Materials RevisionMetals, Plastics, and Woods

This powerpoint runs through materials and their properties, fixing methods (temporary and permanent), and finishing techniques

Metals can be broken down into two main categories:

Categories of metals

Non-ferrous Metals don’t contain iron

aluminium, copper, tin and lead are all non-ferrous.

Ferrous Metals contain iron

will corrode unless protected

attracted by a magnet.

Alloys

A mixture of two or more metals

Brass is an alloy of 65% copper and 35% zinc

High tensile steel is an alloy of low carbon steel and nickel

Stainless steel is an alloy of steel, chromium, nickel and magnesium.

Categories of metals

Materials can be joined temporarily or permanently. Three methods of joining metals are shown below.

Joining metals

RivetingNut, bolt &

washerMIG Welding

Working with metals – finishing techniques

Several surface finishing techniques can be used on metals. The most common ones are detailed below:

Paint

Plastic Coating

Lacquering

Enamelling

Surface must be smooth & de-greasedPrimer requiredHammerite is a good one-coat metal paint.

Suitable for most metalsObject is heated and dipped in a tank of powder paintObject is returned to oven to ensure a smooth, glossy finish.

Helps to prevent corrosion after polishingA layer of cellulose or varnish is appliedOften used on jewellery.

Powdered glass is melted onto the metal surfaceProvides a hard (but brittle) finish with different colours and textures.

Plastics can be broken down into two categories: thermoplastics and thermosets.

Categories of plastics

Thermoplastics

Soften when heatedCan be reshapedMore commonly used in schools

Thermosets

Initially set by heatCannot be reshaped once setExtremely strong and durable

Plastics have an extremely wide range of uses. Here are some common products made from thermoplastics.

Uses of plastics (thermoplastics)

Acrylic

High DensityPolyethene

Polystyrene ABS

Low DensityPolyethene

Polypropene

Thermosets have different qualities to thermoplastics. Here are some uses for thermosets.

Uses of plastics (thermosets)

Melamine formaldehyde

Ureaformaldehyde

GRP

Phenol formaldehyde

Epoxyresin

Working with plastics – other processes

Plastics can also be worked in other ways.

Buffer

Oven

Scroll Saw

Drill

Hot wire strip heater

Materials can be joined temporarily or permanently. Three methods of joining plastic are shown below.

Joining plastics

Nut, bolt and washer

RivetingAdhesive

Working with plastics – finishing techniques

Plastics have excellent surface qualities. As they are self-finishing, plastics require little or no surface finish. However, when designers want a specific colour or texture, spray paints can be used.

Use wet and dry paper (wet) to smooth the surface down and create a ‘key’ for the primer to grip to.Primer is used to create an undercoat to protect the plastic and provide a good surface finish for the top coat. The primer should be rubbed down using wet and dry paper between coats.Top coat is applied once the primer has completely hardened. There are different surface textures: gloss, matt and metallic being the most common. Top coat is applied in several layers to build up a thick, tough surface layer on the top of the primer.

Timbers can be broken down into three categories:

Categories of timbers

Hardwoodscome from deciduous treescan be very expensive.

Softwoodscome from coniferous treesgrow in colder climates.

Manufactured boardsavailable in sheet formuser friendly.

A closer look at hardwoods

A closer look at softwoods

A closer look at manufactured boards

Working with timber – other processes

Timber can also be worked in other ways.

Scroll Saw

Drill

Belt Sander

Wood Lathe

Materials can be joined temporarily or permanently. Two methods of joining timbers are shown below.

Joining timbers

Screws

Nails

Can you think of any other methods?

Working with timber – finishing techniques

Timbers can be treated with several surface finishes. They have different purposes and are chosen depending on where the product is going to be used and what type of visual appearance is desired:

Paint

Stain

Wax

Varnish

Indoor and outdoor useWood is sealed with a primer firstCoats the surface of timberCost effective

Enhances the grainPenetrates the surface of timberA variety of colours is available

Gives a dull gloss shineEnhances the grainSurfaces must be sealed

Tough surface developsResistant to heat and waterCan be coloured