Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level DT > 1.4 Forming, Redistribution and Addition Processes > Flashcards

1.4 Forming, Redistribution and Addition Processes Flashcards

1
Q

POLYMERS

injection moulding

A
  1. plastic granules fed into machine via hopper & pushed to end using Archimedes screw
  2. plastic is melted by the heater
  3. molten molten plastic is pushed to the end, the end is narrower to build up pressure
  4. the piston is drawn back then pushed forward with great force by the hydraulic system
  5. this forces the molten plastic into the mould
  6. plastic could & hardens in the mould & is removed
    USES: toys, bottle caps, one piece furniture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

POLYMERS

blow moulding

A
  1. plastic tube (parison) is extruded (polymer is viscous to retain shape)
  2. mould is closed
  3. air is blown through the mould and the tube inflates to fill it, forming product
  4. waste (flash) is trimmed off
    USES: bottles, jars, hollow objects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

POLYMERS

extrusion

A
  1. plastic granules fed in via hopper, pushed down tube using Archimedes screw
  2. granules are melted by heater
  3. process is continuous
  4. melted plastic is pushed through die to form product
  5. cooled as it is pushed out by water jacket
  6. cut to desired length
  7. can be used for both hollow & solid shapes
    USES: window frames, hose pipes, garden trellis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

POLYMERS

vacuum forming

A
  1. thermoplastic sheet is heated until softened
  2. heater is turned off & air blown through machine from bottom- raises sheet to slight bubble
  3. platen is raised so it touches the sheet
  4. vacuum removes air between platen & sheet
  5. atmospheric pressures on top presses sheet onto mould
  6. platen lowered & moulding removed
    USES: yoghurt pots, trays, coffee cups
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

POLYMERS

compression moulding

A

1 .powdered preform is heated & put in mould
2. mould is closed & compresses the powder into shape
3. heated so powder melts & forms cross links
4. cool & remove
5. uses thermosets
USES: switches, electrical housing, bowls

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

POLYMERS

line bending

A
  1. line drawn on both sides of the sheet where it will be bent
  2. sheet is heated on both sides along the line
  3. once softened enough the sheet is bent around a former
    USES: display stands, leaflet dispensers, garden furniture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

POLYMERS

calendaring

A
  1. ingredients blended & fluxed
  2. plastic is transported to a 2 roll mill and banded onto one roll
  3. ribbon of fluxed roll is stripped from the 1st roll and fed into nip rollers
  4. the rollers heat the plastic
  5. space between rollers can be adjusted. Machine usually has 3 sets of rollers to thin plastic gradually
  6. transferred to post-calender train- series of rollers which gradually cools the sheet
  7. sheet is would onto a take-up roller
    USES: thin polymer sheet (eg clingfilm)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

POLYMERS

rotational moulding

A
  1. plastic powder added to mould & closed
  2. mould transferred to oven & heated
  3. mould rotated slowly around 2 axes and polymer coats inside of mould
  4. once correct thickness achieved mould is cooled w/ fan/water spray
  5. product shrinks slightly & is removed
    USES: traffic cones, kayaks, water tanks, toys
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

POLYMERS

lamination (lay-up process)

A
  1. mould/former prepared & coated with release agent (pva, wax)
  2. gel coat applied (polyester resin mixed with pigment- may also have other additives to prevent UV degradation etc)
  3. fibreglass matting is laid over the former and polyester resin brushed on with a roller (pushes out air bubbles)
  4. repeated until desired thickness reached
  5. final layer of tissue used on top layers
  6. layers may be compressed using a vacuum bag
    USES: sports equipments, bikes, boat hulls, sports car bodies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q 
POLYMERS
thermoforming (mechanical)
A
  1. usually used to add additional detail or mould thick polymer sheet
  2. plastic sheet clamped above a mould & heated
  3. plug pushes sheet into mould while vacuum sucks the sheet down
  4. the two moulds traps the polymer and allow extra detail to be added to the moulding
    USES: fruit punnets, medical equipment covers, cake boxes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

POLYMERS

thermoforming (pressure)

A
  1. polymer sheet is preheated and clamped above mould in vacuum chamber
  2. chamber is sealed and air pressure applied to sheet from above
  3. air between mould & polymer sheet is sucked out by a vacuum & sheet forced down into mould
    USES: medical equipment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

METALS

drop forging

A
  1. die secured on top of anvil
  2. ram equipped with die
  3. metal billet heated to above recrystallisation temperature- stops work hardening
  4. billet is placed into anvil die and ram brought down with force
  5. ram is lifted & product removed
    USES: spanners, pliers, screwdriver
    - maintains strength of metal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

METALS

recrystallisation temperature?

