Shape & Form Polymers (AQA GCSE Design & Technology): Revision Note

How to cut polymers

• Polymers are available in a range of stock forms, including sheets and lengths/rod

• Depending on the stock form, there are a wide choice of cutting methods which can be used

• For sheets of polymers including acrylic, hand tools including a coping saw can be used to carefully saw the material

• For thinner sheets of polymers including polypropylene, a craft knife can be used to score and cut the material

• For both sheet forms thin and thick, a laser cutter is an example of Computer Aided Manufacturing (CAM) that can be used to cut the material

• Very thin polymer sheet such as vinyl can be cut using a plotter, which is another example of CAM which uses a sharp blade instead of a laser to cut material

• For thicker rods or lengths, a coping saw or junior hacksaw can be used to cut the polymer

How to drill polymers

• To drill into polymer sheet, length or rod, a maker can choose between a hand held electric drill or a machine known as a pillar drill

• For both pieces of equipment, the maker needs to choose the appropriate size and type of drill bit

  • This is the cutting tool used to drill a hole

• For a 6mm hole, a M6 drill bit would be chosen

• Polymer lengths and rods are typically clamped in place, with some scraps of timber or space underneath

  • This is in case the drill bit need to travel all the way through the polymer being drilled

• For sheets, a scrap piece of material such as MDF is placed underneath

  • This is so that once the drill breaks through the polymer sheet, it does not damage what is below

• The drill bit is mounted into the chuck of the drill hand or equipment and tightened into position

• The drill is lowered through the polymer, either to a specific depth using a depth stop, to a depth judged by the maker, or all the way through the material

How to cast polymers

• Thermoset Polymers including epoxy or polyester resin can be cast

  • Both of these materials are made from two parts a catalyst and a resin

  • These can be mixed whilst the polymer is a liquid, so that it can be poured into a mould

• Polymers such as silicon can also be cast due to being in a liquid state sufficient to pour

• Some makers will cast the resin or silicon into a smooth mould made from another polymer, metal or ceramic, which will not bond to the polymer as it sets/hardens

• The hardened part, which will no longer be a liquid, can be removed carefully from the mould ready to use

• For the mass production of parts from thermoplastics including ABS and polystyrene, the liquid polymer can be “injected” into a closed cavity mould using a process called injection moulding

  • In the process of injection moulding, the polymer starts as a granule

  • It is then fed into a heated chamber which forces the material out of a small nozzle and into a closed steel mould

  • The mould has an open space inside called a cavity

  • The polymer cools and hardens, allowing the finished part to be removed

How to deform polymers

• Polymer sheets including High Impact Polystyrene (HIPS) can be heated and deformed using a process called vacuum forming

• Vacuum forming occurs when:

  • A sheet of HIPS is clamped above a former which is in the shape required

  • The sheet is heated until it has softened

  • The former is pushed up into the material

  • At the same time air is drawn from underneath

  • This results in a tightly shaped polymer sheet which hugs the surface of the former

• For polymer sheets, rods and lengths such as those made from acrylic, a heat gun can be used to provide directed heat to an area

  • This softens the part ready to be bent

• For sheets of acrylic, a machine called a strip heater can be used to heat the material along a line

  • This allows a maker to bend the heated line and fold the polymer sheet into a shape

• Lastly, sheets, rods and lengths can be heated in a polymer convection oven

  • This heats the entire part up allowing the maker to shape and form it

How to print polymers

• Polymer filament a long reel of thin material can be printed through a process called additive manufacturing

• The filament, either PLA or ABS, can be heated in the head of a 3D printer,

  • It is then extruded out much like a glue gun squirts out hot melt glue

• The print head moves around the print bed, extruding the filament and building up layers to create a 3D object

How to weld polymers

• Thermo polymers can be welded using friction

• The surfaces of two parts of the same material are rapidly vibrated in contact with each other

  • This creates high temperatures through friction, and causes the surfaces to become liquid

  • When the materials are allowed to cool the two parts will have bonded together resulting in a welded joint

• Thermo polymers can also be welded using solvent

  • This is a liquid chemical that is painted onto the surface of the polymer part, which causes it to dissolve slightly

  • When two surfaces that are in contact with one another have solvent applied, they both dissolve which causes the two parts to weld together

  • The solvent evaporates leaving a clean welded joint