processes, techniques and specialists tools

Question 1

what is heat treatment

Answer 1

how heating up a metal can change its properties

Question 2

what is hardening

Answer 2

medium and high carbon steels are heated for a given time then quenched, increases hardness but also brittleness

Question 3

what is tempering

Answer 3

reduces some of the hardness and brittleness from a hardened metal whilst increasing the toughness and ductility, metal is heated below the critical point then air cooled

Question 4

what is case hardening

Answer 4

hardens surface of steels with less than 0.4% carbon content

Question 5

case hardening process

Answer 5

steel is placed in ceramic box which is fill with carbon , heated to 950 degrees C, long the exposure to carbon thicker the layer of carbon, metal heated to 760 degrees C and quenched

Question 6

what is annealing

Answer 6

the heating and slow cooling of work-hardened material to make it easier to work with, less brittle and more ductile

Question 7

what is normalising

Answer 7

low carbon steel to give the metal a fine grained structure, material is heated to the same temperature for hardening then quenched and left to cool, increases brittleness and toughness

Question 8

what are alloys

Answer 8

metal made of 2 or more metals, eg stainless steel

Question 9

what is sand casting

Answer 9

cope is placed on the drag, mould made of sand, runner and riser, molten metal poured through the runner and when it comes up the riser you can tell there’s enough molten metal in it
labour intensive, low quality finish, suitable for one-off or batch production
eg clamps, train wheels

Question 10

what is gravity die casting

Answer 10

a permanent mould casting process, where the molten metal is poured from a vessel or ladle into the mould, the molten metal is poured down the runner and when it comes up the riser you know the mould is full
lower melting point (aluminium), used for thicker moulding sections, suitable for large scale production
eg engine parts, door knobs

Question 11

what is pressure casting

Answer 11

a process in which molten metal is forced under pressure into a securely locked metal die cavity, where it is held by a powerful press until the metal solidifies
lower melting point (aluminium), molten metal stored in chamber then forced into die, fast process, large scale production
eg toy cars, doorknobs

Question 12

what is blow moulding

Answer 12

the forming of a hollow object by inflating or blowing a thermoplastic molten tube called a “parison” in the shape of a mould cavity, for making hollow thin walled components, high tooling costs, used for continuous production, eg shampoo bottles

Question 13

advantages and disadvantages of blow moulding

Answer 13

adv- lower cost than other similar processes, one piece construction, automated
dis- only hollow parts, low strength, trimming is necessary, have to use thermoplastics

Question 14

what is injection moulding

Answer 14

The molding machine heats the plastic until it is liquid. The nozzle of the injection molding machine then injects the melted plastic into the mold (injection pressure). The cavity of the mold is now filled with the plastic liquid. This will then cool down to form a solid product
eg TVs, calculators

Question 15

adv and dis of injection moulding

Answer 15

adv- faster than similar processes, large scale construction, complex shapes are possible
dis- high initial costs, costly to run, some limitations to shape, moulds take time to make and are expensive

Question 16

what is vacuum forming

Answer 16

heats a plastic sheet until it becomes pliable, stretches the material onto a mold, and then uses vacuum pressure to obtain the desired part geometry
eg trays, coffee cups

Question 17

adv and dis of vacuum forming

Answer 17

adv- cost effective, excess plastic can be recycled, moulds are easy to create
dis- excess moisture can cause unwanted bubbles to form, limit to the angle on the mould

Question 18

what is rotational moulding

Answer 18

A hollow mold is filled with powdered plastic resin. The mold begins rotating bi-axially and is transferred into an oven. The mold continues to rotate as the resin melts and coats the walls of the mold.
eg kayaks, traffic cones

Question 19

adv and dis or rotational moulding

Answer 19

adv- most cost-effective for production volumes of less than 3,000 annually, uniform wall thickness, high stability
dis- few material options, high process durations

Question 20

what is offset lithography (adv and dis)

Answer 20

• a method of mass-production printing in which the images on metal plates are transferred (offset) to rubber blankets or rollers and then to the print media
• adv- consistent high quality image, high volume print runs, long life of printing plates
• dis- expensive set up costs for small quantities

Question 21

what is flexography (adv and dis)

Answer 21

• form of rotary printing in which ink is applied to various surfaces by means of flexible rubber (or other elastomeric) printing plates
• adv- high print speeds, suited for long runs, prints on large range of materials, low cost of equipment (least expensive printing process), low maintenance
• dis- cost of printing plates is high but can last for a long time, time consuming to change what is being printed

Question 22

what is green printing (adv and dis)

Answer 22

• the process of transferring a stencilled design onto a flat surface using a mesh screen, ink and a squeegee
• adv- minimal setup costs due to ice of basic equipment
• dis- slow process, high cost per product

Question 23

what is gravure (adv and dis)

Answer 23

• the paper is pulled between two rollers (impression roller and printing cylinder) where a doctoring blade takes off excess paint from the painting cylinder and so as the paper goes between these two rollers the paint gets printed on the paper
• adv- good print quality and speed, simple process
• dis- not economic for small runs, not good for fine text lettering, expensive set up costs

Question 24

what is milling/routing

Answer 24

• milling makes small holes or channels in wood or metal
• milling is a slower process than routing but can be linked to CNC
• routing machines make slots or holes in wood and can be done by hand or with a CNC router

Question 25

what is drilling

Answer 25

• a rotating drill bit drills into static material

- the drill produces holes for items such as dowels, screws or fittings

Question 26

what is turning

Answer 26

• uses a lathe which can be used for wood or metal and can be CNC
• the material is rotated and a cutting tool is pressed against the material surface to remove excess material and make the required shape
• makes products such as table legs, doorknobs or chess pieces

Question 27

what is stamping

Answer 27

• sheet material is removed using a CNC stamping process which removes shapes out of the sheet
• the sharing action off the upper tool die and the lower tool die removes the material
• usually for smaller production runs of sheet material from 0.5-0.6 mm

Question 28

what is pressing

Answer 28

• sheet material is pressed into a 3D form between 2 dies

- good for large scale or mass produced products such as car body panels

Question 29

what is the layup lamination process

Answer 29

• the procedure of overlapping all the layers in the correct order and with the correct orientation
• polyester resin used ads the polymer and top gel coat can provide pigment colour
• eg kayaks, boat hulls or theatre props

Question 30

what is laminating wood

Answer 30

• bonds material together using adhesive and pressure as the wood has adhesive applied and is then bent over a former and when dry they form a thicker board in the shapes of the former
• wood held over former whilst drying either by clamps or in a vacuum bag
• eg furniture chairs, stair banisters or chair backs