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ENGINEERING, PPT 2024 HSC 9 MC

When producing glass, what molten material is the glass floated on in order to obtain a smooth surface?

  1. Aluminium
  2. Bronze
  3. Steel
  4. Tin
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\(D\)

Show Worked Solution
  • In the glass manufacturing process, molten glass is poured onto a bed of molten tin.
  • Tin provides an extremely flat and smooth surface due to tin’s high density and surface tension, allowing the glass to float and spread evenly while cooling.

\(\Rightarrow D\)

♦♦ Mean mark 33%.

ENGINEERING, PPT 2016 HSC 24a

An image of a truck is shown.
 

Compare the selection of laminated glass with toughened glass as a windscreen for this vehicle.   (3  marks)

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Toughened glass

  • Scratch resistant from dust and road debris.
  • More impact resistant than laminated glass.
  • Breaks into small cubes when broken and fracture shards are safe if shattering occurs.
  • Easy to clean, lighter and cheaper to manufacture.

Laminated Glass

  • Scratch resistant from dust and road debris and also retains visibility if windscreen fractures.
  • Easy to clean and corners can be drilled and shaped.
  • When broken laminated windscreens retain structural integrity.
  • Defrosting elements can be installed internally.
  • Light fading internally is reduced as more UV light absorbed.
Show Worked Solution

Successful answers should include 2-3 comparisons from the below lists.

Toughened glass

  • Scratch resistant from dust and road debris.
  • More impact resistant than laminated glass.
  • Breaks into small cubes when broken and fracture shards are safe if shattering occurs.
  • Easy to clean, lighter and cheaper to manufacture.

Laminated Glass

  • Scratch resistant from dust and road debris and also retains visibility if windscreen fractures.
  • Easy to clean and corners can be drilled and shaped.
  • When broken laminated windscreens retain structural integrity.
  • Defrosting elements can be installed internally.
  • Light fading internally is reduced as more UV light absorbed.

ENGINEERING, PPT 2022 HSC 21a

The following images show an older bus and a contemporary bus.
 

  1. Older buses had flat, toughened glass windscreen panels.
  2. How is toughened glass manufactured?   (2 marks)
  1. Contemporary buses have windscreens which curve around the front of the bus.
  2. Describe the manufacturing process used to make these windscreens.   (3 marks)
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i.    Toughened glass is formed by:-

  • heating the glass to annealing temperature (approximately 600 degrees) and quenching/rapidly cooling the outside layers using a jet of water.
  • Alternatively toughened glass can be created by soaking the glass in potassium nitrate for an extended period.

ii.    Production of curved glass panels:

  • Windscreens are produced by placing a flat sheet of glass above a metal mould.
  • The glass is then evenly heated until it falls and takes the shape of the mould, and then allowed to cool.
  • Once cooled, the glass is then laminated.
  • Laminating involves placing a layer of polymer between two identically shaped sheets of glass, in this case curved windshields.
Show Worked Solution

i.    Toughened glass is formed by:-

  • heating the glass to annealing temperature (approximately 600 degrees) and quenching/rapidly cooling the outside layers using a jet of water.
  • Alternatively toughened glass can be created by soaking the glass in potassium nitrate for an extended period.

♦ Mean mark (i) 43%.

ii.    Production of curved glass panels:

  • Windscreens are produced by placing a flat sheet of glass above a metal mould.
  • The glass is then evenly heated until it falls and takes the shape of the mould, and then allowed to cool.
  • Once cooled, the glass is then laminated.
  • Laminating involves placing a layer of polymer between two identically shaped sheets of glass, in this case curved windshields.

♦ Mean mark (ii) 39%.