Tools, Equipment & Processes — Deforming & Reforming (AQA GCSE Design & Technology): Revision Note
Exam code: 8552
Vacuum forming
Vacuum forming heats a thermoplastic sheet and draws it over a former using atmospheric pressure (removing the air from below the mould)
How vacuum forming works
A sheet such as HIPS is clamped and heated until soft
The mould/former rises into the sheet and a vacuum removes air underneath
The sheet cools and keeps the shape of the mould/former
Draft angles and rounded corners help the formed part release
Where there are possible air traps (small holes), are drilled so that trapped air can escape
Typical products and prototypes
Packaging trays, model shells, masks and prototype casings
Waste and quality
The sheet is reformed rather than cut during shaping, but the finished part must be trimmed, producing edge waste
Worked Example
Explain why small holes may be drilled in a vacuum-forming mould/former.
[2 marks]
Answer
The holes allow trapped air to be removed from detailed areas [1] so the softened sheet is pulled closely against the mould/former. [1]
Examiner Tips and Tricks
For processes with multiple steps (like vacuum forming), practice drawing out the steps and labelling each step with the parts.
Creasing
Creasing compresses paper or card along a line so the material folds accurately without cracking
How creasing works
A blunt rule, scoring tool or machine crease is used
The crease displaces and weakens fibres in the sheet paper/card without cutting through the material
It is important on thicker boards and printed packaging which are difficult to bend accurately without creasing
The fold is normally made along the crease after it has been formed
Typical products and prototypes
Cartons, greetings cards, folders and card prototypes
Waste and quality
Creasing reforms the fibres and creates almost no waste; however inaccurate creases can ruin a component
Worked Example
Why is creasing preferable for folding thick card?
[1 mark]
Answer
The crease controls where the fibres bend, producing a straight fold and reducing surface cracking. [1]
Pressing
Pressing uses force between shaped tools or dies to form, compact or cut material
How pressing works
Metal sheet can be pressed into panels using male and female dies
Paper and card can be embossed or die cut in a press
Textiles can be heat pressed to apply prints or fuse interfacing
High tooling cost makes industrial pressing suitable for larger quantities
Typical products and prototypes
Car-body panels, embossed packaging, formed metal lids and printed textiles
Waste and quality
The main material is reformed; trimming and blanking may create offcuts; accurate blanks reduce excess waste
Worked Example
Explain why pressing is suitable for mass-producing metal panels for a car?
[2 marks]
Answer
A press using dies can form each panel quickly and consistently for the production of cars. [1] The high tooling cost is spread across a large production quantity. [1]
Drape forming
Drape forming heats a thermoplastic sheet and allows it to soften and bend over a former under gravity or light pressure
How drape forming works
The technique is commonly used with acrylic sheet
The sheet is heated evenly in an oven until flexible
It is placed over or into a former and allowed to drape to shape
The part cools while held in position
Typical products and prototypes
Curved display stands, covers, light diffusers and prototype shells
Waste and quality
The polymer is reformed with little process waste, although edges may need trimming
Worked Example
State one difference between drape forming and vacuum forming.
[1 mark]
Answer
Drape forming uses gravity or light pressure to form polymer sheets, whereas vacuum forming uses a vacuum to pull the softened sheets tightly over a former. [1]
Bending
Bending changes a material from a straight or flat form into an angle or curve without separating it
How bending works
Sheet metal may be bent using a folding machine
Acrylic can be line bent using a strip heater
Timber can be steam bent or laminated around a former
A bend allowance is needed because the material stretches on the outside of the bend
Typical products and prototypes
Brackets, stands, furniture parts and polymer displays
Waste and quality
Bending creates very little waste, but over-bending, cracking or incorrect bend positions can cause rejects
Worked Example
Why is a bend allowance included when marking out sheet metal?
[1 mark]
Answer
Material around the bend changes length, so the allowance ensures the finished sides reach the required dimensions after bending.[1]
Folding
Folding turns sheet or flexible material over along a line to create an edge, layer or three-dimensional form
How folding works
Paper and card are folded after scoring or creasing
Sheet metal folds increase stiffness and form flanges
Textiles are folded to make hems, pleats and enclosed edges
Folding can reduce the need for separate components or fixings
Typical products and prototypes
Packaging, sheet-metal boxes, textile hems and collapsible products
Waste and quality
Folding reforms the existing material and usually creates no direct waste
Worked Example
Explain how folding can increase the stiffness of sheet material.
[1 mark]
Answer
A flat sheet bends easily, but a folded edge creates a three-dimensional section that resists bending more effectively. [1]
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