As Flashcards
What is the process of bonding timber together?
Lamination
How is lamination performed?
Wood veneers or thin MDF are glued together before being bent over a former.
As the glue dries the materials set in the former shape.
Clamps or a vacuum bag prevent any movement
Glue of choice is usually cascamite
How is using a vacuum bag in lamination beneficial and how does it work.
Prevents any gaps forming.
Veneers and former placed under polythene sheet.
Edges are then taped down to the table.
A valve and vacuum pump suck out all the air and so the resulting pressure pulls the laminates hard together
Benefits of lamination
Aesthetically pleasing
Versatility, can make whatever thickness desired
Affordability, much cheaper than buying solid wood and cutting it out (less wastage too)
Less liable to warping and cracking as reinforced
Increased strength
Disadvantages of lamination
Potentially more labourious as mould needs to be created
What is an adhesive?
A substance used to stick materials together
What are the two main types of adhesives?
Cascamite
PVA
What is cascamite?
Strong glue used when laminating flexible plywood together.
3 parts cascamite and one part water
Sanded once dry for smooth finish
Dries in 24-48 hours
Advantages of cascamite?
Weatherproof
Strong even at high temp
Advantages of PVA?
Waterproof
Readily available
Dries clear
Affordable
Why cascamite over PVA?
Stronger under sharp temp changes
Weatherproof not just water proof
Stronger in general
Why PVA over cascamite?
More readily available
Dries clear and faster
Still waterproof
Versatile
Cascamite typical uses
Anything outdoors
etc, boats, dinghy’s
Name three types of composite wood
MDF
Hardboard
Chipboard
Plywood (flexy ply)
Advantages of using composite wood
Cost effective when needing curves (don’t have to buy big lump of timber or machinery)
Versatility
Doesn’t have weak points which natural wood is prone to having (no warping or cracking)
Normal woods can have splits and shakes
Uses and features of plywood
Odd number of layers of veneer glued together at right angles
Can be stained or painted
Used in shelving and construction due to its strength
Uses and features of chipboard
Compacted wooden chips which is laminated
Strong, but not water resistant
Protects items better than corrugated in shipping
Used in flooring and veneered worktops
Hardboard features and uses
Made from exploded wood fibres to increase the density
Less durable and unnatural finish but can be painted and oiled
Quite cheap
Used in furniture and construction
MDF uses and features
Made from normal wooden fibres
Dense but not as dense as hard board
Not water resistant
Commonly used in decorative furniture etc
Who is related to the arts and craft movement and what did he do?
William Morris
British textile designer, poet, novelist, translator, painter, and social activist. Significant in the revival of British textile arts and textile construction methods.
What are the features of the arts and craft movement?
Raw materials with natural qualities and beauty
Designs, motifs and patterns inspired by nature
Natural materials
Craftsmanship (eg hand printing) and experimentation
Natural colour tones
Belief that all objects that surround a person should be of good quality and well made
Simplicity
Form follows function
Affordability to appeal to wider community
Proportionality
What years did the arts and crafts movement last
1880-1920
What are the 5 polymer processes
Injection moulding Rotational moulding Blow moulding Extrusion Vacuum forming
What is anodising?
Enhance the natural oxide layer via electrolysis to increase hardness and toughness
MIG welding over one solid piece
More wastage of material
Individual parts can be adjusted and used elsewhere
Solid over MIG
Faster cycle times on CNC
Aesthteivally pleasing
Less labour time
Benefits of ABS
Hard
Non toxic
Rotational moulding
What is die casting?
Advantages of high pressure die casting?
Ability to create thin walls of exact dimensions
Create large volumes of complex products in short times leading to lower lead times which is more cost effective
Has a good surface finish
Disadvantages of high pressure die casting?
Porosity caused by entrapped gases, resulting in weak points and potentially ruining aesthetic
High startup costs, not effective for small scale production runs
Finished products cannot be fully heat treated
Setup of CNC machine
Design product on CAD software
Ensure machine knows which tool is being used (number of teeth, size etc)
Tell machine which material is being used and the speed (rpm) feed rate and speed
Align tool to the datem point (origin 0,0)
Test cut without material
If all is ok then put material in and line up with datem point
Send around at a 50% rate to ensure it works
Carry out an inspection (quality check) and then peer assess
Advantages of sand casting
Simple production process
Low cost moulds and therefore low production costs with short lead times
Wide material choice with complex shapes able to be made
Easily repeatable
Ideal for one off production
Disadvantages of sand casting
Low dimensional accuracy
Rough surface finish
Predominantly handmade so more liable to small errors which could result in unstable casting quality
How does rotational moulding?
- A hollow mould created using CAD software
- Mould with plastic in pellet form or powder
- This is heated to 300 degrees Celsius and then rotated about 2 axes
- During the rotation the mould is heated causing the polymer to melt and then “lay up” on the sides of the mould, evenly dispersing it.
- Once fully melted it is moved into the cooling station where cool air surrounds the mould
- This causes the plastic to solidify, once solid rotation stopped and product removed
Advantages of rotational moulding
Even stress levels so walls have even thickness limiting number of weak points
Can make very large components
Low mould equipment costs
Easy colour and mould changes
High strength and stability due to thick corners and lack of exposure to external pressure
Disadvantages of rotational moulding
Only simple shapes
Limited material choice, as has to be in powder form
Limited mechanical properties due to thick walls
High cycle times
Poor dimensional tolerance control
Positive obsolescence
Newest products, apple iPhone, status symbol
Safety, after length of time products can be harmful (eg a battery), risk to your health as user
