to wood joints
Strong bond, can’t be used, end to end, takes 24 hours to dry, requires clamping
What is epoxy resin used for and good for
Anything
Very strong, heat resistance, chemical resistance, waterproof, takes time to dry, requires two parts
What is contact adhesive used for and good for
Anything
Strong, instant bond (yet had to be placed on both and left to dry first), can’t be positioned once placed
What is hot melt glue used for and good for
Modelling
Quick, cheap, can be reheated and edited, weak
What is tensol cement used for and good for
Joining thermoplastics
Good at gap filling, excellent bond, can damage surface, gives off fumes
What is polystyrene cement used for and good for
Joining thermoplastics
Gives excellent bond, placed outside gap and it is drawn in, the surface has to be flat
What are rivets used for and good for
Attaching metal sheets together
Good, strong permanent joint, access to both sides is required
Explain oxy-acetylene welding
- When preparing to weld, it is important to assemble all of the materials you will need, once you begin welding.
- Gather parts, equipment, fixtures, safety gear, filler rods and the material you will be welding.
- You should first thoroughly clean the materials you will be welding to remove any contaminants that can cause welding defects later.
- The next step is to place the materials you will be welding in the required place using clamps or vise grips, and then choose the correct size nozzle for the type of weld you will be performing.
- Using the correct size nozzle will make the welding process much easier.
- Open the main valve located on the cylinder by rotating it 90 degrees clockwise. After opening the valve of the oxygen tank and adjusting the amount of pressure, feel comfortable to ignite the flame.
Explain MIG welding
MIG weld welding requires three things, electricity to produce heat, an electrode to fill the joint, and shielding gas to protect the weld from the air. MIG welding is done using a very small electrode that is fed continuously, while the operator controls the amount of weld being done. In some cases when a robot takes over this process, it becomes automatic welding. The way this all works is the welder squeezes the trigger of the MIG gun then the electricity charges the electrode while the feeded starts feeding the wire and finally the shielding gas is feed through the MIG gun nozzle. What happens is as soon as the electrode contacts the metal it arc’s and starts melting the weld joint and filler metal at the same time while being shielded from the air by the shielding gas.
Explain brazing
Brazing joins two metals by heating and melting a filler (alloy) that bonds to the two pieces of metal and joins them. The filler obviously must have a melting temperature below that of the metal pieces. Brazing can join dissimilar metals such as aluminum, silver, copper, gold, and nickel. Flux is often used during brazing. It is a liquid that promotes wetting, which lets the filler flow over the metal parts to be joined. It also cleans the parts of oxides so that the filler bonds more tightly to the metal parts. In addition, fluxes are used in welding to clean the metal surfaces.
Explain hard soldering
Soldering is a low-temperature analog to brazing. By the American Welding Society’s definition, soldering takes place with fillers (also known as solders) that melt at below 840°F (450°C). Metals that can be soldered include gold, silver, copper, brass, and iron. The filler, called solder, melts. When it solidifies, it is bonded to the metal parts and joins them. The bond is not as strong as brazed joint or welded one. Solder was once made mainly of lead, but environmental concerns are pushing industry to lead-free alternatives.
Why is flux used
A fluxing agent is required for all brazing and soldering applications. The purpose of the flux is to remove oxides from the base material and to prevent oxidation during the heating process, thus promoting the free flow of the brazing filler metal
What is MIG and TIG welding
Metal Inert Gas
Tungsten Inert Gas
What are the benefits and disadvantages to standard hex nuts
Can be applied and removed multiple times
Prone to vibrations
What are the benefits and disadvantages to wing nuts
Can be applied and removed multiple times
Prone to vibrations
‘Wings’ make use easier
What are the benefits and disadvantages to washers
Add thickness
Reduce impact of vibrations
What are the benefits and disadvantages to locking nuts
Rubberized interior makes nuts harder to remove and therefore are more permanent
What are the benefits and disadvantages to pop rivets
Can be applied from just one side
Weak in compared to snap rivets
What are the 6 knock-down (KD) fittings
Block connector Cam and dowel Corner plate Insert nut T-nut and bolt PLY90 connector
What are 5 traditional fittings
Mortise and tenon T-bridle Finger joint Dowel joint Biscuit joint
Explain oil based paints
Oil based paints are normally only available in gloss finishes. They are tough and long-lasting and are appropriate for metals and woods. When you paint it is important to prime the material first. This primer helps the paint stick to the material better and produces a better finish. Always use a good brush or roller and clean them after with a turps substitute or white spirit. Most new oil based paints are suitable for use on children’s toys and can be used for internal or external work.
Explain water based paints
Water based paints unlike oil based paints are available in a wide range of finishes from matt to high gloss. A few water based paints are only suitable for light work such as painting walls for example ‘matt vinyl emulsion’. They are mainly suitable for wood only, however there are some available for metals. Water based paints are not as durable as oil based paints but you only need warm water and detergent to clean up afterwards.
Explain solvent based paints
Solvent based paints are often found in spray cans and dry a lot faster than other types of paints. There are non spray types available but these are hard to apply with brushes. These paints include fascinating finishes such as speckled, hammered, etc. Solvent sprays can be very expensive but give very good results on small projects. A cellulose based solvent is needed for cleaning up. Good ventilation is compulsory as the vapours are very toxic and flammable.
What is a varnish
Varnish is a transparent, hard, protective finish or film that is primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent.
Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of “flatting” agents. Varnish has little or no color, is transparent, and has no added pigment, as opposed to paints or wood stains, which contain pigment and generally range from opaque to translucent. Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish.
How is varnish applied
Varnishes are applied in a similar way to paint. Usually in thin coats with a brush (but can sometimes be sprayed).
Once dried, the surface is lightly sanded using a fine glass paper to remove any dust or imperfections, before a second coat is applied.
How does varnish work
After being applied, the film-forming substances in varnishes either harden directly, as soon as the solvent has fully evaporated, or harden after evaporation of the solvent through curing processes, primarily chemical reaction between oils and oxygen from the air (autoxidation) and chemical reactions between components of the varnish. Resin varnishes “dry” by evaporation of the solvent and harden almost immediately upon drying. Acrylic and waterborne varnishes “dry” upon evaporation of the water but will experience an extended curing period. Oil, polyurethane, and epoxy varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to tacky or sticky, to dry gummy, to “dry to the touch”, to hard.
What is the difference between varnishes and sealants
Unlike varnish, sealants tend to have a less shiny appearance and can raise out the grain of the wood. Sealants are usually not as ‘hard’ as varnishes and may not offer the same level of protection, but do not crack or flake off in the same way as varnish can.
Why are preservatives used on woods
Outdoor timbers are especially liable to decay and often the only reliable way to preserve them is when they are being installed. An attack of dry rot, wet rot or woodworm can be prevented by using efficient wood preservers on new wood as they contain fungicides and chemicals that attack wood boring beetles etc..
Unlike paint, which protects the surface from the weather, preservatives penetrate the outer layer of the wood., which can be particularly effective when used outdoors.
How should preservatives be applied
All timber should be dry and free from bark, paint, varnish and other surface coatings. All surfaces must be treated. Most preservatives are carried in an organic solvent which enables them to penetrate into the wood.
What is the three ways preservatives are applied
Brush- at least 2 coats must be ‘painted’ onto the wood so that it flows over the wood
Spraying- similar to brushing with at least 2 coats and amount applied
Dipping-the most effective method by leaving it soaked for at least an hour
What is anodizing
Aluminum anodizing is an electrochemical process in which an oxide (anodic) layer is chemically built on the surface of the metal. This oxide layer acts as an insulator and can be dyed in a wide variety of colors. Anodizing provides surface corrosion protection along with an excellent substrate for decorative finishes.
How is aluminium anodized
Anodizing is accomplished by immersing the aluminum into an acid electrolyte bath and passing an electric current through the medium. A cathode is mounted to the inside of the anodizing tank; the aluminum acts as an anode, so that oxygen ions are released from the electrolyte to combine with the aluminum atoms at the surface of the part being anodized. Anodizing is, therefore, a matter of highly controlled oxidation—the enhancement of a naturally occurring phenomenon.
Why is electro-plating used
Electrolysis is used to electroplate objects. This is useful for coating a cheaper metal with a more expensive one, such as copper or silver.
How does electro-plating work
The negative electrode should be the object that is to be electroplated
The positive electrode should be the metal that you want to coat the object with
The electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate
As a current is passed the covering metal moves and bonds around the outside of the metal underneath
What are the benefits of powder coating
Powder coating is a high-quality finish found on thousands of products you come in contact with each day. Powder coating protects the roughest, toughest machinery as well as the household items you depend on daily. It provides a more durable finish than liquid paints can offer, while still providing an attractive finish. Powder coated products are more resistant to diminished coating quality as a result of impact, moisture, chemicals, ultraviolet light, and other extreme weather conditions. In turn, this reduces the risk of scratches, chipping, abrasions, corrosion, fading, and other wear issues.
It’s tough. It looks great. And it lasts a long, long time. In addition to being durable, powder coating is an attractive choice due to environmental advantages.
How is powder coating applied
This application method uses a spray gun, which applies an electrostatic charge to the powder particles, which are then attracted to the grounded part.
After application of the powder coating, the parts enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density.
These molecular chains are very resistant to breakdown. This type of application is the most common method of applying powders. Powder coatings can also be applied to non-metallic substrates such as plastics and medium density fiberboard (MDF).
What is galvanizing and how does it work
The metal is hot dipped into a vat of 450ºC zinc so a layer surrounds the metal. This adds corrosion resistance without the expense of stainless steel, and is the most environmentally friendly
What is cathodic protection
The principle of cathodic protection is in connecting an external anode to the metal to be protected and the passing of an electrical dc current so that all areas of the metal surface become cathodic and therefore do not corrode.
The external anode may be a galvanic anode where the current is a result of the potential difference (a natural voltage) between the two metals.
Or it may be an impressed current anode, where the current is produced from an external dc power source.
What is the main use of cathodic protection
Its main use is to protect steel structures buried in soil or immersed in water. It cannot be used to prevent atmospheric corrosion. Structures commonly protected are the exterior surfaces of pipelines, ships’ hulls, jetties, foundation piling, steel sheet-piling, and offshore platforms. Cathodic protection is also used on the interior surfaces of water-storage tanks and water-circulating systems.
What does boiled linseed oil do
BLO protects wooden surfaces with its deep penetration, soaking into the grain and bringing out added contrast and character. Rather than being a surface treatment, boiled linseed oil soaks deep into the wooden fibres, to the core of smaller depth pieces of wood, strengthening it throughout.
What can boiled linseed oil be used on
Deceptively recognised as a wood treatment, it can also be used on metal.