A
  • below melting point of metal
  • possible to change size & shape of grains in the metal
  • prevents work hardening > makes it brittle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

METALS

hot rolling

A
  1. metal heated above recrystallisation temperature
  2. passed through sets of rollers to decrease thickness
    - uniform mechanical properties throughout
    - rolling while hot = no deformation/stress (could lead to fault)
    - surface usually coated with carbon deposits which need to be removed > leads to more generous tolerances
    USES: I beams, railway tracks, bars & plates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

METALS

cold rolling

A
  1. usually done at room temperature
  2. metal is forced through sets of rollers to reduce thickness
    - tighter tolerance than hot rolling > no carbon deposits
    - surface finish therefor better
    USES: home appliances, filing cabinets, steel drums
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

METALS

spinning

A
  1. former (mandrel) put on chuck
  2. sheet metal blank held in place between mandrel & tailstock
  3. roller tool moved into blank and rotated with mandrel- starts to stretch metal over mandrel
  4. roller tool moved along mandrel as pressure maintained against rotating blank
  5. roller tool moved to end & finishes product
  6. removed & excess trimmed
    USES: plates, bowls (alternative to press forming)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

METALS

cupping/deep drawing

A
  • deep drawing = depth exceeds diameter
    1. blank clamped over die
    2. hydraulic press pushes blank into cavity using deep drawing punch
    3. cup pressed further down into die to make desired shape
    USES: fire extinguishers, aerosol cans
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

METALS

bending

A
  • machine called ‘press brake’
    1. stock metal clamped between a matching punch & die
    2. piece is held in place by a brake while punch is lowered down
  • modern brakes use a back gauge to correctly position piece
    > back gauge can be controlled by computer to allow metal to be repeatedly bent
    USES: seams between sheets of metal, hemming sheet to make it safer to handle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

METALS

press forming

A
  • shape sheet metal into 3D forms
  • often combined with punching to remove parts of sheet/trim excess
  • can be used in conjunction with robots (sheet metal lifted on and off machine)
  • medium carbon steel & aluminium often used due to malleability
  • used in mass production/large batch production due to high cost & complexity of dies
  • making dies is highly skilled & very costly
    USES: metal seats, car body panels, boxes/containers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

METALS

wrought iron forging

A
  • wright iron has very low carbon content so is malleable & suitable for hammering into shape
  • can be shaped using hydraulic/mechanical rams & anvil or using hand tools
  • wrought iron is heated in a gas or coke-fired forge
  • then shaped by holding it with tongs and hammering over an anvil
  • one-off/limited batch production- no requirement to make formers or dies (also highly skilled workers needed)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

METALS

low temperature pewter casting

A
  • pewter is an alloy with a low melting point
  • easy to make moulds (MDF won’t catch fire, aluminium or steel have a higher melting point)
    1. mould made from MDF/high density modelling foam, mould includes a sprue for pouring in
    2. mould sandwiched between two pieces of MDF & clamped together
    3. pewter is melted in a ladle and poured in
    4. once cooled casting is removed & sprue cut off
    5. filed & polished
    USES: jewellery, key fobs, decorative components
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

METALS

investment casting

A
  • used to cast intricate/awkward shapes
  • repeatable as wax patterns cast from master mould
    1. exact replica of product is made using wax
    2. wax pattern is dip coated in refractory clay then fired in a kiln. the wax is burned away leaving a hollow clay mould
    3. molten metal is poured into the mould
    4. clay mould broken away to reveal casting
    5. runner & connecting channels machined off
    USES: jewellery, collectables, medical (joint replacements)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

