DT essentials (cramming) Flashcards
What are physical properties?
- properties of any material that can be measured in their natural state
What physical properties are there?
- absorbency
- denisty
- electrical conductivity
- fusibility
- thermal conductivity
What is absorbency?
- ability of a material to soak up or draw in heat, light or moisture
What is density?
- the mass per unit volume of any material
- how solid a material is
What is electrical conductivity?
- measure at which a material can transport electricity
What is fusibility?
- the ability of a material to be converted to a solid to fluid state by heat and combined with another material
What is thermal conductivity?
- measure of a material’s ability to transfer heat
What are working properties?
- how a material responds when it is manipulated or worked
What working properties are there?
- ductility
- elasticity
- hardness
- malleability
- strength
- toughness
What is ductility?
- ability of a material to be stretched or drawn or pulled without breaking
What is elasticity?
- ability to return to original shape after stretching or compression
Lycra used for sportswear - freedom of movement
What is hardness?
- ability to withstand impact, wear, abrasion and identation
tungsten = hard, used for saws, knives, drills
What is malleability?
- ability to be bent or shpaed without cracking or splitting
What is strength?
- ability to withstand a force
- eg pressure, compression, tension or shear
What is toughness?
- ability to absorb shock without fracturing
What is compression?
give an example
- pushing force applied to either end of material
concrete pillar holding up building
What is bending?
give an example
- tension on bottom
- compression on top
eg aluminum diving board
What is torsion?
give an example
- when a material is twisted
eg brass key
What is tension?
give an example
- pulling force on either end of material
nylon climbing rope
What is shear?
- acts on object parallel to its length
low carbon steel screw used to hang something on a wall
What are the differences between hardwood and softwood?
- hardwood = grows slower, more expensive
- softwood = grows faster, cheaper
How are timber converted into a workable form?
- felled
- debarked - removes bark + branches
- conversion and sawing = converts logs into more managable planks
- seasoned - reduces moisture content = less prone to shrinkage, warping (air dried or kiln dried)
- planer thicknesser used to make timber smooth all round, precise dimensions
Describe air dried seasoning
- timber separated and stacked under protective, roofed structure
- open sides = air circulates
- 3 months - 1 year
- cheap
Describe kiln-dried seasoning
and draw a diagram
- kiln filled with steam
- moisture content gradually reduced
- more expensive
- 3-5 days
What is linear movement?
- movement in one direction along a straight line
What is reciprocating motion?
- repetitive up and down or back and forth linear motion
What is rotary motion?
- movement on or around an axis
What is oscillating movement?
- movement backwards and forwards along a curved path
What is a first order lever?
example
fulcum in middle
pliers
What is a second order lever?
example
- load in middle
- wheelbarrow
What is a third order lever?
example
- effort in middle
- tweezers
How do you calculate mechanical effort?
load/effort
What are the six Rs?
1) Rethink
2) Refuse
3) Reduce
4) Reuse
5) Repair
6) Recycle
What is rethink?
- is there better way of designing product?
- impact of design
responsibility of desinger, manufacturer
What is refuse?
- avoid using materials that are not socially/ environmentally unacceptable
- don’t buy a product if you don’t need it
responsibility of the consumer
What is reduce?
- make durable and long-lasting products
- reduce consumption and waste
- reduce energy and transport
responsibility of designer, manufacturer, distributor
What is reuse?
- produce used again for another purpose
responsibility of consumer
What is repair?
- repair where possible instead of replace
responsibility of designer, manufacturer, consumer
What is recycle?
- take product apart
- convert parts into usable materials
responsibility of designer, manufacturer, consumer
What is turning?
draw a diagram
- wastage process, typically wood + metal
- lathes used to turn timber/metal at speed
- wood turned on rotating chuck
- tool = stationary, moved into path of work piece (or done by CNC machines)
- speed of rotation of work piece altered (reflect diameter, material being turned)
- long pieces of work = support from both ends
- produces bowls, spindles in wood
- bore holes, turn threads, allow drilling operations in all materials
What is batch production?
- make consistent products
- produced in large batches, reduce overall cost of item
- templates, jigs, moulds ensure consistency of production
- each batch tested for quality and uniformity
- machinery may need recalibration between batches = down time
seasonal items, newpapers, baked goods
2-thousands
What is mass production?
- standardised products in large quantities
- automation of processes, assembly lines = efficient for high volume
- fewer workers
- set-up costs for machinery/ robots = high
- costs spread over large no. of goods (reduces cost per unit)
vehicles, mobile phones
1000s to millions
What is a prototype?
- representation of product
- evaluate + test design
- confirm design methods + costs
- eg physical/ CAD models
1
What is one-off production?
- manufacture of single item
- high quality, bespoke
- high cost
bespoke furniture, hand made wedding dress
What is continuous production?
- 24 hrs a day, 7 days a week
- expensive to run
- highly automated, small work force
- machinery = large volumes of 1 item
millions to billions
components
How is MDF made?
1) wood processed into chips/particles
2) mixed with adhesive
3) compressed into shape with rollers, heated to cure adhesive
4) boards trimmed to standard sizes
What is 3D printing?
Draw a diagram of 3D printing
- builds 3D object using reels of thermoplastic
- use CAD files that are converted to series of co-ordinates (G-code)
- printer follows to build up object in layers
- monitor printing process - nothing goes wrong
- remove from printing bed
- additive manufacturing
What is laser cutting?
Diagram
- directs laser beam at precise focal length to cut, etch or engrave on material
- material placed on bed, CAD file loaded
- speed, power and dimension settings according to material
- accurate- laser beam does not blunt or wear out
- consumes lots of power
How is plywood made?
- thin veneers of wood at 90 degrees to each other
- glued to create composite
- pressed and heated until adhesive sets
- decorative laminate surface added (flooring, furniture)
Process of tanalisation
1) vaccum empties air from cells of timber
2) flooded with preservative under vaccum
3) preservative forced deep, high pressure
4) vaccum extracts excess
5) draws in surface excess under low pressure = left to dry
What is tolerance?
- amount of error allowed for task
- used in quality checking
- products + systems = perform correctly given criteria
What is ergonomics?
- designing workspaces + environments to fit ppl who use them
- minimises risk of injury
What is anthropometrics?
- study of human body, its measurements and proportions
What is a design specification and what is it used for?
- measurable criteria (more specfic than design brief)
- used to test and evaluate design concepts/ at end of project
- summarises research
- modify design as iterative design process
Describe primary data
- data collected first hand
- created by those needing data
tailored to specific needs
up to date, relevant
time consuming, large number of ppl needed
What are sources of primary data?
- interviews
- surveys
- focus groups
- product analysis
Describe secondary data
- information created by others
already collected, free, large amount available
Give examples of secondary data
- books
- government data
- exemplar work from others
out of date, not specific enough
