3 Processes, techniques and specialist tools

Question 1

How is copper annealed

Answer 1

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

Question 2

How is aluminium annealed

Answer 2

Apply soap to aluminium
Gently heat until soap turns black
Remove heat source
Cool under running cold water

Question 3

How is ferrous metals normalized

Answer 3

Heat up to 900ºC (Cherry Red)
Remove heat source
Allow to cool slowly in air

Question 4

Why should some metal be hardened

Answer 4

When a metal is hardened the atoms are re arranged, which increases the metals hardness yet also increases its brittleness

Question 5

How is ferrous metals hardened

Answer 5

Heat up to 900ºC (Cherry Red)

Quench in water

Question 6

Why are metals annealed

Answer 6

Work hardened metal can be hard to work with, so releases pressure built up in the metal

Question 7

What is work hardening

Answer 7

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

Question 8

What is normalising

Answer 8

When a hardened metal needs to be made softer and less brittle so it is easier to work with

Question 9

What is stainless steel an alloy of

Answer 9

Steel & Chromium optionally with Nickel + Molybdenum

Question 10

What is duralumin an alloy of

Answer 10

aluminium, copper & magnesium (AKA Al-Cu 2000 alloys)

Question 11

What is brass an alloy of

Answer 11

Copper & Zinc

Question 12

What is bronze an alloy of

Answer 12

Copper & Tin

Question 13

What is solder an alloy of

Answer 13

Lead & Tin

Question 14

What is nitinol an alloy of

Answer 14

Nickel & Titanium

Question 15

What is an alloy

Answer 15

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.

Question 16

What is steel used for

Answer 16

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.

Question 17

What is stainless steel used for

Answer 17

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.

Question 18

What is aluminium used for

Answer 18

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.

Question 19

What is nitinol used for

Answer 19

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.

Question 20

What is offset lithography printing

Answer 20

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.

Question 21

What is offset lithography printing used for

Answer 21

Lithography is used for medium and long print runs of products such as magazines, posters, packaging and books

Question 22

What is flexography printing used for

Answer 22

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

Question 23

What is flexography printing

Answer 23

Flexography uses a relief image on thin, flexible printing plates made of rubber

Question 24

What is screen-printing

Answer 24

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

Question 25

what is screen-printing used for

Answer 25

Screen printing is used to print small runs of posters, display boards, fabrics, wallpaper and control panels of electronic products

Question 26

What is gravure printing

Answer 26

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

Question 27

What is gravure printing used for

Answer 27

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

Question 28

What are the 4 printing colours

Answer 28

Cyan
Magenta
Yellow
Black

Question 29

How is sand casting done

Answer 29

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

Question 30

How is gravity die casting done

Answer 30

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

Question 31

How is pressure die casting done

Answer 31

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.

Question 32

Why is suds used

Answer 32

To act as a lubricant and reduce friction and therefore heat created between the tool and the metal that is being worked on

Question 33

Whats the difference between milling and routing

Answer 33

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.

Question 34

Explain blow moulding

Answer 34

1. The plastic is fed in granular form into a ‘hopper’ that stores it.
2. A large thread is turned by a motor which feeds the granules through a heated section.
3. In this heated section the granules melt and become a liquid and the liquid is fed into a mould.
4. Air is forced into the mould which forces the plastic to the sides, giving the shape of the bottle.
5. The mould is then cooled and is removed.

Question 35

Explain injection moulding

Answer 35

1. Granulated or powdered thermoplastic plastic is fed from a hopper into the Injection Moulding machine.
2. 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.
3. 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.
4. 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.

Question 36

Explain vacuum forming

Answer 36

1. 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.
2. The mould is then placed into the vacuum former oven. A plastic sheet is then clamped above, but not on the mould.
3. In the oven, the heater is positioned above the plastic. This will heat up, warming the plastic & allowing it to become flexible & mouldable.
4. After a few minutes, the plastic should be at a temperature to allow moulding.
5. The shelf on which the wooden mould is sat on, is moved upwards & into the flexible plastic using a handle.
6. The vacuum is then switched on, removing all air from the oven. This allows the plastic to form to the shape of the mould.
7. Once cooled, the sheet is then removed from the oven, the mould is removed & any excess trimmed.

Question 37

Explain extrusion

Answer 37

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.

Question 38

Explain rotational moulding

Answer 38

1. 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.
2. 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.
3. The mould moves onto the cooling stage. Cool air is blown around the mould, aided by large fans. The mould cools slowly and solidifies.
4. The finished product is then removed.