METALS

sand casting

A
  • for high melting point metals
  • often carried out in foundries
  • slow & labour intensive, single use moulds
  • surface finish is not high quality
    1. a pattern is made (wood) of the product & placed in a steel box called a ‘drag’. this is packed with sand around the pattern
    2. drag is turned over & second box called ‘cope’ clamped over drag. the top half of the pattern is placed in to match other half. wooden stakes form the sprue/runner
    3. sand pack around these. a small depression forms the pouring basin
    4. stakes & pattern carefully removed. connecting channels cut, mould is reassembled
    5. vent holes may be created to allow gases to escape
    6. molten metal is poured in. when full it fills the riser indicating cavity is full. sprue, riser & channels machined off.
    USES: railway carriage wheels, woodworking clamps, bollards, drain covers, post boxes
24
Q 
METALS
die casting (basic info)
A
  • used for lower melting point metals (aluminium, zinc-based alloys)
  • uses tool steel moulds- reusable
  • very high quality surface finish
    USES: alloy wheels, engine components, toy cars, collectibles, door knobs
25
Q

METALS

gravity die casting

A
  • simplest form
  • molten metal is poured into the mould
  • relies of gravity to help material flow through mould
  • there is a runner & riser
  • generally used to make parts that have a thicker or heavier section than pressure die casting but thinner than sand casting
26
Q

METALS

pressure die casting (hot chamber)

A
  • cast items quickly in high volumes
    1. molten metal stored in a chamber which is part of of the machine
    2. a pneumatic/hydraulic plunger forces a ‘shot’ of molten metal through the goose neck into the die
    3. high pressure means all of the mould is filled & allows for fine detail
    4. very fast as molten metal not stored separately
  • no aluminium (picks up iron from steel chamber)
27
Q

METALS

pressure die casting (cold chamber)

A
  1. molten metal kept separately in a melting crucible
  2. ladled into shot chamber
  3. hydraulic ram forces molten metal into mould cavity
  4. casting removed
28
Q

METALS

MIG welding

A
  • MIG = metal inert gas
  • uses an electric arc to create heat
    > melts joint area
  • wire electrode (same metal) melts in the arc and fills the gap
  • welding gun is wired as it moves over joint to form continuous bead of weld
  • uses inert gas (eg arcon CO2) to form flux shield over join, shield replaces oxygen to prevent oxidisation
    + heat is localised- will not burn/distort metal
    + simple
  • expensive equipment
  • unsuitable for thick metals
  • not suitable for vertical/overhead welding
    USES: climbing frames, bike frames, vehicle exhausts
29
Q

METALS

TIG welding

A
  • TIG = tungsten inert gas
  • used for stainless steel & non-ferrous metals
  • electric arc process but tungsten does not melt- a separate filler rod is used
  • gas shield protects from oxidisation
    + greater control
    + more accurate
    + stronger
  • slow
  • greater level of skill required
    USES: stainless steel ladders for boats/pools, stainless steel car exhausts
30
Q

METALS

oxy-acetylene welding

A
  • uses mixture of high pressure gases (oxygen & acetylene) to form intense flame
  • gases stored separately & mixed together in the blow torch
  • intensity & temperature can be adjusted through valves- allows for flame cutting, welding or brazing
  • metal is prepared by grinding at an angle on the edges (so weld runs through whole thickness of metal)
  • joint heated to form melt pool & steel rod introduced to joint area
  • melt pool extended to form continuous bead along the joint
  • molten metal flows to hottest part of the metal
  • by moving the torch along the joint line a continuous seam is formed
    + does not require electricity
    + low cost
    + portable
  • almost obsolete because of MIG & TIG
  • weld lines much rougher
31
Q

METALS

spot welding

A
  • copper electrodes apply pressure & heat to weld area by conveying an electrical current through the weld pieces
  • material melts & fuses together
  • pressure remains while cooling
    + low cost, easy
    + no filer material
    + can join dissimilar materials
    + easy to automate
  • size & shape of electrodes determine size & strength of weld
  • join forms only where electrodes were
  • can be ugly
    USES: welding 2+ metal sheets together, automotive & aerospace industry
32
Q

METALS

brazing (hard soldering)

