Production Aids With Polymers (AQA GCSE Design & Technology): Revision Note
Exam code: 8552
The use of production aids with polymers
Production aids are used when polymers are:
marked
cut
drilled
bent
vacuum formed
moulded
assembled
Polymer sheet can scratch and some thermoplastics soften when heated,
This means production aids must support the material without damaging its surface
Production aids are often made from MDF, plywood, acrylic, aluminium or steel, depending on the heat, pressure and number of uses involved
Measuring and reference points for polymers
A straight “factory” edge can be used as a datum when measuring polymer sheet
Materials such as protective film need to be kept in place while marking and cutting
A steel rule and engineer's square can be used for straight lines
A fine permanent marker can be used instead of a scriber where a scriber might cause unwanted scratches
Centre lines and hole centres are marked before drilling, where a small pilot hole can help locate a larger drill
Reference lines are used when strip heating acrylic so the heated line and final bend occur in the correct position
On a laser cutter or CNC router, the CAD origin is the digital datum
This means that components must be positioned accurately on the virtual (computer) sheet before manufacture
Measurements must allow for material thickness, bend radius and tolerances where parts slot or press together
Worked Example
Explain why the protective film is often left on acrylic sheet during marking and cutting
[1 mark]
Answer
The film protects the surface from scratches and marks while the material is measured, handled and cut. [1]
Templates and patterns for polymers
Templates can be used on polymer sheets to mark:
Repeated outlines
Hole positions
Bend lines
A routing template guides a router to produce the same edge profile on several acrylic or solid-surface components
A former is a three-dimensional shape used in vacuum forming
A heated thermoplastic sheet is pulled over the former by air pressure
Vacuum-forming formers need smooth surfaces, rounded corners and draft angles so the cooled moulding can be removed without damage
Split lines, undercuts and air holes must be considered when designing formers and moulds
A mould is a negative cavity used to shape liquid resin or molten polymer, while a former is usually a positive shape over which sheet is formed
Worked Example
State two design features needed on a vacuum-forming former
[2 marks]
Answer
Any two from:
Draft angle
Rounded corners
A smooth surface
Small air holes where needed
Jigs for polymers
A drilling jig supports polymer sheet and guides the drill to prevent holes being positioned differently on each part
A bending jig or former holds heated thermoplastic at a fixed angle until it cools and becomes rigid again
An assembly jig locates several moulded parts while they are solvent welded, screwed or ultrasonically welded
A trimming jig can hold a vacuum-formed shell while excess material is cut away along a consistent line
Soft pads or smooth contact surfaces may be added so the jig does not scratch the polymer
Jigs used near heat must be made from a material that will not soften, distort or stick to the polymer
Worked Example
Explain why a bending jig is useful after acrylic has been heated with a strip heater
[2 marks]
Answer
The jig holds the softened acrylic at the required angle and position while it cools, [1] producing consistent bends and preventing the part from springing out of shape. [1]
Unlock more, it's free!
Join the 100,000+ Students that ❤️ Save My Exams
the (exam) results speak for themselves:
Was this revision note helpful?
