DT Revision materials and processes

There are two types of metals: ferrous (contains iron) and non- ferrous (without iron)

Ferrous

Iron and stainless steel

Non- ferrous

aluminum, gold, silver, copper,brass 

(brass is an alloy as is stainless steel)

Stock forms of metals include: bar, rod, sheet, tube, u shaped channel

Metals are coated via:

Painting - weatherproof finish, plastic coating, plating - electroylsis barrier, lacquering - transparent coating

Woods are either hardwood or softwood:

HARDWOOD:                                                                                                                       grown in warmer climates & take a long time to grow therefore they are expensive e.g. mahogany, oak and ash

SOFTWOOD:                                                                                                                         grown in colder climates & quick to grow (they are usually evergreen) therefore are cheap e.g. scots pine and parana pine

finishings...

woodstain - enhance apperance

oil - can protect wood to outdoors

paint

polyurethene varnish

Two types:

thermoplastics and thermosetting polymers

Thermoplastics are easy to shape and mould and are recycleable e.g. acrylic, acetate and PVC

Thermosettings can't be remoulded (are rigid) and are non recycleable e.g. epoxy resin, urea formaldihyde and glass reinforced plastic

plastics are made from crude oil and are joined via polymerisation, crude oil is finite so it will run out eventually.

stock forms: rod, sheet, tube, rolls. granules and foam

plastics don't need finishes as they are very resistant to erosion but to smoothen edges wet and dry paper can be used or in mass production a buffer machine

paper is grown via the cutting down of trees, being made into wood chips, added to chemicals to make pulp and washed and bleached and rolled to make paper.

types of paper:

cartridge paper, grid paper, tracing paper, layout paper

types of card:

corrugated cardboard made up of fluted inner core and two surrounding layers, duplex board, solid white board

laminating paper means to add another layer of material for example paper cups are coated with polethene to make them waterproof. 

Lithography -water and ink are added and the image is pressed on via a printing plate and a roller

offset lithography - paper doesnt come into contact with printing plate, image is transferred via a rubber roller

flexography -printson flexible printing plates made from rubber

gravure - holes are filled with ink and pressed against the plate

blow moulding - air is blown in largening the plastic shape

injection moulding - plastic granules are heated and moulded into a specific shape

press moulding - former is pushed onto the 'fermale mould' and with heat it liquifys forming the permenant shape

die casting- melting material into a mould

embossing - textured roller presses onto material to impress the image

new materials have useful properties e.g. cornstarch polymers instead of plastic as cornstarch is renewable and better for the environment.

smart materials react to surrounding environment for example thermochromic materials which change colour according to their hotness.

nanomaterials have useful properties e.g. self cleaning glass and odour free socks

intergrated electronics are built in circuits, they are made in with a design. they usually have quatum tunneling compsotites which become more electronically charged the more squashed it becomes.