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SYSTEMS PREPARATION QUESTIONS 2007 - 15 |
V. Ryan © 2007 - 2009 |
1. A model railway system is remotely controlled using a handheld unit (shown below). The unit is manufactured from plastic and inside is an electronic circuit. The unit controls the movement of model trains, barriers, traffic lights etc.....
Name a suitable plastic for the casing: ____________________________
2. What are the properties of the plastic you name in the previous question that make it suitable for the manufacture of the handheld control unit? |
PROPERTIES: |
ANSWERS |
Name a suitable plastic for the casing: HIGH DENSITY POLYSTYRENE |
PROPERTIES: High density polystyrene has a relatively low melting point. This material is a thermoplastic - which means when heated and then pressured in a mould it can be formed into different shapes |
3. It has been decided that the casing is to be manufactured through the process of injection moulding. In the space below draw a suitable diagram representing this process. Include labels and notes explaining the process. |
NOTES: |
ANSWER |
NOTES |
Granules of plastic powder are poured or fed into a hopper which stores it until it is needed. A heater heats up the tube and when it reaches a high temperature a screw thread starts turning. A motor turns a thread which pushes the granules along the heater section which melts then into a liquid. The liquid is forced into a mould where it cools into the shape of the casing. The mould then opens and the coupling is removed. |
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