A
  • can be done using oxy-acetylene or in gas & compressed air brazing hearth
  • uses filler rod of brass
  • two pieces clamped together
  • flux is applied (prevent oxidising)
  • joint is heated with torch
  • brazing rod applied & brazing ‘shelter’ flows along joint via capillary action to hottest part
    > made to follow joint line by manipulating torch
    + lower temperature than welding
    + join dissimilar materials
  • not as strong as welding
  • colour of joint often different to main piece
    USES: school projects, prototypes
33
Q

METALS

soldering

A
  • no gap between materials being joined
  • uses filler metal with lower melting point than main materials (usually tin & copper alloy)
  • gas/air torch used to create heat
  • electrical solder = tin lead alloy
    1. metal cleaned & degreased
    2. joint area clamped/wired up
    3. metal heated up to melting point of solder
    4. solder added to metal, flows along joint- capillary action
    5. cleaned to remove flux residue
    + low power & temperature required
    + easily automated
    + dissimilar materials can be joined
  • not very strong
  • some solders contain toxic materials
  • not suitable for joining large sections
    USeS: join precious metals, joining components to circuit boards
34
Q

METALS

riveting

A
  • metal fasteners with a head at one end & shaft/tail at the other
  • pieces to be joined are overlapped & drilled, rivet shaft inserted
  • rivet head is dome shaped & set tool/snap is placed over it the end of shaft is hammered over to squeeze the two pieces together
    + cheap, durable
    + join dissimilar materials
    + doesn’t produce fumes
    + lighter than bolts & screws
    + can be made vertical, overhead etc
  • takes long time compared to welding, labour cost high
  • not aesthetically pleasing
  • holes may weaken plate cross section
  • not a light/leak proof joint
    USES: joining sheet metal/plate (eg handle of trowel to blade)
35
Q

METALS

pop riveting

A
  • have a rivet & pin
  • head is pushed through the hole
  • riveting pliers grip and pull pin
  • head squashes & pulls the two pieces together
  • pin breaks off & is disposed
    + cheap, durable
    + quick & easy
  • larger than traditional rivets
  • difficult to remove
    USES: joining thin sheet metal, joints where underside is inaccessible, aircraft production
36
Q

PAPERS & BOARDS

die cutting

A
  • sheet material slid into press
  • press pushes steel rule die & creasing rule into sheet
  • cuts out & creases product
  • plywood substrate ensures steel rule die & creasing rule stay fixed
  • creasing channels help create a clear crease which can easily be folded
37
Q

PAPERS & BOARDS

tessellation (definition & why used)

A
  • the arrangement of shapes in the most efficient way so that they are very close but do not overlap
  • ensures most efficient use of materials
    > reduces waste
    > saves money
38
Q

PAPERS & BOARDS

advantages of laser cutting (6)

A
  • very precise & accurate so complex designs can be made
  • highly repeatable
  • quick
  • efficient
  • can be used to cut or engrave
  • pieces can be cut straight out of the middle
39
Q

PAPERS & BOARDS

disadvantages of laser cutting (5)

A
  • very expensive to set up
  • not as fast as die cutting
  • operators need to be specially trained
  • can Gove off toxic fumes, ventilation is expensive to install
  • not all types of metals can be cut using a laser cutter and only up to certain thicknesses (approx 15-20mm)
40
Q

WOODS

dovetail joint

A
  • have directional strength
  • shape of tails & pins means impossible to pull apart once glued
  • can be cut by hand (requires lots of skill & practise)
  • or using router & jig
  • very aesthetically pleasing
    USES: drawers, boxes
41
Q

WOODS

comb/finger joint

A
  • series of alternating notches & square pins which interlock
  • increased surface area for gluing = very strong joint
  • easy to cut using bandsaw/laser cutter or by hand with tenon saw & chisel
  • aesthetically pleasing
    USES: boxes
42
Q

WOODS

housing joint

A
  • made by cutting grove across one piece & inserting end of second piece into it
  • made using tenon saw & chisel, or a router
  • can be glued. making it permanent or left unglued & adjustable
  • structurally strong joint
    USES: framework construction, cabinets, shelving
43
Q

WOODS

half lap joint

A
  • made by cutting the end of each piece to half its width & gluing together so they overlap
  • dovetail halving can also be used if extra strength is needed
    USES: frames (eg door frames)
44
Q