Question 39

What is the three types of laminated boards

Answer 39

Laminated board (lamin board)
Block board
Plywood

Question 40

What is laminated board (lamin board)

Answer 40

Manufactured boards made up of strips of natural timber that are between 5/7mm thickness

Question 41

What is block board

Answer 41

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

Question 42

What is plywood

Answer 42

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

Question 43

What is polyvinyl acetate (PVA) used for and good for

Answer 43

Wood to wood joints

Strong bond, can’t be used, end to end, takes 24 hours to dry, requires clamping

Question 44

What is epoxy resin used for and good for

Answer 44

Anything

Very strong, heat resistance, chemical resistance, waterproof, takes time to dry, requires two parts

Question 45

What is contact adhesive used for and good for

Answer 45

Anything

Strong, instant bond (yet had to be placed on both and left to dry first), can’t be positioned once placed

Question 46

What is hot melt glue used for and good for

Answer 46

Modelling

Quick, cheap, can be reheated and edited, weak

Question 47

What is tensol cement used for and good for

Answer 47

Joining thermoplastics

Good at gap filling, excellent bond, can damage surface, gives off fumes

Question 48

What is polystyrene cement used for and good for

Answer 48

Joining thermoplastics

Gives excellent bond, placed outside gap and it is drawn in, the surface has to be flat

Question 49

What are rivets used for and good for

Answer 49

Attaching metal sheets together

Good, strong permanent joint, access to both sides is required

Question 50

Explain oxy-acetylene welding

Answer 50

1. When preparing to weld, it is important to assemble all of the materials you will need, once you begin welding.
2. Gather parts, equipment, fixtures, safety gear, filler rods and the material you will be welding.
3. You should first thoroughly clean the materials you will be welding to remove any contaminants that can cause welding defects later.
4. 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.
5. Using the correct size nozzle will make the welding process much easier.
6. 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.

Question 51

Explain MIG welding

Answer 51

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.

Question 52

Explain brazing

Answer 52

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.

Question 53

Explain hard soldering

Answer 53

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.

Question 54

Why is flux used

Answer 54

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

Question 55

What is MIG and TIG welding

Answer 55

Metal Inert Gas

Tungsten Inert Gas

Question 56

What are the benefits and disadvantages to standard hex nuts

Answer 56

Can be applied and removed multiple times

Prone to vibrations

Question 57

What are the benefits and disadvantages to wing nuts

Answer 57

Can be applied and removed multiple times
Prone to vibrations
‘Wings’ make use easier

Question 58

What are the benefits and disadvantages to washers

Answer 58

Add thickness

Reduce impact of vibrations

Question 59

What are the benefits and disadvantages to locking nuts

Answer 59

Rubberized interior makes nuts harder to remove and therefore are more permanent

Question 60

What are the benefits and disadvantages to pop rivets

Answer 60

Can be applied from just one side

Weak in compared to snap rivets

Question 61

What are the 6 knock-down (KD) fittings

Answer 61

Block connector
Cam and dowel
Corner plate
Insert nut
T-nut and bolt
PLY90 connector

Question 62

What are 5 traditional fittings

Answer 62

Mortise and tenon
T-bridle
Finger joint
Dowel joint
Biscuit joint

Question 63

Explain oil based paints

Answer 63

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.

Question 64

Explain water based paints

Answer 64

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.

Question 65

Explain solvent based paints

Answer 65

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.

Question 66

What is a varnish

Answer 66

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.

Question 67

How is varnish applied

Answer 67

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.

Question 68

How does varnish work

Answer 68

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.

Question 69

What is the difference between varnishes and sealants

Answer 69

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.

Question 70

Why are preservatives used on woods

Answer 70

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.

Question 71

How should preservatives be applied

Answer 71

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.

Question 72

What is the three ways preservatives are applied

Answer 72

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

Question 73

What is anodizing

Answer 73

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.

Question 74

How is aluminium anodized

Answer 74

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.

Question 75

Why is electro-plating used

Answer 75

Electrolysis is used to electroplate objects. This is useful for coating a cheaper metal with a more expensive one, such as copper or silver.

Question 76

How does electro-plating work

Answer 76

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

Question 77

What are the benefits of powder coating

Answer 77

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.

Question 78

How is powder coating applied

Answer 78

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).

Question 79

What is galvanizing and how does it work

Answer 79

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

Question 80

What is cathodic protection

Answer 80

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.

Question 81

What is the main use of cathodic protection

Answer 81

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.

Question 82

What does boiled linseed oil do

Answer 82

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.

Question 83

What can boiled linseed oil be used on

Answer 83

Deceptively recognised as a wood treatment, it can also be used on metal.