bending and forming

bending

• physically deforming material

• easier to bend when heated

• some metals must be annealled

• former: helps make accurate bend

• bending jigs, hydraulic bending machines: when lots of parts need to be bent to the same shape

• thermoplastics will break if not heated

• strip heater: heats a specific area that you want to bend

folding

• bending material over itself, one part covers the other

• bigger direction change than bends

• bending bar/mallet or hydraulic press and former

press forming

• fly press: hand operated, a small number of items

• hydraulic press: large/multiple parts, hundreds of tons of force

• moulds: made of high carbon steeel, hard and resists wear. Difficult to machine and expensive.

• 3D parts from a metal sheet (domes, bowls, car body panels)

1. sheet of material fit between two moulds or a ram and die

2. moulds/ram and die fit together with a small gap in the required shape

3. press applies pressure to permanently deform material

4. extra material removed

Press moulding

• press forming for polymers

1. thermoplastic heated until flexible

2. placed between parts of a mould (plug and yoke)

3. mould pressed together

4. plastic cools/hardens

5. plastic removed from mould

   1. extra plastic removed

punching & stamping

• cut shapes in metal sheet

• pressure applied to push tool through sheet

• punching/piercing: hole is made, and material pushed out is scrapped

• stamping/blanking: hole is made, material pushed out is needed

composite lay up

• for composite materials

• smooth on one side, rough on the other

• male mould: smooth inside

• female mould: smooth outside

1. mould polished & coated with release agent

2. gel coat resin brushed on - gives a good finish on smooth side & adds colour

3. reinforcement material layers (e.g. glass fibres) put in mould

4. material soaked in resin to form matrix - this can be painted or dabbed on with a brush (stippled)

5. more layers added/soaked until required thickness

6. if the product needs to be high performance, everythings put into plastic sheets can a vacuum sucks the air out - ensures resin has been pulled into glass fibre spaces, reducing local weakness

7. part cured, resin becomes hard. You can either leave it alone for a few hours, heat it gently in an oven, or put it in an autoclave (giving pressure + heat)