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Product Design > unit 3 Performance characteristics of woods > Flashcards

unit 3 Performance characteristics of woods Flashcards

1
Q

What are the stock forms of wood?

A

Rough sawn
Planed square edge (PSE)
Planed all round (PAR)

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2
Q

What is timber categorized into?

A

natural timbers - hard/softwoods and manufactured boards

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3
Q

how is a tree made to timber?

A

tree trunk is cut into standard sizes
Rough sawn timber will be sold off at this stage
Machines called planer thicknessers are used to trim rough sawn timber to PAR and PSE timbers

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4
Q

Rough sawn timber

A

cheapest stock form of timber
rough surface
used in saw mill and construction frames

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5
Q

planed timber

A

Planed timber is prepared using a planer and thicknesser
Material is wasted away, little by little, to achieve a 90° edge on one or more sides

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6
Q

What is PSE timber?

A

one square edge
around 3mm from surface
smooth

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7
Q

What is PAR timber?

A

square on all sides
smooth
3mm from surface

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8
Q

What is moulding?

A

machined profiles made for functional and aesthetic purposes
used for decorative features for products and interiors

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9
Q

What is manufactured boards?

A

sold as full or hall boards
available in range of thickness

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10
Q

What is good about softwoods?

A

low cost
fast growth
long straight shape

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11
Q

What are examples of soft woods?

A

Pine Spruce
Douglas fir Cedar
Redwood Larch

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12
Q

Pine

A

furniture and flooring
lightweight
good elaticity
resist to shrinking swelling

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13
Q

Redwood giants

A

rot and fire proof
Lightweight, soft, good strength to weigh ratio
Used for construction, decking and musical instruments

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14
Q

Flying Trees Spruce

A

was widely used in the construction of aircraft in World War I and II

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15
Q

Cedar

A

high oil content so resistant to decay
lightweight
knot free
fairly toxic
used for boats and paneling

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16
Q

Larch

A

strong stiff durable dense
fence posts, garden furniture and boats

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17
Q

Douglas Fir

A

toughest wood
cheap and strong
large scale projects such as housing frames
stable
smooth finish
rot and moisture resistant

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18
Q

What are hardwoods

A

slow growing and need more land, both these factors make them expensive
aesthetic qualities
dense and so are usually stronger and more durable than softwoods

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19
Q

What are examples of hardwood?

A

Oak Ash
Mahogany Birch
Teak Beech

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20
Q

Birch

A

Fine grain
Even texture
Ideal for veneers
Low cost
Resistant to rot

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21
Q

Beech

A

Hard and tough
Odourless
Close straight grain
Easy to work with
Flexible

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22
Q

Plywood

A

Strong in every direction
Can’t spilt along grain
Hard and smooth
Some knots

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23
Q

Flexible plywood

A

Aero ply and flexiply
Can be formed/curved

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24
Q

Aeroply

A

To form around frameworks and plane wings
Made from several birch veneers

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25
Q

Flexiply

A

consists of a thin central veneer with two softer outers
Used in lamination and fireworks covers

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26
Q

What is melamine formaldehyde laminates

A

Give protective and attractive finish to low cost timbers
Makes them hard
Resistant to heat moister and chemicals

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27
Q

Wood veneers

A

Stuck to surface and edges to improve aesthetics

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28
Q

grain pattern

A

markings that appear on surface of wood caused by growth rings

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29
Q

grain direction

A

the way the markings run along surface of wood strongest with the grain

30
Q

surface defects

A

insect/fungal/desease/water/knots damage

31
Q

warpage

A

caused by moisture contents it can change shape

32
Q

shrinkage

A

as wood drys volume decreases

33
Q

splitting

A

as wood dries fibres separate

34
Q

joining

A

ability to join different materials together through joints/fixings

35
Q

machining qualities

A

if the grain is tighter the wood will machine better as large chunks are less likely to break

36
Q

wood grain

A

can affect cost and workability
end grain is the pattern which can be seen in the wood

37
Q

wood structure

A

wood fibres are from hollow stew like cells held in lignin carry water and nutrients make wood strong

38
Q

surface defects

A

knots-make wood shrink hard to work
machining-creates marks
woods damaged from insects
defects affect overall stability

39
Q

distortions

A

must be seasoned to prevent
hygroscopic-absorbs moisture

40
Q

air dried

A

stored under cover left to dry naturally
cheap
lots at a time
no energy needed

41
Q

kiln dried

A

uses steam to artificially dry timber
quicker
expensive

42
Q

shrinkage

A

wood swells and shrinks with seasons or with levels of moisture

43
Q

a
b
c

A

a- square sections shrink to diamonds
b-boards tend to cup
c-uniform shrinkage

44
Q

working properties of seasoned timber

A

stronger and more stable
less likely to decay
less likely to corrode metals
absorbs preservatives quickly

45
Q

forming woods

A

consists of both additives manufacturing and wasting processes as well as manipulation

46
Q

steam bending

A

uses heat and moisture to make wood pliable beech/ash steam well as they have an open pore structure

47
Q

laminating

A

combines wood and adhesives for different purposes

48
Q

resistance to decay

A

can be treated to increase resistance to decay through fungal and insect attack as well as rot

49
Q

insect attack

A

beetles/termites are attracted to wood to the starches and sugars

50
Q

fungal attack

A

damp or poor ventilated conditions make ideal environment to fungal attack dry wood has lower risk

51
Q

toxic trees

A

tree sap and saw dust can cause health risks

52
Q

regulations of COSHH

A

state that wood dust must be limited to 5mg per cubic meter

53
Q

What is MDF?

A

fine wood dust particles bonded with resin
smooth finish and uniform density
Ideal for CNC milling
very resilient

54
Q

What is PSE and PAR?

A

PSE - one square edge
PAR - square on all sides
pay more for less materials

55
Q

What is a flat-pack

A

standardized components or knock down fittings used to enable quick assembly

56
Q

What can woods be tested for?

A

strength
toughness
hardness
density
corrosion
malleability
elasticity

57
Q

Tensile strength

A

tested by applying weight to test a piece and monitoring how much materials bend

58
Q

Hardness tests

A

hit a centre punch into a material and measure the size of the dent created

59
Q

Toughness tests

A

hold each test piece in a vice then hit hit each one in turn with the same force

60
Q

how can tensile strength be measured

A

applying weight to a test piece and monitoring how much the material bends or defects

61
Q

hardness

A

how easily materials resist abrasion and indentation

62
Q

jaka hardness test

A

measures ability of wood to resist scratches or dents

63
Q

ultrasonic tests

A

detects internal defects using sound waves

64
Q

x ray testing

A

x ray beams are passed through a material and protect image on screen

65
Q

preservatives

A

guard against insect attack

66
Q

wood stain

A

doesnt need perservatives soaks into wood

67
Q

teak oil

A

natural oils and solvents weatherproof

68
Q

varnishes

A

liquid coatings sit on surface creates film

69
Q

waxes

A

soak into surface makes it a little water resistant

70
Q

paint

A

surface finish sits on top

Product Design (6 decks)

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