Polymers: Specialist Techniques & Processes
Design & Technology: AQA GCSE, topic 5.4.2
Line Bending, Press Moulding and 3d Printing
Many products are made from polymers. There are a number of processes used for making polymer-based products.
Line bending
- Line bending allows polymers to be bent into a shape.
- Line bending is used for thin pieces of polymers.
- The polymer is laid onto a line bender or strip heater.
- The heat softens the area above the heated wire.
- The polymer can be bent to the desired angle and left to cool.
- Once cool, it will harden and stay at that angle.
Press / compression moulding
- Press / compression moulding involves compressing a sheet of polymer over a 3D shape.
- The pressure from the yoke / upper mould focuses the sheet to replicate the mould below it.
- A waste material called flashing is removed from around the edge.
3D printing
- 3D printing allows products drawn on CAD to be printed in a 3D form.
- CAD stands for Computer-Aided Design.
- The printer takes the image and slices it into layers.
- The printer can print these layers to build up the shape of the product.
- 3D printing helps speed up prototyping and idea generation.
Injection Moulding and Vacuum Forming
Injection moulding and vacuum forming are used for making polymer-based products.
Injection moulding
- Injection moulding produces complex 3D shapes.
- For example, plastic chairs and Lego bricks.
- Injection moulding can run continuously.
Process of injection moulding
- Granules are fed into a hopper where an archimedean screw rotates.
- This moves the granules down the tube.
- This heats the granules up.
- The liquid is forced through a sprue gate by a hydraulic ram.
- This pushes the liquid forward.
- The mould is filled up with liquid plastic and left to cool.
- The 3D product is released.
Vacuum Forming
- Vacuum forming produces hollow 3D objects.
- For example, trays and masks.
Process of vacuum forming
- A 3D mould is placed into the machine.
- A sheet of thermoforming polymer is clamped above the mould.
- HIPS is the thermoforming polymer that is usually used.
- A heater begins to soften the HIPS, making it malleable.
- The mould is lifted up into the HIPS, forming the 3D shape.
- The vacuum removes any air, wrapping the HIPS around the 3D mould.
Test yourself on Polymers: Specialist Techniques & Processes
What process produces complex 3D shapes?
What thermoforming polymer is usually used in vacuum forming?