WOODS

mortise and tenon joint

A
  • made using a tenon saw and mortiser
  • mostly used for furniture such as chairs as there is no joint visible on the outside making it aesthetically pleasing
    USES: furniture
45
Q

WOODS

dowel joint

A
  • measure & mark dowel position
  • drill holes in each piece of wood & hammer in dowel centres
  • dowels usually hardwood (eg ramin) for strength
  • have grooves- allow glue to flow easily down dowel
  • large range of diameters
  • easy to use & strong (interconnect the two pieces)
    USES: flatpack furniture
46
Q

WOODS

knock-down fittings

A
  • used to manufacture flat-pack furniture
  • enable manufacturers to supply products that are not assembled
  • reduces cost to consumer & manufacturer
  • reduces making time
  • easier to store & transport products
  • easy to fit with simple tools
  • allows customers to buy in store & take home immediately
  • easy to carry through doorways & up stairs
  • wide range
  • standardised and interchangeable so can be used on wide range of products
47
Q

WOODS

modesty blocks

A
  • small rigid polymer blocks
  • moulded holes to take screws- used to join block to panels
  • simple to use
  • not very strong
  • unattractive
    USES: cupboards, storage units
48
Q

WOODS

barrel nut & bolt

A
  • very common
  • uses a cross dowel fitted into one of the pieces to be joined
  • bolt is inserted through to other piece of timber and tightened into cross dowel using Allen key
  • USES: assemble flat pack furniture- bed frames, tables etc
49
Q

WOODS

cam-lock connector

A
  • metal dowel screwed into one of the pieces by inserting a screwdriver into a slot in the side
  • cam is a disk that fits into pre-drilled hole in other piece
  • when disk rotated with screw driver collar of dowel locks into cam and pulls both pieces tightly together
    USES: bookshelves (where shelves attached to sides)
50
Q

WOODS

advantages of knock-down fittings (6)

A
  • cheaper to manufacture
  • require little skill to put together so no need to pay skilled workers & customers can put together themselves
  • standardised so easy to mass produce
  • only require basic tools (Allen key, screwdriver, etc)
  • fittings Cana be assembled & disassembled unlike regular joints
  • faster to put together than traditional joints
51
Q

WOODS
timber wasting processes:
milling

A
  • usually too slow for timbers (mostly used for metals & plastics)
  • used for small, basic jobs (eg prototyping)
  • can be hand operated or CNC
52
Q

WOODS
timber wasting processes:
routing

A
  • used to make slots & holes or decorating ‘mouldings’
  • continuous grooves can be cut along timber
  • bit turns at high speeds to cut the wood (faster than milling)
53
Q

WOODS
timber wasting processes:
turning (turning between centres)

A
  • normally done by hand using gouges & scrapers
  • these are held on tool rest and moved in & out along length of spindle
    USES: chair/table legs, reduce diameter of a spindle
54
Q

WOODS
timber wasting processes:
turning (turning on a faceplate)

A
  • thick piece of timber is screwed to a faceplate

- can be machined to turn outside circumference (domes) or inside (bowls)

55
Q

WOODS
timber wasting processes:
turning (turning in a chuck)

A
  • grips item while machined

- eg when end of spindle needs to be drilled

56
Q

WOODS

laminating

A
  • wood veneers or thin manufactured boards (eg plywood) are glued together
  • veneers should be larger than product to be made so it can be cut down & shaped accurately
  • bent over former so they form a solid board in desired shape
  • laminates are held in place using clamps/vacuum bag
57
Q

WOODS

steam bending

A
  • when heated above 100°C wood cell structure softens and becomes pliable
  • timber is put in a steam box where it will soften & absorb steam. steam box often angled to allow condensed steam to drain
  • then bent over former & clamped in place so that it dries in desired shape
  • timber likely to break on outside bends where there is a lot of tension so compression strap used (thin strip of stainless steel/steel spring) to pull wood tight around former & clamp in place. should be removed after 1 hr to prevent discolouration
  • wood is then transferred to drying jig- less robust version of former
  • quicker than lamination, less wasteful- doesn’t need to be cut down

A Level DT (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions